XMM-Newton study of the Serpens star-forming region

Abstract

We analyze a XMM-Newton X-ray observation of the Serpens dark cloud with a total MOS-equivalent exposure time of 57 ksec. We find 45 individual X-ray sources. None of the class 0 protostars, only one of the class I protostars, and two of the flat-spectrum objects in the region are detected in X-rays. The optically invisible flat-spectrum source EC 95, a very young intermediate mass object, is the strongest X-ray source in the Serpens cloud. The analysis of its X-ray spectrum shows that the hydrogen column density towards EC 95 is considerably lower than expected from the extinction determined from near-IR spectroscopy and photometry. Possible reasons for this inconsistency are discussed.