Abstract
We present a new eclipsing post-common-envelope binary, identified inside the Kepler field prior to the launch of the spacecraft. Multifilter photometry and radial velocity data are analysed with an eclipsing-binary modelling code to determine the physical parameters of the binary. Spectra of the system within the primary eclipse and uneclipsed allow us to identify the spectral characteristics of the primary and secondary components. The primary component of the binary is a DA white dwarf, with M? 0.61 M?, log g? 7.95 and Teff? 20 500 K. The detection of two flares and the emission signatures displayed in the spectra show that the secondary component of the system is chromospherically active and is classified as an active M4 main- sequence star. Its mass, radius and temperature are estimated as M similar or equal to 0.39M(circle dot), R similar or equal to 0.37 R-circle dot and T-eff similar or equal to 3200 K. The ephemeris of the system is HJD = 245 3590.436 126( 10) + 0.350 468 722(6) x E. This binary is a newpost-common-envelope binary (PCEB), with physical parameters within the range found in other systems of this small group of evolved binaries.
Highlights
Short-period binaries composed of a white dwarf and a mainsequence star belong to the group known as post-common-envelope binaries (PCEB)
In order to determine the spectral type of the secondary star, we used the spectra collected with the Telescopio Nazionale Galileo Galilei (TNG)-DOLORES spectrograph on-eclipse and the 2007 William Herschel Telescope (WHT)–ISIS spectrum in the red range taken 69 per cent off-eclipse, where the contribution of the white dwarf is low
The newly discovered variable USNO-B1.0 1377−0415424, 2MASS 19423720+4745486 and KIC–10544976 is a postcommon-envelope eclipsing binary system, which seems to be composed of a primary DA white dwarf and an active M4V secondary star
Summary
Short-period binaries composed of a white dwarf and a mainsequence star belong to the group known as post-common-envelope binaries (PCEB). The precursors of these systems are considered to be wide-separation binaries, where the more massive component evolves as a red giant and reaches the secondary, leading to a common envelope phase. C 2012 The Authors Monthly Notices of the Royal Astronomical Society C 2012 RAS the physical parameters of the components: radii, masses and effective temperatures. This is one of the very few cases in which the mass and radii of the white dwarfs can be measured independently if precise enough measurements are performed The new system is composed of a white dwarf ( considered as the primary component throughout the paper) and a main-sequence M star (the secondary component)
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