Browse
this table...

NGC6530XMM - NGC 6530 XMM-Newton X-Ray Point Source Catalog

HEASARC
Archive

Overview

This table contains the results of a 20 ks XMM-Newton observation of the Lagoon Nebula (M 8). The EPIC images of this region reveal a cluster of point sources, most of which have optical counterparts inside the very young open cluster NGC 6530. The bulk of these X-ray sources are probably associated with low and intermediate mass pre-main sequence stars. One of the sources experienced a flare-like increase of its X-ray flux making it the second brightest source in M 8 after the O4 star 9 Sgr. The X-ray spectra of most of the brightest sources can be fitted with thermal plasma models with temperatures of kT ~ a few keV. Only a few of the X-ray selected PMS candidates are known to display H-alpha emission and were previously classified as classical T Tauri stars. This suggests that most of the X-ray emitting PMS stars in NGC 6530 are weak-line T Tauri stars. In addition to 9 Sgr, the EPIC field of view contains also a few early-type stars.

This table contains information on 117 of the 119 X-ray sources (2 sources, a point source associated with 9 Sgr and an extended source associated with the Hourglass Nebula were excluded from this table by the authors) that were detected using the SAS source detection algorithms in the soft band (0.5 - 1.2 keV) of an EPIC observation of 9 Sgr which have either a combined likelihood >= 20 and are detected in the individual images from all 3 EPIC instruments with -ln p_i >= 3.0 or (in two cases) where clearly detected in 2 of the 3 instruments but fell outside of the FOV of the third. The faintest sources in this category have about 10-3 cts s-1 over the 0.5 - 1.2 keV band of the MOS instruments. Assuming a 1 keV thermal spectrum with a neutral hydrogen column density of 0.17 x 1022 cm-2, the faintest sources correspond to an observed flux of about 8.9 x 10-15 erg cm-2 s-1 and an unabsorbed flux of 13.1 x 10-15 erg cm-2 s-1 in the 0.5 - 5.0 keV energy range. Note that the corresponding observed flux in the 0.5 - 1.2 keV soft band would be 5.2 x 10-15 erg cm-2 s-1.

72 X-ray sources have a single optical counterpart from the Sung et al (2000, CDS Cat. <J/AJ/120/333>) catalog or in the SIMBAD database within a radius of less than 9 arcsec. The average angular separation between the X-ray source and the optical counterpart is 4.1 +/- 2.1 arcseconds. 17 X-ray sources have two or more optical stars falling within the 9 arcsec radius. Seven of these sources have at least one known H-alpha emission star inside their error box. 28 sources do not have an optical counterpart in the catalogue of Sung et al. The authors have cross-correlated these sources with the Guide Star Catalog and, in most cases, they find one or several GSC objects inside the 9 arcsec radius. These optical counterparts are usually very faint (V or R >=17) except for sources 91, 92 and 94 that have counterparts with R magnitudes 15.0, 14.6 and 13.3 respectively (note that these sources fall outside the area investigated by Sung et al.). Sources 93, 96, 98, 99, 100, 101, 102 and 112 have no GSC counterpart. Most of the objects in Table 3 are therefore X-ray sources with high X-ray to visual luminosity ratios. Given the galactic coordinates of NGC 6530 (l_II = 6.14, b_II = -1.38), the total galactic column density along this line of sight must be extremely large and the number of extragalactic sources in the soft detection energy band should be extremely low.


Catalog Bibcode

2002A&A...395..499R

References

An XMM-Newton observation of the Lagoon Nebula and
the very young open cluster NGC 6530.
    Rauw G., Naze Y., Gosset E., Stevens I.R., Blomme R., Corcoran M.F.,
    Pittard J.M., Runacres M.C.
   <Astron. Astrophys. 395, 499 (2002)>
   =2002A&A...395..499R

Provenance

This table was created by the HEASARC in March 2007 based on CDS catalog J/A+A/395/499 files table1.dat, table2.dat and table3.dat.

Parameters

Source_Number
A running source number uniquely identifying the X-ray source.

Name
The name for the X-ray source using the 'XMMU' prefix for an XMM-Newton X-ray source, and the truncated J2000.0 coordinates (JHHMMSS.s+DDMMSS).

Alt_Name
An alternative name for the X-ray source using the '[RNG2002]' prefix (for Rauw, Naze and Gosset, 2002) and the source number, as recommended by the CDS Dictionary of Nomenclature of Celestial Objects.

RA
The Right Ascension of the X-ray source in the selected equinox based on the name of the X-ray source. This was given in J2000.0 coordinates to a precision of 0.1 seconds of time in the original table.

