- ID:
- ivo://nasa.heasarc/ngc1333cxo
- Title:
- NGC 1333 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC1333CXO
- Date:
- 11 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- NGC 1333, a highly active star formation region within the Perseus molecular cloud complex, has been observed on 2000 July 12.96 - 13.48 with the ACIS-I detector on board the Chandra X-Ray Observatory. The aim point of the array was 3 29 06.1, +31 19 38 (J2000,0 RA and Dec), the satellite roll angle was 95.7 degrees, and the effective exposure time after removing time intervals contaminated by background flaring was 37.8 ks. In this image with a sensitivity limit in luminosity of ~10<sup>28</sup> erg/s for X-ray sources at the 318 pc distance of NGC 1333, 127 X-ray sources were detected, most with sub-arcsecond positional accuracy. While 32 of these sources appear to be foreground stars and extragalactic background objects, 95 X-ray sources are identified with known cluster members. The X-ray luminosity function of the discovered young stellar object (YSO) population spans a range of log L<sub>X</sub> ~= 28.0 - 31.5 erg s<sup>-1</sup> in the 0.5 - 8 keV band, and the absorption column densities range from log N<sub>H</sub> ~=20 to 23 cm<sup>-2</sup>. Most of the sources have plasma temperatures between 0.6 and 3 keV, but a few sources show higher temperatures up to ~7 keV. Comparison with K-band source counts indicates that all of the known cluster members with K < 12 and about half of the members with K > 12 were detected. (K ~= 11, the peak of the K-band luminosity function, corresponds to 0.2 - 0.4 M_solar stars for a cluster age of ~1 Myr). Seven of the 20 known YSOs in NGC 1333 which are producing jets or molecular outflows were detected, as well as one deeply embedded object without outflows. No evident difference in X-ray emission of young stars with and without outflows is found. This present table contains X-ray, optical and near-infrared information on the 109 X-ray sources that were detected above a source significance threshold of 1 x 10<sup>-6</sup> in any of 3 energy bands: soft: 0.5 - 2.0 keV, hard: 2.0 - 8.0 keV, or full: 0.5 - 8.0 keV, excluding 8 sources that were deemed to be spurious on visual examination of the images. The faintest on-axis source emerging from the wavelet detection procedure has 5 extracted counts, corresponding to a source of log L<sub>X</sub> ~ 28.0 in the total (0.5 - 8.0 keV) band for a source with negligible interstellar absorption (A<sub>V</sub> ~ 1) and a typical source spectrum of a kT ~ 1 keV thermal plasma. This limit increases to 28.6 (29.3) if the absorption is increased to A<sub>V</sub> ~ 5 (10). The sensitivity decreases by a factor of 4 at the edge of the field compared to the central regions. 80 of the significant 109 sources (73%) have counterparts in a non-X-ray band. This table does not include 18 tentative X-ray sources listed in Table 3 of the reference paper that were found by the authors by searching for concentrations of photons spatially coincident with known sources from near-IR, mm/sub-mm, and radio catalogs of this region which did not reach the detection significance given above. Most of these tentative sources are believed to be real sources. This table was created by the HEASARC in March 2007 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/575/354">CDS catalog J/ApJ/575/354</a> files table1.dat and table2.dat. This is a service provided by NASA HEASARC .
