Siste publikasjoner ved ITA

• McKevitt, James; Matthews, Sarah; Brooks, David H.; Shimizu, Toshifumi; Tei, Akiko & Ugarte-Urra, Ignacio [Vis alle 22 forfattere av denne artikkelen] (2026). Pre-flare and active region plasma flows and structure seen by the short wavelength camera on SOLAR-C/EUVST. Publications of the Astronomical Society of Japan (PASJ). ISSN 0004-6264. 78(4), s. 1524–1545. doi: 10.1093/pasj/psag078. Fulltekst i vitenarkiv Vis sammendrag

  The mechanisms triggering solar flares and driving coronal heating occur across wide temperature ranges on small spatial scales and short timescales, making them difficult to observe with current instrumentation. The upcoming SOLAR-C mission, launching in the late 2020s, will provide unprecedented plasma diagnostic capability with its high-throughput extreme-ultraviolet (EUV) spectroscopic telescope (EUVST), capable of 0.2 arcsec/pix spatial sampling (⁠~0.4 arcsec resolution), continuous temperature coverage from 0.02 to 15 MK, and exposure times down to 0.5 s. We present forward modelling of the spectrograph’s short wavelength camera (170.0–212.3 Å; SOLAR-C/EUVST-SW) and its response to log T ~ 6.2 coronal plasma in a three-dimensional MHD-simulated pre-flare active region. We compare this performance to that of the previous-generation EUV Imaging Spectrometer (EIS) on Hinode (SOLAR-B). Our results demonstrate that SOLAR-C/EUVST can distinguish individual flux tubes in simulated active region loops, which Hinode/EIS cannot resolve. In simulated pre-flare plasma, SOLAR-C/EUVST captures sharp velocity gradients between adjacent upflowing and downflowing plasma which Hinode/EIS is unable to resolve. Doppler velocity measurement accuracy will reach better than 1 km/s in active regions. We show that this next-generation spectrograph can be expected to directly observe processes potentially related to flare triggering, such as plasma flows from low-altitude reconnection linked to emerging flux, and determine whether active region loops consist of a small number of strands or the hundreds predicted by magnetic reconnection-induced nanoflare heating models.

• Dalda, Alberto Sainz; Rodríguez, Jaime de la Cruz; Hansteen, Viggo Haraldson; Pontieu, Bart Walter De & Gošić, Milan (2026). The IRIS^2+ Inversion Tool: Recovering the Radiative Losses and the Thermodynamics in the Lower Solar Atmosphere. The Astrophysical Journal (ApJ). ISSN 0004-637X. 997(2). doi: 10.3847/1538-4357/ae274c. Fulltekst i vitenarkiv Vis sammendrag

  We introduce an improved and fast inversion tool that is able to provide the thermodynamics of the solar atmosphere from the photosphere to the top of the chromosphere, as well as the integrated radiative losses (IRLs) in the chromosphere for data observed by the Interface Region Imaging Spectrograph (IRIS). This NASA mission has been observing the Sun and providing, among other kinds of data, multiline spectral observations sensitive to changes in the lower solar atmosphere since 2013. In this paper, we explain the new inversion tool IRIS2+ based on the IRIS2+ database, which is based on 135,472 synthetic representative profiles (RPs), each of them consisting of six chromospheric lines and six photospheric lines, their corresponding representative model atmospheres (RMA), and the IRL associated with these atmospheres. A nearest neighbor (k-nn) model algorithm is trained with the synthetic representative profiles to predict the closest RP in the database to the one observed, at which point IRIS2+ assigns the RMA and the IRL to the location of that observed profile. We have compared the results obtained by IRIS2+ with results obtained from the state-of-the-art inversion code STiC, which is also used to build the IRIS2+ database. We find that the thermodynamics and the IRL obtained with both methods are comparable in most cases. Therefore, IRIS2+ is a fast and reliable inversion tool that provides approximate values of the thermodynamic state and the radiative losses in the lower solar atmosphere for a large variety of solar scenes observed with IRIS.

• Eskilt, Johannes Røsok (2026). Cosmic birefringence from a joint analysis of ACT and Planck. Physical Review D. ISSN 2470-0010. 114(4). doi: 10.1103/HCSM-39QW. Fulltekst i vitenarkiv Vis sammendrag

  Dark matter and dark energy could be ultralight pseudoscalar fields that couple to electromagnetism through a Chern-Simons term. This would cause a parity-breaking rotation of the plane of linearly polarized light from the cosmic microwave background, known as cosmic birefringence, which is not predicted by Λ cold dark matter. Recent hints of a nonzero cosmic birefringence angle have been found in both the Planck Data Release 4 and Atacama Cosmology Telescope Data Release 6 datasets independently. This work jointly analyzes the polarized maps of both, leveraging the cross-power spectra between the two telescopes. Taking the reported instrumental priors at face value, the joint analysis yields 𝛽 =0.27⁢7°±0.05⁢7°, which is nonzero with a statistical significance of 4.8⁢𝜎. A robustness test mitigating contamination from dust emission excludes 𝛽 =0° at 3.5⁢𝜎, and retrieving 𝛽 =0° would require both the dust 𝐸⁢𝐵 modeling and instrumental priors to fail simultaneously. However, unresolved systematics in the data must be understood before we can draw strong cosmological conclusions.

• Bate, W.; Gordovskyy, M.; Prasad, Avijeet; Brun, A. S.; Strugarek, A. & Sieyra, M. V. [Vis alle 10 forfattere av denne artikkelen] (2026). Energetics and Emission in a Simulated Solar Flare Initialized by a Non-force-free Magnetic Field. The Astrophysical Journal (ApJ). ISSN 0004-637X. 1006(2). doi: 10.3847/1538-4357/ae7c69. Fulltekst i vitenarkiv Vis sammendrag

  Solar flare simulations are commonly initialised using nonlinear force-free field (NLFF) extrapolations derived from photospheric vector magnetograms. However, the force-free assumption neglects plasma forces and may limit the available free magnetic energy. In this work, we perform a controlled comparison of two three-dimensional resistive magnetohydrodynamic simulations of the X2.1-class flare that occurred on 2011 September 6 in NOAA Active Region 11283. The simulations differ only in their initial magnetic configuration: one is based on a conventional NLFF extrapolation, while the other employs a non-force-free extrapolation. Both models are evolved in an identical stratified atmosphere using the same numerical framework, enabling direct assessment of how the initial magnetic assumptions influence flare dynamics and energetics. We find that the non-force-free model undergoes more extensive magnetic restructuring and releases approximately twice as much magnetic energy (≈4.4 × 10^31 erg) as the NLFF case (≈2.3 × 10^31 erg), bringing the energy budget into closer agreement with expectations for X-class flares. Synthetic extreme-ultraviolet emission in the 94 Å channel is computed for both simulations and compared with observations from the Solar Dynamics Observatory. The non-force-free model produces a brighter and more spatially extended emission structure that more closely resembles the observed flare morphology and light curve. These results demonstrate that assumptions made in constructing the preflare coronal magnetic field can significantly affect flare energetics and observable signatures and suggest that non-force-free extrapolations provide a promising pathway toward more realistic data-constrained flare modelling.

• Feldman, Juan Ignacio Domínguez; Pereyra, Luis A.; Hansen, Frode Kristian; Toscano, Facundo & Lambas, Diego Garcia (2026). Cosmic filaments confirm unexplained CMB temperature decrements in two independent redshift ranges. Physical Review D. ISSN 2470-0010. 113(4). doi: 10.1103/s1v4-3cky. Fulltekst i vitenarkiv Vis sammendrag

  Recent papers have reported an unexplained cooling of cosmic microwave background (CMB) photons passing through galaxies in nearby cosmic filaments 𝑧<0.02 at the >5⁢𝜎 level. Here we show for the first time that this effect is also present at higher redshifts 0.02 <𝑧 <0.04. Instead of calculating the CMB temperature around individual galaxies as in previous works, we analyze mean CMB temperature profiles associated to cosmic filaments in three dimensions. We have considered different thresholds in the linear K-band luminosity density of the filaments as a proxy to mass density. Furthermore, we have analyzed the dependence of the results on the average orientation of filaments with respect to the line of sight. These studies were implemented to test the expected dependence on mass density as well as on photon trajectory length within the cosmic filaments. We find a 3 −4⁢𝜎 detection of a CMB temperature decrement trend toward the spine of the filaments, the larger the mass and the more radially oriented the filament, the stronger the CMB temperature decrement. This trend is seen independently in both redshift ranges 0.004 <𝑧 <0.02 and 0.02 <𝑧 <0.04. We therefore conclude that our results provide strong evidence for a lower CMB temperature along massive cosmic filaments in the nearby Universe 𝑧 <0.04.

• Ornig, Sascha & Carlsson, Mats (2026). Characterization of white-light enhancements under umbral conditions in one-dimensional simulations of solar flares. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 711. doi: 10.1051/0004-6361/202660723. Fulltekst i vitenarkiv Vis sammendrag

  Context. Solar flares with signatures in the optical continuum (white light, WL) pose a challenge not only to the standard flare model, but also to solar flare simulations. In particular, simulations are so far not able to convincingly reproduce observed WL enhancements. Aims. We investigate the effect of different electron beams on an umbral atmosphere and what the differences and similarities to the quiet-Sun response are. Methods. We characterized WL emission in one-dimensional simulations of solar flares using the radiation hydrodynamics code RADYN. We created such simulations with a similar setup as the F-CHROMA grid, but with a starting atmosphere describing umbral conditions. We investigated the influence of different temporal profiles of an electron beam on this umbral atmosphere. Results. Our simulations show maximum WL increases between 40 and 335%, which is comparable to observed values. The reduced umbral background is the main reason for these large increases. We identify hydrogen recombination in an optically thin chromosphere as the dominant process responsible for the increases, with the radiation from the heated photosphere becoming substantial in the later stages (a few seconds after beam heating is turned o ) due to the longer timescale of the cooling of the photosphere compared to hydrogen recombination in the chromosphere. The short timescale of recombination results in very short gradual phases of excess emissions in our simulations. Shorter, more intense beams (i.e., beams with a higher maximum energy flux) lead to a faster and more dramatic atmospheric evolution. Such beams also cause larger WL enhancements due to a higher electron density in the relevant layers. Both the Balmer ratio and the Paschen ratio are substantially higher in our simulations compared to simulations with a quiet-Sun atmosphere. Conclusions. The detectability and amplitude of excess WL emissions depends both on the spectral and temporal structure of the electron beam impacting on the atmosphere as well as the underlying background radiation. The combination of a short, intense beam and an umbral atmospheric structure provides an excellent seed for substantial WL enhancements.

