Orion Trapezium-A View into the Astrophysics of Young Stars with the ROSAT PSPC
Abstract
A ROSAT-PSPC image, a 10 ks exposure centered on the Orion Trapezium region, has been taken. Apparently all of the diffuse X-ray component, which was suspected to surround the Trapezium based on an EINSTEIN image, could be resolved into point sources. Due to the high surface density of bright sources (about 1.4 per square arcmin) we developed a special methodology in order to derive source parameters. We obtained a list of 172 sources inside the so-called inner ring of the ROSAT FOV, to a count rate of about 2.5×10-3. The principal findings are: (1) The strongest source in the field is (expectedly) θ1 Ori C. Since its unexpectedly hard spectrum cannot be explained by interstellar extinction, it is necessary to postulate circumstellar absorption, possibly originating from a special Helium shell inside the stellar wind as predicted by Kudritzki et al. 1992. (2) The majority of the sources can be identified with pre-main sequence stars of the Orion Id/Ic cluster. (3) The physical features of the bright x-ray sources for which spectral information could be derived show a strongly correlated bimodal distribution, which is equally strongly correlated to the distribution in rotational periods (where this information is available). One can conclude, that one group needs an additional amount of circumstellar absorbing material and has a higher plasma temperature. We propose, that these stars belong to the subgroup d of the Orion OB1 association.
- Publication:
-
The Soft X-ray Cosmos
- Pub Date:
- 1994
- DOI:
- 10.1063/1.46738
- Bibcode:
- 1994AIPC..313..275G
- Keywords:
-
- 98.20.Af;
- 95.85.Nv;
- 98.70.Qy;
- Associations of stars in the Milky Way;
- X-ray;
- X-ray sources;
- X-ray bursts