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M31CFCXO - M 31 Central Field Chandra HRI X-Ray Point Source Catalog

HEASARC
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Overview

The central field of the Andromeda galaxy (M 31) was monitored from 2006 to 2012 using the Chandra HRC-I detector (about 0.1 - 10 keV energy range) with the main aim of detecting X-rays from optical novae. The authors present a systematic analysis of all X-ray sources found in the 41 nova monitoring observations, along with 23 M 31 central field HRC-I observations available from the Chandra data archive starting in December 1999. Based on these observations, they studied the X-ray long-term variability of the source population and especially of the X-ray binaries in M31. The authors created a catalog of sources detected in the 64 available observations that adds up to a total exposure time of about 1 Ms. To study the variability, they developed a processing pipeline to derive long-term Chandra HRC-I light curves for each source over the 13 years of observations, and also searched for extended X-ray sources in the merged images. This table contains the point-source catalog of 318 X-ray sources with detailed long-term variability information, 28 of which are published for the first time. The spatial and temporal resolution of the catalog allows the authors to classify 115 X-ray binary candidates showing high X-ray variability or even outbursts, as well as 14 globular cluster X-ray binary candidates showing no significant variability. The analysis may suggest that outburst sources are less frequent in globular clusters than in the field of M 31. Seven supernova remnants (not included in the point-source catalog) were detected, one of which is a new candidate, and also the first X-rays from a known radio supernova remnant were resolved. In addition to 33 known optical nova/X-ray source correlations, the authors discovered one previously unknown super-soft X-ray outburst and several new nova candidates. A large sample of detailed long-term X-ray light curves of sources in the M31 central field has been obtained in this study (see Appendix B.1 of the reference paper), which helps in understanding the X-ray population of our neighboring spiral galaxy M 31.

Based on all the available Chandra HRC-I observations (see Table A.1 in the reference paper for the complete list), a source catalog has been created (available in this HEASARC table) and the energy flux of each source in every individual observation derived (these are not available in this HEASARC table, but are obtainable at the CDS: for more details, see the files ftp://cdsarc.u-strasbg.fr/pub/cats/J/A%2BA/555/A65/ReadMe and ftp://cdsarc.u-strasbg.fr/ftp/cats/J_A%2BA/555/A65/table2.dat.gz). One thing to be aware of is that, in the latter file, upper limits are denoted by a '>' symbol rather than the more usual '<' symbol!). These fluxes were calculated assuming a generic power law spectrum and Galactic foreground absorption for each source.


Catalog Bibcode

2013A&A...555A..65H

References

X-ray source variability study of the M 31 central field using Chandra HRC-I.
    Hofmann F., Pietsch W., Henze M., Haberl F., Strum R., Della Valle M.,
    Hartmann D.H., Hatzidimitriou D.
    <Astron. Astrophys. 555, A65 (2013)>
    =2013A&A...555A..65H        (SIMBAD/NED BibCode)

Provenance

This table was created by the HEASARC in August 2013 based on the CDS catalog J/A+A/555/A65 files table1.dat and xcorr.dat.

Parameters

Source_Number
A running X-ray source number in order of increasing J2000.0 Right Ascension which uniquely identifies each point source

Name
The name for the Chandra X-ray source based on the '[HPH2013]' prefix (for Hofmann, Pietsch, Henze 2013) and the X-ray source number, created by the HEASARC in anticipation of its recommendation by the CDS Dictionary of Nomenclature of Celestial Objects.

RA
The Right Ascension of the Chandra X-ray source in the selected equinox. This was given in J2000.0 decimal degree coordinates to a precision of 10-5 degrees (0.036 arcseconds) in the original table.

Dec
The Declination of the Chandra X-ray source in the selected equinox. This was given in J2000.0 decimal degree coordinates to a precision of 10-5 degrees (0.036 arcseconds) in the original table.

LII
The Galactic Longitude of the Chandra X-ray source.

BII
The Galactic Latitude of the Chandra X-ray source.

Error_Radius
The positional uncertainty of the Chandra X-ray source, in arcseconds. This is defined as (presumably the root mean square of) three times the statistical 1-sigma positional error as obtained from wavdetect, not including systematic errors due to centroid offsets at far off-axis positions, and the adopted systematic catalog error from offset correction compared to the 2MASS reference catalog of 0.38 arcseconds (see Section 2.1 of the reference paper for more details).

Counts
The net source counts in the source extraction region in the 0.2 - 10 keV bandpass.

Counts_Error
The uncertainty in the net source counts in the source extraction region in the 0.2 - 10 keV bandpass.

Bck_Counts
The estimated background counts in the source extraction region in the 0.2 - 10 keV bandpass.

Count_Rate
The source count rate, in ct s-1, in the 0.2 - 10 keV bandpass.

Count_Rate_Error
The uncertainty in the source count rate, in ct s-1, in the 0.2 - 10 keV bandpass.

Bck_Count_Rate
The estimated background count rate within the source extraction region, in ct s-1, in the 0.2 - 10 keV bandpass.