• Ornig, Sascha; Voort, Luc Rouppe van der; Carlsson, Mats; Baso, Carlos José Díaz; Øyre, Eilif Sommer & Poquet, Ignasi Josep Soler [Vis alle 7 forfattere av denne artikkelen] (2026). Investigating white-light flare mechanisms via the Paschen jump using high-resolution continuum observations from the Swedish 1-m Solar Telescope. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 712. doi: 10.1051/0004-6361/202660421. Fulltekst i vitenarkiv Vis sammendrag

  Context. The continuum is understood to contain a large portion of the energy emitted by a solar flare. The optical continuum, known as white light (WL), is particularly relevant since it may be observed by ground-based instruments. Aims. We measured the WL enhancements short- and longward of the Paschen jump in order to gain insights into the possible mechanism(s) behind the creation of these increases in our two case studies. Methods. We took measurements from the Swedish 1-m Solar Telescope of the pseudo-continuum around the Ca II 8542 Å line as well as the true continuum around the K I 7699 Å and the Fe I 6173 Å line, providing us with observations on both sides of the Paschen jump. Results. We observe WL enhancements of over 40% against the dark (pen-) umbral background in both flares. No WL excess is detectable against the granulation outside the sunspots. The WL excess in flare 1 is co-temporal with the derivative of the GOES soft X-ray and hard X-ray (HXR) measurements from the Advanced Space-based Solar Observatory (ASO-S), and the flare is compatible with the Neupert effect. For the second flare, a preceding smaller flare may be the cause of the temporal discrepancy. Signatures of chromospheric evaporation and condensation are found in the WL area for both flares. The ratio of intensities blueward and redward of the Paschen jump (i.e., the Paschen ratio) in flare 1 is below one for most WL pixels. This is in disagreement with the accepted WL formation mechanisms, which are both of photospheric and chromospheric origin. We believe this is a consequence of the Ca II 8542 Å pseudo-continuum being affected by line wing opacity changes. Conclusions. The co-temporality of WL and HXR enhancements suggests that the WL emission enhancements in flare 1 (and parts of flare 2) are a result of direct electron precipitation. We conclude that more reliable continuum measurements free of any nearby line influence are necessary in order to obtain conclusive evidence for the formation mechanism(s) behind optical continuum enhancements from such analysis as presented in this work.

• Cliver, Ed; Hudson, Hugh & Fletcher, Lyndsay (2026). Tension in the solar energetic proton paradigm for historical cosmogenic nuclide events. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. ISSN 1364-503X. 384(2329). doi: 10.1098/rsta.2025.0291. Fulltekst i vitenarkiv Vis sammendrag

  ‘Miyake events’ are exceptional increases in atmospheric 14C recorded in tree rings that, if confirmed, are accompanied by simultaneous 10Be and 36Cl enhancements in ice cores. During the last 15 000 years, six such events have been confirmed. They are generally thought to originate in solar flares that produce strong high-energy solar proton events. The 774 CE Miyake event is currently estimated to have been produced by a flare with a soft X-ray (SXR) flare classification of X430. A recently constructed size distribution of SXR events from 1975 to 2022 permits an estimate of the ‘return time’ for any given SXR event. We extrapolate the observed distribution to obtain a flare return time of ⋟106 years for all six of the Miyake events. We examine various possibilities (e.g. overestimates of greater than 200 MeV proton fluences, episodes of multiple smaller flares) to reduce the tension between the estimated long return (waiting) times for these extreme flares and the 15 000-year observation interval. We conclude that the most likely explanation for the inferred outsized proton events is a yet unknown Dragon-King type mechanism or scenario that can increase high-energy solar proton fluences in certain events by one to two orders of magnitude.

• Jewitt, David; Luu, Jane & Kim, Yoonyoung (2026). Investigation of Split Comet 240P/NEAT. Astronomical Journal. ISSN 0004-6256. 172(2). doi: 10.3847/1538-3881/ae83ac. Fulltekst i vitenarkiv Vis sammendrag

  We present time-series observations of the split comet 240P/NEAT near perihelion, obtained using the Nordic Optical Telescope. The brighter component, 240P-A, has an estimated radius in the range 400─600 m, and loses dust at the peak rate 130 kg s^−1. The ejected dust has characteristic size ∼50 μm, is expelled sunward at ∼25 m s^−1, with a total ejected mass in the period of observation ∼1.5 × 10^9 kg. Mass loss from the fainter component, 240P-B, peaks at ∼35 kg s^−1 and the total ejected mass was 2.3 × 10^8 kg. The radius of 240P-B is uncertain, with a best estimate ∼300 m and an absolute lower limit 50 m. 240P-A and 240P-B are currently separating at about 1 m s^−1, a speed that is likely accelerating as a result of differential outgassing forces, and have a separation age of >3 yr. The splitting of 240P is incompatible with the action of tides, impact, and internal pressure build up. 240P fits a developing picture, in which small comets are destroyed by rotational instabilities triggered by outgassing torques, an explanation that can be tested in 240P by future observations.

• Campos, A.; Yin, B.; Dodelson, S.; Amon, A.; Alarcon, A. & Sánchez, C. [Vis alle 114 forfattere av denne artikkelen] (2026). Enhancing weak lensing redshift distribution characterization by optimizing the Dark Energy Survey Self-Organizing Map Photo-z method. The Open Journal of Astrophysics. 9. doi: 10.33232/001c.165871. Fulltekst i vitenarkiv Vis sammendrag

  Characterization of the redshift distribution of ensembles of galaxies is pivotal for large scale structure cosmological studies. In this work, we focus on improving the Self-Organizing Map (SOM) methodology for photometric redshift estimation (SOMPZ), specifically in anticipation of the Dark Energy Survey Year 6 (DES Y6) data. This data set, featuring deeper and fainter galaxies than DES Year 3 (DES Y3), demands adapted techniques to ensure accurate recovery of the underlying redshift distribution. We investigate three strategies for enhancing the existing SOM-based approach used in DES Y3: 1) Replacing the Y3 SOM algorithm with one tailored for redshift estimation challenges; 2) Incorporating g-band flux information to refine redshift estimates (i.e. using griz fluxes as opposed to only riz); 3) Augmenting redshift data for galaxies where available. These methods are applied to DES Y3 data, and results are compared to the Y3 fiducial ones. Our analysis indicates significant improvements with the first two strategies, notably reducing the overlap between redshift bins. By combining strategies 1 and 2, we have successfully managed to reduce redshift bin overlap in DES Y3 by up to 66%. Conversely, the third strategy, involving the addition of redshift data for selected galaxies as an additional feature in the method, yields inferior results and is abandoned. Our findings contribute to the advancement of weak lensing redshift characterization and lay the groundwork for better redshift characterization in DES Year 6 and future stage IV surveys, like the Rubin Observatory.

• Li, Ting; Duan, Xuchun; Hou, Yijun; Aulanier, Guillaume; Zimovets, I. V. & Zhang, Jun [Vis alle 16 forfattere av denne artikkelen] (2026). Unprecedented Fast Winking of Solar Flares Triggered by Bursty Magnetic Reconnection. The Astrophysical Journal (ApJ). ISSN 0004-637X. 1006(1). doi: 10.3847/1538-4357/ae80ae. Fulltekst i vitenarkiv Vis sammendrag

  Flare ribbons form as a result of energy deposition associated with particles accelerated in low layers of the solar atmosphere. The fine-scale structures of flare ribbons, also called ribbon kernels, offer a potentially powerful diagnostic of the flare reconnection process, however, to date the dynamic evolution of ribbon kernels has not been fully characterized in statistical studies. Here, we checked the state-of-the-art observations (cadence ≤2.5 s) of solar flares in the ultraviolet from space by Interface Region Imaging Spectrograph over the past 12 yr. Our results showed the first statistical study of multiple spatially resolved flare kernel quasiperiodic pulsation events for 31 flares, with the period of 6–24 s. The ribbon kernels have a spatial scale of 480–1200 km and some kernels exhibit an unprecedented fast “winking” process, i.e., quasiperiodic pulsation-like flashing of individual kernels. The shortest heating time reaches about 2–3 s, implying that the energy is deposited only in a small localized region within flare ribbons, persisting for only a few seconds. Meanwhile, some ribbon kernels were observed to slip along the ribbon at speeds of 20–1800 km s−1. These observations strongly imply a joint picture for the dynamics and the bursty nature of ribbon kernels as being due to coupled effects of plasmoid formation and three-dimensional magnetic reconnection in the overlaying coronal current sheet. We suggest that the observed flare behaviors provide strong observational evidences of 3D bursty reconnection.

• Chaurasiya, Ravi; Pereira, Tiago & Bayanna, Ankala Raja (2026). Multi-thermal dynamics and transverse oscillations of solar spicules revealed by coordinated SST, IRIS, and SDO observations. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 712. doi: 10.1051/0004-6361/202660406. Fulltekst i vitenarkiv Vis sammendrag

  Context. Solar spicules are highly dynamic chromospheric jets that play an important role in the mass and energy balance of the solar atmosphere, even though their connection to the transition region and corona remains unclear. Aims. We investigated the dynamical and multi-thermal properties of spicules, their connection to higher atmospheric layers, and their transverse oscillations and associated energy flux. Methods. We analyzed coordinated high-resolution observations from the Swedish 1-m Solar Telescope in Hα, the Interface Region Imaging Spectrograph in Si IV 1400 Å, and the Solar Dynamics Observatory/Atmospheric Imaging Assembly coronal channels. Space-time diagrams, spectral analysis, and wavelet techniques were used to study temporal evolution, Doppler velocities, and oscillatory properties. Transverse displacements of spicules were tracked to estimate wave properties and energy flux. Results. Space-time analysis reveals a clear correspondence between chromospheric spicules and coronal emission in AIA 171 Å, evolving coherently with spicule extension. Doppler velocities from Hα and Si IV show opposite signs, indicating multi-thermal plasma flows. Wavelet analysis reveals frequently dominant ~3-minute oscillations, along with high-frequency transverse oscillations (65–270 s) with velocity amplitudes of 3.3–9.9 km s−1 and a mean energy flux of (2.14 ± 0.78) × 103 W m−2. Conclusions. These results demonstrate that spicules are multi-thermal dynamic structures connected to the transition region and corona and that transverse waves carry substantial energy, highlighting their role in coronal heating.

• Yang, Dongting; Liu, Hong li; Qin, Sheng li; Liu, Tie; Jiao, Wenyu & Garay, Guido [Vis alle 31 forfattere av denne artikkelen] (2026). Evolution of Starless Cores in Massive Clumps Seen by the ALMA ASHES and QUARKS Surveys. The Astrophysical Journal (ApJ). ISSN 0004-637X. 1006(2). doi: 10.3847/1538-4357/ae81ab. Fulltekst i vitenarkiv Vis sammendrag

  We present a systematic comparative analysis of 324 starless cores in early-phase infrared-dark clouds (IRDCs; ASHES survey) and evolved-phase infrared-bright clouds (IRBCs; QUARKS survey) using 1.3 mm continuum and line data by the Atacama Large Millimeter/submillimeter Array. Despite having comparable sizes (∼2500 au), starless cores in IRBCs exhibit systematically higher median mass (1.5 M⊙ versus 0.6 M⊙), number density, and surface density—enhancements of approximately a factor of 2 relative to starless cores in IRDCs. Starless cores in IRBCs also display relatively stronger nonthermal motions (σ ∼ 0.5 km s−1 versus 0.3 km s−1), higher total virial parameters (median αvir,tot ∼ 2.3 versus 1.0), and steeper density profiles, indicating more centrally concentrated structures in feedback-driven, turbulence-enhanced environments. These findings support a dual evolutionary origin: (i) new core formation in evolved IRBCs under altered initial conditions and (ii) subsequent dynamical mass growth via accretion from extended reservoirs. The prevalence of low-mass starless cores—even in late-stage IRBC environments—challenges models requiring massive prestellar cores and instead favors competitive-like dynamical mass accretion scenarios for high-mass star formation.

