The orbital period study and photometric analysis of XY Ursae Majoris

Abstract

Abstract. Photoelectric observations of the eclipsing binary XY UMa have been carried out in B and V colours at the Ege University Observatory. Combining these newly obtained data with the previous ones available in the literature, the problem pertaining to the orbital period of the system has been investigated through a detailed description of the O−C diagram. The sinusoidal and secular changes have been found. Such variations of the orbital period have been examined in terms of three plausible mechanisms, namely (i) a light-time effect due to a third body, (ii) the orbital period modulation due to magnetic activity cycle of a component star, and (iii) a mass loss case in which the ejected material escapes out from the binary system. A combination of a magnetic activity cycle mechanism and a mass loss case is found to reproduce satisfactorily the period changes. Further, the observed photoelectric light curves of the system have been analyzed with the Wilson-Devinney approach. This analysis shows that the asymmetries of the light curves of XY UMa can be interpreted in terms of cool star-spot covering 7% of the stellar photosphere of the primary component of this binary. The system is found to be a β Lyrae type detached binary. The absolute elements of the system are also deduced.

An active binary XY UMa revisited

“…Erdem & Güdür (1998) accepted this possibility as a suitable explanation for the long-term period and brightness changes of the system. Lanza & Rodonò (1999) included XY UMa to their list of 46 close binaries displaying magnetic modulation of the orbital period.…”

“…However, this did not explain the overall acitivity of the system. The (O-C) diagram exhibits both erratic period changes due to the LC asymmetries and long-term period changes interpreted either by the light-time effect (LITE) caused by an another body in the system (Chochol et al 1998, hereafter C&P) or Applegate's mechanism (e.g., Erdem & Güdür 1998). However, the latter possibility was not tested observationally.…”

A Photometric Study of the Short-Period Close Binary V432 Persei and Its Implications for the Star's Evolution

“…One such example is XY UMa: Chochol et al (1998) interpreted the sinusoidal behavior of the O-C residuals of the system as a light-time effect due to a third body, while Erdem & Güdür (1998) cited a magnetic-activity cycle. In another interesting case, the period change of the RS CVntype binary CG Cyg was announced to be due to a magnetic cycle by Hall (1991), but Afşar et al (2004) claimed that two periodicities of 50.7 and 22.5 yr exist in the O-C residuals and indicate, respectively, a light-time effect due to a third body of 0.9 M and a magnetic cycle with a period similar to that of the luminosity variation.…”

A spectroscopic study of the eclipsing binaries SV Camelopardalis and XY Ursae Majoris

“…Since then it has been observed in the optical (Greyer 1980;Zeilik et al 1982;Jassur 1986;Heckert & Zeilik 1988;Qisheng et al 1989;Zeilik et al 1988;Hilditch & Bell 1994;Jeffries et al 1995;Collier Cameron & Hilditch 1997;Erdem & Güdür 1998), the radio (Drake et al 1986;Morris & Mutel 1988), the infrared (Arévalo & Lázaro 1990;Mitrou et al 1996), the ultraviolet (Greyer & Hoffmann 1981) and the X-ray (Bedford & Greyer 1986;Bedford et al 1990;Dempsey et al 1993).…”