- ID:
- ivo://nasa.heasarc/lalaboocxo
- Title:
- LALA Bootes Field Chandra X-Ray Point Source Catalog
- Short Name:
- LALABOOCXO
- Date:
- 02 May 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the results of an analysis of a deep, 172 ks Chandra observation of the Large Area Lyman Alpha survey (LALA) Bootes field which was obtained with the Advanced CCD Imaging Spectrometer (ACIS-I) on board the Chandra X-Ray Observatory. This is one of the deepest Chandra images of the extragalactic sky, with only the 2 Ms Chandra Deep Field North (CDF-N) and the 1 Ms Chandra Deep Field South (CDF-S) observations being substantially deeper. In this table, the X-ray source catalog obtained from this image is presented, along with some results from an analysis of the X-ray source counts and optical identifications. The X-ray image is composed of two individual observations obtained in 2002 and reaches 0.5 - 2.0 and 2.0 - 10.0 keV flux limits of 1.5 x 10<sup>-16</sup> and 1.0 x 10<sup>-15</sup> ergs/cm<sup>2</sup>/s, respectively, for point sources near the aim point. A total of 168 X-ray sources were detected: 160 in the 0.5 - 7.0 keV band, 132 in the 0.5 - 2.0 keV band, and 111 in the 2.0 - 7.0 keV band. Since X-ray source number 122 has two possible optical counterparts, it is listed twice, once for each counterpart, and the total number of entries in this table is this 169. The primary optical data are R-band imaging from the NOAO Deep Wide-Field Survey (NDWFS), with a limiting magnitude of R = 25.7 magnitudes, (Vega, 3-sigma detection level, and a 4" diameter aperture). Optical counterparts within 1.5" or the 3-sigma X-ray positional uncertainties, whichever was larger, were detected above this level in the R band for 144 of the 168 X-ray sources. At least 90% of the optical counterparts should be the correct matches, and, at worst, there might be ~14 false matches. This table was created by the HEASARC in March 2007 based on the CDS table J/AJ/127/213 file table1.dat, This is a service provided by NASA HEASARC .
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- ID:
- ivo://nasa.heasarc/lalacetcxo
- Title:
- LALA Cetus Field Chandra X-Ray Point Source Catalog
- Short Name:
- LALACETCXO
- Date:
- 02 May 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The 174 ks Chandra Advanced CCD Imaging Spectrometer (ACIS) exposure of the Large Area Lyman Alpha Survey (LALA) Cetus field is the second of the two deep Chandra images on LALA fields. In their paper, the authors present the Chandra X-ray sources detected in the Cetus field, along with an analysis of X-ray source counts, the stacked X-ray spectrum, and the optical identifications. A total of 188 X-ray sources were detected: 174 in the 0.5-7.0 keV band, 154 in the 0.5-2.0 keV band, and 113 in the 2.0-7.0 keV band. The X-ray source counts were derived and compared with the 172 ks exposure LALA Bootes field (available as the LALABOOCXO table in Browse). Interestingly, the authors find consistent hard-band X-ray source density, but a (36 +/- 12)% higher soft-band X-ray source density in the Cetus field. The weighted stacked spectrum of the detected X-ray sources can be fitted by a power law with photon index Gamma = 1.55. Based on the weighted stacked spectrum, the authors find that the resolved fraction of the X-ray background drops from (72 +/- 1)% at 0.5-1.0 keV to (63 +/- 4)% at 6.0-8.0 keV. The unresolved spectrum can be fitted by a power law over the range 0.5-7 keV, with a photon index Gamma = 1.22. Optical counterparts are also presented for 154 of the X-ray sources, down to a limiting magnitude of r' = 25.9 (Vega), using a deep r'-band image obtained with the MMT. This table was created by the HEASARC in October 2010 based on the CDS table J/ApJ/669/765 file table1.dat This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/lkha101cxo
- Title:
- LkH-alpha 101 Star Formation Region Chandra X-Ray Point Source Catalog
- Short Name:
- LKHA101CXO
- Date:
- 02 May 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains some of the results from a multi-wavelength study of a partially embedded region of star formation centered on the Herbig Be star LkH-alpha 101. Using two 40 ks Chandra observations, The authors have detected 213 X-ray sources in the ~ 17' x 17' ACIS-I field. They combine the X-ray data with Two Micron All Sky Survey (2MASS) near-IR observations and Spitzer Space Telescope (SST) IRAC and MIPS 24-micron observations to obtain a complete picture of the cluster. A total of 158 of the X-ray sources have infrared counterparts. Of these, the authors find nine protostars, 48 Class II objects, five transition objects, and 72 Class III objects. From the Spitzer data, they identify an additional 10 protostars, 53 Class II objects, and four transition disk candidates which are not detected by Chandra. (These objects are not included in this HEASARC table which contains the multi-wavelength data for only the 213 detected X-ray sources). The authors obtained optical spectra of a sample of both X-ray-detected and non-X-ray-detected objects. Combining the X-ray, Spitzer, and spectral data, they obtain independent estimates of cluster distance and the total cluster size - excluding protostars. The authors obtain consistent distance estimates of 510 (+100,-40) pc and a total cluster size of 255 (+50,-25) stars. They find the Class II:III ratio is about 5:7 with some evidence that the Class III sources are spatially more dispersed. The cluster appears very young with three sites of active star formation and a median age of about 1 Myr. The field was observed by Chandra on 2005 March 6 starting at 17:16 UT for 40.2 ks of total time and 39.6 ks of the so-called good time (Chandra ObsID 5429). It was observed again on 2005 March 8 starting at 17:43 UT for essentially the same duration (Chandra ObsID 5428). The ACIS was used in the nominal imaging array (chips I0-I3) which provides a field of view of approximately 17' x 17'. The aimpoint was at RA, Dec = 04:30:14.4, +35:16:22.2 (J2000.0) with a roll angle of 281 degrees. In addition, the S2 and S3 chips were active; however, the analysis of these data is not presented here. For purposes of point-source detection, the data from the two observations were merged into a single event list following established CIAO procedures to create a merged event list. To identify point sources, photons with energies below 300 eV and above 8.0 keV were filtered out from this merged event list. This excluded energies which generally lack a stellar contribution. By filtering the data as described, contributions from hard, non-stellar sources such as X-ray binaries and active galactic nuclei (AGNs) are attenuated, as is noise. A monochromatic exposure map was generated in the standard way using an energy of 1.49 keV which is a reasonable match to the expected peak energy of the stellar sources and the Chandra mirror transmission. The CIAO tool WavDetect was then run on a series of flux-corrected images binned by 1, 2, and 4 pixels. The output source lists were combined and this resulted in the detection of 231 sources. The authors defined false detections as any sources with < 4 net counts or any sources more than 5' off-axis with < 7 net counts. By this definition, 18 of the 231 detections were rejected as false detections. A post facto check confirmed that none of these (spurious) sources had an infrared counterpart. This table was created by the HEASARC in July 2010 based on the versions of Tables 1, 2, 3, 7 and 9 from the paper which were obtained from the electronic ApJ web site. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/lmc30drcxo
- Title:
- LMC 30 Doradus Complex Chandra X-Ray Point Source Catalog
- Short Name:
- LMC30DRCXO
- Date:
- 02 May 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the results of a study of the X-ray point-source population of the 30 Doradus (30 Dor) star-forming complex in the Large Magellanic Cloud (LMC) using high spatial-resolution X-ray images and spatially-resolved spectra obtained with the Advanced CCD Imaging Spectrometer (ACIS) on board the Chandra X-Ray Observatory. The observation of ~21 ks was made on 1999 September 21 and placed the cluster R136 at the aim point of the ACIS Imaging Array (ACIS-I). This table lists the the X-ray sources detected in the 17' x 17' field centered on R136, the massive star cluster which lies at the center of the main 30 Dor nebula. 20 of the 32 Wolf-Rayet stars in the ACIS field are detected. The cluster R136 is resolved at the sub-arcsecond level into almost 100 X-ray sources, including many typical O3-O5 stars, as well as a few bright X-ray sources which had been previously reported. Over 2 orders of magnitude of scatter in the X-ray luminosity L<sub>x</sub> (calculated assuming a distance of 50 kpc) is seen among R136 O stars, suggesting that X-ray emission in the most massive stars depends critically on the details of wind properties and the binarity of each system, rather than reflecting the widely reported characteristic value L<sub>x</sub>/L<sub>bol</sub> ~ 10<sup>-7</sup>. Such a canonical ratio may exist for single massive stars in R136, but these data are too shallow to confirm this relationship. Through this and more recent X-ray studies of 30 Dor, the complete life cycle of a massive stellar cluster can be revealed. This HEASARC table contains both the primary high-significance X-ray sources as well as some lower-significance tentative X-ray sources. The latter sources should not be considered definitive. A subsequent Chandra observation of this field, with several times the exposure of this observation, will result in a longer, more complete list of point sources than that given in this paper. This table was created by the HEASARC in February 2007 based on the merger of electronic versions of Tables 1, 2 and 5 from the above reference which were obtained from the AJ website. It does not include the results from the spectral analysis of 49 of the X-ray sources having a photometric significance (signal-to-noise ratio) greater than 2 which are presented in Tables 3 and 4 of the reference paper. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/lmcn11cxo
- Title:
- LMC N11 Giant HII Region Chandra X-Ray Point Source Catalog
- Short Name:
- LMCN11CXO
- Date:
- 02 May 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- A very sensitive X-ray investigation of the giant H II region N11 in the Large Magellanic Cloud (LMC) was performed using the Chandra X-ray Observatory in which 165 point sources were detected. The 300-ks observation reveals X-ray sources with luminosities (if at the 50 kpc distance of the LMC) down to 10<sup>32</sup> erg s<sup>-1</sup>, increasing the number of known point sources in the field by more than a factor of five. Among these detections are 13 massive stars (3 compact groups of massive stars, 9 O stars, and one early B star) with log(L<sub>X</sub>/L<sub>BOL</sub>) ~ -6.5 to -7, which may suggest that they are highly magnetic or colliding-wind systems. On the other hand, the stacked signal for regions corresponding to undetected O stars yields log(L<sub>X</sub>/L<sub>BOL</sub>) ~ -7.3, i.e., an emission level comparable to similar Galactic stars despite the lower metallicity. Other point sources coincide with 11 foreground stars, 6 late-B/A stars in N11, and many background objects. This observation also uncovers the extent and detailed spatial properties of the soft, diffuse emission regions, but the presence of some hotter plasma in their spectra suggests contamination by the unresolved stellar population. The Chandra ACIS-I observations of N11 were made in six separate segments within two months in 2007. As summarized in Table 1, the exposure time of each segment was 42-49 ks and the roll angle ranged from 130 to 188 degrees Cleaning of significant background flares, together with a correction for the dead time of the six observations, resulted in a total of 280 ks useful exposure for the subsequent analysis. A combination of source detection algorithms (wavelet, sliding-box, and maximum likelihood centroid fitting) were applied to unsmoothed data in three bands: soft (S): 0.5-2.0 keV, hard (H): 2-8 keV, and total (T): 0.5-8 keV. The final source list contains 165 sources with local false detection probability P < 10<sup>-6</sup> in at least one band (Poisson statistics were used in calculating the significance of a source detection above the local count background). The