Pre-main-sequence population in NGC 1893 region: X-ray properties

Abstract

Continuing the attempt to understand the properties of the stellar content in the young cluster NGC 1893 we have carried out a comprehensive multi-wavelength study of the region. The present study focuses on the X-ray properties of T-Tauri Stars (TTSs) in the NGC 1893 region. We found a correlation between the X-ray luminosity, Lx , and the stellar mass (in the range 0.2–2.0 Mꙩ ) of TTSs in the NGC 1893 region, similar to those reported in some other young clusters, however the value of the power-law slope obtained in the present study (~0.9) for NGC 1893 is smaller than those (~1.4–3.6) reported in the case of TMC, ONC, IC 348 and Chameleon star forming regions. However, the slope in the case of Class III sources (Weak line TTSs) is found to be comparable to that reported in the case of NGC 6611 (~1.1). It is found that the presence of circumstellar disks has no influence on the X-ray emission. The X-ray luminosity for both CTTSs and WTTSs is found to decrease systematically with age (in the range ~0.4–5 Myr). The decrease of the X-ray luminosity of TTSs (slope ~-0.6) in the case of NGC 1893 seems to be faster than observed in the case of other star-forming regions (slope -0.2 to -0.5). There is indication that the sources having relatively large NIR excess have relatively lower Lx values. TTSs in NGC 1893 do not follow the well established X-ray activity – rotation relation as in the case of main-sequence stars.