Open AccessCalculated spectra for HeH + and its effect on the opacity of cool metal‐poor stars
Author(s) -
Engel Elodie A.,
Doss Natasha,
Harris Gregory J.,
Tennyson Jonathan
Publication year - 2005
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2005.08611.x
Subject(s) - opacity , physics , metallicity , isotopologue , helium , spectral line , stars , atomic physics , astrophysics , hydrogen , effective temperature , astronomy , optics , quantum mechanics
The wavelength and Einstein A coefficient are calculated for all rotation–vibration transitions of 4 He 1 H + , 3 He 1 H + , 4 He 2 H + and 3 He 2 H + , giving a complete line list and the partition function for 4 HeH + and its isotopologues. This opacity is included in the calculation of the total opacity of low‐metallicity stars and its effect is analysed for different conditions of temperature, density and hydrogen number fraction. For a low helium number fraction (as in the Sun), it is found that HeH + has a visible but small effect for very low densities (ρ≤ 10 −10 g cm −3 ) , at temperatures around 3500 K. However, for high helium number fraction, the effect of HeH + becomes important for higher densities (ρ≤ 10 −6 g cm −3 ) , its effect being most important for a temperature around 3500 K. Synthetic spectra for a variety of different conditions are presented.