- ID:
- ivo://nasa.heasarc/ngc2362cxo
- Title:
- NGC 2362 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC2362CXO
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the results of an observation of the young cluster NGC 2362 in X-rays with Chandra ACIS-I in which 387 point X-ray sources, most of which are shown to be cluster members, were detected using PWDetect, a wavelet-based source detection algorithm, with a detection threshold chosen to ensure no more than one spurious detection in the entire ACIS FOV. The table lists all of the detected X-ray sources and their basic X-ray properties, as well as their proposed identifications with optical stars, using data from Moitinho et al. (2001ApJ...563L..73M; UBVRI photometry) and Dahm (2005, <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/AJ/130/1805">CDS Cat. <J/AJ/130/1805></a>; H-alpha data), as well as newer photometric data from Moitinho et al. (2005, in 'Cores to Clusters' [A&SSL, 324], 167). A matching position of less than 4 times the X-ray positional uncertainty of the X-ray source from PWDetect was used. Also included in the table is a classification of the optically-identified X-ray sources, based on their positions in the HR Diagram, which helps to separate rather clearly the cluster members from interloping field objects. This table was created by the HEASARC in March 2007 based on CDS table J/A+A/460/133 files table2.dat and table3.dat. This is a service provided by NASA HEASARC .
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- ID:
- ivo://nasa.heasarc/ngc404cxo
- Title:
- NGC 404 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC404CXO
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains a comprehensive X-ray point-source catalog of NGC 404, the closest face-on (inclination angle of 11 degrees) S0 galaxy to the Milky Way, which was obtained as part of the Chandra Local Volume Survey (CLVS) and originally published in Binder et al. (2013). A new 97-ks Chandra ACIS-S observation of NGC 404 was combined with archival observations for a total exposure of ~123 ks. This survey yields 74 highly significant X-ray point sources and is sensitive to a limiting unabsorbed luminosity of ~6 x 10<sup>35</sup> erg/s in the 0.35-8 keV band. To constrain the nature of each X-ray source, cross-correlations with multi-wavelength data were generated. The authors searched overlapping Hubble Space Telescope (HST) observations for optical counterparts to their X-ray detections, but found only two X-ray sources with candidate optical counterparts. They found 21 likely low-mass X-ray binaries (LMXBs), although this number is a lower limit due to the difficulties in separating LMXBs from background active galactic nuclei (AGN). The X-ray luminosity functions (XLFs) in both the soft and hard energy bands are presented in the 2013 reference paper. The XLFs in the soft band (0.5-2 keV) and the hard band (2-8 keV) have a limiting luminosity at the 90% completeness limit of 10<sup>35</sup> erg/s and 10<sup>36</sup> erg/s, respectively, significantly lower than previous X-ray studies of NGC 404. The authors find the XLFs to be consistent with those of other X-ray populations dominated by LMXBs. However, the number of luminous (>10<sup>37</sup> erg/s) X-ray sources per unit stellar mass in NGC 404 is lower than is observed for other galaxies. The relative lack of luminous XRBs may be due to a population of LMXBs with main-sequence companions formed during an epoch of elevated star formation ~0.5 Gyr ago. NGC 404 was observed during Chandra X-Ray Observatory Cycle 12 on 2010 October 21-22 for 97 ks using the ACIS-S array (Obs. ID 12339). The authors additionally utilized archival observations: NGC 404 was observed on 1999 December 19 (Obs. ID 870) for ~24 ks and on 2000 August 30 (Obs. ID 384) for ~2 ks, both using the ACIS-S array. The authors created images in the following energy bands (keV): 0.35-8.0, 0.35-1.0, 1.0-2.0, 2.0-8.0 with bin sizes of 1, 2, 3, and 4. 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 404 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 404 contains 74 sources. Given the survey size of these NGC 404 observations, there are expected to be ~1.6 false sources included in this NGC 404 final source catalog. Three HST fields were used to search for optical counterparts for each of the X-ray sources. One field (labeled "DEEP") was taken as part of the Advanced Camera for Surveys (ACS) Nearby Galaxy Survey Treasury (ANGST, GO-10915; Dalcanton et al. 2009, ApJS, 183, 67), while the other two shallower fields (labeled "NE" and "SW") were obtained as part of GO-11986. Details of the HST data acquisition and data reduction are provided in Williams et al. (2010, ApJ, 716, 71). This table was created by the HEASARC in September 2015 primarily based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/763/128">CDS Catalog J/ApJ/763/128</a> files table3.dat, table4.dat, table5.dat, table6.dat, table10.dat, table12.dat and table13.dat (Binder et al. 2013) which contain the properties of the 74 Chandra point sources found in this study.and of their multi-wavelength counterparts. As noted above, the HEASARC has added an extra parameter b4_flux which was taken from the machine-readable version of Table 5 of Binder et al. (2015). This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc6530cxo