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- ID:
- ivo://nasa.heasarc/ngc2403cx2
- Title:
- NGC 2403 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC2403CX2
- Date:
- 11 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains a comprehensive X-ray point source catalog of the galaxy NGC 2403, an outlying member of the M 81 group of galaxies, as part of the Chandra Local Volume Survey. The combined archival observations of this galaxy have an effective exposure time of 190 ks. When combined with the catalogs of sources in NGC 55 and NGC 4214 given in this same reference paper, and the authors' previously published catalogs for NGC 300 (Binder et al. 2012, ApJ, 758, 15) and NGC 404 (Binder et al. 2013, ApJ, 763, 128), the CLVS contains 629 high-significance X-ray sources total down to a limiting unabsorbed luminosity of ~ 5 x 10<sup>35</sup> erg s<sup>-1</sup> in the 0.35-8.0 keV band in each of the five galaxies. In the reference paper, the authors present X-ray hardness ratios, spectral analysis, radial source distributions, and an analysis of the temporal variability for the X-ray sources detected at high significance. To constrain the nature of each X-ray source, they carried out cross-correlations with multi-wavelength data sets. They searched overlapping Hubble Space Telescope observations for optical counterparts to their X-ray detections to provide preliminary classifications for each X-ray source as a likely X-ray binary, background active galactic nucleus, supernova remnant, or foreground star. The authors utilized archival X-ray observations: NGC 2403 was observed by the Chandra X-Ray Observatory using the ACIS-S array on five occasions for a total of 190 ks: <pre> Obs. ID Date Eff. Exposure time (ks) 2014 2001 Apr 17 35 4627 2004 Aug 09 31 4628 2004 Aug 23 42 4629 2004 Oct 03 40 4630 2004 Dec 22 42 </pre> The iterative source detection strategy that was used is described in Section 2.3 of Binder et al. (2012, ApJ, 758, 15). ACIS-Extract (AE) was run a final time on the source list that was produces after an initial run of wavdetect followed by several iterations of AE, and the Poisson probability of not being a source (pns) value was computed in each of the following nine energy bands: 0.5 - 8.0, 0.5 - 2.0, 2.0 - 8.0, 0.5 - 1.0, 1.0 - 2.0, 2.0 - 4.0, 4.0 - 8.0, 0.35 - 1.0 or 0.35 - 8.0 keV. To be included in the final NGC 2403 catalog, a source was required to have a pns value less than 4 x 10<sup>-6</sup> in any of the nine energy bands. The final CLVS source catalog for NGC 2403 contains 190 sources. This table was created by the HEASARC in September 2015 based on machine-readable versions of those parts of Table 5 and 8 from the reference paper which pertained to the 190 high-significance (pns < 4 x 10<sup>-6</sup>) X-ray sources which were detected in NGC 2403. It does not include the 108 lower-significance sources in NGC 2403 which had 4 x 10<sup>-6</sup> < pns < 1.0 x 10<sup>-3</sup>, some of which are likely to be genuine X-ray sources. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc6231cxo
- Title:
- NGC 6231 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC6231CXO
- Date:
- 11 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- NGC 6231 is a massive young star cluster, near the center of the Sco OB1 association. While its OB members are well studied, its low-mass population has received little attention. In the reference paper, the authors present high-spatial resolution Chandra ACIS-I X-ray data, wherein they detect 1,613 point X-ray sources. Their main aim was to clarify the global properties of NGC 6231 down to low masses through a detailed membership assessment, and to study the cluster stars' spatial distribution, the origin of their X-ray emission, the cluster age and formation history, and its initial mass function. The authors use X-ray data, complemented by optical and IR data, to establish cluster membership. The spatial distribution of different stellar subgroups also provides highly significant constraints on cluster membership, as does the distribution of X-ray hardness. In their study, the authors perform spectral modeling of group-stacked X-ray source spectra. The X-ray properties of the sources detected in the Chandra observations of NGC 6231, and their cross-identifications in the catalogs of Sung, Sana, and Bessell (2013 AJ, 145, 37; hereafter SSB); VPHAS+ (Drew et al., 2014, MNRAS, 440, 2036); and 2MASS (<a href="https://cdsarc.cds.unistra.fr/ftp/cats/II/246">CDS Cat. II/246</a>), and information about membership, H-alpha or IR excess, mass and luminosity are also provided. SSB