M31XRAY - ROSAT PSPC Survey of M31

Overview

This paper reports on results of the analysis of the first M-31 survey with the ROSAT PSPC performed in July 1991. Within the =~ 6.3 deg^2 field of view 396 individual X-ray sources were detected with (0.1 keV - 2.4 keV) fluxes ranging from =~ 5x10^-15^erg/cm^2/s to =~ 4x10^-12^erg/cm^2/s. Of these 396 sources, 43 have been tentatively identified with foreground stars, 29 with globular clusters, 17 with supernova remnants, 3 with other galaxies (including M-32), and 3 with radio sources. A detailed analysis of the integral flux distribution of the sources shows that approximately one fifth are likely to be background objects. By comparison with the results of the Einstein M-31 survey, we find 327 newly detected sources, 15 moderately variable sources, 3 bright and 6 faint possible transient sources. For those sources in M-31, the observed luminosities range from =~ 3x10^35^erg/s to =~ 2x10^38^erg/s (at 690 kpc). The total (0.1 keV - 2.4 keV) luminosity of M-31 is (2.9+/-0.3)x10^39^erg/s, roughly one third of which is from the bulge and two thirds of which are from the disk. The luminosity of a diffuse component within the bulge region is estimated to be less than 3.2x10^38^erg/s. An explanation in terms of hot gaseous emission leads to a maximum total gas mass of 1.7x10^6^M_Sun. We find that the integral luminosity distribution of sources associated with globular clusters is similar to that of the Milky Way. Finally, the results of spectral fits to 56 of the brightest sources are discussed; we classify 15 objects as 'supersoft sources' according to their spectral characteristics.

Parameters

Name
The name of the current source derived from the position coordinates in the year 2000.

RA
The Right Ascension of the object.

Dec
The Declination of the object.

LII
The Galactic longitude of the object.

BII
The Galactic latitude of the object.

Object_Class

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       a: Galactic foreground star
       b: Background galaxy
       c: Radio source
       d: Globular cluster
       e: SNR
       *: bulge source
       +: Sources with uncertain count rate
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Source_Number
Running source number in catalogue (1-396).

Position_Error
1 sigma position error in arcsec.

Detect_Class
Source classification; the X-ray sources are classified due to the quality of their detection, which has an influence on the determined properties: 1 = best, 2 = medium, 3 = moderate.

Max_Like
Maximum likelihood.

Max_Detection_Band
Energy band with highest detection. 

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     The ROSAT energy bands are coded as:
     -----------------------------------------------------------------------------
       B  = Broad = 0.1-2.4 keV
       S  = Soft  = 0.1-0.4 keV
       1  = Hard1 = 0.5-0.9 keV
       2  = Hard2 = 0.9-2.0 keV
       H  = Hard  = 0.5-2.0 keV (= H1 + H2).
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Upper_Limit_Flag
B,S,H,1,2 signifies that rate in broad, soft, hard, hard1, and/or hard2 is a 3-sigma upper limit only. 

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     Bands defined as:
     -----------------------------------------------------------------------------
        B  = Broad = 0.1-2.4 keV
        S  = Soft  = 0.1-0.4 keV
        1  = Hard1 = 0.5-0.9 keV
        2  = Hard2 = 0.9-2.0 keV
        H  = Hard  = 0.5-2.0 keV (= H1 + H2).
--------------------------------------------------------------------------------

Rate_B_Flag
Flag on count rate in the B-band.

Rate_B
Count rate in the B-band in ct/ks. 'B' = Broad = 0.1-2.4 keV.

Rate_B_Error
RMS uncertainty on Rate_B units in ct/ks. The listed count rate errors are only statistical. The systematic errors are expected to be less than 15%. A conversion of count rates into fluxes depends on the assumed spectral shape. For M31-Sources a power law with Gamma=-2.0 and N_H_=9x10^20^cm^-2 may be used, leading to the conversion factor 1 cts/ks=3.12x10^-14^erg/cm^2/s in the 0.1-2.4 keV B-band. For foreground stars the application of this conversion factor leads to an over-estimate of the fluxes.

Rate_S_Flag
Flag on Count rate in the S-band.

Rate_S
Count rate in the S-band in ct/ks. S = Soft = 0.1-0.4 keV.

Rate_S_Error
RMS uncertainty on Rate_S in ct/ks.

Rate_H_Flag
Flag on Count rate in the H-band.

Rate_H
Count rate in the H-band in ct/ks. H = Hard = 0.5-2.0 keV (= H1 + H2).

Rate_H_Error
RMS uncertainty on Rate_H in ct/ks.

Rate_H1_Flag
Flag on Count rate in the H1-band.

Rate_H1
Count rate in the H1-band in ct/ks. H1 = Hard1 = 0.5-0.9 keV.

