WD1CXO - Westerlund 1 Chandra X-Ray Point Source Catalog

Overview

The nature of the X-ray point source population within the young massive cluster Westerlund 1 (Wd 1) is investigated. Chandra X-ray Observatory (CXO) observations were used to determine the X-ray properties of emitters within Wd 1, while a comprehensive multi-wavelength dataset was employed to constrain their nature. Wd 1 (l=339.5, b=-0.4) was observed with the CXO Advanced CCD Spectrometer Spectroscopic array on 2005 May 22 for 18 ks (sequence 6283) and 2005 June 20 for 42 ks (sequence 5411). 241 sources were found above a sensitivity threshold that corresponded to a 10^-6 chance per PSF element of detecting a spurious source. X-ray emission from a multitude of different stellar sources within Wd 1, including both evolved high mass and low-mass pre-MS stars, is found.

Catalog Bibcode

2008A&A...477..147C

References

Unveiling the X-ray point source population of the Young Massive Cluster
Westerlund 1.
    Clark J.S., Muno M.P., Negueruela I., Dougherty S.M., Crowther P.A.,
    Goodwin S.P., De Grijs R.
   <Astron. Astrophys., 477, 147-163 (2008)>
   =2008A&A...477..147C

Provenance

This table was created by the HEASARC in May 2008 based on CDS table J/A+A/477/147 files table1.dat and table3.dat.

Parameters

Name
The X-ray source name based on the '[CMN2008]' prefix (for Clark, Muno, Negueruela 2008) and a numerical string based on the J2000.0 coordinates, e.g., '[CMN2008] JHHMMSS.s+DDMMSS', as recommended by the CDS Dictionary of Astronomical Nomenclature.

RA
The Right Ascension of the X-ray source in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 10^-5 degrees in the original table. An astrometric correction was applied to the original ACIS positions in order to register them to the 2MASS frame.

Dec
The Declination of the X-ray source in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 10^-5 degrees in the original table. An astrometric correction was applied to the original ACIS positions in order to register them to the 2MASS frame.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Off_Axis
The angular offset of the X-ray source from the aim point of the observation, in arcminutes.

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

Exposure
The detector live time for the X-ray source, in seconds.

Counts
The net (background-subtracted) counts of the X-ray source in the 0.5 - 8.0 keV band from within the 90% contour of the PSF.

Counts_Pos_Err
The positive uncertainty in the net counts in the 0.5 - 8.0 keV band, calculated by summing the squares of the 1-sigma uncertainties from both the total and background counts.

Counts_Neg_Err
The negative uncertainty in the net counts in the 0.5 - 8.0 keV band, calculated by summing the squares of the 1-sigma uncertainties from both the total and background counts.

Hardness_Ratio
The hardness ratio HR = (H - S)/(H + S) of the X-ray source, where H is the number of counts in the 2.0 to 8.0 keV band, and S is the counts in in the 0.5 - 2.0 keV band.

Hardness_Ratio_Pos_Err
The positive uncertainty in the hardness ratio, calculated according to Eq. 1.31 in Lyons (1991, A Practical Guide to Data Analysis for Physical Science Students, p. 26).

Hardness_Ratio_Neg_Err
The negative uncertainty in the hardness ratio, calculated according to Eq. 1.31 in Lyons (1991, A Practical Guide to Data Analysis for Physical Science Students, p. 26).

Photon_Flux
The X-ray photon flux in the 0.5 - 8.0 keV band, in photons cm^-2 s^-1.

Var_Flag
This parameters is set to 's' and/or 'l' to indicate X-ray source variability on short or long timescales, i.e, within an individual observation on a timescale of hours, or detected in one but not the other observation, respectively.

Opt_Ctrprt_Flag
This parameter is a flag which indicates whether an X-ray source has an optical or near-IR counterpart, and if populated, identifies the catalog or catalogs. The codes for the source catalogs utilized are:

        1 = Clark et al. (2005A&A...434..949C)
        2 = Piatti et al. (1998, Cat. J/A+AS/127/423
        3 = the 2MASS catalogue (Cutri et al., 2003, Cat. II/246)
        4 = the USNO-B1.0 survey (Monet et al., 2003, cat. I/284)

Source_Flag
This parameter is set to 'i' for the source '[CMN2008] J164706.2-455048', which was found to be variable in these observations.

Number_In_Chart
The number of the optical counterpart to the X-ray source in the finding chart (Fig. 6 of the reference paper). The authors strongly advise that these numbers should not form the basis for a new naming convention.

Optical_Name
The designation of the optical counterpart to the X-ray source. Sources with 2MASS or Piatti et al. (1998, Cat. J/A+AS/127/423, Cl* Westerlund 1 PBC NNN in Simbad) designations are indicated.

Bmag
The B magnitude of the optical counterpart to the X-ray source.

Vmag
The V magnitude of the optical counterpart to the X-ray source.

Rmag
The R magnitude of the optical counterpart to the X-ray source.

Imag
The I magnitude of the optical counterpart to the X-ray source.

Spect_Type
The MK spectral type of the optical counterpart to the X-ray source. For those sources for which no entry is given but for which photometric data are available, we predict a spectral classification earlier than B0.5Ia (Sect. A.3 of the reference paper).

Opt_Var_Flag
This parameter is a flag which indicates variability of the optical counterpart to the X-ray source Flag for stars from Bonanos (2007AJ....133.2696B), as follows:

        E = Eclipsing photometric variable
        P = Periodic photometric variable
        A = Aperiodic photometric variables

Class
The HEASARC Browse object classification of the optical counterpart to the X-ray source, based on the spectral type (the spect_type parameter).

Contact Person

Questions regarding the WD1CXO database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: Wednesday, 29-Jan-2020 16:35:53 EST