derive a distance modulus for NGC 6231 of 11.0 (1,585 pc), a reddening E(B - V) = 0.47, and a nearly normal reddening law with R = 3.2. The present authors adopt these values for this work. NGC 6231 was observed twice in X-rays with the ACIS-I detector on-board the Chandra X-ray Observatory on 2005, July 3 to 4 (ObsId 5372) and 16 to 17 (ObsID 6291), respectively. The two pointings share the same center (aimpoint) but were performed with a different roll angle. Effective exposure times for the observations were 76.19 and 44.39 ks, respectively, making the total exposure time 120.58 ks. The data were filtered to retain the energy band 0.3 - 8.0 keV, and the full-field lightcurves were inspected to search for high-background periods, but none were found. Exposure maps were computed using standard CIAO software tasks. To these prepared datasets, the authors applied the source detection software PWDetect, a wavelet-based detection algorithm developed at INAF-Osservatorio Astronomico di Palermo. The PWDetect version used here is a modified one, able to detect sources in combined datasets, thus taking full advantage of the deep total exposure. The detection threshold was chosen such as to yield ten spurious detections in the field of view (FOV), for the given background counts. This is a more relaxed constraint than the more usual limit of one spurious detection per field, but is justified when the lowered threshold allows the detection of more than one hundred additional faint sources, as it was the case here or in the COUP Program's Orion data. This HEASARC table contains the list of 1,613 detected X-ray point sources and information about their optical and IR counterparts, where known. It does not contain the 275 additional candidate cluster members (where their candidacy was based on their having H-alpha or IR excesses) which lack X-ray counterparts and that were also listed in Table B.2 of the reference paper. This table was created by the HEASARC in December 2016 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/596/A82">CDS Catalog J/A+A/596/A82</a> file tableb.dat, which is the merger of tables B.1 (the list of 1,613 X-ray sources) and B.2 (the list of 1,888 optical and near-IR identifications of X-ray sources and of IR- and H-alpha-excess stars) from the reference paper, but excluding the 275 stars listed in the latter whose candidacy was based on their having H-alpha or IR excesses and which lack X-ray counterparts. # This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc4636cxo
- Title:
- NGC 4636 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC4636CXO
- Date:
- 11 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This catalog lists the X-ray point-source population in the nearby Virgo elliptical galaxy NGC 4636 from three Chandra X-ray observations. These observations, totaling ~193 ks after time filtering, were taken with the Advanced CCD Imaging Camera (ACIS) over a three-year period. Using a wavelet decomposition detection algorithm, the authors detected 318 individual point sources. For their analysis, they used a subset of 277 detections with >= net 10 counts (a limiting luminosity of approximately 1.2 x 10<sup>37</sup> erg s<sup>-1</sup> in the 0.5-2 keV band, outside the central 1.5 arcminutes bright galaxy core). This table contains this subset of 277 X-ray sources. The authors discuss the radial distribution of the point sources. Between 1.5 and 6 arcminutes from the center, 25% of the sources are likely to be background sources (active galactic nuclei (AGNs)) and 75% to be low-mass X-ray binaries (LMXBs) within the galaxy, while at radial distances greater than 6 arcminutes, background sources (AGN) will dominate the point sources. The authors explore short and long-term variability (over timescales of 1 day to three years) for X-ray point sources in this elliptical galaxy. 54 sources (24%) in the common ACIS fields of view show significant variability between observations. Of these, 37 are detected with at least 10 net counts in only one observation and thus may be "transient." In addition, ~10% of the sources in each observation show significant short-term variability. The cumulative luminosity function (LF) for the point sources in NGC 4636 can be represented as a power law of slope Alpha = 1.14 +/- 0.03. The authors do not detect, but estimate an upper limit of ~4.5 x 10<sup>37</sup> erg s<sup>-1</sup> to the current X-ray luminosity of, the historical supernova SN1939A. They find 77 matches between X-ray point sources and globular cluster (GC) candidates found in deep optical images of NGC 4636. In