Rate_H1_Error
RMS uncertainty on Rate_H1 in ct/ks.

Rate_H2_Flag
Flag on Count rate in the H2-band.

Rate_H2
Count rate in the H2-band in ct/ks. H2 = Hard2 = 0.9-2.0 keV.

Rate_H2_Error
RMS uncertainty on Rate_H2 in ct/ks.

ROS_Flux
Source flux measured by ROSAT in 0.1fW/m2. Source flux obtained by applying the spectral model of TF (thermal bremsstrahlung with kT=5 keV and N_H_=7x10^20^cm^-2) in the 0.2-4.0 keV energy band.

ROS_Flux_Error
RMS uncertainty on ROS_Flux in 0.1fW/m2.

EIN_Number
Einstein source number.

EIN_Flux
Source flux measured by Einstein in 0.1fW/m2. Source flux obtained by applying the spectral model of TF (thermal bremsstrahlung with kT=5 keV and N_H_=7x10^20^cm^-2) in the 0.2-4.0 keV energy band.

EIN_Flux_Error
RMS uncertainty on Ein_Flux in 0.1fW/m2.

ER_Distance
Distance between sources. This represents the distance between the ROSAT source and the corresponding tabulated Einstein source, if available.

ER_Distance_Sigma
If non-empty, this gives the distance between the ROSAT source and the corresponding tabulated Einstein source, expressed in sigma of their combined 1-sigma position error.

ER_Flux_Ratio
ROSAT-Einstein source flux ratio. If non-empty, signifies the ratio between the ROSAT source and the corresponding tabulated Einstein source.

ER_Flux_Ratio_Error
RMS uncertainty on ER_Flux_Ratio. Gaussian error propagation used.

Fit_Extra_Circle
Photon collection circle. Expressed in sigma of the point spread function of the instrumentation ROSAT XRT+PSPC.

Fit_Counts
Number of photons used for the fit.

NH_G
Hydrogen absorption. Column density for Gamma in 1E+20cm-2.

NH_G_U_Error
Error in NH_G (upper limit) in 1E+20cm-2.

NH_G_L_Error
Error in NH_G (lower limit) in 1E+20cm-2.

Gamma
Power law index.

Gamma_U_Error
Error in Gamma (upper limit).

Gamma_L_Error
Error in Gamma (lower limit).

Chi2_Gamma
Reduced Chi2 for Gamma.

NH_B
Hydrogen column density in 1E+20cm-2 for bremsstrahlung fit

NH_B_U_Error
Error in NH_B (upper limit) in 1E+20cm-2.

NH_G_L_Error
Error in NH_B (lower limit) in 1E+20cm-2.

KT_B
Thermal Bremsstrahlung temperature in keV.

KT_B_U_Error
Error in KT_B (upper limit) in keV.

KT_B_L_Error
Error in KT_B (lower limit) in keV.

Chi2_KT_B
Reduced Chi2 for kT_B.

Alt_Fit_Flag
Spectral fit model indicator for alternate fit: 'B'= blackbody fit, 'T' = thermal plasma fit

NH_Alt
Hydrogen column density for alternate Fit in 1E+20cm-2.

Chi2_Alt
Reduced Chi2 for alternate Fit.

NH_Alt_U_Error
Error in NH_Alt for alternate fit (upper limit) in 1E+20cm-2.

NH_Alt_L_Error
Error in NH_Alt for alternate fit (lower limit) in 1E+20cm-2.

KT_Alt
Thermal Plasma or Blackbody temperature in keV.

KT_Alt_U_Error
Error in KT_Alt for alternate fit (upper limit) in keV.

KT_Alt_L_Error
Error in KT_Alt for alternate fit (lower limit) in keV.

Power
Power law index.

Power_Error
RMS uncertainty on Power.

Chi2_Power
Reduced Chi2 for Power.

Class
BROWSE classification type. The classification is based on the `Type` parameter, if one is available.

References

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      Supper R., Hasinger G., Pietsch W., Truemper J., Jain A.,
      Magnier E.A., Lewin W.H.G., van Paradijs J.
      Astron. Astrophys. 317, 328 (1997)
      1997A&A...317..328S      (SIMBAD/NED BibCode)
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Provenance

This database was created at the HEASARC in December 1997 based on a computer-readable version of Tables 5, 6, 8, and 9 of Supper R. et al. (1997) that was obtained from the CDS (their catalog 317, 328 (1997).

Contact Person

Questions regarding the M31XRAY database table can be addressed to the HEASARC User Hotline.
Page Author: Browse Software Development Team
Last Modified: Thursday, 18-Jul-2002 13:13:01 EDT

A service of the Astrophysics Science Division at NASA/GSFC.