AlH Lines In The Blue Spectrum Of Proxima Centauri

The recently-computed ExoMol line lists for isotopologues of AlH are used to analyse the blue spectrum (4000-4500 Å) of Proxima Cen (M5.5 V). Comparison of the observed and computed spectra enables the identification of a large number of 27AlH lines of the A1{\Pi} – X1{\Sigma}+ band system: the spectral range covering 1-0, 0-0 and 1-1 bands is dominated by clearly resolved AlH lines.

We reveal the diffuse nature of transitions close to the dissociation limit which appears in the form of increasingly wider(up to 5 Å) and shallower (up to the continuum confusion limit) AlH line profiles. The predicted wavelengths of AlH diffuse lines are systematically displaced. The effect broadening by pre-dissociation states on the line profiles is included by increasing the radiative damping rate by up to 5 orders of magnitude.

We determine empirical values of damping rates for a number of the clean 0-0 Q-branch transitions by comparing the observed and synthetic stellar spectra. We find excellent agreement between our damping rates and lifetimes available in the literature. A comparison of 27Al1H ExoMol and REALH spectra shows that the observed spectrum is better described by the ExoMol line list. A search for 26Al1H lines in the Proxima Cen spectrum does not reveal any notable features; giving an upper limit of 27Al1H/26Al1H {>} 100.

Yakiv V. Pavlenko, Jonathan Tennyson, Sergei N. Yurchenko, Mirek R. Schmidt, Hugh R.A. Jones, Yuri Lyubchik, A. Suárez Mascareño

Comments: 22 pages, 6 tables, 10 figs, accepted by MNRAS
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2209.03037 [astro-ph.SR] (or arXiv:2209.03037v1 [astro-ph.SR] for this version)
Submission history
From: Yakiv Pavlenko V.
[v1] Wed, 7 Sep 2022 10:03:32 UTC (1,217 KB)
Full paper: https://arxiv.org/abs/2209.03037
Astrobiology