TV Corvi revisited: Precursor and superhump period derivative linked to the disk instability model

¹ Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Concepción, Casilla 160-C, Concepción, Chile e-mail: muemura@cepheid.cfm.udec.cl
² Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502, Japan
³ Department of Astronomy, Kyoto University, Sakyou-ku, Kyoto 606-8502, Japan
⁴ Hida Observatory, Kyoto University, Kamitakara, Gifu 506-1314, Japan
⁵ 19 Greenland Drive, Drouin 3818, Victoria, Australia
⁶ Variable Star Observers League in Japan (VSOLJ), 1-401-810 Azuma, Tsukuba 305-0031, Japan
⁷ RMB 2493, Ellinbank 3820, Australia
⁸ Department of Biosphere-Geosphere Systems, Faculty of Informatics, Okayama University of Science, Ridaicho 1-1, Okayama 700-0005, Japan
⁹ Barfold Observatory, Mia Mia, Victoria, Australia
¹⁰ 295 Camberwarra Drive, Craigie 6025, Western Autralia

Received: 14 September 2004
Accepted: 1 November 2004

Abstract

We report optical photometric observations of four superoutbursts of the short-period dwarf nova TV Crv. This object experiences two types of superoutbursts; one with a precursor and the other without. The superhump period and period excess of TV Crv are accurately determined to be  d and , respectively. This large excess implies a relatively large mass ratio of the binary components (), though it has a short orbital period. The two types of superoutbursts can be explained by the thermal-tidal instability model for systems having large mass ratios. Our observations reveal that superhump period derivatives are variable in distinct superoutbursts. The variation is apparently related to the presence or absence of a precursor. We propose that the superhump period derivative depends on the maximum disk radius during outbursts. We investigate the relationship of the type of superoutbursts and the superhump period derivative for known sources. In the case of superoutbursts without a precursor, superhump period derivatives tend to be larger than those in precursor-main type superoutbursts, which is consistent with our scenario.