source detection, though optimized for point-like sources, includes a few strong peaks of diffuse X-ray emission, chiefly associated with the SNR N11L, which lies about ~7' west of the field center. The authors calculated the net (background-subtracted) count rates in four sub-bands (S1 = 0.5-1.0 keV, S2 = 1-2 keV, H1 = 2-4 keV and H2 = 4-8 keV, which were later added to form the count rates in the broader bands (S, H, and T). Source counts for each sub-band were then extracted within the 70% energy-encircled radius (EER) of the PSF, whose size depends on the off-axis angle of the source in the exposure and of the energy band under consideration. A background correction was also applied. Finally, count rates were derived by dividing source net counts by their effective exposure times (values at the source positions in the exposure map of the energy band under consideration), leading to equivalent on-axis values. It should be noted that the presented count rates have thus been corrected for the full PSF and for the effective exposure, which accounts not only for the telescope vignetting, but also for the degradation of the detector sensitivity over time. Therefore, the actual number of counts in a detection aperture is not simply a count rate multiplied by an exposure of 280 ks. The difference could be up to a factor of ~2, depending on a source's spectral shape. The authors searched for counterparts to their X-ray sources in several catalogs: the USNO-B1.0 Catalog (Monet et al. 2003), the Guide Star Catalog V2.3.2 (GSC, Lasker et al. 2008), the 2MASS All-Sky Catalog of Point Sources (Cutri et al. 2003), the Magellanic Clouds Photometric Survey (MCPS; Zaritsky et al. 2004, AJ, 128, 1606), the IRSF Magellanic Clouds Point Source Catalog (Kato et al. 2007, PASJ, 59, 615)), the DENIS Catalogue toward Magellanic Clouds (DCMC; Cioni et al. 2000, A&AS, 144, 235), and JHK<sub>s</sub> photometry of N11 young stellar objects ([HKN2006]; Hatano et al. 2006, AJ, 132, 2653). A best correlation radius of 1" was found to be optimal and was thus used to derive the final list of optical and infrared counterparts to the Chandra X-ray sources: 71 of the 165 sources have at least one counterpart within 1". The HEASARC has modified the counterpart names given in this table compared to those given in the reference paper so that they comply with the forms recommended by the CDS Dictionary of Nomenclature of Celestial Objects. This table was created by the HEASARC in August 2014 based primarily on the contents of Tables 2, 3 and 4 from the reference paper, machine-readable versions of which were obtained from the ApJS web site. Some information from Table 8 of the reference paper, viz., a number of the spectral types quoted for individual stars, was also used in populating the HEASARC-created class parameter. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/moxc
- Title:
- Massive Star-Forming Regions Omnibus X-Ray Catalog
- Short Name:
- MOXC
- Date:
- 02 May 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the Massive Star-forming Regions (MSFRs) Omnibus X-ray Catalog (MOXC), a compendium of X-ray point sources from Chandra/ACIS observations of a selection of MSFRs across the Galaxy, plus 30 Doradus in the Large Magellanic Cloud. MOXC consists of 20,623 X-ray point sources from 12 MSFRs with distances ranging from 1.7 kpc to 50 kpc, and comprises Table 3 of the reference paper. In their paper, the authors show the morphology of the unresolved X-ray emission that remains after the cataloged X-ray point sources are excised from the ACIS data, in the context of Spitzer and WISE observations that trace the bubbles, ionization fronts, and photon-dominated regions that characterize MSFRs. In previous work, they have found that this unresolved X-ray emission is dominated by hot plasma from massive star wind shocks. This diffuse X-ray emission is found in every MOXC MSFR, clearly demonstrating that massive star feedback (and the several-million-degree plasmas that it generates) is an integral component of MSFR physics. The Chandra observations used for the Massive Star-forming Regions Omnibus X-ray Catalog (MOXC) are summarized in Table 2 of the reference paper and have dates ranging from 2000-04-03 to 2013-01-31 for the 12 MSFRs: the 7 MYStIX targets NGC 6334, NGC 6357, M 16, M 17, W 3, W 4 and NGC 3576, and the 5 "beyond-MYStIX" targets G333.6-0.2, W 51A, G29.96-0.02, NGC 3603 and 30 Doradus. A similar table to MOXC for other MYStIX targets was presented by Kuhn et al. (2013, ApJS, 209, 27, available as the HEASARC MYSTIXXRAY table). The main difference between that table and the MOXC version is that the present authors have chosen to omit absorption-corrected X-ray source luminosities from the XPHOT algorithm (Getman et al. 2010, ApJ, 708, 1760) herein, because those quantities are given in Broos et al. (2013, ApJS, 209, 32, available as the HEASARC MYSTIXMPCM table) for relevant MYStIX X-ray sources (those classified as pre-main sequence stars). For beyond-MYStIX targets, the authors chose to postpone XPHOT calculations until the X-ray sources were classified, since XPHOT estimates are only appropriate for pre-MS stars. The XPHOT code is available (Getman et al. 2012, Astrophysics Source Code Library, record ascl.soft12002) if others wish to use it on MOXC sources. All photometric quantities in this table are apparent (not corrected for absorption). The HEASARC has used prefixes 'fb_', 'sb_' and 'hb_' (replacing the suffixes '_t', '_s' and '_h' used in the reference paper) on the names of the X-ray photometric quantities which designate the full (total, 0.5 - 8 keV), soft (0.5 - 2.0 keV) and hard (2-8 keV) energy bands. Correction for finite extraction apertures is applied to the ancillary reference file (ARF) calibration products (see Broos et al. 2010, ApJ, 714, 1582, Section 5.3); the total_counts and counts quantities characterize the extraction and are not aperture-corrected. The only calibrated quantities presented are the apparent photon fluxes, in units of photon cm<sup>-2</sup> s<sup>-1</sup> (see Broos et al. 2010, ApJ, 714, 1582, Section 7.4), and estimates for the apparent energy fluxes, in units of erg cm<sup>-2</sup> s<sup>-1</sup> (Getman et al. 2010, ApJ, 708, 1760). This table was created by the HEASARC in October 2014 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJS/213/1">CDS Catalog J/ApJS/213/1</a> files table3.dat (the MOXC X-ray Source Catalog) and table6.dat (the list of MOXC sources in previously published Chandra catalogs). This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/mystixxray
- Title:
- MassiveYoungStar-FormingComplexStudyinIR&X-Rays:X-RaySourceCatalog
- Short Name:
- MYSTIXXRAY
- Date:
- 02 May 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The Massive Young Star-forming complex Study in Infrared and X-ray (MYStIX) uses data from the Chandra X-Ray Observatory to identify and characterize the young stellar populations in 20 Galactic (d < 4 kpc) massive star-forming regions. In this present study, the X-ray analysis for Chandra ACIS-I observations of 10 of the MYStIX fields is described, and a catalog of > 10,000 X-ray sources is presented in this table. In comparison to other published Chandra source lists for the same regions, the number of MYStIX-detected faint X-ray sources in a region is often doubled. While the higher catalog sensitivity increases the chance of false detections, it also increases the number of matches to infrared stars. X-ray emitting contaminants include foreground stars, background stars, and extragalactic sources. The X-ray properties of sources in these classes are discussed in the reference paper. The X-ray observations were made with the imaging array on the Advanced CCD Imaging Spectrometer (ACIS-I) on board the Chandra X-Ray Observatory. This array of four CCD detectors subtends 17' x 17' on the sky. The number of different Chandra pointings for each region, the total exposures for these pointings, and details of how the observations were taken are provided in Table 1 of the reference paper. Overall, 29 Chandra ObsIDs are included with typical integration times for a pointing of 40 - 100 ks, sufficient to detect most OB stars and lower-mass pre-main-sequence stars down to ~ 0.5 - 1 solar masses for the MYStIX