• Scialpi, M.; Mannucci, F.; D’Amato, Q.; Marconcini, C.; Cresci, G. & Marconi, A. [Vis alle 37 forfattere av denne artikkelen] (2026). Cosmic Duets: I. High-spatial resolution spectroscopy of dual and lensed active galactic nuclei with MUSE-NFM. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 709. doi: 10.1051/0004-6361/202558548. Fulltekst i vitenarkiv Vis sammendrag

  We present the first-year results of the MUSE Large Program “Cosmic Duets”, whose goal is to obtain adaptive-optics assisted MUSE observations with a typical angular resolution of 0.1″ − 0.2″ in order to provide integral-field spectroscopy of sub-arcsec separation dual and lensed active galactic nucleus (AGN) candidates. These observations reveal previously unexplored properties of dual and lensed systems that are key to understanding galaxy evolution, supermassive black hole mergers, and strong-lensing modeling. Targets were efficiently selected using the Gaia multipeak (GMP) technique, which identifies pairs of point-like sources with angular separations below 0.8″ in the Gaia catalog. MUSE spatially resolved spectroscopy provides accurate redshifts, ionization diagnostics, and identification of absorption systems along the line of sight. We report results for 30 GMP-selected targets at z = 0.5 − 3.5. All systems show at least two spatially resolved components. Nineteen objects are confirmed as AGN multiplets, including six dual AGN, ten doubly lensed quasars, and three quadruply lensed systems, while the remaining 11 correspond to chance alignments with foreground stars. Among all the spectroscopically confirmed dual AGN in the literature, 27 pairs have projected separations below 7 kpc in this redshift regime, and our sample accounts for 22% of the total. We studied dual and lensed AGN distributions as a function of redshift, magnitude, and projected separation while accounting for selection effects, and we find that bright systems (J ≲ 16.5) are dominated by lensed quasars, whereas the relative fraction of dual AGN increases at fainter magnitudes. This first-year sample demonstrates the high efficiency of GMP preselection combined with MUSE spectroscopy for identifying sub-arcsec dual and lensed AGN. The full program, targeting ∼150 systems, will enable statistical studies of dual AGN incidence as a function of redshift, separation, and luminosity and allow for precise characterization of the mass composition and distribution in strong lensing galaxies.

• Chouliaras, Georgios; Wyper, Peter F.; Dahlin, Joel T. & Fletcher, Lyndsay (2026). Automatic Detection of Flare Ribbon Fine Structures as Proxies for Plasmoid Dynamics in Flare Reconnection. The Astrophysical Journal (ApJ). ISSN 0004-637X. 1006(2). doi: 10.3847/1538-4357/ae7c75. Fulltekst i vitenarkiv Vis sammendrag

  Flare ribbons often display fine structures along their fronts that are commonly interpreted as signatures of intermittent reconnection dynamics including plasmoid formation in the flare current sheet. We introduce an automated method that detects and tracks the spiral- and wave-like imprints of these structures and as a proof of concept apply it to maps of magnetic field-line length from a high-resolution 3D eruptive-flare simulation. The workflow applies the correlation-dimension method, density-based clustering, and a minimum-area ellipse fit to summarize each feature. We show that across the simulated flare, the detected spirals remain locked to the ribbon’s outward motion while drifting coherently along the ribbon. The two ribbons show opposite along-ribbon drift and motion away from their hooks in accordance with theoretical expectations, with instantaneous speeds of 10–800 km s^−1, all well below the local surface Alfvén speed. Occurrence, lifetimes, and mean magnetic flux of the features peak during the impulsive phase. The distribution of per-spiral mean unsigned flux shows a scale-free tail above roughly 6 × 10^18 Mx with a power-law exponent near 3.4. Together, these results show that bursty, plasmoid-mediated flare reconnection leaves a clear, measurable signature on the flare ribbons. The method provides a practical surface diagnostic of ribbon fine structure that can potentially be used to inform our understanding of three-dimensional magnetic reconnection in the flare current sheet.

• Aussel, H.; Tereno, I.; Schirmer, M.; Alguero, G.; Altieri, B. & Balbinot, E. [Vis alle 409 forfattere av denne artikkelen] (2026). Euclid Quick Data Release (Q1): I. Data release overview. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 711. doi: 10.1051/0004-6361/202554610. Fulltekst i vitenarkiv Vis sammendrag

  The first Euclid Quick Data Release, Q1, comprises 63.1 deg2 of the Euclid Deep Fields (EDFs) to the nominal wide-survey depth. It encompasses visible and near-infrared space-based imaging and spectroscopic data, ground-based photometry in the u, g, r, i, and z bands, as well as corresponding masks. Overall, Q1 contains about 30 million objects in three areas near the ecliptic poles around EDF-North and EDF-South, as well as the EDF-Fornax field in the constellation of the same name. The purpose of this data release – and its associated technical papers – is twofold. First, it is meant to inform the community of the enormous potential of the Euclid survey data, to describe what is contained in these data, and to help prepare expectations for the forthcoming first major data release DR1. Second, it enables a wide range of initial scientific projects with wide-survey Euclid data, ranging from the early Universe to the Solar System. The Q1 data were processed with early versions of the processing pipelines, which already demonstrate a good performance, with numerous improvements in implementation compared to pre-launch development. In this paper, we describe the sky areas released in Q1, the observations, a top-level view of the data processing of Euclid and associated external data, the Q1 photometric masks, and how to access the data. We also give an overview of initial scientific results obtained using the Q1 dataset by Euclid Consortium scientists, and conclude with important caveats when using the data. As a complementary product, Q1 also contains observations of a star-forming area in Lynd’s Dark Nebula 1641 in the Orion A Cloud, observed for technical purposes during Euclid’s performance-verification phase. This is a unique target, of a type not commonly found in Euclid’s nominal sky survey.

• Bergamini, P.; Meneghetti, M.; Acebron, A.; Clément, B.; Bolzonella, M. & Grillo, C. [Vis alle 378 forfattere av denne artikkelen] (2026). Euclid Quick Data Release (Q1): XXXIII. The first catalogue of strong-lensing galaxy clusters. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 711. doi: 10.1051/0004-6361/202554577. Fulltekst i vitenarkiv
• Hill, R.; Abghari, A.; Scott, D.; Bethermin, M.; Chapman, S. C. & Clements, D. L. [Vis alle 304 forfattere av denne artikkelen] (2026). Euclid Quick Data Release (Q1): XXIII. The average far-infrared properties of Euclid-selected star-forming galaxies. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 711. doi: 10.1051/0004-6361/202557514. Fulltekst i vitenarkiv Vis sammendrag

  The first Euclid Quick Data Release (Q1) contains millions of galaxies with excellent optical and near-infrared (IR) coverage. To complement this dataset, we investigate the average far-IR properties of Euclid-selected main sequence (MS) galaxies using existing Herschel and SCUBA-2 data. We used 17.6 deg^2 (2.4 deg^2) of overlapping Herschel (SCUBA-2) data, containing 2.6 million (240 000) MS galaxies. We binned the Euclid catalogue by stellar mass and photometric redshift and performed a stacking analysis following SimStack, which accounts for galaxy clustering and bin-to-bin correlations. We detected stacked far-IR flux densities across a significant fraction of the bins. We fitted modified blackbody spectral energy distributions in each bin and derived mean dust temperatures (Td), dust masses (Md), and star-formation rates (SFRs). We find similar mean SFRs compared to the Euclid catalogue, and we show that the average dust-to-stellar mass ratios decreased from z  ≃  1 to the present day. Average dust temperatures are largely independent of stellar mass and are well-described by the function T2  +  (T1  −  T2) e^−t/τ, where t is the age of the Universe, T1  =  (79.7 ± 7.4) K, T2  =  (23.2 ± 0.1) K, and τ  =  (1.6 ± 0.1) Gyr. We argue that since the dust temperatures converge to a non-zero value below z  =  1, the dust is now primarily heated by the existing cooler and older stellar population, as opposed to hot young stars in star-forming regions at higher redshifts. We show that since the dust temperatures are independent of stellar mass, the correlation between dust temperature and SFR depends on stellar mass. Lastly, we estimate the contribution of the Euclid catalogue to the cosmic IR background (CIB), finding that it accounts for > 60% of the CIB at 250, 350, and 500 μm. As the Euclid mission progresses, larger catalogues will allow us to probe the far-IR properties of MS galaxies out to higher redshifts and lower stellar masses, potentially recovering the complete CIB.

• Roster, W.; Salvato, M.; Buchner, J.; Shirley, R.; Lusso, E. & Landt, H. [Vis alle 318 forfattere av denne artikkelen] (2026). Euclid Quick Data Release (Q1): XVI. Optical and near-infrared identification and classification of point-like X-ray selected sources. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 711. doi: 10.1051/0004-6361/202554616. Fulltekst i vitenarkiv Vis sammendrag

  To better understand the role of active galactic nuclei (AGN) in galaxy evolution, it is crucial to work with a complete and pure AGN sample. X-ray surveys are key to doing so, but their larger positional uncertainties complicate counterpart (CTP) association, further compounded by the limited availability of deep, uniform multi-wavelength ancillary data. Euclid is revolutionising this identification effort, offering extensive coverage of nearly the entire extragalactic sky, particularly in the near-infrared bands, where AGN are more easily detected. Using the first Euclid Quick Data Release (Q1), we validated the methods for identifying and classifying Euclid CTPs of known point-like sources from major X-ray surveys, including XMM-Newton, Chandra, and eROSITA. Using Bayesian statistics, combined with machine learning (ML), as incorporated in the algorithm NWAY, we identified the CTPs of 11 286 X-ray sources from the three X-ray telescopes. For the large majority of 10 194 sources, the association is unique, with the remaining ∼10% of multi-CTP cases equally split between XMM-Newton and eROSITA. Six percent of the Euclid CTPs are detected in more than one X-ray survey. We then used ML to distinguish between Galactic (8%) and extragalactic (92%) sources. We computed photo-zs using deep learning for the 9259 sources detected in the tenth data release of the DESI Legacy Survey, reaching an accuracy and a fraction of outliers of roughly 5%. Based on their X-ray luminosities, all CTPs identified as extragalactic are classified as AGN, most of which appear as type I AGN according to their hardness ratios. With this paper, we release our catalogue, which includes identifiers, basic X-ray properties, the reliability of the associations, and additional property extensions, such as Galactic- or extragalactic classifications and photometric/spectroscopic redshifts. We also provide probabilities for sub-selecting the sample based on purity and completeness, in order to allow users to tailor the sample according to their specific needs.

• Duffy, C.; Cappellaro, E.; Botticella, M. T.; Hook, I. M.; Poidevin, F. & Moriya, T. J. [Vis alle 177 forfattere av denne artikkelen] (2026). Euclid: Quick Data Release (Q1) – Photometric studies of known transients. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 711. doi: 10.1051/0004-6361/202554600. Fulltekst i vitenarkiv Vis sammendrag

  We report on serendipitous Euclid observations of previously known transients, using the Euclid Q1 data release. By cross-matching with the Transient Name Server (TNS) we identify 164 transients that coincide with the data release. Although the Euclid Q1 release only includes single-epoch data, we are able to make Euclid photometric measurements at the location of 161 of these transients, where 67 had a significant flux measurement in at least one band. Euclid obtained deep photometric measurements or upper limits of these transients in the I_E, Y_E, J_E, and H_E bands at various phases of the transient light curves, including before, during, and after the observations of ground-based transient surveys. Approximately 70% of known transients reported in the six months before the Euclid observation date and with a discovery magnitude brighter than 24 were detected in Euclid I_E images. Our observations include one of the earliest near-infrared detections of a Type Ia supernova (SN 2024pvw) 15 days prior to its peak brightness, and the late-phase (435.9 days post peak) observations of the enigmatic core-collapse SN 2023aew. Euclid deep photometry provides valuable information on the nature of these transients such as their progenitor systems and power sources, with late-time observations being a uniquely powerful contribution. In addition, Euclid is able to detect the host galaxies of some transients that were previously classed as hostless. The Q1 data demonstrate the power of the Euclid data even with only single-epoch observations available, as will be the case for much larger areas of sky in the Euclid Wide Survey.

