Unveiling the Nature of an X-ray flare from 3XMM J014528.9+610729: A candidate spiral galaxy

Abstract

We report an X-ray flare from 3XMM J014528.9+610729, serendipitously detected during the observation of the open star cluster NGC 663. The colour-colour space technique using optical and infrared data reveals the X-ray source as a candidate spiral galaxy. The flare shows fast rise and exponential decay shape with a ratio of the peak and the quiescent count rates of $\sim$60 and duration of $\sim$5.4 ks. The spectrum during the flaring state is well fitted with a combination of thermal ({\sc Apec}) model with a plasma temperature of $\rm{1.3\pm0.1}$ keV and non-thermal ({\sc Power-law}) model with power-law index of $\rm{1.9\pm0.2}$. However, no firm conclusion can be made for the spectrum during the quiescent state. The temporal behavior, plasma temperature and spectral evolution during flare suggest that the flare from 3XMM J014528.9+610729 can not be associated with tidal disruption events.

14 pages; 6 figures; 3 figures in supplementary material; Accepted for publication in MNRAS