IC2944XMM - IC 2944/2948 XMM-Newton X-Ray Source Catalog

Overview

Using XMM-Newton data, the authors have studied for the first time the X-ray emission of the young star clusters HM1 and IC 2944/2948. Low-mass, pre-main sequence objects with an age of a few Myr are detected, as well as a few background or foreground objects. Most massive stars in both clusters display the usual high-energy properties of that kind of objects, though with log(L_x/L_bol) apparently lower in HM1 than in IC 2944/2948. Comparing with studies of other clusters, it seems that low S/N at soft energies, due to the high extinction, may the main cause of this difference. In HM1, the two Wolf-Rayet stars show contrasting behaviors: WR89 is extremely bright, but much softer than WR87. It remains to be seen whether wind-wind collisions or magnetically confined winds can explain such emissions. In IC 2944/2948, the X-ray sources concentrate around HD 101205; a group of massive stars to the north of this object appears rather isolated, suggesting that there exist two sub-clusters in the field of view.

This tables provides the list of 368 detected X-ray sources in/toward the Cen OB2 association cluster(s) IC 2944/2948 only, i.e., the 58 X-ray sources detected in/toward the HM1 cluster are not contained herein. This tables lists the basic X-ray source properties (position, count rates, hardness ratios) and their probable optical/infrared counterparts (offset angular distance, name).

XMM-Newton has observed IC 2944/2948 for 40 ks on XMM-Newton Rev. 2209 (with the THICK filter). No background flare affected the observation, and no source is bright enough to suffer from pile-up.

Catalog Bibcode

2013A&A...555A..83N

References

X-ray properties of the young open clusters HM1 and IC 2944/2948.
    Naze Y., Rauw G., Sana H., Corcoran M.F.
   <Astron. Astrophys. 555, A83 (2013)>
   =2013A&A...555A..83N   (SIMBAD/NED BibCode)

Provenance

This table was created by the HEASARC in September 2013 based on CDS Catalog J/A+A/555/A83 files table3.dat and table4.dat.

Parameters

Source_Number
A uniquely identifying source number (referred to as 'XID' in the reference paper) for each detected IC 2944/2948 X-ray source in the catalog.

Name
The X-ray source designation created by the HEASARC in the standard IAU-recommended source number-based format, i.e., '[NRS2013] IC 2944 XID', where the prefix stands for 'Naze, Rauw, Sana 2013 IC 2944/2948' and the numerical string is the source number (XID).

Source_Flag
This flag parameter has the following possible non-null values:

        ? = probably spurious source;
      ext = extended source.

Raw_RA
The raw (uncorrected) Right Ascension of the XMM-Newton X-ray source in the selected equinox. This was given in J2000.0 equatorial coordinates to a precision of 0.001 seconds of time in the original table.

Raw_Dec
The raw (uncorrected) Declination of the XMM-Newton X-ray source in the selected equinox. This was given in J2000.0 equatorial coordinates to a precision of 0.01 arcseconds in the original table.

RA
The corrected Right Ascension of the XMM-Newton X-ray source in the selected equinox. This was given in J2000.0 equatorial coordinates to a precision of 0.001 seconds of time in the original table. When the positions of the massive O-stars in the field were superimposed on the X-ray image, a shift was clearly seen. Comparing the Hipparcos positions of the massive O-stars with their associated X-ray sources (excluding HD 101413 and HD 101436, which were heavily distorted because of their off-axis positions), the authors found an average shift of RA_Hip - RA_XMM = 0.45 s in Right Ascension and Dec_Hip - Dec_XMM = 0.41" in declination. They thus corrected the coordinates of the X-ray sources by adding these values to the ones found by the detection algorithm, and only then correlated with other existing catalogs.

Dec
The corrected Declination of the XMM-Newton X-ray source in the selected equinox. This was given in J2000.0 equatorial coordinates to a precision of 0.01 arcseconds in the original table. When the positions of the massive O-stars in the field were superimposed on the X-ray image, a shift was clearly seen. Comparing the Hipparcos positions of the massive O-stars with their associated X-ray sources (excluding HD 101413 and HD 101436, which were heavily distorted because of their off-axis positions), the authors found an average shift of RA_Hip - RA_XMM = 0.45 s in Right Ascension and Dec_Hip - Dec_XMM = 0.41" in declination. They thus corrected the coordinates of the X-ray sources by adding these values to the ones found by the detection algorithm, and only then correlated with other existing catalogs.

LII
The Galactic Longitude of the XMM-Newton X-ray source based on the corrected equatorial coordinates.

BII
The Galactic Latitude of the XMM-Newton X-ray source based on the corrected equatorial coordinates.

M1_Count_Rate
The MOS1 count rate of the XMM-Newton X-ray source for the total band (0.3-10 keV), in ct/s. (This was converted by the HEASARC from the ct/ks units given in the original tables.) Missing values are for cases where this count rate could not be calculated, e.g. the source was in a gap, over a bad column, or out of the field-of-view for this instrument.