• Marca, A. La; Wang, L.; Margalef-Bentabol, B.; Gabarra, L.; Toba, Y. & Mezcua, M. [Vis alle 336 forfattere av denne artikkelen] (2026). Euclid Quick Data Release (Q1): XVII. First Euclid statistical study of galaxy mergers and their connection to active galactic nuclei. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 711. doi: 10.1051/0004-6361/202554579. Fulltekst i vitenarkiv Vis sammendrag

  Galaxy major mergers are indicated as one of the principal pathways to trigger active galactic nuclei (AGN). We present the first statistical analysis of the major merger and AGN connection in the Euclid Deep Fields, and showcase the statistical power of the Euclid data. We constructed a stellar-mass-complete (M★ > 10^9.8 M⊙) sample of galaxies from the quick data release (Euclid Quick Release Q1 2025) in the redshift range z = 0.5–2. We selected AGN using X-ray detections, optical spectroscopy, and mid-infrared (MIR) colours, and by processing I_E observations with an image decomposition algorithm. We used convolutional neural networks trained on cosmological hydrodynamic simulations to classify galaxies as mergers and non-mergers. We found a larger fraction of AGN in mergers compared to the non-merger controls for all AGN selections, with AGN excess factors ranging from two to six. The largest excess we observed was in the MIR AGN. Likewise, a generally larger merger fraction (f_merg) was seen in active galaxies than in the non-active controls, with the excess depending on the AGN selection method. Furthermore, we analysed fmerg as a function of the AGN bolometric luminosity (L_bol) and the contribution of the point-source component to the total galaxy light in the I_E-band (f_PSF) as a proxy for the relative AGN contribution fraction. We uncovered a rising f_merg, with an increasing f_PSF up to f_PSF ≃ 0.55, after which we observed a decreasing trend. In the range f_PSF = 0.3–0.7, mergers appear to be the dominant AGN fuelling mechanism. We then derived the point-source luminosity (L_PSF) and showed that f_merg monotonically increases as a function of L_PSF at z < 0.9, with f_merg ≥ 50% for LPSF ≃ 2 × 10^43 erg s−1. Similarly, at 0.9 ≤ z ≤ 2, f_merg rises as a function of L_PSF, though mergers do not dominate until L_PSF ≃ 10^45 erg s−1. For the X-ray and spectroscopically detected AGN, we derived the bolometric luminosity, L_bol, which has a positive correlation with f_merg for X-ray AGN, while there is a less pronounced trend for spectroscopically selected AGN due to the smaller sample size. At L_bol > 10^45 erg s−1, AGN mostly reside in mergers. We conclude that mergers are most strongly associated with the most powerful and dust-obscured AGN, which are typically linked to a fast-growing phase of the supermassive black hole, while other mechanisms, such as secular processes, might be the trigger of less luminous and dominant AGN.

• Bhargava, S.; Benoist, C.; Gonzalez, A. H.; Maturi, M.; Melin, J. B. & Stanford, S. A. [Vis alle 354 forfattere av denne artikkelen] (2026). Euclid Quick Data Release (Q1): XXXIV. First detections from the Euclid galaxy cluster workflow. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 711. doi: 10.1051/0004-6361/202554937. Fulltekst i vitenarkiv Vis sammendrag

  The first survey data release by the Euclid mission covers approximately 63 deg2 in the Euclid Deep Fields to the same depth as the Euclid Wide Survey. This paper showcases, for the first time, the performance of cluster finders on Euclid data and presents examples of validated clusters in the Quick Release 1 (Q1) imaging data. We identify clusters using two algorithms (AMICO and PZWav) implemented in the Euclid cluster-detection pipeline. We explore the internal consistency of detections from the two codes, and cross-match detections with known clusters from other surveys using external multi-wavelength and spectroscopic data sets. This enables assessment of the Euclid photometric redshift accuracy and also of systematics such as mis-centring between the optical cluster centre and centres based on X-ray and/or Sunyaev–Zeldovich observations. We report 426 joint PZWav and AMICO-detected clusters with high signal-to-noise ratios over the full Q1 area in the redshift range 0.2 ≤ z ≤ 1.5. The chosen redshift and signal-to-noise thresholds are motivated by the photometric quality of the early Euclid data. We provide richness estimates for each of the Euclid-detected clusters and show its correlation with various external cluster mass proxies. Due to the limited area and evolving data quality, the sample is not intended to serve as a reference for cosmological applications, but to verify and validate the cluster workflow. Out of the full sample, 77 systems are potentially new to the literature. Overall, the Q1 cluster catalogue demonstrates a successful validation of the workflow ahead of the Euclid Data Release 1, based on the consistency of internal and external properties of Euclid-detected clusters.

• Allen, N.; Oesch, P. A.; Bowler, R. A.A.; Toft, S.; Matharu, J. & Weaver, J. R. [Vis alle 311 forfattere av denne artikkelen] (2026). Euclid Quick Data Release (Q1): XXV. Hunting for luminous z > 6 galaxies in the Euclid Deep Fields – Forecasts and the first bright detections. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 711. doi: 10.1051/0004-6361/202557785. Fulltekst i vitenarkiv Vis sammendrag

  The evolution of the rest-frame ultraviolet luminosity function (UV LF) is a powerful probe of early star formation and galaxy stellar mass build-up. At z > 6, its bright end (MUV < −21) remains poorly constrained due to small survey volumes of existing near-infrared (NIR) space-based imaging surveys. The Euclid Deep Fields (EDFs) will cover 53 deg^2 with NIR coverage down to a magnitude of 26.5 AB, providing a factor of 100 increase in area compared to previous space-based surveys. They thus offer an unprecedented opportunity to select bright z > 6 Lyman break galaxies (LBGs) and definitively constrain the bright end of the UV LF. With its NIR coverage extending to ∼2 μm, Euclid has the power to detect galaxies out to z ∼ 13. Here, we present a forecast for the number densities of z > 6 galaxies that Euclid is expected to observe in the final EDF dataset. Using synthetic photometry from spectral energy distribution (SED) templates of z = 5–15 galaxies, z = 1–4 interlopers, and Milky Way M-, L-, and T-type dwarfs, we investigate optimal selection methodologies for high-z LBGs in the EDF datasets. We find that a combination of signal-to-noise ratio (S/N) cuts with SED fitting (over optical to MIR bands) yields the highest fidelity sample, recovering more than 76% of the input synthetic z > 6 LBGs, while limiting low-z contamination to less than 10%. This contamination does not include effects from instrumental artefacts, which will impact the first Euclid data releases. Auxiliary data prove critical: optical coverage from the Hyper Suprime Camera and Vera C. Rubin Observatory will distinguish genuine Lyman breaks from contaminant features, while Spitzer Space Telescope/IRAC data are vital for recovering z > 10 sources. Based on empirical double power-law LF models, we expect more than 100 000 LBGs at z = 6–12 and more than 100 sources as far back as z > 12 in the final Euclid data release. In contrast, the steeper Schechter LF models predict no detections of z > 12 LBGs. In this work, we also present two ultra-luminous (M_UV < −23.5) candidates selected from the Q1 EDF-N dataset (Euclid Quick Data Release). If their redshifts are reliable, their magnitudes suggest a DPL UV LF model at z > 9. This highlights the power of Euclid in constraining the bright end of the UV LF in the early Universe and in identifying the most luminous sources that are valuable for further follow-up observations.

• Corcho-Caballero, P.; Ascasibar, Y.; Kleijn, G. Verdoes; Lovell, C. C.; Lucia, G. De & Cleland, C. [Vis alle 320 forfattere av denne artikkelen] (2026). Euclid Quick Data Release (Q1): XV. A probabilistic classification of quenched galaxies. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 711. doi: 10.1051/0004-6361/202554582. Fulltekst i vitenarkiv Vis sammendrag

  Investigating what drives the quenching of star formation in galaxies is key to understanding their evolution. The Euclid mission will provide rich spatial and spectral data from optical to infrared wavelengths for millions of galaxies, and enable precise measurements of their star formation histories. Using the first Euclid Quick Data Release (Q1), we developed a probabilistic classification framework that combines the average specific star-formation rate (sSFR_log(τ)) inferred over two timescales (τ = 10^8, 10^9 yr) to categorise galaxies as ‘ageing’ (secularly evolving), ‘quenched’ (recently halted star formation), or ‘retired’ (dominated by old stars). We validated this methodology using synthetic observations from the IllustrisTNG simulation. Two classification methods were employed: a probabilistic approach, which integrates posterior distributions, and a model-driven method, which optimises sample purity and completeness using IllustrisTNG. At z < 0.1 and M* ≳ 3 × 10^8 M⊙, we obtain Euclid class fractions of 68–72%, 8–17%, and 14–19% for ageing, quenched, and retired populations, respectively, which is consistent with previous studies. Ageing and retired galaxies dominate at the low- and high-mass end, respectively, while quenched galaxies surpass the retired fraction for M* ≲ 10^10 M⊙. The evolution with redshift shows increasing and decreasing fractions of ageing and retired galaxies, respectively. The fraction of quenched systems shows a weaker dependence on stellar mass and redshift, varying between 5 and 15%. We find tentative evidence that more massive galaxies usually undergo quenching episodes at earlier times with respect to their low-mass counterparts. We analysed the mass-size-metallicity relation for each population. Ageing galaxies generally exhibit disc morphologies and low metallicities. Retired galaxies show compact structures and enhanced chemical enrichment, while quenched galaxies form an intermediate population that is more compact and chemically evolved than ageing systems. Despite potential selection biases, this work demonstrates Euclid’s great potential for elucidating the physical nature of the quenching mechanisms that govern galaxy evolution.

• Laigle, C.; Gouin, C.; Sarron, F.; Quilley, L.; Pichon, C. & Kraljic, K. [Vis alle 345 forfattere av denne artikkelen] (2026). Euclid Quick Data Release (Q1): XXXVI. Galaxy shapes and alignments in the cosmic web. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 711. doi: 10.1051/0004-6361/202554651. Fulltekst i vitenarkiv Vis sammendrag

  Galaxy morphologies and shape orientations are expected to correlate with their large-scale environments, since they grow by accreting matter from the cosmic web and are subject to interactions with other galaxies. We extracted cosmic filaments in projection from the Euclid Quick Data Release 1 (covering 63.1 deg2) at 0.5 < z < 0.9 in tomographic slices of 170 comoving h−1 Mpc using photometric redshifts. Galaxy morphologies are accurately retrieved thanks to the excellent imaging resolution of the visible camera (VIS) of Euclid. The distribution of massive galaxies (M* > 1010 M⊙) in the projected cosmic web is analysed as a function of morphology measured from VIS data. Specifically, the 2D alignment of galaxy shapes with large-scale filaments is quantified as a function of Sérsic indices and masses. We find the known trend that more massive galaxies are closer to filament spines. At fixed stellar masses, morphologies correlate both with densities and distances to large-scale filaments. In addition, the large volume of this data set allows us to detect a signal indicating that there is a preferential alignment of the major axis of massive early-type galaxies along projected cosmic filaments. Overall, these results demonstrate our capabilities to carry out detailed studies of galaxy environments with Euclid, which will be extended to higher redshift and lower stellar masses with the future Euclid Deep Survey.