- Title:
- NGC 6530 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC6530CXO
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- In a deep 60 ks Chandra ACIS-I X-ray observation of the very young (~ 1.5 - 2.0 Myr) cluster NGC 6530 on 2001 Jun 18-19, the authors have detected 884 X-ray point sources and argue that a very large fraction of them (90%-95%) must be pre-main-sequence (PMS) cluster members, mostly low-mass stars. This is a significant enlargement of the known NGC 6530 stellar population with respect to previous optical studies, including H-alpha surveys. They identify 220 X-ray sources with catalogued stars down to V = 17, while most unidentified sources have fainter counterparts. Moreover, they find an infrared counterpart in the 2MASS (CDS. No. <II/246>) Catalog for 731 X-ray sources. The optically identified cluster X-ray sources are found in a band in the H-R diagram above the main sequence, in the locus of 0.5 - 1.5 Myr PMS stars, with masses down to 0.5 - 1.5 solar masses (M_sun). The pointing direction for the Chandra observation was the NGC 6530 cluster center at RA = 18^h 04^m 24.38^s, Dec = -24^o 21' 05.8" (J2000.0). The PWDetect algorithm found 884 X-ray point sources in the ACIS-I image above a detection significance threshold chosen to ensure only 1 spurious detection on the average. The Sung et al. (2000, AJ, 120, 333; <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/AJ/120/333">CDS Cat. <J/AJ/120/333></a>) = SCB Catalog of optical objects against which the X-ray point source list was compared doed not cover the easternmost 2.25' of the ACIS FOV (RAs later than 18^h 04^m 52^s), notice, which comprises about 13% of the ACIS FOV. There are 46 detected X-ray sources (5.2% of the total) in the area not covered by the SCB Catalog. A matching distance of 4 times the X-ray error radius or 2.0" (whichever is greater) was used to identify optical counterparts to the X-ray sources, after a systematic shift between the X-ray and optical positions of -0.4" and 1.84" in RA and declination, respectively, was applied. The authors estimate that as many as 28 of their 220 optical identifications may be spurious, preferentially those in the outer parts of the FOV where the positional uncertainties are larger. There are 8792 'good' 2MASS sources in the ACIS FOV. A matching distance of 4 times the X-ray error radius or 1.5" (whichever is greater) was used to identify 2MASS counterparts to the X-ray sources, after systematic corrections of 0.3" and 1.75" in RA and declination, respectively, were applied to the 'raw' X-ray positions. There are 13 cases where there are two possible IR counterparts to a single X-ray source, and 2 cases where there are three possible IR Counterparts to a single X-ray source. (Notice that, in such cases, this table contains multiple entries, one for each counterpart, and hence there are 901 entries compared to 884 X-ray sources.) The authors conclude that the plausible number of spurious X-ray-2MASS identifications is between 30 and 50. Overall, there remain 146 X-ray sources with no optical or IR identification. This table was created by the HEASARC in December 2006 based on CDS table J/ApJ/608/781, the file table1.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc1893cxo
- Title:
- NGC 1893 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC1893CXO
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The outer Galaxy, where the environmental conditions are different from the solar neighbourhood, is a laboratory in which it is possible to investigate the dependence of the star formation process on the environmental parameters. The authors investigate the X-ray properties of NGC 1893, a young cluster (~ 1 - 2 Myr) in the outer part of the Galaxy (galactic radius >= 11 kpc), where they expect differences in the disk evolution and in the mass distribution of the stars, so as to explore the X-ray emission of its members and compare it with that of young stars in star forming regions near to the Sun. The authors analyze 5 deep Chandra ACIS-I observations with a total exposure time of 450 ks. Source events of the 1021 X-ray sources have been extracted with the IDL-based routine ACIS-Extract. Using spectral fitting and quantile analysis of X-ray spectra, they derive X-ray luminosities and compare the respective properties of Class II and Class III members. They also