Issue |
A&A
Volume 433, Number 3, April III 2005
|
|
---|---|---|
Page(s) | 1085 - 1095 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20042121 | |
Published online | 29 March 2005 |
HST/FOS time-resolved spectral mapping of IP Pegasi at the end of an outburst
1
Departamento de Física, Universidade Federal de Santa Catarina, Trindade, 88040-900, Florianópolis, SC, Brazil e-mail: saito@astro.ufsc.br
2
School of Physics and Astronomy, University of St. Andrews, KY16 9SS, Scotland, UK
Received:
5
October
2004
Accepted:
21
December
2004
We report an eclipse mapping analysis of time-resolved ultraviolet
spectroscopy covering three eclipses of the dwarf nova IP Pegasi on
the late decline of the 1993 May outburst. The eclipse maps of the
first run show evidence of one spiral arm, suggesting that spiral
structures may still be present in the accretion disc 9 days after the
onset of the outburst. In the spatially resolved spectra the most
prominent lines appear in emission at any radius, being stronger in
the inner disc regions. The spectrum of the gas stream is clearly
distinct from the disc spectrum in the intermediate and outer disc
regions, suggesting the occurrence of gas stream overflow. The full
width half maximum of C IV is approximately constant with radius, in
contrast to the expected law for a gas in
Keplerian orbits. This line probably originates in a vertically
extended region (chromosphere + disc wind). The uneclipsed component
contributes ~4% of the flux in C IV in the first run, and
becomes negligible in the remaining runs. We fit stellar atmosphere
models to the spatially resolved spectra. The radial run of the disc
color temperature for the three runs is flatter than the expected
law for steady-state optically thick discs
models, with
K in the inner regions and
K in the outer disc regions. The solid angles that
result from the fits are smaller than expected from the parameters of
the system. The radial run of the solid angle suggests that the disc
is flared in outburst, and decreases in thickness toward the end of
the outburst.
Key words: stars: individual: IP Peg / stars: binaries: eclipsing / methods: data analysis
© ESO, 2005
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