• Lines, N. E.P.; Collett, T. E.; Holloway, P.; Rojas, K.; Schuldt, S. & Metcalf, R. B. [Vis alle 304 forfattere av denne artikkelen] (2026). Euclid Quick Data Release (Q1): XXXII. From simulations to sky: Advancing machine-learning lens detection with real Euclid data. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 711. doi: 10.1051/0004-6361/202558456. Fulltekst i vitenarkiv
• Lines, N. E.P.; Collett, T. E.; Walmsley, M.; Rojas, K.; Li, T. & Leuzzi, L. [Vis alle 352 forfattere av denne artikkelen] (2026). Euclid Quick Data Release (Q1): XXVIII. The Strong Lensing Discovery Engine C – Finding lenses with machine learning. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 711. doi: 10.1051/0004-6361/202554542. Fulltekst i vitenarkiv Vis sammendrag

  Strong gravitational lensing has the potential to provide a powerful probe of astrophysics and cosmology, but fewer than 1000 strong lenses have been confirmed so far. With a 0.16 arcsec resolution covering a third of the sky, the Euclid telescope will revolutionise the identification of strong lenses, with 170 000 lenses forecasted to be discovered amongst the 1.5 billion galaxies it will observe. We present an analysis of the performance of five machine-learning models at finding strong gravitational lenses in the quick release of Euclid data (Q1) covering 63 deg^2. The models have been validated by citizen scientists and expert visual inspection. We focus on the best-performing network: a fine-tuned version of the Zoobot pretrained model originally trained to classify galaxy morphologies in heterogeneous astronomical imaging surveys. Of the one million Q1 objects that Zoobot was tasked to find strong lenses within, the top 1000 ranked objects contain 122 grade A lenses (almost-certain lenses) and 41 grade B lenses (probable lenses). A deeper search with the five networks combined with visual inspection yielded 250 (247) grade A (B) lenses, of which 224 (182) are ranked in the top 20 000 by Zoobot. When extrapolated to the full Euclid survey, the highest ranked one million images will contain 75 000 grade A or B strong gravitational lenses.

• Zatarain, T. Matamoro; Fotopoulou, S.; Ricci, F.; Bolzonella, M.; Franca, F. La & Viitanen, A. [Vis alle 357 forfattere av denne artikkelen] (2026). Euclid Quick Data Release (Q1): XX. The active galaxies of Euclid. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 711. doi: 10.1051/0004-6361/202554619. Fulltekst i vitenarkiv Vis sammendrag

  We present three catalogues of candidate active galactic nuclei (AGN) in the Euclid Quick Release (Q1) fields. For each Euclid source, we collected multi-wavelength photometric and spectroscopic information from surveys such as the Galaxy Evolution Explorer (GALEX), Gaia, the Dark Energy Survey (DES), the Wide-field Infrared Survey Explorer (WISE), Spitzer, the Dark Energy Spectroscopic Instrument (DESI), and the Sloan Digital Sky Survey (SDSS), including spectroscopic redshifts from public compilations when available. We investigated the AGN content of the Q1 fields using multiple selection methods. Applying Euclid colours and WISE-AllWISE cuts, we identified 292 222 and 65 131 candidates, respectively. We compiled a high-purity QSO catalogue based on Gaia DR3 information, containing 1971 candidates. Using spectroscopic information from DESI, we performed broad-line and narrow-line AGN selections, yielding 4392 AGN candidates across the Q1 fields. We investigated and refined the Euclid Q1 probabilistic random forest QSO population, selecting a refined sample of 180 666 candidates. Additionally, we performed spectral energy distribution (SED) fitting on sources with available z_spec, and utilising the derived AGN fraction, we identified 7766 AGN candidates. To improve the purity of the selection, we defined two new colour criteria (JH_I_EY and I_EH_gz), finding 313 714 and 267 513 candidates, respectively, across the Q1 fields. We have found a total of 229 779 AGN candidates equivalent to an AGN surface density of 3641 deg^−2 for 18 < _IE ≤ 24.5 and a subsample of 30 422 candidates corresponding to an AGN surface density of 482 deg^−2 when limiting the depth to 18 < I_E ≤ 22. The AGN surface densities recovered are consistent with predictions based on AGN X-ray luminosity functions.

• Busillo, V.; Tortora, C.; Metcalf, R. B.; Nightingale, J. W.; Meneghetti, M. & Gentile, F. [Vis alle 315 forfattere av denne artikkelen] (2026). Euclid Quick Data Release (Q1): XXXI. LEMON – LEns MOdelling with Neural networks. Automated and fast modelling of Euclid gravitational lenses with singular isothermal ellipsoid mass profile. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 711. doi: 10.1051/0004-6361/202554538. Fulltekst i vitenarkiv Vis sammendrag

  The Euclid mission aims to survey around 14 000 deg2 of extragalactic sky, providing around 105 gravitational lens images. Modelling of gravitational lenses is fundamental to estimate the total mass of the lens galaxy, along with its dark matter content. Traditional modelling of gravitational lenses is computationally intensive and requires manual input. In this paper, we use a Bayesian neural network, LEns MOdelling with Neural networks (LEMON), to model Euclid gravitational lenses with a singular isothermal ellipsoid mass profile. Our method estimates key lens mass profile parameters, such as the Einstein radius, while also predicting the light parameters of foreground galaxies and their uncertainties. We validate LEMON’s performance on both mock Euclid datasets, real lenses observed with Hubble Space Telescope (HST) that have been degraded to match observations with the same depth of the Euclid Wide Survey, and real Euclid lenses, demonstrating the ability of LEMON to predict parameters of both simulated and real lenses. Results show promising accuracy and reliability in predicting the Einstein radius, mass and light ellipticities, effective radius, Sérsic index, lens magnitude, and unlensed source position for simulated lens galaxies. The application to real data, including the latest Quick Release 1 strong lens candidates, provides encouraging results in the recovery of the parameters for real lenses. We also verified that LEMON has the potential to accelerate traditional modelling methods, by giving to the classical optimiser the LEMON predictions as starting points, resulting in a speed-up of up to 26 times the original time needed to model a sample of gravitational lenses, a result that would be impossible with randomly initialised guesses. Moreover, LEMON can be used to cross-validate results from the traditional modelling methods, and thus has the potential to reduce the failure rate of the Euclid modelling pipeline. This work represents a significant step towards efficient, automated gravitational lens modelling, which is crucial for handling the large data volumes expected from Euclid.

Se alle arbeider i NVA

• Lilje, Per Barth (2026). Skjulte spor i stjernestrømmer. Astronomi. ISSN 0802-7587. 2026(3), s. 12–17. Fulltekst i vitenarkiv Vis sammendrag

  Kavliprisen i astrofysikk for 2026 hedrer forskerne som har kartlagt hvordan galaksen vår vokser

• Lilje, Per Barth (2026). Kavliprisen i astrofysikk 2026: Skjulte spor i stjernestrømmer. Fra Fysikkens Verden. ISSN 0015-9247. 88(3), s. 88–91. Fulltekst i vitenarkiv Vis sammendrag

  Kavliprisen deles ut i Oslo annen hvert år innen fagfeltene astrofysikk, nanovitenskap og nevrovitenskap for å hedre "de største, de minste og de mest komplekse størrelsesskalaene". Her omtales Kavliprisen i astrofysikk for 2026, som hedrer forskerne som har kartlagt hvordan galaksen vår vokser.

• Mylius-Kroken, Johan; Wally, Youssef; Mota, David & Wickstrøm, Kristoffer (2026). Hyperbolic Representation Learning for Astrophysical Photometric Survey Data. doi: https:/openreview.net/forum?id=hGV1cIU2N1&referrer=%5BAuthor%20Console%5D%28%2Fgroup%3Fid%3Dthecvf.com%2FECCV%2F2026%2FWorkshop%2FBEW%2FAuthors%23your-submissions%29. Fulltekst i vitenarkiv Vis sammendrag

  We compare unsupervised representation learning on the miniJPAS narrow-band photometric survey using three architecturally identical autoencoders whose latent spaces differ only in geometry: Euclidean $\mathbb{R}^{32}$ and two variants on the Lorentz hyperboloid $\mathbb{H}^{32}$. The hyperbolic choice is motivated by Gromov $\delta$-hyperbolicity analysis, which confirms that the miniJPAS feature space has intrinsically tree-like geometry. Training on a reconstruction objective without label supervision, the Lorentzian models produce qualitatively different embeddings: stars concentrate in compact regions near the Poincar\'{e} disc boundary, and an emergent photometric redshift gradient is visible across all three latent spaces, though the embedding does not yet exhibit the radial, tree-like organisation that hyperbolic geometry in principle affords. Classification accuracy is comparable across all three models ($\approx$78\%), confirming that these structural differences emerge at no discriminative cost. These results motivate a more systematic investigation of geometry-aware training objectives for astrophysical survey data.

• Lilje, Per Barth (2026). Roman-teleskopet skal oppdage tusenvis av nye verdener og kaste lys over mørk energi. [Internet]. Forskning.no. Fulltekst i vitenarkiv Vis sammendrag

  NASAs nye romteleskop vil få mange forskjellige oppgaver, sier ekspert. Hva skiller det fra andre romteleskoper der ute?

• Liakh, Valeriia (2026). Prominence Modeling in the Era of High-Resolution Solar Observations. Fulltekst i vitenarkiv Vis sammendrag

  Prominences are complex but fascinating phenomena observed in the outer region of the solar atmosphere, the solar corona. Interest in these structures is driven by space weather research in the context of the initiation of coronal mass ejections. Prominences demonstrate a wide variety of morphologies and dynamics, and despite decades of observational, theoretical, and modeling studies, many aspects of their evolution remain not entirely understood. In this talk, we will discuss examples of the different types of evolution observed in solar prominences, from formation to eruption or, alternatively, gradual disappearance, and how we use numerical modeling to explain the physical processes behind them. We will also highlight the perspectives for synergistic studies in the era of high-resolution solar observations and sophisticated simulations performed with modern numerical codes.

• Liakh, Valeriia; Druett, Malcolm & Dubart, Maxime (2026). 2.5D flare simulations with MPI-AMRVAC. Fulltekst i vitenarkiv
• Liakh, Valeriia (2026). Toward Realistic Modeling of Solar Prominences Across Their Life Cycle. Fulltekst i vitenarkiv Vis sammendrag

  Despite decades of both observational and modeling efforts, a self-consistent picture of the formation and evolution of solar prominences remains unclear. In this talk, we review progress in prominence modeling, beginning with current ideas on their formation and the physical processes responsible for mass supply. We then discuss their subsequent dynamical evolution, including counter-streaming flows, mass drainage, and oscillatory phenomena. Additionally, the modeling of the prominence dynamics will be discussed in the context of the prominence stability. Recent numerical studies highlight the need for increasingly realistic simulations to capture the prominence complexity. Therefore, in the final part of the talk, we outline the major open questions and promising directions for future research needed to strengthen the link between simulations and observations.

• Liakh, Valeriia (2026). Numerical Modeling of Prominence Dynamics induced by Coronal Waves. Fulltekst i vitenarkiv Vis sammendrag

  Energetic events, such as solar flares and eruptions, are frequently accompanied by coronal waves that propagate far from their source region and interact with various structures, including coronal holes, prominences, and coronal loops. Interpreting such interactions with prominences directly from observations remains challenging and requires realistic magnetohydrodynamic (MHD) modeling to understand the underlying physical mechanisms and types of induced oscillation. In this talk, we present recent advances in MHD simulations of the interaction between large-scale coronal waves and solar prominences. Particular emphasis will be placed on the propagation of the coronal waves in the non-uniformly magnetized solar corona, the formation of the secondary fronts, the development of thermal instability within the prominence-hosting flux rope, and the excitation of prominence oscillations.

