First photometric study of W UMa binary star LU Lac
Introduction
LU Lac is a very short period binary system with an orbital period of 0.29880110 days (Kreiner, 2004). According to the General Catalogue of Variable Stars (Samus et al., 2007-2012), the apparent magnitude of LU Lac is B = 14.6–15.45 mag. Miller and Wachmann (1971) discovered the light variations of LU Lac and pointed out it is a W UMa type eclipsing binary with a period shorter than 0.3 days. The first light ephemeris was given by them. LU Lac was included in Name-list of variable stars by Kukarkin et al. (1972). After that, Hoffmann (1981) observed it using five nights between different seasons, the B photoelectric light curve and three times of light minimum were obtained. Since then, some times of light minimum are available. Up to now, no light-curve solution has been published; therefore, LU Lac was put into our observational list. In this paper, the first complete BVRI light curves of LU Lac are presented. Then, the orbital period changes are analyzed and a photometric solution is obtained. Finally, the triplicity is discussed.
Section snippets
New CCD photometric observations
The first multi-color CCD photometric light curves of LU Lac were observed on 2012 August 22 with the PI TE CCD photometric system attached to the 85 cm telescope at the Xinglong Station of National Astronomical Observatories of China (NAOC). The effective field of view is . The filter system is a standard Johnson-Cousins-Bessel multicolor CCD photometric system mounted on the primary focus (Zhou et al., 2009). The exposure time for each image was set as 30 s for the B band, 20
Orbital period changes
LU Lac has been neglected for period study. By using our data together with those collected from the literature (e.g., from gateway, http://var.astro.cz/ocgate/), the values with respect to the following linear ephemeris were computed and the corresponding curve is plotted in the upper panel of Fig. 2, with the period given by Kreiner (2004).It is revealed in the Fig. 2 that the diagram of LU Lac is variable as expected. During fit of
Photometric solutions
Using the 2003 version of the W-D program (Wilson and Devinney, 1971, Wilson, 1990, Wilson, 1994, Wilson, 2003), photometric model fitting to the BVRI light curves of LU Lac was simultaneously done. According to the value of 1, the temperature for Star 1 was fixed to K (Cox, 2000). Gravity-darkening coefficient of (Lucy, 1976), and the bolometric albedo of (Ruciński, 1969), were used because of
Discussions and conclusions
Based on our one-night BVRI light curves, the first photometric solutions for LU Lac are derived in the previous section. It is suggested that LU Lac is a marginal contact W-type W UMa system with a degree of contact of , a mass ratio of . The effective temperature of the more massive component is lower than of the less massive one. The high orbital inclination of 82.20 () indicates that the system is a total-eclipsing binary. Therefore, the derived photometric solutions
Acknowledgments
This work is partly supported by the Chinese Natural Science Foundation (Nos. 11133007, 11325315), West Light Foundation of the Chinese Academy of Sciences, and Key Laboratory Foundation of Chinese Academy of Sciences).
References (26)
- et al.
NewA
(2009) - et al.
NewA
(2006) ApJ
(1992)Allens Astrophysical Quantities
(2000)Space Sci. Rev.
(1989)IBVS
(1981)AcA
(2004)- et al.
IBVS
(1972) MNRAS
(2006)- et al.
MNRAS
(2010)
AJ
ApJ
RA
Cited by (11)
Orbital period cut-off of W UMa-type contact binaries
2020, Monthly Notices of the Royal Astronomical SocietyNew multi-color photometric investigations of solar-like contact binary V680 per
2020, Research in Astronomy and AstrophysicsThe contact binary V344 Lacertae: is it a triple system?
2020, Astrophysics and Space ScienceSpectroscopic and photometric studies of four W UMa-type eclipsing binaries – II
2020, Monthly Notices of the Royal Astronomical SocietyV1005 Her: A solar-type shallow-contact binary in a triply fossil system
2019, Monthly Notices of the Royal Astronomical Society