The contact binary system TYC 7275-1968-1 as seen by optical, UV and X-ray observations

Abstract

We present an analysis of publicly available X-ray and optical observations of TYC 7275-1968-1, a contact binary, red nova progenitor candidate. The long optical time series of ASAS-SN, SuperWASP, CRTS, GAIA, ASAS-3, and TESS enabled us to improve its orbital period to 0.3828071 $\pm$ 0.0000026 d. We show the presence of an X-ray and UV source associated with TYC 7275-1968-1 from Neil Gehrels Swift Observatory, that was previously assumed to be the counterpart of CD -36 8436 (V1044 Cen), a symbiotic star located 22 arcsec from the red nova candidate. The X-ray data indicate the presence of a region with a temperature of $kT$ = 0.8$^{+0.9}_{-0.1}$ keV and a luminosity of 1.4$^{+0.1}_{-0.2}$ $\times$ 10$^{31}$ erg s $^{-1}$ in the range 0.3 - 10 keV. The detection of X-rays and modulated UV emission suggests that both components of the binary are chromospherically active.