• Kirkaune, Mats; Wedemeyer, Sven; Carlsson, Mats & Brunvoll, Aline Rangøy (2026). Exploring synthetic nanoflare signatures at millimetre wavelengths. Fulltekst i vitenarkiv Vis sammendrag

  Nanoflares have long been considered to be promising candidates for heating the solar corona to millions of degrees. However, their assumed small sizes, short durations, and subtle signals in accessible observables have made direct detection difficult. In the millimetre regime, the Atacama Large (sub-)Millimeter Array (ALMA) offers the capability of measuring chromospheric temperatures at very high temporal and comparatively high spatial resolution. Yet, it is not clear if the currently offered solar observing mode of ALMA is capable of detecting nanoflares. To explore possible millimetre signatures of nanoflares, the F-CHROMA grid of 1D RADYN flare models has been extended to lower total flare energies, into the nanoflare domain. These models simulate the response of a coronal loop to an electron beam inserted at its top. The new simulations were run as a combined effort to characterise nanoflare signatures at different wavelengths. The radiative transfer code RH1.5 was used to compute the millimetre signatures of the modelled nanoflares. These signatures were then degraded to the temporal and spatial resolution achievable with ALMA. The synthetic ALMA light curves indicate that, in principle, ALMA should be able to detect nanoflare signatures, especially when using wider array configurations in combination with a higher frequency band to maximise spatial resolution. This suggests that dedicated ALMA observations could, in principle, place important constraints on atmospheric heating from nanoflares.

• Kirkaune, Mats & Wedemeyer, Sven (2026). Observing the Sun with AtLAST. Fulltekst i vitenarkiv Vis sammendrag

  The Atacama Large Aperture Submillimeter Telescope (AtLAST) has great potential for solar physics. AtLAST’s unique combination of a large aperture, a wide field-of-view, fast mapping speed, and multi-pixel instrumentation could enable it to map the full solar disk across multiple frequencies at high temporal resolution, effectively mapping the thermal and magnetic structure across the chromosphere, and how these change in time. This would help address several important solar science cases. AtLAST’s capabilities would be complementary to the Atacama Large (sub-)Millimeter Array (ALMA) and to other major solar(-capable) observatories of the future, such as the Square Kilometer Array Observatory (SKAO) in South Africa and Australia, and the European Solar Telescope in Spain.

• Ornig, Sascha (2026). Tackling the Enigma of Solar White-Light Flares in Simulations and Observations. Fulltekst i vitenarkiv
• Kirkaune, Mats; Wedemeyer, Sven; Marrewijk, Joshiwa van; Mroczkowski, Tony & Morris, Thomas (2026). Simulated solar observations with the Atacama Large Aperture Submillimetre Telescope (AtLAST). Fulltekst i vitenarkiv Vis sammendrag

  Millimetre observations offer a highly complementary view of the Sun, providing insight into the thermal and magnetic structure of the chromosphere. The field of solar millimetre astronomy has seen considerable progress since the advent of solar observations with the Atacama Large (sub-)Millimeter Array (ALMA), offering a view of the solar chromosphere at high spatial and temporal resolution. However, some highly dynamic phenomena, such as solar flares, are hard to predict, and therefore challenging to capture with ALMA’s small field of view. The proposed Atacama Large Aperture Submillimetre Telescope (AtLAST), a next-generation 50-m aperture multi-purpose facility, could greatly complement ALMA, offering diagnostic capabilities not currently provided by existing facilities. AtLAST’s large field of view, fast scan speed, and multi-band instruments could allow for mapping the solar disk at adequate spatial resolution, at several frequencies simultaneously, and at a comparatively high cadence. The utilisation of multi-pixel instruments would make AtLAST capable of completing such scans on short timescales, enabling the creation of three-dimensional maps of the solar chromosphere at high temporal resolution. This would allow for monitoring the temperature and magnetic field of the active chromosphere on a global scale, and at an unprecedentedly high cadence, going beyond the capabilities of current facilities in the (sub-)millimetre regime. It is evident that AtLAST has the potential to produce data that would prove highly useful for solar physics. In the presented study, we have therefore explored its potential capabilities by using the multi-purpose (sub-)mm telescope simulator maria. By testing different instrumental setups and scan strategies, we find that 1st generation instrumentation at AtLAST should be able to produce full-disk solar maps on sub-minute timescales across its frequency range. With a more ambitious 2nd generation instrument, it is likely that the temporal resolution could be pushed to a few seconds. The foreseen capabilities would facilitate the detection of all solar flares above AtLAST’s sensitivity threshold, as continuously scanning the solar disk is likely to capture any fast-evolving dynamic phenomena at the covered spatial and temporal scales.

• Popovas, Andrius (2026). Whole Sun Simulations: Riding Exascale to the Core. Fulltekst i vitenarkiv Vis sammendrag

  In this talk I highlight our global simulations of the entire convection zone of the Sun and point to the outstanding bottleneck that exascale simulations will encounter - data and analysis.

• Popovas, Andrius; Nordlund, Åke; Szydlarski, Mikolaj & Zhou, Yixiao (2026). Towards Resolving the Solar Convective Conundrum: A staged approach in progress. doi: 10.5281/ZENODO.20642947. Fulltekst i vitenarkiv Vis sammendrag

  The solar convective conundrum — the order-of-magnitude discrepancy between helioseismically inferred deep convective velocities and those predicted by global simulations — has resisted resolution for over a decade. Three suspects have been proposed: missing physics, insufficient resolution, and the way simulations are configured. ReCon² addresses all three together in a single controlled programme, with the third element implemented through a novel staged column-relaxation strategy: solar convection is first developed in a narrow horizontal column, where large-scale unstable modes are geometrically excluded, then progressively expanded to production widths while carrying the equilibrated small-scale physics forward. This poster, presented at Cool Stars 23 (Tokyo, 15–19 June 2026), reports first-stage results from the cz_f25_d100 run: a 25 Mm wide column at Δx = 100 km finest resolution, with fully realistic physics (OPAL/FreeEOS equation of state with ionization, OP opacities and radiative diffusion in the interior, multi-bin short-characteristics radiative transfer at the surface, fully compressible MHD, entropy-based HLLS solver), initialized from rest. Horizontally-averaged entropy perturbation statistics over 300 hours of simulated time show a coherent thermal mixing layer descending ~140 Mm into the convection zone. The active layer is strongly negative-skewed (≤ −2) — the statistical signature of entropy rain (Käpylä 2025), indicating distributions dominated by narrow cold extremes. A compensating positive-skew layer at the leading edge marks warm material displaced by penetrating cold plumes, and discrete late-time arcs at z ≈ 480–540 Mm correspond to individual extreme plumes reaching ~200 Mm depth, exhibiting Käpylä's predicted "tree" morphology. A complementary photospheric kinetic-energy spectrum from an exploratory wider-box run shows that the surface convective physics matches established surface-tracking diagnostics within the box-resolved range.

• Popovas, Andrius; Nordlund, Åke & Szydlarski, Mikolaj (2026). Recent updates on global Sun modeling with DISPATCH. Fulltekst i vitenarkiv Vis sammendrag

  In this talk i present an update on our global simulations of the solar convection. I demonstrate that we can simulate the entire convection zone from below the tachocline all the way to lower chromosphere with smallest cell size near the surface of 98km. Then I discuss "entropy rain" and it's effects on the convection morphology.

• Kohutova, Petra (2026). Studying the solar atmosphere. Fulltekst i vitenarkiv
• Kohutova, Petra (2026). Spectropolarimetric Observations of the Solar Corona with DKIST/CryoNIRSP. Fulltekst i vitenarkiv
• Bose, Souvik (2026). Heating of the chromosphere and corona in the active regions of the Sun. Fulltekst i vitenarkiv Vis sammendrag

  The solar chromosphere serves as the critical interface through which magnetoconvective energy must pass to heat the million-degree corona. While 3D radiative-MHD simulations and high-resolution observations have revealed a host of candidate heating mechanisms--ranging from waves and shocks to flux emergence and reconnection, identifying which processes dominate remains a major challenge. In this talk, I will present recent progress in sharpening this picture by confronting coordinated ground- and space-based observations with state-of-the-art numerical models. Our results demonstrate that heating in active-region plage is tightly coupled across atmospheric layers down to scales of a few hundred kilometers, driven by the dissipation of currents from magnetic braiding. Crucially, our recent work pinpoints the locus of this energy release: it occurs not within the strong-field cores of magnetic flux tubes, but along their weaker-field edges. This strongly implicates magnetic geometry, rather than field strength alone, as the governing factor in atmospheric heating. I will conclude by discussing how upcoming capabilities with DKIST, SOLAR-C, and MUSE will allow us to put these geometric heating models decisively to the test.

• Aakre, Gina & Brunvoll, Aline Rangøy (2026). I kveld kan vi se månen dekke nesten hele sola. [Internet]. Forskning.no. Fulltekst i vitenarkiv Vis sammendrag

  Mens vi ser på formørkelsen, prøver solforsker Aline Rangøy Brunvoll å nøste i et av solas største mysterier. Hvorfor er den ytterste atmosfæren varmere enn overflaten?

• Aakre, Gina & Brunvoll, Aline Rangøy (2026). I kveld kan vi se månen dekke nesten hele sola - Titan.uio.no. Fulltekst i vitenarkiv
• Pereira, Tiago (2026). 22. juli - Reiseradioen - NRK Radio. [Radio]. NRK. Fulltekst i vitenarkiv Vis sammendrag

  Reiseradioen gir deg sommerfølelsen. I dag skal vi slå av en prat med Harald Stanghelle, som for tiden er på Orknøyene. Reporter Even Lusæter er i Honningsvåg og vi får en stemningsrapport derfra i dag.

• Pereira, Tiago (2026). Dagsnytt 18 - TV - NRK TV. [TV]. NRK. Fulltekst i vitenarkiv Vis sammendrag

  Dagsnytt 18 er NRK nyheters daglige aktualitets- og debattprogram. Programledere er Sigrid Sollund og Espen Aas.

• Glans-Doré, Marie & Wedemeyer, Sven (2026). Steven Spielberg er overbevist om at vi ikke er alene i universet. Fulltekst i vitenarkiv Vis sammendrag

  Hva er oddsen for at stjerneregissøren har rett? Økende, skal vi tro forskerne.

• Hestvik, Ingebjørg & Wedemeyer, Sven (2026). Nå vet vi mer om hvilke planeter som kan ha liv - Titan.uio.no. Fulltekst i vitenarkiv
• Brunvoll, Aline Rangøy (2026). Arbeidsliv, Nyheter | Aline (26) tar doktorgrad i solforskning. Fulltekst i vitenarkiv Vis sammendrag

  26 år gamle Aline Rangøy Brunvoll fra Jeløy er såpass fascinert av sola at hun nå er midt i en doktorgrad innen solforskning.

• Åkervall, Bente Storsveen & Brunvoll, Aline Rangøy (2026). Mossejenta Aline gjør doktorgrad i solfysikk på La Palma. Fulltekst i vitenarkiv Vis sammendrag

  26 år gamle Aline Rangøy Brunvoll fra Moss forsker på solen ved Roque de los Muchachos-observatoriet på La Palma. Møt den norske doktorgradsstudenten som studerer nanoflares og solens mysterier.

• Brønn, Kathrine; Stenbek, Finn Børge & Brunvoll, Aline Rangøy (2026). Eftan: Et aldri så lite sol-mysterium - Distriktsprogram - Østfold - NRK Radio. [Radio]. NRK. Fulltekst i vitenarkiv Vis sammendrag

  Goood mandag! Finn Børge og Kathrine er stemmene i radioen din denne uka. Vi forsker litt på sola, sammen med mossingen Aline. Hun tar doktorgard i solfysikk ved UiO.

• Brønn, Kathrine; Stenbek, Finn Børge & Brunvoll, Aline Rangøy (2026). Mossing forsker på sola: Bruker digert teleskop – NRK. [Internet]. NRK. Fulltekst i vitenarkiv Vis sammendrag

  Aline Rangøy Brunvoll elsker sola - ikke for å bli brun, men for å lære mer om alle mysterier på - og rundt den. Da bruker hun et digert teleskop som står på kanariøya La Palma.

