HRI/Orion ivo://nasa.heasarc/orionxray NASA/GSFC HEASARC Gagne, Caillault, Stauffer 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source 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 . 1995ApJ...445..280G https://heasarc.gsfc.nasa.gov/W3Browse/all/orionxray.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=orionxray& GET text/xml 180 99999 true 83.665 -5.668611 0.0166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=orionxray GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_orionxray&Action=More+Options&Action=Parameter+Search&ConeAdd=1 STAR CATALOG 0.0166666666666667 X-ray public orionxray ROSAT Survey of the Orion Nebula name Designation derived from Id number meta.id;meta.main char nullable flag_mult_id Multiple Optical Counterparts char nullable ra Right Ascension in default equinox degree pos.eq.ra;meta.main double nullable dec Declination degree pos.eq.dec;meta.main double nullable count_rate Corrected ROSAT HRI Count Rate ct/s phot.count;em.X-ray double nullable count_rate_error RMS uncertainty on Count Rate ct/s stat.error;phot.count;em.X-ray double nullable "__x_ra_dec" System unit vector column double nullable "__y_ra_dec" System unit vector column double nullable "__z_ra_dec" System unit vector column double nullable "__row" System index column char nullable dec_offset_1 Offset Declination arcsec short nullable dec_offset_3 Offset Declination Second Candidate arcsec short nullable variable_name_1 Variable Optical Counterpart Candidate char nullable dec_offset_2 Offset Declination First Candidate arcsec short nullable mem_prob_2 Membership Probability First Candidate short nullable jones_name_1 Jones & Walker 1988 Optical Counterpart char nullable ra_offset_3 Offset Right Ascension Second Candidate arcsec short nullable lii Galactic Longitude degree pos.galactic.lon double nullable bii Galactic Latitude degree pos.galactic.lat double nullable ra_offset_1 Offset Right Ascension arcsec short nullable ra_offset_2 Offset Right Ascension First Candidate arcsec short nullable jones_name_2 Jones & Walker 1988 Name First Candidate char nullable jones_name_3 Jones & Walker 1988 Name Second Candidate char nullable parenago_name_2 Parenago Designation First Candidate char nullable parenago_name_1 Parenago 1954 Optical Counterpart char nullable mem_prob_3 Membership Probability Second Candidate short nullable mem_prob_1 Membership Probability short nullable xray_number X-ray Number short nullable parenago_name_3 Parenago Designation Second Candidate char nullable