2025/12/12 by Lu, Cicero X., Rebollido, Isabel, Brittain, Sean +12
#Earth and Planetary Astrophysics (astro-ph.EP) #FOS: Physical sciences #Solar and Stellar Astrophysics (astro-ph.SR)
paper · doi:10.48550/arxiv.2512.11972
We have obtained a high-resolution, JWST NIRSpec 2.87 -- 5.14 μm spectrum of the debris disk around HD 131488. We discover CO fundamental emission indicating the presence of warm fluorescent gas within ∼10 AU of the star. The large discrepancy in CO's vibrational and rotational temperature indicates that CO is out of thermal equilibrium and is excited with UV fluorescence. Our UV fluorescence model gives a best fit of 1150 K with an effective temperature of 450, 332, and 125 K for the warm CO gas kinetic temperature within 0.5, 1, and 10 AU to the star and a gas vibrational temperature of 8800 K. The newly discovered warm CO gas population likely resides between sub-AU scales and ∼ 10 AU, interior to the cold CO reservoir detected beyond 35 AU with HST STIS and ALMA. The discovery of warm, fluorescent gas in a debris disk is the first such detection ever made. The detection of warm CO raises the possibility of unseen molecules (H2O, H2, etc) as collisional partners to excite the warm gas. We estimated a lower mass limit for CO of 1.25× 10-7M⊕, which is 10-5 of the cold CO mass detected with ALMA and HST. We demonstrate that UV fluorescence emerges as a promising avenue for detecting tenuous gas at 10-7 Earth-mass level in debris disks with JWST.