• Grøndahl, Beate & Brunvoll, Aline Rangøy (2026). Morran: Vi teller geitekillinger! - Distriktsprogram - Østfold - NRK Radio. [Radio]. NRK. Fulltekst i vitenarkiv Vis sammendrag

  God morgen Østfold! Beate og Kathrine våkner opp med deg på en dag hvor vi drømmer oss til La Palma hvor mossingen Aline forsker på sola. Møt henne i Morran i Østfold

• Vogt, Yngve & Voort, Luc Rouppe van der (2026). Astrofysikere avslører stadig nye mysterier på solen | Tu.no. Fulltekst i vitenarkiv Vis sammendrag

  Solen er ikke så stabil som du tror. Hver dag eksploderer det flere hundre tusen bomber på soloverflaten.

• Poirier, Nicolas Aurelien Corentin (2026). Et strålende samarbeid. Fulltekst i vitenarkiv
• Vogt, Yngve & Carlsson, Mats (2026). Astrofysikere avslører stadig nye mysterier på solen | Tu.no. [Internet]. Tu.no. Fulltekst i vitenarkiv Vis sammendrag

  Solen er ikke så stabil som du tror. Hver dag eksploderer det flere hundre tusen bomber på soloverflaten.

• Kanestrøm, Jorunn & Wedemeyer, Sven (2026). Derfor trenger vi et nasjonalt romværvarsel - Forskningsnytt. Fulltekst i vitenarkiv
• Kanestrøm, Jorunn & Wedemeyer, Sven (2026). Kraftige soleksplosjoner kan frigjøre energi tilsvarende Norges strømforbruk i millioner av år - Titan.uio.no. Fulltekst i vitenarkiv
• Øyvann, Stig & Carlsson, Mats (2026). Kraftig solstorm ga GPS-forstyrrelser i Nord-Norge. [Internet]. Telecomrevy.no. Fulltekst i vitenarkiv Vis sammendrag

  En kraftig solstorm i januar har ført til betydelige forstyrrelser i satellittnavigasjon og radiosamband, særlig i Nord-Norge. Forskere advarer om at solaktiviteten er inne i en fase der både GPS-tjenester og deler av den digitale infrastrukturen er mer sårbar enn normalt.

• Vogt, Yngve & Wedemeyer, Sven (2026). Drømmen er å varsle soleksplosjoner før de skjer - Titan.uio.no. Fulltekst i vitenarkiv
• Carlsson, Mats & Tveito, Ole Jon (2026). Nordlys, Naturfenomen | Massivt nordlys over Tinn. Fulltekst i vitenarkiv Vis sammendrag

  Kraftige solstormer som har funnet sted på sola fører nå til massivt nordlys over store deler av Norge. Over Gausta var det tirsdag kveld flott nordlys.

• Vogt, Yngve & Wedemeyer, Sven (2026). Bedre romværvarsler kan redde satellitter og strømnettet - Forskningsnytt. Fulltekst i vitenarkiv
• Carlsson, Mats (2026). Solstorm, Astronomi | Professor varsler solstormer som kan føre til store skader på jorda. [Internet]. Hamar Arbeiderblad. Fulltekst i vitenarkiv Vis sammendrag

  Aktiviteten på sola er nå på sitt høyeste. Det kan medføre en så voldsom eksplosjon at den kan ramme satellitter, telekommunikasjon og strømforsyning på jorda.

• Vogt, Yngve & Carlsson, Mats (2026). Eksplosjoner på solen kan lamme det moderne livet på jorden | Tu.no. [Internet]. TU.no. Fulltekst i vitenarkiv Vis sammendrag

  Solaktiviteten er nå på sitt høyeste. Faren er til stede for at en voldsom eksplosjon på solen, i år eller neste år, kan skade alt fra satellitter og telekommunikasjon til strømforsyningen på jorden.

• Carlsson, Mats (2026). Professor varsler solstormer som kan føre til store skader på jorda. [Internet]. MSN. Fulltekst i vitenarkiv
• Carlsson, Mats (2026). Kan skape kaos på jorda: - – Ville ha vært katastrofalt. [Internet]. Sol.no. Fulltekst i vitenarkiv Vis sammendrag

  Aktiviteten på sola er nå på sitt høyeste. Det kan medføre en så voldsom eksplosjon at den kan ramme satellitter, telekommunikasjon og strømforsyning på jorda.

• Carlsson, Mats (2026). Solstormer kan føre til store skader på jorda. Fulltekst i vitenarkiv Vis sammendrag

  Aktiviteten på sola er nå på sitt høyeste. Det kan medføre en så voldsom eksplosjon at den kan ramme satellitter, telekommunikasjon og strømforsyning på jorda. – Det er ikke et spørsmål om hvorvidt det skjer igjen, men om når, sier professor Mats Carlsson på Astrofysisk institutt ved UiO.

• Carlsson, Mats (2026). Solstormer, Astronomi | Professor varsler solstormer som kan føre til store skader på jorda. Fulltekst i vitenarkiv Vis sammendrag

  Aktiviteten på sola er nå på sitt høyeste. Det kan medføre en så voldsom eksplosjon at den kan ramme satellitter, telekommunikasjon og strømforsyning på jorda.

• Carlsson, Mats (2026). Professor varsler solstormer som kan føre til store skader på jorda. [Internet]. Energiwatch. Fulltekst i vitenarkiv
• Carlsson, Mats & Vogt, Yngve (2026). Eksplosjoner på solen kan lamme det moderne livet på jorden - Forskningsnytt. Fulltekst i vitenarkiv
• Kohutova, Petra (2026). Spectropolarimetric observations of coronal oscillations with DKIST/Cryo-NIRSP. Fulltekst i vitenarkiv
• Bose, Souvik (2026). Magnetic edges dominate heating in the solar atmosphere. Fulltekst i vitenarkiv Vis sammendrag

  At the interface between the Sun’s million-degree corona and its surface lies the chromosphere: cooler and far denser than the corona, yet it processes essentially all of the magnetoconvective energy that ultimately powers the outer atmosphere. How and where that energy is converted into heat remains a central open question in astrophysics. Here we combine high-resolution observations from IRIS, Hinode and SDO with a state-of-the-art 3D radiative-MHD simulation to show that the key sites of energy release in active-region plage are not the familiar strong-field cores, but their magnetic edges. Machine-learning-assisted chromospheric inversions (IRIS2+) reveal that radiative losses per unit magnetic flux sharply peak in weak-to-intermediate fields at the expanding rims of plage flux tubes, whereas kG cores are comparatively “dark”, carrying most of the flux yet contributing only a minor fraction of the losses. The simulation reproduces this rim-bright, core-dim pattern and indicates that magnetic geometry—rather than field strength alone—governs atmospheric heating.These results identify flux-tube boundaries as primary sites of energy conversion in active regions and provide a new observational constraint for models of chromospheric and coronal heating, with clear, testable predictions for upcoming facilities such as MUSE, Solar-C and next-generation ground-based observatories.

• Joshi, Reetika (2026). Solar flares and transient events. Fulltekst i vitenarkiv
• Joshi, Reetika (2026). Observational Advances Enabling Detailed Investigation of Solar Filaments. Fulltekst i vitenarkiv
• Joshi, Reetika (2026). Resolving Fine-Scale Structures in the Solar Chromosphere. Fulltekst i vitenarkiv
• Joshi, Reetika (2026). Chromospheric fibril singularity: SST, Solar Orbiter, and IRIS observations. Fulltekst i vitenarkiv
• Wedemeyer, Sven (2026). Radio and Millimeter Observations of the Sun - Probing the Solar Origins of Space Weather. Fulltekst i vitenarkiv
• Wedemeyer, Sven (2026). Fra solstorm til nordlys: Solens påvirkning på jorden. Fulltekst i vitenarkiv
• Wedemeyer, Sven (2026). The Heliosphere and Its Protective Role in Planetary Systems. Fulltekst i vitenarkiv
• Wedemeyer, Sven (2026). Radio and (Sub-)Millimeter Observations of the Sun: Current Status, Future Perspectives, and the Path Toward AtLAST. Fulltekst i vitenarkiv
• Wedemeyer, Sven (2026). 3D CO + MHD simulations with CO5BOLD. Fulltekst i vitenarkiv
• Wedemeyer, Sven (2026). The Sun observed at long wavelengths. Fulltekst i vitenarkiv
• Baso, Carlos José Díaz (2026). Information content of solar spectra. Fulltekst i vitenarkiv Vis sammendrag

  High-resolution observations and advanced data analysis techniques are essential for uncovering fine-scale physical processes in the solar atmosphere. In this presentation, we explore three recent methodological and observational lessons learned from high-cadence solar telescope data. First, we examine the evolution of an eruptive flare observed with the TRIPPEL instrument at the Swedish 1-m Solar Telescope, demonstrating how combining magnetic extrapolations with non-local thermodynamic equilibrium inversions bridges observational and theoretical domains to quantify released magnetic energy and atmospheric heating. Second, we address the challenge of disentangling complex, multi-component spectral line profiles during mini-filament eruptions, showing how linear optimization techniques efficiently resolve overlapping atmospheric components. Finally, we introduce the application of normalizing flows as powerful density estimators to model multi-dimensional spectral probability distributions, enabling the automated detection of statistically rare and unusual phenomena in quiet Sun time-series datasets. Together, these approaches highlight how advanced modeling and machine learning techniques can optimize our analysis of massive observational data rates and reveal hidden solar dynamics.

• Baso, Carlos José Díaz (2026). AI in Solar Physics. Fulltekst i vitenarkiv Vis sammendrag

  Solar physics is entering an unprecedented data-rich era driven by advanced solar observatories generating massive volumes of high-resolution spatiotemporal and spectropolarimetric observations. Analyzing these extensive datasets presents severe computational bottlenecks, as traditional numerical modeling and radiative transfer inversions are extremely time-consuming. In this work, we explore how artificial intelligence and modern machine learning frameworks can revolutionize solar data analysis across three critical domains. First, we implement probabilistic generative models, including diffusion models, to perform efficient unsupervised anomaly detection, allowing researchers to automatically isolate rare and physically interesting phenomena within terabytes of observations by evaluating data probability distributions. Second, we integrate large language model agents as automated optimizers to accelerate complex mathematical inversions, solving systems with hundreds of thousands of unknowns orders of magnitude faster. Finally, we examine the application of large-scale foundation models in heliophysics, such as spatiotemporal transformers trained on extensive Solar Dynamics Observatory archives, demonstrating their potential for zero-shot forecasting of solar conditions and the prediction of explosive events. Together, these approaches demonstrate how advanced AI methodologies help overcome the challenges of big data, opening new avenues for automated discovery and physical understanding in solar physics.

