X-Ray Flares from a Late B-Type Star, HD 38563S, in NGC 2068 Observed with Chandra X-Ray Observatory

Abstract

A report is made on the Chandra archival data analysis of NGC 2068, which is one of the nearest ($\sim 400 \,\mathrm{pc}$) and X-ray active star-forming regions, with an estimated age of $10^{5-6} \,\mathrm{yr}$. The observation was made for 100 ks. Using the wavdetect tool, 152 X-ray sources were detected, of which 52 had counterparts in the 2MASS survey. One of the brightest X-ray sources is apparently identified with a $V = 10.42$ late B-type main-sequence star, HD 38563S. During the observation, it exhibited two X-ray flares, with the 0.5–8.0 keV luminosity reaching $\sim 10^{31.6} \,\mathrm{erg} \,\mathrm{s}^{-1}$. The flare X-rays evolved on a time scale of several hours, and showed a thermal spectrum of temperature of $\sim 5 \,\mathrm{keV}$. These results suggests that this star forms an active binary, although contamination by a T Tauri star also remains an alternative possibility.