the annulus from 1.5 to 6 arcminutes of the galaxy center, 48 of the 129 X-ray point sources (37%) with >=10 net counts are matched with GC candidates. Since they expect 25% of these sources to be background AGN, the percentage matched with GCs could be as high as 50%. Of these matched sources, the authors find that ~70% are associated with the redder GC candidates, those that are thought to have near-solar metal abundance. The fraction of GC candidates with an X-ray point source match decreases with decreasing GC luminosity. The authors do not find a correlation between the X-ray luminosities of the matched point sources and the luminosity or color of the host GC candidates. The LFs of the X-ray point sources matched with GCs and those that are unmatched have similar slopes over 1.8 x 10<sup>37</sup> erg s<sup>-1</sup> <= L<sub>x</sub> <= 1 x 10<sup>38</sup> erg s<sup>-1</sup>. This table was created by the HEASARC in July 2009 based on electronic versions of Tables 2 and 3 from the paper obtained from the ApJ web site, but excluding the 7 entries in Table 3 which corresponded to weaker X-ray sources which were not listed in Table 2. Some of the values for the name parameter in the HEASARC's implementation of this table were corrected in April 2018. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc6231cx2
- Title:
- NGC 6231 Chandra X-Ray Point Source Catalog 2
- Short Name:
- NGC6231CX2
- Date:
- 11 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- NGC 6231 is a young cluster (age ~2-7 Myr) dominating the Sco OB1 association (distance ~1.59 kpc) with ~100 O and B stars and a large pre-main-sequence stellar population. The authors combine a reanalysis of archival Chandra X-ray data with multi-epoch near-infrared (NIR) photometry from the VISTA Variables in the Via Lactea (VVV) survey and published optical catalogs to obtain a catalog of 2148 probable cluster members. This catalog is 70% larger than previous censuses of probable cluster members in NGC 6231. It includes many low-mass stars detected in the NIR but not in the optical and some B stars without previously noted X-ray counterparts. In addition, the authors identify 295 NIR variables, about half of which are expected to be pre-main-sequence stars. With the more complete sample, they estimate a total population in the Chandra field of 5700-7500 cluster members down to 0.08 M<sub>sun</sub> (assuming a universal initial mass function) with a completeness limit at 0.5 M<sub>sun</sub>. A decrease in stellar X-ray luminosities is noted relative to other younger clusters. However, within the cluster, there is little variation in the distribution of X-ray luminosities for ages less than 5 Myr. The X-ray spectral hardness for B stars may be useful for distinguishing between early-B stars with X-rays generated in stellar winds and B-star systems with X-rays from a pre-main-sequence companion (>35% of B stars). A small fraction of catalog members have unusually high X-ray median energies or reddened NIR colors, which might be explained by absorption from thick or edge-on disks or being background field stars. This work makes use of some basic cluster properties available from the literature. Summaries of older studies are provided by Sana et al. (2006, J/A+A/454/1047), available in <a href="/W3Browse/xmm-newton/ngc6231xmm.html">NGC6231XMM</a>, and Reipurth (2008hsf2.book.....R). Expanded catalogs of cluster members have been provided by Sung et al. (2013, J/AJ/145/37) and Damiani et al. 2016, J/A+A/596/A82 (DMS2016), available at <a href="/W3Browse/chandra/ngc6231cxo.html">NGC6231CXO</a>. Chandra X-ray observations were made using the imaging array on the Advanced CCD Imaging Spectrometer (ACIS-I; Garmire et al. 2003SPIE.4851...28G). This instrument is an array of four CCD detectors that subtends 17'x17'. The target was observed in 2005 July (Sequence 200307; PI: S. Murray) in two observations (ObsID 5372 and 6291), and the data were retrieved from the Chandra Data Archive. The NIR ZYJHK<sub>s</sub> data were obtained from the VVV survey (Minniti et al. 2010NewA...15..433M; Saito et al. 2012, Cat. II/337). VVV is a multi-epoch NIR survey that covers both the Galactic bulge and an adjacent Galactic disk region and was carried out using the 4.1 m VISTA telescope on Cerro Paranal. The VVV data were taken with the VISTA Infrared CAMera (VIRCAM; Dalton et al. 2006SPIE.6269E..0XD), a 4x4 array of Raytheon VIRGO 2048x2048 20 micron pixel detectors with a pixel scale of 0.34". In addition to the VVV photometry, public optical or infrared catalogs are available from surveys and publications. We have included VPHAS+ photometry (Drew et al. 2014, J/MNRAS/440/2036), UBVRI (Johnson-Cousins system) and H-alpha photometry from Sung et al. (2013, J/AJ/145/37), and Spitzer/IRAC photometry from the GLIMPSE survey (Benjamin et al. 2003, Cat. II/293). This table was created by the HEASARC in October 2020 based upon the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/AJ/154/87">CDS Catalog J/AJ/154/87</a> file table1.dat, table3.dat, and table5.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc4472cxo
