Discovery of periodic dips in the brightest hard X-ray source of M31 with EXTraS

摘要: We performed a search for eclipsing and dipping sources in the archive of EXTraS project - systematic characterization temporal behaviour XMM-Newton point sources. discovered dips X-ray light curve 3XMM J004232.1+411314, which has been recently associated with hard source dominating emission M31. A analysis observations revealed 13 40 (total exposure time $\sim$0.8 Ms). Among them, four show two dips, separated by $\sim$4.01 hr. Dip depths durations are variable. The occur only during low-luminosity states (L$_{0.2-12}<1\times10^{38}$ erg s$^{-1}$), while reaches L$_{0.2-12}\sim2.8\times10^{38}$ s$^{-1}$. propose this system to be new Low-Mass Binary M31 seen at high inclination (60$^{\circ}$-80$^{\circ}$), observed periodicity is orbital period system. blue HST within Chandra error circle most likely optical counterpart accretion disk. luminosity makes it luminous dipper known date.