M1_Count_Rate_Error
The uncertainty in the MOS1 count rate of the XMM-Newton X-ray source for the total band (0.3-10 keV), in ct/s. (This was converted by the HEASARC from the ct/ks units given in the original tables.)

M2_Count_Rate
The MOS2 count rate of the XMM-Newton X-ray source for the total band (0.3-10 keV), in ct/s. (This was converted by the HEASARC from the ct/ks units given in the original tables.) Missing values are for cases where this count rate could not be calculated, e.g. the source was in a gap, over a bad column, or out of the field-of-view for this instrument.

M2_Count_Rate_Error
The uncertainty in the MOS2 count rate of the XMM-Newton X-ray source for the total band (0.3-10 keV), in ct/s. (This was converted by the HEASARC from the ct/ks units given in the original tables.)

PN_Count_Rate
The pn count rate of the XMM-Newton X-ray source for the total band (0.3-10 keV), in ct/s. (This was converted by the HEASARC from the ct/ks units given in the original tables.) Missing values are for cases where this count rate could not be calculated, e.g. the source was in a gap, over a bad column, or out of the field-of-view for this instrument.

PN_Count_Rate_Error
The uncertainty in the pn count rate of the XMM-Newton X-ray source for the total band (0.3-10 keV), in ct/s. (This was converted by the HEASARC from the ct/ks units given in the original tables.)

Hardness_Ratio_1
The hardness ratio HR1 of the X-ray source as measured by the pn instrument. The three energy bands defined by the authors were soft (S), the 0.3-1.0 keV energy band, medium (M), the 1.0-2.0keV energy band and hard (H), the 2.0-10.0 keV energy band. These were used to compute two hardness ratios: HR1 = (M-S)/(M+S) and HR2 = (H-M)/(H+M).

Hardness_Ratio_1_Error
The uncertainty in the hardness ratio HR1 of the X-ray source as measured by the pn instrument.

Hardness_Ratio_2
The hardness ratio HR2 of the X-ray source as measured by the pn instrument. The three energy bands defined by the authors were soft (S), the 0.3-1.0 keV energy band, medium (M), the 1.0-2.0 keV energy band and hard (H), the 2.0-10.0 keV energy band. These were used to compute two hardness ratios: HR1 = (M-S)/(M+S) and HR2 = (H-M)/(H+M).

Hardness_Ratio_2_Error
The uncertainty in the hardness ratio HR2 of the X-ray source as measured by the pn instrument.

Ctrpart_Flag
This flag parameter is set to '+' to indicate the presence of a second 2MASS counterpart to the X-ray source farther away than the first 2MASS counterpart (listed herein), but still within 3 arcseconds.

XMM_2MASS_Offset
The angular distance, in arcseconds, between the X-ray source and the nearest 2MASS counterpart (if any) within 3 arcseconds.

TwoMASS_Name
The designation of the nearest 2MASS counterpart (if any) within 3 arcseconds. Cross-correlation with 2MASS yielded 260 counterparts to the 368 X-ray sources within 3 arcseconds. (This radius seemed the best to avoid spurious identifications.) Among these, a second object was found within the same radius in only 11 cases.

XMM_MGcat_Offset
The angular distance, in arcseconds, between the X-ray source and the nearest counterpart in the catalog of optical sources of McSwain and Gies (MG: 2005, ApJS, 161, 118), if any, within 3 arcseconds.

MGcat_Name
The designation of the nearest MG counterpart to the X-ray source (if any) within 3 arcseconds, e.g., 'Cl* IC 2944 MG NNN'. Only 13 of the 368 X-ray sources have a counterpart in the MG catalog. Note that for XID 100, there is a second counterpart in the MG catalog, 'Cl* IC 2944 MG 23', at a separation of 2.38", which has an equivalent width of -13.0 Angstrom, i.e., is in emission.

H_Alpha_EW
The equivalent width, EW, of the H-alpha line in the MG counterpart to the X-ray source, in arcseconds. The MG data were converted into H-alpha equivalent widths using formula (4) of McSwain and Gies (2005, ApJ, 622, 1052). Equivalent widths are positive when H-alpha is in absorption. In six cases, H-alpha can be considered in emission as the absolute equivalent widths exceed 10 Angstroms.

XMM_SIMBAD_Offset
The angular distance, in arcseconds, between the X-ray source and the nearest SIMBAD counterpart, if any, within 3 arcseconds.

SIMBAD_Name
The name of the SIMBAD counterpart to the X-ray source (if any) within 3 arcseconds. 28 of the 368 X-ray sources have a SIMBAD counterpart. Ten of these objects are massive O-stars recently studied by Sana et al. (2011, MNRAS, 416, 817), six other objects display a B-type, one an A-type, and three an F-type spectrum. The latter cases are probably foreground sources unrelated to the cluster. The remaining eight objects have no known spectral type.

Comments
Additional information on the counterparts to the X-ray sources, e.g.,spectral types, periods, potentially spurious counterparts (of which there are 21).

Contact Person

Questions regarding the IC2944XMM database table can be addressed to the HEASARC Help Desk.

Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:29:05 EDT