Dec
The Declination of the X-ray source in the selected equinox based on the name of the X-ray source. This was given in J2000.0 coordinates to a precision of 1 arcsecond in the original table.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

M1_Count_Rate
The vignetting- and background-corrected EPIC-MOS1 count rate in the 0.5 - 1.2 keV band, in ct/s. For sources affected by the gaps between the detectors, the count rate for the corresponding instrument is not given.

M1_Count_Rate_Error
The RMS uncertainty in the MOS1 count rate, in ct/s.

M1_Count_Rate_Flag
This flag parameter is set to 'a' to indicate that the X-ray source was outside the MOS1 field of view.

M2_Count_Rate
The vignetting- and background-corrected EPIC-MOS2 count rate in the 0.5 - 1.2 keV band, in ct/s. For sources affected by the gaps between the detectors, the count rate for the corresponding instrument is not given.

M2_Count_Rate_Error
The RMS uncertainty in the MOS2 count rate, in ct/s.

M2_Count_Rate_Flag
This flag parameter is set to 'a' to indicate that the X-ray source was outside the MOS2 field of view.

PN_Count_Rate
The vignetting- and background-corrected EPIC-pn count rate in the 0.5 - 1.2 keV band, in ct/s. For sources affected by the gaps between the detectors, the count rate for the corresponding instrument is not given.

PN_Count_Rate_Error
The RMS uncertainty in the pn count rate, in ct/s.

SCB_Number_1
The star number NNNN of the optical counterpart to the X-ray source as given in the Sung et al. (2000, Cat. <J/AJ/120/333> or SCB) Catalog. Such stars are designated as 'Cl* NGC 6530 SCB NNNN' in Simbad.

Offset_1
The angular separation between the X-Ray source and SCB positions, in arcseconds.

Vmag
The V magnitude of the optical counterpart to the X-ray source. The photometric data are taken from the Sung et al. (2000, Cat. <J/AJ/120/333> or SCB) Catalog, except for V1752 Sgr, and are given only for cases where there is a single counterpart to the X-ray source in the SCB Catalog.

BV_Color
The B-V color index of the optical counterpart to the X-ray source. The photometric data are taken from the Sung et al. (2000, Cat. <J/AJ/120/333> or SCB) Catalog, except for V1752 Sgr, and are given only for cases where there is a single counterpart to the X-ray source in the SCB Catalog.

VI_Color
The V-I color index of the optical counterpart to the X-ray source. The photometric data are taken from the Sung et al. (2000, Cat. <J/AJ/120/333> or SCB) Catalog, except for V1752 Sgr, and are given only for cases where there is a single counterpart to the X-ray source in the SCB Catalog.

Variability_Flag
This flag parameter indicates whether variability was detected in the X-ray source at the 95% confidence level ('Y') or not ('N'). Those sources flagged with a '?' show some hints of variability in ther light curves, but this was not found to be significant by the Kolmogorov-Smirnov test.

Comments
This field contains comments about the optical counterparts properties, such as information about their spectral types, pre-main sequence classification, or their membership probability (P_mu) according to the proper-motion study of van Altena & Jones (1972A&A....20..425V).

SCB_Number_2
For X-ray sources with multiple SCB optical counterparts, the star number NNNN of the second possible optical counterpart to the X-ray source as given in the Sung et al. (2000, Cat. <J/AJ/120/333> or SCB) Catalog. Such stars are designated as 'Cl* NGC 6530 SCB NNNN' in Simbad.

SCB_Number_3
For X-ray sources with multiple SCB optical counterparts, the star number NNNN of the third possible optical counterpart to the X-ray source as given in the Sung et al. (2000, Cat. <J/AJ/120/333> or SCB) Catalog. Such stars are designated as 'Cl* NGC 6530 SCB NNNN' in Simbad.

Offset_2
The angular separation between the X-Ray Source and the second possible optical counterpart positions, in arcseconds.

Offset_3
The angular separation between the X-Ray Source and the third possible optical counterpart positions, in arcseconds.

Source_Flag
This flag parameter contains codes [abc], indicating the presence of notes concerning individual sources, as follows:

        a = SCB 1028 is classified as a PMS star, while SCB 1039 is a PMS
            candidate (Sung et al. 2000).
        b = SCB 142 is a H{alpha} emitting star (LkH{alpha}106) while
            SCB 1019 is a PMS star (Sung et al., <J/AJ/120/333>).
        c = Source #75 (XMMU J180350.5-242110) lies within the wings of the
            PSF of 9 Sgr. Therefore no accurate count rates can be provided.
  

Contact Person

Questions regarding the NGC6530XMM database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 5-Mar-2012