Bck_Count_Rate_Error
The uncertainty in the estimated background count rate within the source extraction region, in ct s-1, in the 0.2 - 10 keV bandpass.

Exposure
The exposure time of the most significant detection of the Chandra X-ray source, in seconds.

Max_SNR
The highest detection significance of the Chandra X-ray source that was found in any individual observation

Detect_Image_Number
The number of the highest resolution image in which the source was detected (see Section 2.1 of the reference paper for more details):

  Image #   Image Size   0.13" Pixel Binning

    1       200" x 200"    1 x 1
    2       400" x 400"    2 x 2
    3       800" x 800"    4 x 4
    4      1400" x 1400"   8 x 8
    5      1800" x 1800"  16 x 16 (entire HRC-I)
  

Flux
The energy flux of the Chandra X-ray source in the 0.2 - 10 keV band, in erg s-1 cm-2. This was calculated for a power-law spectrum with a photon index of 1.7 and an assumed Galactic foreground absorption (column density) of NH = 6.6 x 1020 atoms cm-2.

Flux_Error
The uncertainty in the energy flux of the Chandra X-ray source in the 0.2 - 10 keV band, in erg s-1 cm-2.

Lx
The X-ray luminosity of the Chandra X-ray source, in erg s-1, assuming it is located in M 31 at a distance of 780 kpc and is emitting isotropically..

Lx_Error
The uncertainty in the X-ray luminosity of the Chandra X-ray source, in erg s-1.

Near_Neighbor_Offset
The angular distance from the Chandra X-ray source to its nearest neighbor, in arcseconds.

LT_Var_Significance
The source variability parameter, svar, describing the overall variability of the X-ray source over the 13 years of Chandra observations, and as defined in Section 3.3 and Equation 2 of the reference paper. It is essentially the flux difference between the minimum (or 3-sigma upper limit thereof if that is lower than the lowest detection) and the maximum observed fluxes in terms of standard deviations.

Max_To_Min_Ratio
The variability ratio, fvar, which stands for the ratio of the maximum over the minimum flux Fmax/Fmin of the Chandra X-ray source. To calculate these properties, the authors used data points for which the significance of the respective source given by the CIAO tool "aprates" was higher than 1 sigma.

Fraction_Detections
The fractional number, ndet, of > 1-sigma data points in the light curve of the X-ray source with respect to the number of observations in which the source is in the HRC-I detector's FOV.

ST_Var_Significance
The maximum value of the source variability parameter, ssvar, defined in the same way as svar except that it describes the overall variability of the X-ray source between any two neighboring observations (see Section 3.3 of the reference paper). The observations have different spacings in time, but the highest variability between them is still a good measure for the variability on time scales from about ten days to one year.

Max_Flux
The maximum flux of the Chandra X-ray source in any individual observation, in the 0.2 - 10 keV band, and in units of erg s-1 cm-2.

Max_Flux_Error
The uncertainty in the maximum flux of the Chandra X-ray source in any individual observation, in the 0.2 - 10 keV band, and in units of erg s-1 cm-2.

Min_Flux
The minimum flux of the Chandra X-ray source in any individual observation, in the 0.2 - 10 keV band, and in units of erg s-1 cm-2.

Min_Flux_Error
The uncertainty in the minimum flux of the Chandra X-ray source in any individual observation, in the 0.2 - 10 keV band, and in units of erg s-1 cm-2.

Light_Curve_Class
The derived light curve classification of the Chandra X-ray source,as discussed in Section 3.4 of the reference paper, and coded as follows:

     HV - highly variable, i.e., ndet > 0.3 and (ssvar > 4 or svar > 5)
     OB - outburst, i.e., ndet < 0.3 and fvar > 15 and svar > 5
  

Nova_Name
The nova designation of the optical nova associated with the X-ray source, if any, using the nova identifier format: 'M31N YYYY-MMa' for the M31 nova in the year YYYY and month MM, where the appended letter a is used to distinguish multiple novae occurring in the same month.

Globular_Cluster_Name
The globular cluster associated with the X-ray source, if any, and its quality classification. The names and quality flags are taken from the Revised Bologna Catalog of M31 globular clusters and candidates (Galleti et al. 2007, A&A, 471, 127). Thus, 'B055 1' means that the globular cluster's name is B055 and the quality of its identification as a globular cluster is 1, which means it is considered to be a confirmed globular cluster. The other values for this flag for globular clusters herein are 3 ('controversial object') and 6 ('confirmed star(s)').

Broad_Type
The source type, based on the identifications in the X-ray, radio, and optical wavelengths, as described in Sect. 3.2 of the reference paper and using the criteria listed in Table 5 therein and summarized below:

      Class    Meaning and Criteria

      XRB     -X-ray binary: hard X-ray source, HV or OB lightcurve
      GlC     -correlation with optically confirmed globular cluster,
                 hard spectrum
      SSS     -supersoft source: X-rays mostly below 1 keV
      nova    -correlation with optical nova
      SNR     -supernova remnant: softer X-ray source and/or extent,
                 correlation with radio or optical SNR
      AGN     -active galactic nucleus: hard X-rays, radio identifications
      fgStar  -foreground star: softer X-rays, optical identification unclassified
  

Broad_Type_Flag
This flag parameter is set to '?' if the type classification is considered to be tentative, i.e., the object is a candidate member of the specified class: in the authors' terminology, such objects are considered to be 'classified' and means that the source has only been a candidate in previous studies or the classification has been obtained only from the variability analysis. If a classification is given and the broad_type_flag is ' ', then the source is regarded as 'identified', meaning that it has been clearly identified in previous studies and this identification is compatible with the HRC-I analysis.

