A multicolor photometric study of the neglected eclipsing binary FT Ursae Majoris

The multicolor photometric observations of the neglected eclipsing binary FT Ursae Majoris (FT UMa) were obtained in 2010. The 2003 version of the Wilson-Devinney code was used to analyze the light curves in the B, V and R bands simultaneously. Based on the spectroscopic mass ratio q = 0.984 published by Pribulla et al., it is found that FT UMa is an evolved contact binary with a contact degree of 15.3%. The low amplitude of light variations, ～ 0.15 mag, arises mainly from a moderately low inclination angle...     

An Orbital Period Study of the Contact Binary CK Bootis

1　ＩｎｔｒｏｄｕｃｔｉｏｎＣＫＢｏｏｗａｓｄｉｓｃｏｖｅｒｅｄａｎｄｃｏｎｆｉｒｍｅｄｔｏｂｅａｃｏｎｔａｃｔｂｉｎａｒｙｂｙＢｏｎｄ ( 1 975 ) .Ａｆｔｅｒｉｔｓｄｉｓ ｃｏｖｅｒｙｔｈｅｓｙｓｔｅｍｉｓｏｂｓｅｒｖｅｄｆｒｅｑｕｅｎｔｌｙ (ｅ .ｇ .Ａｓｌａｎ ,1 978;ＡｓｌａｎａｎｄＤｅｒｍａｎ ,1 986 :ＰａｊｄｏｓｚａｎｄＺｏｌａ ,1 987;Ｋｒｚｅｓｉｎｓｋｉｅｔａｌ.,1 991ａｎｄＪｉａｅｔａｌ.,1 992 ) .Ａｓｒｅｐｏｒｔｅｄｂｙｓｅｖｅｒａｌａｕｔｈｏｒｓ,ｔｈｅｌｉｇｈｔｃｕｒｖｅｏｆｔｈｅｓｙ…     

Bm Cas: A Long-Period Eclipsing Binary with A Supergiant and a Common Envelope

New results of UBVR photometry of the long-period eclipsing binary BM Cas obtained at Tallinn Observatory between 1979 and 1996 are discussed.     

A likely candidate of type Ia supernova progenitors: the X-ray pulsating companion of the hot subdwarf HD 49798

HD49798 is a hydrogen depleted subdwarf 06 star and has an X-ray pulsating companion(RX J0648.0-4418).The X-ray pulsating companion is a massive white dwarf.Employing Eggleton's stellar evolution code with the optically thick wind assumption,we find that the hot subdwarf HD 49798 and its X-ray pulsating companion could produce a type Ia supernova(SN Ia)in future evolution.This implies that the binary system is a likely candidate of an SN Ia progenitor.We also discuss the possibilities of some other WD+He star systems(e.g.V445 Pup and KPD1930+2752)for producing SNe Ia.     

A Photometric Study of the W UMa-type Eclipsing Binary System GSC 0445-1993

Several new light minimum times for the eclipsing binary GSC 0445-1993 have been determined from the observations by Koppelman et al. and the orbital period of this system was revised. A photometric analysis was carried out using the 2003 version of the Wilson-Devinney code. The results reveal that GSC 0445-1993 is a W-type eclipsing binary with a mass ratio of q = 0.323(±0.002) and an over-contact degree of f = 22.8%(±4.2%). A small temperature difference between the components of △T = 135 K and an orbital inclination of i = 65.7°(±0.3°) were obtained. The asymmetry of its light curve (i.e., the O'Connell effect) for this binary star is explained by the presence of a dark spot on the more massive component.     

Magnetic interaction in ultra-compact binary systems

This article reviews the current works on ultra-compact double-degenerate binaries in the presence of magnetic interaction, in particular, unipolar induction. The orbital dynamics and evolution of compact white-dwarf pairs are discussed in detail. Models and predictions of electron cyclotron masers from unipolar-inductor compact binaries and unipolar-inductor white-dwarf planetary systems are presented. Einstein-Laub effects in compact binaries are briefly discussed.