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M67CXO - M 67 Chandra X-Ray Point Source Catalog

HEASARC
Archive

Overview

The M 67 Chandra X-Ray Point Source Catalog contains the results of a 47 ks Chandra/ACIS observation of the old (4 Gyr) open cluster M67. The authors detected 25 proper-motion cluster members (including ten new sources) and 12 sources (all new) that they suspect to be M 67 members from their locations close to the main sequence (1 < B-V < 1.7). Of the detected members, 23 are binaries. In addition to cluster members, about 100 background sources were detected, many of which were identified with faint objects in the ESO Imaging Survey (EIS, Momany et al. 2001, A&A, 379, 436).

This table summarizes the X-ray properties of the 158 sources which were detected by Chandra in this observation, and also lists the ROSAT (Belloni et al., 1998A&A...335..517B) and optical (candidate) counterparts.


Catalog Bibcode

2004A&A...418..509V

References

A Chandra observation of the old open cluster M67.
    Van Den Berg M., Tagliaferri G., Belloni T., Verbunt F.
   <Astron. Astrophys., 418, 509-523 (2004)>
   =2004A&A...418..509V

Provenance

This table was created by the HEASARC in January 2007 based on CDS table J/A+A/418/509/table1.dat

Parameters

Source_Number
A running source number, labelled as 'CX' for 'Chandra X-ray (source)' in the original published table, in order of decreasing counts (at least for the first 145 sources), i.e., source number 1 has the most counts (892), and source number 145 has only 3 counts.

Name
The X-ray source name based on the '[VTB2004] CX' prefix (for Van den Berg, Tagliaferri, Belloni... 2004, Chandra X-ray) and the source number, as recommended by the CDS Dictionary of Astronomical Nomenclature.

Significance_Flag
An indicator of the significance of the X-ray detection, where 'L' indicates that the source is detected with the significance threshold set to 10^-6 but not with the threshold set to 10^-7. A blank value indicates that that the source was detected using both detection threshold values.

Off_Axis
The angular distance of the X-ray source from the telescope aimpoint of (8 51 23.1, +11 49 32.7, J2000 RA and Dec), in arcminutes.

RA
The Right Ascension of the X-ray source in the selected equinox derived from the image in the total (0.3 - 7 keV) energy band. The RA was given in J2000.0 coordinates and to a precision of 0.001 seconds of time in the original table. The X-ray positions have been corrected to the optical reference frame by matching sources with EIS counterparts, resulting in a final (X-ray - optical) offset correction to the RAs of -0.23" +/- 0.35".

RA_Error
The uncertainty in the Right Ascension of the X-ray source, in seconds of time. The errors in RA and Declination are the 1-sigma 'wavdetect' errors, including the corrections for small count numbers (See Section 2.3 of the paper for more details). These are often much smaller than the uncertainty in the absolute positions, i.e. than the uncertainty in the offset values in RA and Declination which are about 0.3 arcseconds.

Dec
The Declination of the X-ray source in the selected equinox derived from the image in the total (0.3 - 7 keV) energy band. The Declination was given in J2000.0 coordinates and to a precision of 0.01 arcseconds in the original table. The X-ray positions have been corrected to the optical reference frame by matching sources with EIS counterparts, resulting in a final (X-ray - optical) offset correction to the Declinations of -0.20" +/- 0.33".

Dec_Error
The uncertainty in the Declination of the X-ray source, in arcseconds. The errors in RA and Declination are the 1-sigma 'wavdetect' errors, including the corrections for small count numbers (See Section 2.3 of the paper for more details). These are often much smaller than the uncertainty in the absolute positions, i.e. than the uncertainty in the offset values in RA and Declination which are about 0.3 arcseconds.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Counts
The background-corrected counts in the X-ray source in the total energy band (0.3 - 7 keV) as derived by wavdetect.

Counts_Error
The error in the background-corrected counts.

Count_Rate
The net (i.e., corrected for background counts and for vignetting) count rate in the X-ray source in the total energy band (0.3 - 7 keV), in counts per second.

Band_Flag
The energy band in which the X-ray source had the most significant detection, according to the following codes: 'S' for the 0.3 - 2 keV (soft) band, 'H' for the 2 - 7 keV (hard) band, and 'T' for the 0.3 - 7 keV (total) band.

Hardness_Ratio
The hardness ratio of the X-ray source, HR, defined as (H'-S')/(H'+S') where S' and H' are the number of counts between 0.5 and 1 keV, and 1 and 7 keV, respectively, in the source region of the detection in the total band, and are corrected for vignetting and background counts. (Notice that these band definitions are different then those used in the band_flag parameter). The hardness ratio is given only for sources for which the error in the hardness ratio is less than 0.4. Sources with HR < 0 are considered to have soft spectra, while those with HR > 0 have hard spectra. For sources with no counts between 0.5 and 1 keV, HR = 1.

Hardness_Ratio_Error
The uncertainty in the hardness ratio.

Belloni_Number
The candidate) ROSAT counterpart to the Chandra X-ray source, using the source number NN from Belloni et al. (1998A&A...339..431B). Such ROSAT sources are referred to as '[BVM98] M 67 NN' in Simbad.

Ctrpart_Name
The candidate optical counterpart to the Chandra X-ray source, where the name of the counterpart was selected from (in order of preference):

  Prefix   Reference

  S        Sanders (1977A&AS...27...89S)
  E        Momany et al. (2001A&A...379..436M)
  F        Fan et al. (1996AJ....112..628F)
  
Sources that were identified by eye by examining the EIS V-image to look for faint optical sources that are not included in these catalogs are labelled as 'faint', and their estimated optical positions are given in ftp://cdsarc.u-strasbg.fr/pub/cats/J/A+A/418/509/table4.dat

Notes_Flag
This parameter has non-blank values from 'a' to 'f' to indicate the existence of notes on individual sources in the file ftp://cdsarc.u-strasbg.fr/pub/cats/J/A+A/418/509/notes.dat

Offset
The offset, in arcseconds, between the Chandra X-ray source and the proposed optical counterpart.


Contact Person

Questions regarding the M67CXO database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 25-Jan-2007