Comments_And_Refs
Comments and references on the source, using the following codes:

               Code        Author(s)           ADS Bibcode

              TPC2006   = Trudolyubov et al., 2006ApJ...645..277T
              HHP2009   = Haberl et al., 2009ATel.2262....1H
              GGS2007   = Galache et al., 2007ATel.1171....1G
              HPG2006   = Haberl et al., 2006ATel..881....1H
              BGG2012   = Barnard et al., 2012ApJ...756...32B
              B90       = Braun, 1990ApJS...72..761B
              HPH2010   = Henze et al., 2010A&A...523A..89H
              GGT2009   = Galache et al., 2009ATel.1978....1G
              KGG2009   = Kong et al., 2009ATel.2074....1K
              HHP2012   = Kong et al., 2012ATel.4164....1H
              HPH2012a  = Henze et al., 2012ATel.3890....1H
              HPH2012b  = Henze et al., 2012ATel.3921....1H
              HPH2012c  = Henze et al., 2013A&A...549A.120H
              GGT2008   = Galache et al., 2008ATel.1698....1G
              TP2008    = Trudolyubov & Priedhorsky, 2008ApJ...676.1218T
              HPH2009   = Henze et al., 2009ATel.2356....1H
              KGM2001   = Kong et al., 2001ATel...76....1K
              PBG2008   = Pietsch et al., 2008ATel.1674....1P
              HHP2007   = Harbel et al., 2007ATel.1296....1H
              TBP2001   = Trudolyubov et al., 2001ApJ...563L.119T
              TBP2002   = Trudolyubov et al., 2002ApJ...581L..27T
              PFH2008   = Pietsch et al., 2008ATel.1647....1P
              HPH2009   = Henze et al., 2009A&A...500..769H
              WGM2005   = Williams et al., 2005ApJ...632.1086W
              BK2009    = Barnard & Kolb, 2009MNRAS.397L..92B
              BKO2004   = Barnard et al., 2004A&A...423..147B
              PHH2012   = Pietsch et al., 2010ATel.3038....1P

           Abbreviations used in other comments on sources

              no lc     = no light curve available
              AP        = activity period
              SOB       = short outburst
              rec       = recurrent
              XT[SRCID] = cross-talk with SRCID
              LOB       = long outburst
              ULX       = ultra-luminous X-ray source
              M31*      = nucleus of M 31
              radio B90 = correlation with radio source in B90 catalog
  

Alt_Names
Other previous X-ray identifications of the source, using the following codes and the format: 'reference catalog','source number' and 'type of source information taken from reference;':

            KGP2002 = Kong et al., 2002, ApJ, 577, 38, Notes
            Ka2002  = Kaaret, 2002, ApJ, 578, 114, CXOM31
            PFH2005 = Pietsch et al., 2005, A&A, 434, 483, Class
            SHL2001 = Supper et al., 2001, A&A, 373, 63, n_SII
            SHP97   = Supper et al., 1997, A&A, 317, 328, n_ROSAT
            SPH2008 = Stiele et al., 2008, A&A, 480, 599, Class
            SPH2011 = Stiele et al., 2011, A&A, 534, A55, Class
            VG2007  = Voss & Gilfanov, 2007, A&A, 468, 49, Type
            WGK2004 = Williams et al., 2004, ApJ, 609, 735, Type
            WNG2006 = Williams et al., 2006, ApJ, 643, 356, F
            HPH2011 = Henze et al., 2011, A&A, 533, A52, M31N
            PHS2007 = Pietsch et al., 2007, A&A, 465, 375, M31N
            CSC     = Evans et al., 2010, ApJS, 189, 37, msid
            D2002   = Di Stefano et al., 2002, ApJ, 570, 618, opt_ident
            DKG2004 = Di Stefano et al., 2004, ApJ, 610, 247, category
            O2006   = Orio, 2006, ApJ, 643, 844, type
            OBT2001 = Osborne et al., 2001, A&A, 378, 800, Comments
            SBK2009 = Shaw Greening et al., 2009, A&A, 495, 733, type
            TF91    = Trinchieri & Fabbiano, 1991, ApJ, 382, 82, INDEX
            TP2004  = Trudolyubov & Priedhorsky, 2004, ApJ, 616, 821, optical_id
            TP2006  = Trudolyubov et al., 2006, ApJ, 645, 277, class
  

Class
The HEASARC Browse object classification based on the broad_type parameter value.


Contact Person

Questions regarding the M31CFCXO database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 21-Aug-2013