HST/STIS ultraviolet spectroscopy of the supersoft X-ray source RX J0439.8-6809

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dc.creatorvan Teeseling, A.
dc.creatorGaensicke, B. T.
dc.creatorBeuermann, K.
dc.creatorDreizler, S.
dc.creatorRauch, T.
dc.creatorReinsch, K.
dc.date1999-10-18
dc.date.accessioned2026-07-07T02:33:55Z
dc.date.available2026-07-07T02:33:55Z
dc.descriptionWe present ultraviolet observations of the supersoft X-ray source RXJ0439.8-6809 obtained with the Hubble Space Telescope Imaging Spectrograph. The ultraviolet spectrum is a very blue continuum overlayed with interstellar absorption lines. The observed broad Lyman alpha absorption line is consistent with an interstellar column density of neutral hydrogen Nh=(4.0+-1.0)e20 cm-2. The light curve obtained from the time-tagged dataset puts a 3sigma upper limit of 0.04mag on the ultraviolet variability of RXJ0439.8-6809 on time scales between 10s and 35min. The long-term X-ray light curve obtained from our three-year ROSAT HRI monitoring of RXJ0439.8-6809 shows the source with a constant count rate, and implies that the temperature did not change more than a few 1000K. If RXJ0439.8-6809 is a massive extremely hot pre-white dwarf on the horizontal shell-burning track, opposed to the alternative possibility of a very compact double-degenerate supersoft X-ray binary, its constant temperature and luminosity are a challenge to stellar evolution theory. Interestingly, RXJ0439-6809 is found close to the theoretical carbon-burning main-sequence.
dc.description4 pages A&A-PSLatex, 5 Figures, accepted for publication in A&A Letters
dc.identifierhttps://arxiv.org/abs/astro-ph/9910330
dc.identifierhttp://arxiv.org/abs/astro-ph/9910330
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/15040
dc.subjectAstrophysics
dc.titleHST/STIS ultraviolet spectroscopy of the supersoft X-ray source RX J0439.8-6809
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