X-ray and UV emission of the ultrashort-period, low-mass eclipsing binary system BX Trianguli

Abstract

Context. Close binary systems provide an excellent tool to determine stellar parameters such as radii and masses with a high degree of precision. Due to the high rotational velocities, most of these systems exhibit strong signs of magnetic activity, which has been postulated to be the underlying reason for radius inflation in many of the components. Aims. We aim to extend the sample of low-mass binary systems with well-known X-ray properties. Methods. For this, we analyze data from a singular XMM-Newton pointing of the close, low-mass eclipsing binary system BX Tri. The UV light curve is modeled with the eclipsing binary modeling tool phoebe and data acquired with the EPIC cameras is analyzed to search for hints of orbital modulation. Results. We find clear evidence of orbital modulation in the UV light curve and show that phoebe is fully capable of modeling data within this wavelength range. Comparison to a theoretical flux prediction based on phoenix models shows that the majority of UV emission is of photospheric origin. While the X-ray light curve does exhibit strong variations, the signal-to-noise ratio of the observation is insufficient for a clear detection of signs of orbital modulation. There is evidence of a Neupert-like correlation between UV and X-ray data.

X-Ray and Ultraviolet Flares on AT Microscopii Observed by AstroSat

“…Multiwavelength observations (including the soft X-ray and UV spectral ranges) of AT Mic and other active red dwarfs were performed earlier with the XMM-Newton observatory (e.g., Mitra-Kraev et al 2005;Tsang et al 2012;Perdelwitz et al 2018). In comparison with the XMM-Newton European Photon Imaging Camera (EPIC) (Strüder et al 2001;Turner et al 2001), the AstroSat SXT has a lower sensitivity to soft X-rays, which requires longer accumulation times or time bins to obtain a reliable signal from the same source.…”