- Title:
- NGC 4472 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC4472CXO
- Date:
- 11 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The Chandra X-Ray Point Source Catalog of the giant elliptical galaxy NGC 4472 contains the results of a Chandra ACIS-S/Hubble Space Telescope (HST) study of the point sources of this Virgo Cluster galaxy. The authors ran WAVDETECT from the CIAO 2.2 software package using wavelet scales from 1 to 16 pixels spaced by factors of 2, setting a false-source probability detection threshold of 10<sup>-6</sup>, which should yield an expectation value of slightly less than one false source over the entire ACIS-S chip. They identify 144 X-ray point sources outside the nuclear region, 72 of which are located within the HST fields. An additional 3 sources are within 8" of the center of the galaxy and appear to be associated either with a weak active galactic nucleus or with brightness enhancements in the hot interstellar gas. One additional source (not included in this table) appears to be a spurious detection, as WAVDETECT assigns it a count rate of 1.5 counts, and visual inspection fails to find evidence of a source at that location. The optical data show 1102 sources whose half-light radii are small enough to be globular cluster candidates, 829 of which also have colors consistent with being globular clusters (with only four in the restricted central 10" region). 30 X-ray sources within 0.7" of an optical source with optical colors consistent with being globular clusters were found. Two additional sources show optical colors outside the globular cluster color range and are likely to be either foreground or background objects. The thirty globular cluster matches are likely to be low-mass X-ray binaries (LMXBs) associated with the globular clusters, while ~ 42 of the X-ray sources have no optical counterparts to V <~ 25 and I <~ 24, indicating that they are likely to be predominantly LMXBs in the field star population with a small amount of possible contamination from background active galactic nuclei. Thus approximately 40% of the X-ray sources are in globular clusters and ~ 4% of the globular clusters contain X-ray sources. This HEASARC table contains the X-ray data for the above-mentioned 147 detected X-ray sources, and the correlative optical data for the 30 optical counterparts which have colors consistent with being globular clusters. It does not contain the data from the full list of optical sources which were given in Table 2 of the reference paper. This table was created by the HEASARC in May 2007 based on CDS table J/ApJ/586/814 files table1.dat and table3.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc2516cxo
- Title:
- NGC 2516 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC2516CXO
- Date:
- 11 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The NGC 2516 Chandra X-Ray Point Source Catalog is the result of a comprehensive study of the Chandra X-ray observations of the young open star cluster NGC 2516. The authors have analyzed eight individual Chandra observations, comprising 5 ACIS and 3 HRC-I observations. They have combined these datasets to achieve the greatest sensitivity, reaching down to a threshold level of log f<sub>X</sub> = -14.56 (erg/s/cm<sup>2</sup>), or log L<sub>X</sub> = 28.69 (erg/s) at the 387 pc distance of NGC 2516. Out of 284 X-ray sources detected, 155 are identified with photometric cluster members, with very little ambiguity, another 60 with non-members. There are 4 X-ray sources with two possible optical identifications (one cluster member and one nonmember for each), with no obvious choice between the two candidates. These 4 X-ray sources are listed in this Browse table twice, one for each optical counterpart, hence there are (284 + 4 =) 288 entries. There remain 73 X-ray sources without an optical identification with the authors' optical catalog stars. This Browse table was created by the HEASARC in December 2006, based on CDS table J/ApJ/588/1009, files table4.dat and table5.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc2264cxo
- Title:
- NGC 2264 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC2264CXO
- Date:
- 11 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The NGC 2264 Chandra X-Ray Point Source Catalog contains the results of a Chandra observation of a field in the NGC 2264 star-forming region. The observation was made with Chandra's Advanced CCD Imaging Spectrometer imaging array (ACIS-I) on 2002 February 9, and has an exposure time of 48.1 ks. The catalog contains 263 sources, and includes X-ray luminosity, optical and infrared photometry, and X-ray variability information. The authors found 41 variable sources, 14 of which have a flare-like light curve, and two of which have a pattern of a steady increase or decrease over a 10-hr period. The optical and infrared photometry for the stars identified as X-ray sources are consistent with most of these objects being pre-main sequence stars with ages younger than 3 Myr. The authors found that 213 (81%) of the 263 X-ray sources have optical and/or infrared counterparts, most, but probably not all, of which are likely to be member stars of NGC 2264. There are 51 X-ray sources that lack optical or infrared counterparts: the authors believe that these are most likely extragalactic objects (active galaxies). This table was created by the HEASARC in February 2007 based on CDS table J/AJ/127/2659, files table1.dat, table4.dat and table5.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc300cxo
- Title:
- NGC 300 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC300CXO
- Date:
- 11 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the source catalog from a new Chandra ACIS-I observation of the nearby (2.0 Mpc) SA(s)d spiral galaxy NGC 300 which was obtained as part of the Chandra Local Volume Survey (CLVS). This 63-ks exposure covers ~88% of the D<sub>25</sub> isophote (R ~ 6.3 kpc) and yields a catalog of 95 X-ray point sources detected at high significance down to a limiting unabsorbed 0.35-8 keV luminosity of ~ 10<sup>36</sup> erg/s. Sources were cross-correlated with a previous XMM-Newton catalog, and the authors find 75 "X-ray transient candidate" sources that were detected by one observatory, but not the other. They derive an X-ray scale length of 1.7 +/- 0.2 kpc and a recent star formation rate of 0.12 M<sub>sun</sub>/yr in excellent agreement with optical observations. Deep, multi-color imaging from the Hubble Space Telescope, covering ~ 32% of this Chandra field, was used to search for optical counterparts to the X-ray sources, and the authors have developed a new source classification scheme to determine which sources are likely X-ray binaries, supernova remnants, and background active galactic nucleus candidates. In the reference paper, the authors present the X-ray luminosity functions (XLFs) at different X-ray energies, and find the total NGC 300 X-ray point-source population to be consistent with other late-type galaxies hosting young stellar populations (<~ 50 Myr). They find that the XLF of sources associated with older stellar populations has a steeper slope than the XLF of X-ray sources coinciding with young stellar populations, consistent with theoretical predictions. NGC 300 was observed on 2010 September 25 for 63 ks using ACIS-I during the Chandra X-Ray Observatory Cycle 12, observation ID 12238. The source detection strategy that was used is described in Section 2.3 of the reference paper. ACIS-Extract (AE) was run a final time on the source list that was produces after an initial run of wavdetect followed by several iterations of AE, and the Poisson probability of not being a source (pns) value was computed in each of the following nine energy bands: 0.5 - 8.0, 0.5 - 2.0, 2.0 - 8.0, 0.5 - 1.0, 1.0 - 2.0, 2.0 - 4.0, 4.0 - 8.0, 0.35 - 1.0 and 0.35 - 8.0 keV. To be included in the final NGC 300 catalog, a source was required to have a pns value less than 4 x 10<sup>-6</sup> in any of the nine energy bands; if only the 0.35 - 8 keV band were considered, ~4% of significant sources would have been lost. The final CLVS source catalog for NGC 300 contains 95 sources. This table was initially created by the HEASARC in September 2014 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/758/15/">CDS Catalog J/ApJ/758/15/</a> files table4.dat, table5.dat, table6.dat and table7.dat containing the X-ray properties of the 95 Chandra point sources found in this study. The information on the optical counterparts to (some of) the Chandra X-ray sources and on the X-ray point source classification (presented in Tables 16 and 17, respectively, of the reference paper) is not included herein. It was updated in September 2015 to include the unabsorbed 0.35-8.0 keV energy fluxes (in the parameter herein called b4_flux) from the second reference paper. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc6791cxo