evaluate the variability of sources using the Kolmogorov-Smirnov test and identify flares in the lightcurves. The X-ray luminosity of NGC 1893 X-ray members is in the range 10<sup>29.5</sup> - 10<sup>31.5</sup> erg s<sup>-1</sup>. Diskless stars are brighter in X-rays than disk-bearing stars, given the same bolometric luminosity. The authors find that 34% of the 1021 lightcurves appear variable and that they show 0.16 flares per source, on the average. Comparing their results with those relative to the Orion Nebula Cluster, they find that, after accounting for observational biases, the X-ray properties of NGC 1893 and the Orion stars are very similar. The authors conclude that the X-ray properties of stars in NGC 1893 are not affected by the environment and that the stellar population in the outer Galaxy may have the same coronal properties as nearby star-forming regions. The X-ray luminosity properties and the X-ray luminosity function appear to be universal and can therefore be used for estimating distances and for determining stellar properties. This table was created by the HEASARC in March 2012 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/539/A74">CDS Catalog J/A+A/539/A74</a> file catalog.dat, the catalog of 1021 X-ray sources detected towards NGC 1893. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc2237cxo
- Title:
- NGC 2237 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC2237CXO
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The authors have obtained high spatial resolution Chandra X-ray images of the NGC 2237 young stellar cluster on the periphery of the Rosette Nebula. They detect 168 X-ray sources, 80% of which have stellar counterparts in USNO, Two Micron All Sky Survey, and deep FLAMINGOS images. These constitute the first census of the cluster members with 0.2 <~ M <~ 2 M<sub>sun</sub>. Star locations in near-infrared color-magnitude diagrams indicate a cluster age of around 2 Myr with a visual extinction of 1 <~ AV <~ 3 at 1.4 kpc, the distance of the Rosette Nebula's main cluster NGC 2244. The authors derive the K-band luminosity function and the X-ray luminosity function of the cluster, which indicate a population of ~ 400-600 stars. The X-ray-selected sample shows a K-excess disk frequency of 13%. The young Class II counterparts are aligned in an arc ~3 pc long suggestive of a triggered formation process induced by the O stars in NGC 2244. The diskless Class III sources are more dispersed. Several X-ray emitting stars are located inside the molecular cloud and around gaseous pillars projecting from the cloud. These stars, together with a previously unreported optical outflow originating inside the cloud, indicate that star formation is continuing at a low level and the cluster is still growing. This X-ray view of young stars on the western side of the Rosette Nebula complements the authors' earlier studies of the central cluster NGC 2244 and the embedded clusters on the eastern side of the Nebula. The large-scale distribution of the clusters and molecular material is consistent with a scenario in which the rich central NGC 2244 cluster formed first, and its expanding H II region triggered the formation of the now-unobscured satellite clusters Rosette Molecular Cloud (RMC) XA and NGC 2237. A large swept-up shell of material around the H II region is now in a second phase of collect-and-collapse fragmentation, leading to the recent formation of subclusters. Other clusters deeper in the molecular cloud appear unaffected by the Rosette Nebula expansion. Some sources which have information from published catalogs are listed by their source_number value below, where for convenience, [OI81] = Ogura & Ishida (1981, PASJ, 33, 149), [MJD95] = Massey, Johnson, & Degioia-Eastwood (1995, ApJ, 454, 151) and [BC02] = Berghofer & Christian (2002, A&A, 384, 890): <pre> 53 = [OI81] 14 = [MJD95] 104; spectral type B1V; pmRA=11.0 mas/yr, pmDE=-2.8 mas/yr; 54 = [OI81] 10 = [MJD95] 108; spectral type B2V; pmRA=-2.3 mas/yr, pmDE=-11.9 mas/yr; 61 = V539 Mon [OI81] 13 = [MJD95] 110; MSX6C G206.1821-02.3456; pmRA=2.8 mas/yr, pmDE=0.4 mas/yr; 71 = [OI81] 12 = [MJD95] 102; pmRA=6.8 mas/yr, pmDE=0.6 mas/yr; 128 = [OI81] 35 = [MJD95] 471; spectral type A2:; pmRA=-0.8 mas/yr, pmDE=3.6 mas/yr; 138 = [OI81] 36 = [MJD95] 497; spectral type B5; pmRA=6.5 mas/yr, pmDE=2.1 mas/yr; 141 = [MJD95] 498; pmRA=-3.0 mas/yr, pmDE=1.9 mas/yr; 149 = [BC02] 11; known X-ray source; log(Lx(ROSAT/PSPC))=31.01 erg/s; pmRA=0.6 mas/yr, pmDE=-12.6 mas/yr; 161 = [MJD95] 653; pmRA=-1.0 mas/yr, pmDE=-5.4 mas/yr </pre> This table was created by the HEASARC in July 2010 based on electronic versions of Tables 1, 2, 3 and 4 of the reference paper which were obtained from the electronic ApJ web site. To distinguish between the 130 X-ray sources in the primary sample (Table 1 of the reference paper) and the 38 X-ray sources in the tentative sample (Table 2 of the reference paper), the HEASARC has created a parameter called source_sample which is set to 'P' for the primary sources and to 'T' for the tentative sources. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc752cxo
