Characterization of 9380 contact binaries from the CRTS Variable Sources Catalogue

Abstract

We construct a sample of 9380 contact binaries (W UMa systems) by using the Catalina Real-Time Transient Survey Variables Sources Catalogue. By measuring brightness change rates, light-curve statistics, and temperatures for this sample, we improve the understanding of contact binary light-curve characteristics, and luminosity variability on decadal time-scales. We show that binaries with convective outer envelopes have a different distribution of lightcurve amplitudes and magnitude differences between eclipse minima than binaries with radiative outer envelopes. We find that more than 2000 binaries exhibit a linear change in mean brightness over the 8-yr timespan of observations with at least 3σ significance. We note that 25.9 per cent of binaries with convective outer envelopes exhibit a significant change in brightness, while only 10.5 per cent of radiative binaries exhibit a significant change in brightness. In 205 binaries (2.2 per cent), we find that a sinusoid model better describes the luminosity trend within the 8-yr observation timespan. For these binaries, we report the amplitudes and periods (as estimated using observed half-periods) of this sinusoidal brightness variation and discuss possible mechanisms driving the variation.

Absolute-magnitude Calibration for W UMa-type Systems Based on Gaia Data*

“…The linear fits, in terms of χ 2 values evaluated using observational σ(M V ) errors, appear to worsen as one goes down the period sequence. Keeping in mind the small number of binaries at both ends, we note that we achieved the best linear fit for the systems with P > 0.575 d and the worst linear fit for the systems with P < 0.275 d. This may be related to the recently documented slow trends in mean luminosity (Rucinski & Paczynski 2002) observed in about one third of known EW binaries (Marsh et al 2017). Such trends, which can reach about 0.1 mag, take several years to occur and may possibly be explained by magnetic phenomena.…”

“…In addition, a systematic photometric survey by the Tycho-2 project (Høg et al 2000) provided uniformly calibrated B −V color indices for stars down to V ≃ 10. Temporal variability monitoring and planetary transit surveys such as Super-WASP (Norton et al 2011;Lohr et al 2013), OGLE (Soszyński et al 2015, and CRTS (Marsh et al 2017) 2 have obtained data of high photometric accuracy, but they are typically over smaller sections of the sky than ASAS and at fainter magnitudes than the range relevant for this study (the Gaia targets are all brighter than V ≃ 12, see below). It should be noted that the discoveries of low brightness systems are particularly important in determining the spatial density of the intrinsically faintest systems close to the sharp period cut-off at about 0.2 d (see Rucinski (2007) and references therein).…”

“…Finally, in evaluating the V max values, we entirely neglected slow trends in mean luminosity (Rucinski & Paczynski 2002) observed in about one third of the EW binaries (Marsh et al 2017). These very recently discovered trends will no doubt be studied in the coming years, but at this moment we again had to assume that they will simply increase the σ(M V ) errors.…”

The Catalina Surveys Southern periodic variable star catalogue

“…This is particularly the case when their light curves have a low S/N. Therefore, unlike DR14, we did not attempt to divide the contact (EW) and semidetached binaries (EB) parametric fits to all of the eclipsing binaries light curves, such as performed by Lee (2015) and Marsh et al (2016) on DR14 binaries, should provide a more objective and quantitative separation for all eclipsing binary classes.…”

Pulsating star products from the Palomar Transient Factory: Ultra-long period Cepheids in M31 and RR Lyrae in Kepler field

“…The PTF/iPTF surveys employed a mixed cadence for their time series observations, ranging from few minutes to few days, that depends on various experiments. Besides the studies of transients -the main science goals of PTF/iPTF -, the time series PTF/iPTF data has also been used in the variable stars research with noticeable examples presented in [3][4][5][6][7][8][9][10][11][12]. In this proceedings contribution, I present another two examples of using the PTF/iPTF data in pulsating variable stars works: the study of ultra-long period Cepheids (ULPC) and RR Lyrae.…”