K2 study of the Magnetic Precataclysmic Variable V1082 Sagittarius

Abstract

We present a long-term light curve of the precataclysmic variable (CV) V1082 Sgr obtained by the K2-mission over the course of 81 days. We analyze the entire complex light curve as well as explore several sections in detail with a sliding periodogram. The long dataset allows the first detection of the orbital period in the light curve, as well as the confirmation of cyclical variability on a longer timescale of about a month. A portion of the light curve in deep minimum reveals a clean, near-sinusoidal variability attributed to the rotation of the spotted surface of the donor star. We model that portion of the light curve assuming that the donor star grossly under-fills its Roche lobe, has cool spots similar to a chromospherically active, slightly evolved early K-star, and might be irradiated by the X-ray beam from the magnetically accreting white dwarf. The fast variability of the object in the active phases resembles the light curves of magnetic CVs (polars).

arXiv comment14 pages, 9 figures, accepted for publication in ApJ

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• Quest for the Donor Star in the Magnetic Precataclysmic Variable V1082 Sgr
• V1082-Sgr: A magnetic cataclysmic variable with a lobe-filling companion star
• Revisiting the extremely long-period cataclysmic variables V479 Andromedae and V1082 Sagitarii