- Title:
- NGC 752 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC752CXO
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table provides a list of X-ray sources detected in a ~140 ks Chandra X-ray observation of the open cluster NGC 752. For the sources with 2MASS counterparts, the values of their magnitudes in the J, H and K bands are also given. Very little is known about the evolution of stellar activity between the ages of the Hyades (0.8 Gyr) and the Sun (4.6 Gyr). To gain information on the typical level of coronal activity at a star's intermediate age, the authors have studied the X-ray emission from stars in the 1.9 Gyr-old open cluster NGC 752. They analyzed a ~ 140 ks Chandra observation of NGC 752 and a ~50 ks XMM-Newton observation of the same cluster. They detected 262 X-ray sources in the Chandra data and 145 sources in the XMM-Newton observation. Around 90% of the catalogued cluster members within Chandra's field of view are detected in the X-ray observation. The X-ray luminosity of all observed cluster members (28 stars) and of 11 cluster member candidates was derived. These data indicate that, at an age of 1.9 Gyr, the typical X-ray luminosity L<sub>x</sub> of the cluster members with masses of 0.8 to 1.2 solar masses is 1.3 x 10<sup>28</sup> erg s<sup>-1</sup>, which is approximately a factor of 6 times less intense than that observed in the younger Hyades. Given that L<sub>x</sub> is proportional to the square of a star's rotational rate, the median L<sub>x</sub> of NGC 752 is consistent, for t >= 1 Gyr, with a decaying rate in rotational velocities v<sub>rot</sub> ~ t<sup>-alpha</sup> with alpha ~ 0.75, steeper than the Skumanich relation (alpha ~ 0.5) and significantly steeper than that observed between the Pleiades and the Hyades (where alpha <0.3), suggesting that a change in the rotational regimes of the stellar interiors is taking place at an age of ~ 1 Gyr. The 135 ks observation of NGC 752 was performed by the Chandra ACIS camera on September 29, 2003 starting at 21:11:59 UT. The X-ray source detection was performed on the event list using the Wavelet Transform detection algorithm developed at Palermo Astronomical Observatory PWDETECT, available at <a href="http://oapa.astropa.unipa.it/progetti_ricerca/PWDetect">http://oapa.astropa.unipa.it/progetti_ricerca/PWDetect</a>. Initially, the energy range 0.2 - 10 keV was selected and the threshold for source detection was taken as to ensure a maximum of 1-2 spurious sources per field. 169 sources were detected in this way. The analysis of these sources hardness ratios showed, however, that all the catalogued stars in the field had low hardness ratios, HR < ~ 0.2, where HR is the number of photons in the 2 - 8 keV band over the number in the 0.5 - 2 keV band. Thus, to maximize the detection of stellar sources, PWDETECT was applied to the event list in the energy range from 0.5 - 2 keV. Using a detection threshold which ensures less than 1 spurious source per field leads to the detection of 188 sources, while lowering this threshold to 10 spurious sources per field, allows 262 sources to be identified in this energy range. This is a significant increase (well above the number expected if all the additional sources were spurious), thus the authors retained this list of 262 sources as their final list of sources in the NGC 752 field, with the caveat that ~ 10 sources among them are likely spurious. Note that the existence of ~ 10 spurious sources in the list is not so much of a problem in this context, because cluster members or candidate members are identified by the existence of a visible or near-IR counterpart. The authors searched for 2MASS counterparts to the X-ray sources using the 2MASS Point Source Catalogue (PSC) and a search radius of 3 arcsec and found a counterpart for 43 sources. Searching within the Point Source Reject Table of the 2MASS Extended Mission leads to the further identification of 1 counterpart (source number 87). This table was created by the HEASARC in October 2008 based on the electronic version of Table 6 from the reference paper which was obtained from the CDS website, i.e., their catalog J/A+A/490/113 file table6.dat. 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:
- 07 Mar 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:
- 07 Mar 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/ngc2264cxo
- Title:
- NGC 2264 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC2264CXO
- Date:
- 07 Mar 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:
- 07 Mar 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 .
