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M33CXOXRAY - M33 Chandra X-Ray Point Source Catalog

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Overview

This database table contains a source list for three Chandra observations of the Local Group galaxy M33. The observations were centered on the nucleus and on the star-forming region NGC 604. A total of 261 sources were detected in an area of about 0.2 square degrees down to a flux limit of 3 x 10^-16 erg/s/cm^2, which corresponds to a luminosity of ~2 x 10^34 erg/s at a distance of 840 kpc. The luminosity functions of the X-ray sources observed in M33 have been constructed and are consistent with those of other star-forming galaxies, taking into account background contamination. In addtion, the combination of X-ray color analysis and the existence of "blue" optical counterparts stronly indicates that the X-ray point source population in M33 consists of young objects. Above 3 x 10^35 erg/s, there are few X-ray sources in the locus of the X-ray hardness ratio diagram that is generally populated by low-mass X-ray binaries.

Notice that each of the 261 X-ray sources in the source list has 3 entries in this table, one for each separate Chandra observation, making a total of 783 entries.

The Chandra datasets from which this source list was compiled are available by querying CHANMASTER for obsids 786, 1730, and 2023.


Catalog Bibcode

2005ApJS..161..271G

References

The X-ray binary population in M33: I. Source list and luminosity function.
     Grimm H.-J., McDowell J., Zezas A., Kim D.-W., Fabbiano G.
    <ApJS, 161, 271 (2005)>
    =2005ApJS..161..271G

Provenance

This table was created by the HEASARC in December 2005 based on the machine-readable version of Table 3 in the above-mentioned Grimm et al. (2005) reference obtained from the ApJ Electronic Edition website.

Parameters

Name
The Chandra source name using the recommended 'CXO' prefix and the J2000 equatorial coordinates of the source position.

Source_Flag
This parameter is a flag which is set to 'c' to indicate the X-ray source associated with the nucleus for which, because of pileup, the X-ray counts and flux are not true values.

RA
The Right Ascension of the X-ray source in the selected equinox. This was given in J2000 equatorial coordinates and to a precision of 0.001 seconds of time in the original table.

Dec
The Declination of the X-ray source in the selected equinox. This was given in J2000 equatorial coordinates and to a precision of 0.01 arcseconds in the original table.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Error_Radius
The positional uncertainty of the X-ray source, in arcseconds.

ObsID
The Chandra observation identification number, or ObsID.

Counts_FB_Limit
This parameter is a flag for the total-band (0.3-8.0 keV) counts which is set to '<' if the quoted value is a 99% upper limit. (See Section 3 of the paper for details of how the upper limits were calculated).

Counts_FB
The total-band (0.3-8.0 keV) counts of the X-ray source in the specified Chandra observation.

Counts_FB_Error
The 1-sigma error in the total-band (0.3-8.0 keV) counts, N, computed using the Gehrels approximation, sigma = 1 + (N + 0.75)^0.5.

Counts_FB_Flag
This parameter is a flag which is set to 'b' to indicate that the quoted total-band counts value is the most probable value for the source counts in this band as obtained with the method of Kraft et al. (1991, ApJ, 374, 344): see Section 2 of the paper for more details.

Counts_SB_Limit
This parameter is a flag for the soft-band (0.3-2.0 keV) counts which is set to '<' if the quoted value is a 99% upper limit. (See Section 3 of the paper for details of how the upper limits were calculated).

Counts_SB
The soft-band (0.3-2.0 keV) counts of the X-ray source in the specified Chandra observation.

Counts_SB_Error
The 1-sigma error in the soft-band (0.3-2.0 keV) counts, N, computed using the Gehrels approximation, sigma = 1 + (N + 0.75)^0.5.

Counts_SB_Flag
This parameter is a flag which is set to 'b' to indicate that the quoted soft-band counts value is the most probable value for the source counts in this band as obtained with the method of Kraft et al. (1991, ApJ, 374, 344): see Section 2 of the paper for more details.

Counts_HB_Limit
This parameter is a flag for the hard-band (2.0-8.0 keV) counts which is set to '<' if the quoted value is a 99% upper limit. (See Section 3 of the paper for details of how the upper limits were calculated).

Counts_HB
The hard-band (2.0-8.0 keV) counts of the X-ray source in the specified Chandra observation.

Counts_HB_Error
The 1-sigma error in the hard-band (2.0-8.0 keV) counts, N, computed using the Gehrels approximation, sigma = 1 + (N + 0.75)^0.5.

