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Astron. Astrophys. 330, 999-1004 (1998)

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The Li I resonance line in the spectra of X-ray nova accretion discs

V. Suleimanov and R. Rebolo

1 Kazan State University, Kremlevskaya Str. 18, Kazan, 420008 Russia
2 Instituto de Astrofísica de Canarias, Vía Láctea s/n, E-38200 La Laguna, Tenerife, Spain

Received 11 July 1997 / Accepted 29 August 1997

Abstract

We study the formation of the Li I [FORMULA] 6708 Å resonance doublet in spectra of X-ray novae during the stage of outburst decay. We discuss the general conditions on accretion disc parameters which allow the detection of any spectral line absorption component in spectra of self-irradiated accretion discs. We obtain a simple analytical formula to estimate the equivalent width of the lithium line in the spectra of these discs and, adopting a simple model of self-irradiation, we have conducted more precise numerical calculations of these equivalent widths in the spectra of accretion discs around Schwarzschild black holes. We find that the equivalent width of the Li I doublet can reach [FORMULA] 20-100 mÅ during outburst decay if the luminosity becomes less than 0.01 Eddington luminosity and if the lithium abundance in the discs is about cosmic (log N(Li) [FORMULA] 3). If some lithium production takes place in these discs higher abundances would be possible and consequently stronger lines could be formed. The larger the outer disc radius and the smaller the disc inclination angle to line of sight, the greater the equivalent width of the line.

Key words: accretion discs – stars: abundances – novae – X-rays: stars

Send offprint requests to: V. Suleimanov (vals@astro.ksu.ras.ru)

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© European Southern Observatory (ESO) 1998

Online publication: January 27, 1998
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