- Title:
- NGC 6791 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC6791CXO
- Date:
- 11 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains some of the results from the first X-ray study of NGC 6791, one of the oldest open clusters known (8 Gyr). This Chandra observation was aimed at uncovering the population of close interacting binaries down to an X-ray luminosity (L<sub>X</sub>) of ~1 x 10<sup>30</sup> erg/s (0.3-7 keV). The authors detect 86 sources within 8 arcminutes of the cluster center, including 59 inside the half-mass radius of 4.42 arcminutes. centered on 19<sup>h</sup> 20<sup>m</sup> 53<sup>s</sup>, +37<sup>o</sup> 46' 18" (J2000.0). They identify 20 sources with proper-motion cluster members, which are a mix of cataclysmic variables (CVs), active binaries (ABs), and binaries containing sub-subgiants. With follow-up optical spectroscopy, the authors confirm the nature of one CV. They also discover one new, X-ray variable candidate CV with Balmer and He II emission lines in its optical spectrum; this is the first X-ray-selected CV in an open cluster. The number of CVs per unit mass is consistent with the field, suggesting that the 3-4 CVs observed in NGC 6791 are primordial. The authors compare the X-ray properties of NGC 6791 with those of a few old open clusters (NGC 6819, M67) and globular clusters (47 Tuc, NGC 6397). It is puzzling that the number of ABs brighter than 1 x 10<sup>30</sup> erg/s normalized by cluster mass is lower in NGC 6791 than in M 67 by a factor ~3-7. CVs, ABs, and sub-subgiants brighter than 1 x 10<sup>30</sup> erg/s are under-represented per unit mass in the globular clusters compared to the oldest open clusters, and this accounts for the lower total X-ray luminosity per unit mass of the former. This indicates that the net effect of dynamical encounters may be the destruction of even some of the hardest (i.e., X-ray-emitting) binaries. The authors observed NGC 6791 with the Advanced CCD Imaging Spectrometer (ACIS) on Chandra from 2004 July 1 20:51 UTC until July 2 10:49 UTC for a total exposure time of 48.2ks (ObsID 4510). They obtained low-resolution spectra of candidate optical counterparts to guide the classification of the X-ray sources. A total of 16 candidate counterparts brighter than V ~18.3 were observed with the FAST long-slit spectrograph on the 1.5m Tillinghast telescope on Mt. Hopkins on nine nights between 2005 June 7 to September 2 (coverage from 3480 to 7400 Angstrom and a 3 Angstrom resolution). Candidate optical counterparts fainter than V ~17 were observed with the fiber-fed multi-object spectrograph Hectospec on the 6.5m Multi-Mirror Telescope. A total of 16 candidate counterparts were observed on the nights of 2005 May 13 and July 4-6 (spectra that cover 3700 to 9150 Angstrom with a 6-Angstrom resolution). The authors performed source detections in broad (0.3-7.0 keV), soft (0.3-2.0 keV) and hard (2.0-7.0 keV) energy bands, also used in their Chandra study of M 67 (van den Berg et al. 2004, A&A, 418. 509), so as to facilitate comparison. The CIAO detection routine wavdetect was run for scales of 1.0 to 11.3 pixels, in steps increasing by a factor of sqrt(2), with the larger scales appropriate for large off-axis angles where the point-spread function (PSF) becomes significantly broader. The authors computed exposure maps for the response at 1 keV to account for spatial variations of the sensitivity. The wavdetect detection threshold was set to 10<sup>-6</sup>, from which the authors expect two spurious detections per detection scale (so 16 spurious detections in total) in the area that they consider here. Combination of the broad, soft, and hard-band source lists results in a master catalog of 86 distinct sources within 8 arcmin of the cluster center, of which 59 lie inside the half-mass radius r<sub>h</sub>. To investigate the validity of the sources, the authors also ran wavdetect with a threshold of 10<sup>-7</sup> or an expected number of spurious sources of 1.6. The 14 sources not detected in this run are marked with a value of the source_flag parameter of 'T' in this table (replacing the '*' symbol used in the original table). This table was created by the HEASARC in August 2015 based on the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/770/98">CDS Catalog J/ApJ/770/98</a> files table1.dat and table2.dat. This is a service provided by NASA HEASARC .
