RCW38CXO - RCW 38 Chandra X-Ray Point Source Catalog

Overview

This table contains the results of a 96.7-ks Chandra observation of one of the youngest, most embedded, and most massive young stellar clusters studied to this date in X-rays, namely the embedded young cluster, RCW 38. 460 X-ray sources were detected in the field, of which 360 are confirmed to be associated with the RCW 38 cluster. The cluster members range in luminosity from 10³⁰ to 10^33.5 erg/s. Over 10% of the cluster members with over 100 counts were found to exhibit flares, while about 15% of the cluster members with over 30 counts were variable. Of the sources identified as cluster members, 160 have near-infrared (NIR) counterparts either in the Two Micron All Sky Survey (2MASS) database or which were detected via Very Large Telescope observations. Of these, about 20% appear to have optically thick disks. An additional 353 cluster members were identified through NIR observations, of which at least 50% possess optically thick disks. Over 100 X-ray sources were fit as absorbed Raymond-Smith-type plasmas and the authors found that the column to the cluster members varies from 10^21.5 to 10²³ cm^-2. Comparing the gas to dust absorption signatures in these stars they found N_H = A_V (2 x 10²¹) cm^-2. They also found that the cluster contains 31 candidate OB stars and is centered about 10" (0.1 pc) west of the primary source of its ionization, the O5 star IRS 2. The cluster has a peak central density of about 400 X-ray sources pc^-2. The authors estimate that the total cluster membership exceeds 2000 stars.

The Chandra observation of RCW 38 took place on 2001 December 10-11 and lasted 96.7 ks. It used Advanced CCD Imaging Spectrometer (ACIS) chips 0, 1, 2, 3, 6 and 7 in very faint mode. The combined field of view (FOV) of the 4 chips in the imaging array (0-3, ACIS-I) is 16.9' x 16.9'. The aimpoint of the array was 8 59 19.20, -47 30 22.0 (J2000.0), and Chandra's roll angle was 51 degrees. The source detection algorithm PWDetect was run on the cleaned events list across the entire ACIS-I array, and found 460 sources, including 31 sources with more than 200 net counts, 49 sources with 100-200 net counts, 71 sources with 50-100 net counts, and 78 sources with 20-50 net counts. NIR matches were found for 349 of the 460 X-ray sources, including 294 of the 360 cluster members and 55 of the 100 nonmembers.

Catalog Bibcode

2006AJ....132.1100W

References

X-ray and IR Point Source Identification and Characteristics in the Embedded,
Massive Star-Forming Region RCW 38
    Wolk S.J., Spitzbart B.D., Bourke T.L., Alves J.
   <Astron. J., 132, 1100-1125 (2006)>
   =2006AJ....132.1100W

Provenance

This table was created by the HEASARC in February 2007 based on the merger of Tables 1, 10 and 11 from the reference paper which were obtained from the AJ website. It does not include the results from either the quartile analysis of the sources which were presented in Tables 2 and 3 or of the spectral analysis of some of the sources which were presented in Tables 5 through 9 of the reference paper.

HEASARC Implementation

The HEASARC has created an additional parameter called member_flag whose value is set to 'Y' for probable cluster members (source listed in Table 2 of the reference paper) or to 'N' for probable nonmembers (sources listed in Table 3 of the reference paper).

Parameters

Source_Number
A running source number in order of increasing J2000.0 Right Ascension.

Alt_Name
An alternative name for the X-ray source using the '[WSB2006]' prefix (for Wolk, Spitzbart and Bourke, 2006) and the source number, as recommended by the CDS Dictionary of Astronomical Nomenclature of Celestial Objects.

Name
The standard Chandra X-ray source designation, using the 'CXO J' prefix and the truncated J2000.0 coordinates of the source (HHMMSS.s-DDMMSS).

RA
The Right Ascension of the X-ray source in the selected equinox. This was given in J2000.0 equatorial coordinates to a precision of 0.01 seconds of time in the original reference.

Dec
The Declination of the X-ray source in the selected equinox. This was given in J2000.0 equatorial coordinates to a precision of 0.1 arcseconds in the original reference.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Off_Axis
The off-axis angle of the X-ray source, in arcminutes (converted by the HEASARC from the arcseconds in which it was given in the reference paper).

Counts
The net counts for the X-ray source in the 0.3 - 8.0 keV energy range, background-subtracted and corrected for the source extraction aperture six.

BB_95pc_Number
The number of Bayesian block (BB) intervals in which the X-ray source exhibited constant flux at a significance requirement of 95%. Details of the variability analysis are given in Section 4 of the reference paper, but the key point is that a value for this parameter of greater than 1 indicates a variable source.

BB_99pc_Number
The number of Bayesian block (BB) intervals in which the X-ray source exhibited constant flux at a significance requirement of 99%. Details of the variability analysis are given in Section 4 of the reference paper, but the key point is that a value for this parameter of greater than 1 indicates a variable source.

Ctrpart_Name
The name of the infrared counterpart to the X-ray source, either the 2MASS name or the Very Large Telescope (VLT) name, depending on which data are quoted.

Offset
The angular offset between the X-ray and the infrared positions, in arcseconds.

Jmag
The J-band magnitude of the IR counterpart to the X-ray source.

Jmag_Error
The uncertainty in the J magnitude of the IR counterpart.

Hmag
The H-band magnitude of the IR counterpart to the X-ray source.

Hmag_Error
The uncertainty in the H magnitude of the IR counterpart.

Kmag
The K_s-band magnitude of the IR counterpart to the X-ray source.

Kmag_Error
The uncertainty in the K_s magnitude of the IR counterpart.

Av
The V-band extinction A_V of the IR counterpart to the X-ray source. See Section 6 of the reference paper for a description as to how this quantity was calculated.

Emission_Model
The type of emitting surface assumed in the calculation of the V-band extinction A_V_: this is either a cool M star photosphere ('M star'), a disk ('Disk'), a higher-mass star photosphere ('GK star'), or a star plus disk combination ('Bright').

TwoMASS_Flags
The 2MASS flags for the 2MASS sources, or, for VLT sources that were not detected in all 3 bands and hence were subject to large errors due to the lack of color information, the 'FNT' (for faint) notation. If the source is from VLT then there is no color correction.

Member_Flag
This parameter flags whether ('Y') or not ('N') the object is a probable cluster member and was created by the HEASARC based on the sources presence in Table 2 or Table 3 of the reference paper, respectively.

Contact Person

Questions regarding the RCW38CXO database table can be addressed to the HEASARC Help Desk.

Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:33:40 EDT