Catalog Service:
ROSAT Survey of the Orion Nebula

Description

This catalog presents some of the results from 3 deep ROSAT High Resolution Imager (HRI) observations of the Orion Nebula star-forming region. The fields covered by the X-ray images contain over 1500 catalogued stars in a roughly 0.8 square degree region centered on the Trapezium. In all, 389 distinct X-ray sources were detected, at least two-thirds of which were associated with a single proper-motion cluster member. X-ray emission was detected from stars of all spectral types, from the massive O- and B-type components of the Trapezium to the coolest, low-mass pre-main-sequence (PMS) stars. In the research paper in which these data were presented (Gagne et al. 1995), the authors focussed primarily on X-ray emission from the late-type PMS stars. Of the ~100 late-type cluster members with measured spectral types, approximately three-fourths were detected; the authors derived X-ray luminosity upper limits for the remaining stars. They found that coronal X-ray emission appeared to turn on at around a spectral type of F6, with the upper envelope of activity increasing with decreasing effective temperature. The current database is a concatenation of Tables 2 and 3 from Gagne et al. (1995) which list the 389 distinct X-ray sources and their candidate optical counterparts. A detection criterion of 3 sigma was used, i.e., a sigal-to-noise ratio criterion of 3. 324 of the X-ray sources have a single candidate optical counterpart, 50 of the X-ray sources (listed in Table 3 of the original paper) have multiple candidates for the optical counterparts, and the remainder have no optical counterparts. Notice that Table 6 of Gagne et al. (1995) which presents a compilation of optical and X-ray data for a sub-group of the Orion stars for which data on the spectral types and the spectroscopic rotational velocities or the photometric rotational periods are available is not part of this database. This database was created at the HEASARC in December 1997 based on a computer-readable version of Tables 2 and 3 of Gagne et al. (1995) that was obtained from the CDS (their catalog J/ApJ/445/280). This is a service provided by NASA HEASARC .