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Astron. Astrophys. 325, 1001-1012 (1997)

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The X-ray view of the central part of IC 1396

N.S. Schulz 1, 2, T.W. Berghöfer 2 and H. Zinnecker 3

1  Massachusetts Institute of Technology, Cambridge MA 02139, USA
2  Max-Planck-Institut für extraterrestrische Physik, D-85740 Garching bei München, Germany
3  Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany

Received 9 August 1996 / Accepted 14 January 1997

Abstract

The galactic HII region IC 1396 contains one of the youngest known open star clusters Trumpler 37, Tr 37. Its very core hosts the multiple O-star system HD 206267, which in many respects is similar to the Orion Trapezium. So far X-ray emission has been observed only from HD 206267 with the Einstein observatory. Soft X-ray observations with the ROSAT PSPC revealed X-ray emission from an area of 30' radius around the center of globule IC 1396A, which was resolved into 85 discrete sources. Some of the emission still remains unresolved. Most of the detected X-ray sources, except HD 206267, are very weak, which causes the measured luminosity function to be cut off at log [FORMULA] (erg s-1). X-ray sources are located not only in Tr 37 but are also scattered around the molecular globule IC 1396A. From the distribution of sources, their apparently hard spectra, and a steep luminosity function we argue that this sample contains a large number of previously unknown low-mass PMS stars. The X-ray source centered on HD 206267 appeared extended indicating a multiple source system at the very center of Tr 37. The total X-ray luminosity of the trapezium HD 206267 does compare with the X-ray luminosity of single O-type stars. We set an upper limit of log([FORMULA]) to -6.90 and briefly discuss this result in the context of colliding and eclipsing wind models in early type binaries.

Key words: X-rays: stars – stars: formation – stars: early-type – stars: pre-main sequence

Send offprint requests to: N.S. Schulz, nss@space.mit.edu

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© European Southern Observatory (ESO) 1997

Online publication: April 28, 1998

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