Counts_HB_Flag
This parameter is a flag which is set to 'b' to indicate that the quoted hard-band counts value is the most probable value for the source counts in this band as obtained with the method of Kraft et al. (1991, ApJ, 374, 344): see Section 2 of the paper for more details.

Counts_SCB_Limit
This parameter is a flag for the soft color band (0.3-1.0 keV) counts which is set to '<' if the quoted value is a 99% upper limit. (See Section 3 of the paper for details of how the upper limits were calculated).

Counts_SCB
The soft color band (0.3-1.0 keV) counts of the X-ray source in the specified Chandra observation.

Counts_SCB_Error
The 1-sigma error in the soft color band (0.3-1.0 keV) counts, N, computed using the Gehrels approximation, sigma = 1 + (N + 0.75)^0.5.

Counts_MCB_Limit
This parameter is a flag for the medium color band (1.0-2.1 keV) counts which is set to '<' if the quoted value is a 99% upper limit. (See Section 3 of the paper for details of how the upper limits were calculated).

Counts_MCB
The medium color band (1.0-2.1 keV) counts of the X-ray source in the specified Chandra observation.

Counts_MCB_Error
The 1-sigma error in the medium color band (1.0-2.1 keV) counts, N, computed using the Gehrels approximation, sigma = 1 + (N + 0.75)^0.5.

Counts_HCB_Limit
This parameter is a flag for the hard color band (2.1-8.0 keV) counts which is set to '<' if the quoted value is a 99% upper limit. (See Section 3 of the paper for details of how the upper limits were calculated).

Counts_HCB
The hard color band (2.1-8.0 keV) counts of the X-ray source in the specified Chandra observation.

Counts_HCB_Error
The 1-sigma error in the hard color band (2.1-8.0 keV) counts, N, computed using the Gehrels approximation, sigma = 1 + (N + 0.75)^0.5.

Flux_FB_Limit
This parameter is a flag for the total-band (0.3-8.0 keV) flux which is set to '<' if the quoted value is a 99% upper limit. (See Section 3 of the paper for details of how the upper limits were calculated).

Flux_FB
The total-band (0.3-8.0 keV) flux of the X-ray source in the specified Chandra observation, in units of counts/s/cm^2.

Flux_FB_Error
The 1-sigma error in the total-band (0.3-8.0 keV) flux, in units of counts/s/cm^2.

Flux_FB_Flag
This parameter is a flag which is set to 'b' to indicate that the quoted flux was calculated from a corresponding total-band counts which was of the most probable value type.

Flux_SB_Limit
This parameter is a flag for the soft-band (0.3-2.0 keV) flux which is set to '<' if the quoted value is a 99% upper limit. (See Section 3 of the paper for details of how the upper limits were calculated).

Flux_SB
The soft-band (0.3-2.0 keV) flux of the X-ray source in the specified Chandra observation, in units of counts/s/cm^2.

Flux_SB_Error
The 1-sigma error in the soft-band (0.3-2.0 keV) flux, in units of counts/s/cm^2.

Flux_SB_Flag
This parameter is a flag which is set to 'b' to indicate that the quoted flux was calculated from a corresponding soft-band counts which was of the most probable value type.

Flux_HB_Limit
This parameter is a flag for the hard-band (2.0-8.0 keV) flux which is set to '<' if the quoted value is a 99% upper limit. (See Section 3 of the paper for details of how the upper limits were calculated).

Flux_HB
The hard-band (2.0-8.0 keV) flux of the X-ray source in the specified Chandra observation, in units of counts/s/cm^2.

Flux_HB_Error
The 1-sigma error in the hard-band (2.0-8.0 keV) flux, in units of counts/s/cm^2.

Flux_HB_Flag
This parameter is a flag which is set to 'b' to indicate that the quoted flux was calculated from a corresponding hard-band counts which was of the most probable value type.

Lx_Limit
This parameter is a flag for the total-band (0.3-8.0 keV) luminosity which is set to '<' if the quoted value is a 99% upper limit. (See Section 3 of the paper for details of how the upper limits were calculated).

Lx
The total-band (0.3-8.0 kev) luminosity of the X-ray source, in erg/s.

Lx_Flag
This parameter is a flag which is set to 'b' to indicate that the quoted luminosity was calculated from a corresponding total-band counts which was of the most probable value type.


Contact Person

Questions regarding the M33CXOXRAY database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 19-Dec-2005