Thomas Preibisch

XMM-Newton study of the star forming region NGC 1333

Astronomy and Astrophysics, 401, 543-555 (2003)

We analyze the data of a deep XMM-Newton X-ray imaging observation of the NGC 1333 star forming region. The observation covered a period of about 14 hours and has a total MOS-equivalent exposure time of 235 ksec. In addition to 46 bright X-ray sources revealed by source detection routines, we find weak X-ray emission at the positions of 40 X-ray sources detected originally in a recent Chandra observation of NGC 1333. The XMM-Newton countrates of most sources agree well with their countrates in the Chandra data; about 80\% of the sources vary by a factor of less than 3 between the two X-ray observations which are separated by 18 month. The X-ray lightcurves of several sources reveal large flares with parameters typical for X-ray active young stellar objects. We also construct and analyze the X-ray spectra of the stronger sources and derive plasma temperatures between ~0.7 keV and ~3 keV for the T Tauri stars in NGC 1333, and higher temperatures up to ~12 keV for flaring sources and deeply embedded young stellar objects. We consider in detail the X-ray properties of the optically invisible infrared source SVS 16, which showed a large X-ray flare during our observation. Its X-ray spectrum confirms that the hydrogen column density towards SVS 16 is much lower than expected from the extinction determined from near-IR spectroscopy and photometry. The reason for this inconsistency remains unclear. Finally, we search for, but do not detect any X-ray emission from HH 7-11 or one of the other Herbig-Haro objects in NGC 1333.

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