Astronomy and Astrophysics, volume 325, 1001-1012 (1997/9-3)
The X-ray view of the central part of IC 1396.
SCHULZ N.S., BERGHOEFER T.W. and ZINNECKER H.
Abstract (from CDS):
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 Lx<30.3(erg/s). 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(Lx/Lbol) to -6.90 and briefly discuss this result in the context of colliding and eclipsing wind models in early type binaries.