Boy Lankhaar

• Cozijn, Frank M.J.; Altman, Arthémise; Bogomolov, Alexandr S.; Libert, Alexis; Collignon, Simon & Dierikx, Erik [Vis alle 11 forfattere av denne artikkelen] (2026). Optically derived radio-frequency benchmark in methanol: a sub-kHz reference for astrophysical tests of fundamental physics. Optica. 13(7), s. 1355–1367. doi: 10.1364/OPTICA.593388. Fulltekst i vitenarkiv Vis sammendrag

  Methanol radio lines observed in space provide sensitive probes of whether the proton-to-electron mass ratio has changed over cosmic time, but such tests require laboratory rest frequencies with very high accuracy. Here, we determine the frequency of the astrophysically important 12.2 GHz 3-1 E - 2-0 E transition of CH3OH by measuring near-infrared rovibrational transitions rather than the microwave line directly. Using wavelength-modulated NICE-OHMS locked to an ultra-stable optical frequency comb and referenced via a fiber link to a hydrogen-maser frequency standard, we measure Lamb-dip frequencies near 1.4 µm (216 THz) with 10 Hz statistical reproducibility and absolute uncertainties as low as 130 Hz. Pairs of optical transitions sharing common upper levels form a triangulation scheme that yields the ground-state rotational combination difference. We obtain 12,178,596.415(135) kHz, improving on earlier molecular-beam microwave spectroscopy by a factor of 20 and agreeing with a recent free-induction-decay measurement. This result establishes a sub-kHz laboratory benchmark for a key radio-astronomical methanol line and demonstrates that optical triangulation can be extended to non-chiral molecules with internal rotation.

• Teague, Richard; Lankhaar, Boy; Andrews, Sean M.; Qi, Chunhua; Fu, Roger R. & Wilner, David J. [Vis alle 8 forfattere av denne artikkelen] (2025). A Radially Resolved Magnetic Field Threading the Disk of TW Hya. Astrophysical Journal Letters. ISSN 2041-8205. 991(1). doi: 10.3847/2041-8213/adff4d. Fulltekst i vitenarkiv Vis sammendrag

  We present a new approach to detecting and characterizing a magnetic field in protoplanetary disks through the differential broadening of unpolarized molecular emission from CN. To demonstrate this technique, we apply it to new Atacama Large Millimeter/submillimeter Array observations of the full complement of hyperfine components from the N = 1–0 transition, achieving a spatial and spectral resolution of and 80 m s−1, respectively. By fitting a model that incorporates the velocity structure of the disk, the potential non-LTE excitation of the molecule, and the Zeeman effect, we recover a radially resolved magnetic field with a strength of ∼10 mG between 60 and 120 au. The morphology of the field is also inferred through azimuthal variations in the line broadening, revealing a predominantly poloidal field at 60 au, sharply transitioning to one within the disk plane outside of the gap at 82 au. The signal-to-noise ratio of the data meant that the planar component was unable to be decomposed into toroidal and radial components. Lower limits on the local gas density (n(H2) ≳ 108 cm−3) from the excitation analysis of the CN emission correspond to a lower limit between 0.1 and 0.01 for the plasma β.

Se alle arbeider i NVA