OMEGCENXMM - Omega Centauri XMM-Newton X-Ray Point Source Catalog

Overview

Omega Centauri (NGC 5139) is one of the best studied objects in our galaxy. It is the most massive globular cluster (5.1 x 10⁶ solar masses), and is characterized by large core and half mass radii (154.88 and 250.8 arcseconds, respectively (Harris 1996, AJ, 112, 1487). The authors observed Omega Cen with XMM-Newton on August 13th, 2001. The observation lasted 37 ks and was performed with the medium filter. The authors detected 11 and 27 faint X-ray sources in the core and half mass radii, respectively, searching down to a luminosity of 1.3 x 10³¹ ergs s^-1 in the 0.5 - 5 keV range (for an assumed distance to Omega Cen of 5.3 kpc). Most sources have bolometric X-ray luminosities between ~ 10³¹ - 10³² ergs s^-1. The bulk of sources are hard and spectrally similar to CVs. The lack of soft faint sources might be related to the absence of millisecond pulsars in the cluster. The XMM-Newton observations reveal the presence of an excess of sources well outside the core of the cluster where several RS CVn binaries have already been found. The authors also analyzed a publicly available Chandra ACIS-I observation performed on January 24 - 25th, 2000, to improve the XMM-Newton source positions and to search for source intensity variations between the two data sets. 63 XMM-Newton sources have a Chandra counterpart, and 15 sources within the half-mass radius have shown time variability. Overall, the general properties of the faint X-ray sources in omega Cen suggest that they are predominantly CVs and active binaries (RS CVn or BY Dra). This table lists all 146 X-ray sources detected in the XMM-Newton observation above a maximum likelihood threshold in the 0.5 - 5 keV band of 12, including the 27 sources within the half-mass radius (listed in Table 1 of the reference paper), and the 119 sources outside the half-mass radius (listed in Table 2 of the reference paper). About 9 of the 27 sources within the half-mass radius are expected to be background sources, as are ~ 65 of the sources within 12.5 arcminutes of the cluster center, i.e., a significant fraction of the 146 total observed X-ray sources.

For each XMM-Newton source, its position, count rate, correlation with previous X-ray observation, and their associated errors are given. The detailed spectral information given in Table 5 of the reference paper for 17 selected X-ray sources is however not included in this HEASARC table.

Catalog Bibcode

2003A&A...400..521G

References

An XMM-Newton observation of the globular cluster Omega Centauri.
    Gendre B., Barret D., Webb N.A.
   <Astron. Astrophys. 400, 521 (2003)>
   =2003A&A...400..521G

Provenance

This table was created by the HEASARC in May 2007 based on CDS catalog J/A+A/400/521 files table1.dat, table2.dat and table3.dat.

HEASARC Implementation

For this table, the HEASARC has created a flag parameter called hmr_flag which is set to 'Y' if the X-ray source lies within the half-mass radius of the cluster, i.e, within 250.8" of the cluster center, (such sources are listed in Table 1 of the reference paper), or to 'N' if the X-ray source is outside the half-mass radius, (sources listed in Table 2 of the reference paper).

Parameters

Detection_Instrument
The EPIC instrument by which the source was detected. The majority of the correlated sources were detected by the PN camera because it is more sensitive than the MOS cameras. There were however 9 sources missed by the PN, due to CCD gaps, or bad columns, or the smaller field of view of the PN compared to the MOS; these sources are marked by 'MOS', while the remaining 137 sources are marked by 'PN'. To be precise, of the 146 sources detected by the EPIC cameras; 59 were seen only by the PN, 9 were seen by the MOS only (and all of them were seen in MOS 1 and MOS 2), and the remaining 78 were detected in the PN and at least one MOS camera.

Source_Number
A running source number which uniquely identifies the X-ray source.

Name
The name of the X-ray source using the '[GBW2003]' prefix (for Gendre, Barret, Webb, 2003) together with the X-ray source number, as recommended by the CDS Dictionary of Nomenclature of Celestial Objects.

RA
The Right Ascension of the XMM-Newton X-ray source in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.1 seconds of time in the original tables.

Dec
The Declination of the XMM-Newton X-ray source in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.1 arcseconds in the original tables.

LII
The Galactic Longitude of the XMM-Newton X-ray source.

BII
The Galactic Latitude of the XMM-Newton X-ray source.

Error_Radius
The statistical (90% confidence level) positional error of the XMM-Newton X-ray source, in arcseconds.

Count_Rate
The 0.5 - 5.0 keV band count rate of the XMM-Newton X-ray source, in ct/s.

Count_Rate_Error
The statistical error in the 0.5 - 5.0 keV band count rate of the XMM-Newton X-ray source, in ct/s.

MOS1_Detection
This flag is set to 'Y' if the X-ray source was detected by the MOS1.

MOS2_Detection
This flag is set to 'Y' if the X-ray source was detected by the MOS2.

Core_Flag
This flag is set to 'Y' if the X-ray source was detected in the core of the cluster, i.e, within 154.88" of the cluster center.

Hmr_Flag
This flag is set to 'Y' if the X-ray source lies within the half-mass radius of the cluster, i.e, within 250.8" of the cluster center, as listed in Table 1 of the reference paper, or to 'N' if the X-ray source is outside the half-mass radius, as listed in Table 2 of the reference paper. This parameter was created by the HEASARC.

Chandra_RA_J2000
The J2000 Right Ascension of the Chandra X-ray source which lies within the statistical error box of the XMM-Newton X-ray source.

Chandra_Dec_J2000
The J2000 Declination of the Chandra X-ray source which lies within the statistical error box of the XMM-Newton X-ray source

Chandra_RA_J2000_Error
The statistical positional error of the Chandra X-ray source in the J2000 Right Ascension direction.

Chandra_Dec_J2000_Error
The statistical positional error of the Chandra X-ray source in the J2000 Declination direction.

ROSAT_ID
The ROSAT X-ray source counterpart identifier NNa of the XMM-Newton source ([JVH94] NGC 5139 NNa in Simbad), from Johnston et al. (1994, A&A, 289, 763) and/or Verbunt & Johnston (2000, A&A, 358, 910).

Einstein_ID
The Einstein X-ray source counterpart identifier N of the XMM-Newton source ([HG83b] NGC 5139 N), from Hertz and Grindlay (1983, ApJ, 175, 105).

Contact Person

Questions regarding the OMEGCENXMM database table can be addressed to the HEASARC Help Desk.

Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:32:32 EDT