EDP Sciences
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Volume 367, Number 1, February III 2001
Page(s) 273 - 276
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20000530

A&A 367, 273-276 (2001)
DOI: 10.1051/0004-6361:20000530

Research Note
IY Ursae Majoris: Accretion disc evolution after superoutburst

V. Stanishev1, Z. Kraicheva1, H. M. J. Boffin2 and V. Genkov1

1  Institute of Astronomy, Bulgarian Academy of Sciences, 72 Tsarighradsko Shousse Blvd., 1784 Sofia, Bulgaria
2  Royal Observatory of Belgium, Avenue Circulaire 3, 1180 Brussels, Belgium
vall@astro.bas.bg (VS),zk@astro.bas.bg (ZK), henri.boffin@oma.be (HMJB),nao@mail.orbitel.bg (VG).

(Received 27 July 2000 / Accepted 15 December 2000 )

CCD photometry of the newly discovered eclipsing dwarf nova IY Ursae Majoris is used to study the physical properties of the accretion disc in the late decline and quiescence stages. Eclipse mapping analysis shows that in these stages the accretion disc is cool with approximately flat radial brightness temperature distribution and $T_{\rm BR}\sim5000-5500$ K. The hot spot is found to lie close along the stream trajectory at distance 0.36a and 0.25a from the disc center in February and March. The orbital hump strength decreases by $\sim$30% in a month. Taking the smallest possible size of the hot spot, we derive an upper limit for its brightness temperature, $\sim$15 900 K and $\sim$13 800 K, respectively.

Key words: accretion, accretion disc -- binaries: eclipsing -- stars: individual: IY UMa -- dwarf nova, cataclysmic variables

Offprint request: Z. Kraicheva

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