A study of period changes and light curve analysis of SW Lac


S. Zahabi1, A. Karbassi1,2, A. Hasanzadeh1

1International Occultation Timing Association-Middle East Section (IOTA-ME), Iran; info@iota-me.com

2ISA Observatory, Karaj, Iran


The CCD photometry of the overcontact eclipsing binary SW Lac was carried out by using an SBIG 11000 CCD camera and a 16-inch LX200 Meade Schmidt-Cassegrain telescope. New light curve and times of minima were calculated. Using the evaluated data together with 130 other times of minima published during last 9 years, a new ephemeris was produced. The O-C diagram has been plotted based on the photoelectric and CCD minima times since 1951. The calculation results showed the period to be decreasing at a rate of 1.6086 × 10-2(sec/year). Since this binary is considered to be an overcontact binary system, we could assume a mass transfer rate of . The periodic shape of O-C curve was attributed to the presence of the third and fourth bodies with periods of P3 = 21.7 years and P4 = 44.8 years, respectively with corresponding masses of m3 = 0.76and m4= 0.09. Finally, Binary Maker3 and PHOEBE softwares were used for light curve analysis and calculation of systems parameters.

Keywords: Stars: binaries: Eclipsing, SW Lac

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