Issue |
A&A
Volume 416, Number 3, March IV 2004
|
|
---|---|---|
Page(s) | 1057 - 1067 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20034145 | |
Published online | 09 March 2004 |
Accretion disc evolution in DW Ursae Majoris: A photometric study*
1
Institute of Astronomy, Bulgarian Academy of Sciences, 72, Tsarighradsko Shousse Blvd., 1784 Sofia, Bulgaria e-mail: [zk;vgenkov]@astro.bas.bg
2
Present address: Physics department, Stockholm University, Sweden
3
Royal Observatory of Belgium, Avenue Circulaire 3, 1180 Brussels, Belgium e-mail: [henri.boffin;Christina.Papadaki]@oma.be
4
European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching-bei-München, Germany
5
Institut für Astronomie und Astrophysik Universität Tübingen, Abteilung Astronomie, Sand 1, 72076 Tübingen, Germany e-mail: carpano@astro.uni-tuebingen.de
Corresponding author: V. Stanishev, vall@astro.bas.bg
Received:
1
August
2003
Accepted:
4
December
2003
We present an analysis of CCD photometric observations
of the eclipsing novalike cataclysmic variable DW UMa
obtained in two different luminosity states: high and
intermediate. The star presents eclipses with very different
depth: ~1.2 mag in the high and ~3.4 mag in the intermediate
state. Eclipse mapping reveals that this difference is almost
entirely due to the changes in the accretion disc radius:
from ~ in the intermediate state to ~
in the high state (
is the distance from the white
dwarf to the first Lagrangian point). In the intermediate state, the
entire disc is eclipsed while in the high state, its outer part remains
visible.
We also find that the central intensity of the disc is nearly
the same in the two luminosity states and that it is the increase of the disc
radius that is responsible for the final rise from the 1999/2000 low
state. We find that the intensity profile of the disc is rather
flat and suggest a possible explanation. We also discuss the
effect of using a more realistic limb-darkening law on the disc
temperatures inferred from eclipse mapping experiments.
Periodogram analysis of the high state data reveals “positive
superhumps" with a period of
in 2002 and
in 2003,
in accord with the results of Patterson et al. However, we cannot confirm the
quasi-periodic oscillations reported by these authors. We obtain
an updated orbital ephemeris of DW UMa:
.
Key words: accretion, accretion disks / stars: individual: DW UMa / novae, cataclysmic variables
© ESO, 2004
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