• Baso, Carlos José Díaz (2026). Inspectorch: Efficient rare event exploration. Fulltekst i vitenarkiv Vis sammendrag

  Next-generation facilities like the European Solar Telescope (EST) will observe the Sun with unprecedented spatial and temporal resolution, providing simultaneous multi-wavelength and multi-height diagnostics. However, the sheer volume of high-resolution spectropolarimetric data will make it impossible to fully analyze using conventional methods. While standard machine learning identifies general trends, it routinely overlooks the highly localized, transient, or weak signals crucial for understanding chromospheric heating and flux emergence. Our aim is to introduce an unsupervised probabilistic method to efficiently identify these rare, extreme events in multidimensional solar observations, optimizing our computational resources for the phenomena EST is designed to uncover. To achieve this, we introduce Inspectorch, an open-source framework utilizing flow-based models. These flexible density estimators learn the multidimensional distribution of spectropolarimetric data and assign a probability to each sample, immediately isolating unusual events. We validate this approach using datasets from the Hinode Spectro-Polarimeter, the Interface Region Imaging Spectrograph (IRIS), the Microlensed Hyperspectral Imager (MiHI) at the Swedish 1-m Solar Telescope (SST), and space-based imagers such as the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory and the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter. Across these datasets, the algorithm successfully isolates profiles with uncommon broadening, strong Doppler shifts associated with small-scale reconnection, and complex profiles exhibiting height-dependent magnetic polarity reversals. Its probabilistic nature makes it highly effective at identifying those cases that occupy a tiny fraction of the total number of samples and are overlooked by traditional methods. Inspectorch demonstrates that flow-based density estimation is robust, requires minimal parameter tuning, and can be applied to large datasets with minimal effort. By providing probabilistic anomaly scores, this publicly available framework prepares the solar physics community to rapidly identify and analyze the most physically relevant and elusive phenomena in the massive datasets soon to be produced by EST.

• Baso, Carlos José Díaz (2026). Thermodynamic and magnetic evolution of an eruptive C-class solar flare: Linking small-scale triggers to eruptive potential. Fulltekst i vitenarkiv Vis sammendrag

  Solar flares and filament eruptions are complex phenomena driven by the release of magnetic energy, and they act as primary drivers of space weather. However, a large energy reservoir alone is insufficient to determine their eruptive potential; the localized magnetic topology and small-scale plasma dynamics play a critical role. We investigated the thermodynamic and magnetic properties of the solar atmosphere during the rise, peak, and decay phases of an eruptive C5.1-class flare in active region NOAA 12561 to understand how fine-scale atmospheric responses dictate broader eruptive behavior. High spatial and spectral resolution spectropolarimetric observations of the chromospheric Ca II 8542 Å line and nearby photospheric lines were obtained with the TRIPPEL-SP spectropolarimeter at the Swedish 1-m Solar Telescope. By combining nonlocal thermodynamic equilibrium (NLTE) inversions with non-force-free field (NFFF) magnetic extrapolations, we bridged the observational and theoretical domains to follow the event's evolution. Before the flare, our analysis revealed a complex, sheared magnetic topology with a high free energy content (~2 x 10^30 erg). In this precursor phase, we detected persistent localized heating (temperature increase of ~2000 K) with strong downflows (10-20 km/s) deep in the atmosphere. This heating was co-spatial with a bald-patch region, demonstrating how low-altitude magnetic reconnection can destabilize a larger filament structure. The flare's rise phase was marked by the filament's eruption with speeds exceeding 70 km/s. Following the eruption, free energy decreased by ~30% as post-flare loops channeled the released energy into the lower atmosphere, driving ribbon heating up to 8500 K and significant downflows. These results highlight how combining high-resolution ground-based spectropolarimetry with advanced modeling is essential for understanding how small-scale localized magnetic phenomena scale up to trigger eruptive events with space weather implications.

• Baso, Carlos José Díaz (2026). Inspectorch: a probabilistic framework for efficient rare event exploration in the EST era. Fulltekst i vitenarkiv Vis sammendrag

  Next-generation facilities like the European Solar Telescope (EST) will observe the Sun with unprecedented spatial and temporal resolution, providing simultaneous multi-wavelength and multi-height diagnostics. However, the sheer volume of high-resolution spectropolarimetric data will make it impossible to fully analyze using conventional methods. While standard machine learning identifies general trends, it routinely overlooks the highly localized, transient, or weak signals crucial for understanding chromospheric heating and flux emergence. Our aim is to introduce an unsupervised probabilistic method to efficiently identify these rare, extreme events in multidimensional solar observations, optimizing our computational resources for the phenomena EST is designed to uncover. To achieve this, we introduce Inspectorch, an open-source framework utilizing flow-based models. These flexible density estimators learn the multidimensional distribution of spectropolarimetric data and assign a probability to each sample, immediately isolating unusual events. We validate this approach using datasets from the Hinode Spectro-Polarimeter, the Interface Region Imaging Spectrograph (IRIS), the Microlensed Hyperspectral Imager (MiHI) at the Swedish 1-m Solar Telescope (SST), and space-based imagers such as the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory and the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter. Across these datasets, the algorithm successfully isolates profiles with uncommon broadening, strong Doppler shifts associated with small-scale reconnection, and complex profiles exhibiting height-dependent magnetic polarity reversals. Its probabilistic nature makes it highly effective at identifying those cases that occupy a tiny fraction of the total number of samples and are overlooked by traditional methods. Inspectorch demonstrates that flow-based density estimation is robust, requires minimal parameter tuning, and can be applied to large datasets with minimal effort. By providing probabilistic anomaly scores, this publicly available framework prepares the solar physics community to rapidly identify and analyze the most physically relevant and elusive phenomena in the massive datasets soon to be produced by EST.

• Baso, Carlos José Díaz (2026). Physics-informed machine learning and probabilistic methods for spectropolarimetry. Fulltekst i vitenarkiv Vis sammendrag

  In the last decade, machine learning and neural networks have emerged as powerful tools for analyzing huge collections of solar data, demonstrating versatility in tasks ranging from image reconstruction to the acceleration of spectropolarimetric inversions. However, while these algorithms offer unprecedented speed, they often lack the precision required for detailed physical interpretation and fail to exploit the inherent spatial coherence of the solar atmosphere to increase fidelity. Moreover, the straightforward application of these tools risks merely shifting the bottleneck—from managing huge raw datasets to sifting through massive volumes of inversion results—without effectively isolating the poorly understood phenomena that drive scientific discovery. In this contribution, we address these limitations by reviewing novel applications that combine physical constraints with advanced statistical methods. We specifically highlight Neural Fields, which leverage continuous parameterization to impose spatio-temporal constraints and improve magnetic field reconstruction, and Normalizing Flows, a probabilistic technique optimized for efficiently detecting rare events and extreme spectra that traditional methods overlook. We demonstrate the potential of these approaches using observations from telescopes such as the Swedish 1-m Solar Telescope (SST) and the Interface Region Imaging Spectrograph (IRIS). Finally, we discuss how integrating these tools is essential to maximize the scientific return from current and future missions.

• Fredvik, Terje (2026). Oslo SPICE Status 2026. Fulltekst i vitenarkiv
• Poquet, Ignasi Josep Soler; Baso, Carlos José Díaz & Voort, Luc Rouppe van der (2026). Multi-wavelength observations of Ellerman bombs. Fulltekst i vitenarkiv Vis sammendrag

  Context. Ellerman bombs (EBs) are observational signatures of small-scale magnetic reconnection, key to understanding the lower solar atmosphere. While their role in active regions has been widely studied using the Hα line, near-ultraviolet (NUV) spectra routinely observed by the Interface Region Imaging Spectrograph (IRIS) offer a promising alternative for EB identification, enabling large-scale studies. Aims. We aim to identify the most important spectral signatures of EBs in the IRIS NUV spectra. With this, we seek to develop a robust criterion for their detection solely using the IRIS NUV spectra. In parallel, we determine the typical atmospheric stratification associated with EBs. Methods. We used four coordinated observations between the Swedish 1-m Solar Telescope (SST) and IRIS. Using the Hα line as a reference, we detected 18 different EBs and studied their associated IRIS NUV spectra. In addition, we used the IRIS2+ inversion tool to infer the temperature, line-of-sight velocity, and non-thermal broadening from the EB spectra. Results. The defining feature of EBs in the IRIS NUV is the enhancement of the wings of the subordinated Mg ii triplet between the Mg ii h&k lines. Inversions reveal that these signatures are produced by a localized temperature increase of ∆T ∼ 1670 K around log(τ)= −3.8. Using only the Mg ii triplet signatures, we found a detection criterion that successfully recovered 14 of 18 Hα-detected EBs. In addition, the shape of the Mg ii h&k lines in relation to the Mg ii triplet can serve as a proxy for the EB formation height. Conclusions. The NUV spectrum observed by IRIS is a good candidate for detecting EBs, opening the doors to large-scale studies across the extensive IRIS database, removing the dependence on Hα observations. This capability bridges the gap between small- and large-scale event studies, which was not possible before due to the lack of coordinated observations.

• Voort, Luc Rouppe van der (2026). SST/CRISP2 observations of an active region. Fulltekst i vitenarkiv
• Voort, Luc Rouppe van der (2026). Energetic events following magnetic flux emergence into the photosphere. Fulltekst i vitenarkiv
• Voort, Luc Rouppe van der (2026). SST coordination with Solar Orbiter and other telescopes in space. Fulltekst i vitenarkiv
• Gudiksen, Boris Vilhelm (2026). Large effect of small scales in the solar corona. Fulltekst i vitenarkiv
• Ornig, Sascha; Carlsson, Mats & Voort, Luc Rouppe van der (2026). Characterization of White-Light Enhancements in Solar Flares: A Combined Observational and Modeling Approach. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  Solar flares are among the most energetic events in the solar system. These sudden brightenings of localized regions in the solar atmosphere drive particle acceleration and heat the ambient plasma to several millions of degrees. The enormous amounts of radiation released in these events, combined with associated phenomena such as coronal mass ejections, have a major influence on space weather around our planet Earth, and it is therefore of vital importance for us to understand the mechanisms behind them. The continuum contains a large portion of the energy released in solar flares, yet its formation mechanisms pose a challenge to the standard flare model. The optical part of the continuum, termed white light (WL), allows us to utilize ground-based observatories for our investigations. With complementary output from numerical simulations, we can gain insights into the dominant processes. However, to date several problems remain. This work investigates solar WL flares (WLFs) using a symbiosis of simulations and observations. It is comprised of three papers, each aimed at answering one of our outstanding questions. Paper I makes use of an ensemble of electron beam-driven solar flare simulations — the F-CHROMA grid — created with the radiation hydrodynamics code RADYN. We investigate how WL enhancements appear in these simulations, what the underlying mechanisms are, and whether we can identify a useful proxy for deducing the dominant mechanism from observations. Our results show intensity enhancements caused primarily by enhanced hydrogen recombination radiation in the optically thin chromosphere, with minor contributions from the radiatively backheated photosphere. The simulated WL enhancements are at least one order of magnitude below observed values. We identify the Paschen jump and its associated intensity ratio as an appropriate proxy for increased optically thin hydrogen recombination radiation. For Paper II, we utilize observations from the Swedish 1-m Solar Telescope (SST) to probe the Paschen jump via continuum measurements redward and blueward of the jump. We find WL enhancements in the dark (pen)umbral regions in sunspots, without any flare-related quiet-Sun intensity increases. The WL increases in one of the flares are co-temporal and (partially) co-spatial with hard X-ray increases, suggesting a common electron-beam cause. Our results indicate that the filter used for observations redward of the jump is unsuitable for measurements of the true continuum intensity due to influences from the nearby spectral line. In Paper III, we attempt to close the gap in amplitude between WL enhancements in simulations and observations by using a background atmosphere modeled after the umbra of a sunspot. Our results show WL increases comparable to observations, and we identify the reduced background intensity as the main reason for this outcome. The mechanisms are identical to those identified in the simulations with a quiet-Sun starting atmosphere used for Paper I. We further find that the electron beam flux is strongly correlated with the resulting WL increases. We conclude that one-dimensional simulations of solar flares can satisfactorily model WLFs of type I. Observationally, we lack adequate measurements of the true continuum longward of the Paschen jump in order to utilize it for the deduction of the formation mechanisms behind WLFs

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