regions. The 10 MYStIX MSFRs treated herein are listed in Table 2 of the reference paper. The data were acquired from the Chandra Data Archive from 2001 Jan to Mar 2008 for 10 MYStIX fields (the Flame Nebula, RCW 36, NGC 2264, the Rosette Nebula, the Lagoon Nebula, NGC 2362, DR 21, RCW 38, Trifid Nebula and NGC 1893). The X-ray photometry is from Broos et al. (2010, ApJ, 714, 1582; ACIS Extract); see also the CCCP, Broos et al. (2011, ApJS, 194, 2). The source significance quantities (fb_prob_no_src, sb_prob_no_src, hb_prob_no_src and prob_no_src_min) are computed using a subset of each source's extractions chosen to maximize significance (Broos et al. 2010, ApJ, 714, 1582, Section 6.2). The source position and positional uncertainty quantities are computed using a subset of each source's extractions chosen to minimize the position uncertainty (Broos et al. 2010, ApJ, 714, 1582, Sections 6.2 and 7.1). All other quantities are computed using a subset of each source's extractions chosen to balance the conflicting goals of minimizing photometric uncertainty and of avoiding photometric bias (Broos et al. 2010, ApJ, 714, 1582, Sections 6.2 and 7). The observed and absorption-corrected energy fluxes and their associated errors and the estimated hydrogen column densities and their uncertainties are derived using non-parametric procedures (XPHOT, Getman et al. 2010, ApJ, 708, 1760). XPHOT assumes the X-ray spectral shapes of young, low-mass stars, which come from coronal X-ray emission. XPHOT quantities will therefore be unreliable for high-mass stars, for which X-ray emission is associated with the stellar wind. This table was created by the HEASARC in January 2014 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJS/209">CDS Catalog J/ApJS/209</a> 27 file xmystix.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/m31cxo2
- Title:
- M 31 Bulge Chandra X-Ray Point Source Catalog
- Short Name:
- M31CXO2
- Date:
- 02 May 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The authors explore the population of X-ray point sources in the bulge of M 31 so as to contrast properties of various subpopulations, such as persistent and transient sources and primordial LMXBs and dynamically formed ones. Based on the data from 26 archival Chandra ACIS observations with aim-points within 10 arcminutes of the center of M 31 (J2000 coordinates of 00:42:44.31, +41:16:09.4), the authors study the source content and properties of various subpopulations of X-ray sources to a maximum distance of 12 arcminutes from the center of M 31. To a limiting luminosity of ~10<sup>35</sup> erg s<sup>-1</sup>, the authors find 263 X-ray point sources, with ~1/3 of these being background galaxies. A study of the spatial distribution and the luminosity function of the X-ray sources shows that the distribution of primordial LMXBs is consistent with the distribution of the K-band light and that their luminosity function flattens below ~10<sup>37</sup> erg s<sup>-1</sup> to the dN/dL ~ L<sup>-1</sup> law in agreement with the behavior found earlier for LMXBs in the Milky Way and in Cen A. Within a radius of 12 arcminutes, the luminosity function is independent of distance to the center of M 31, in contrast to earlier Chandra studies. The LMXBs located in globular clusters and within ~1 arcminute from the center of M 31 are presumably created via dynamical interactions. The dynamical origin of the r < 1 arcminute sources is strongly suggested by their radial distribution which follows the rho<sub>*</sub><sup>2</sup> profile rather than the K-band light distribution. Their luminosity function shows a prominent fall-off below log(L<sub>X</sub>) <~ 36.5. Although the statistics are insufficient to claim a genuine low-luminosity cut-off in the luminosity function, the best fit power-law with a slope of -0.6 +/- 0.2 is significantly flatter than the dN/dL ~ L<sup>-1</sup> law. The authors also searched for transients and found 28 sources that varied by a factor larger than 20. Their spatial distribution follows the distribution of the persistent LMXBs within the accuracy allowed by the limited number of transients. This HEASARC table was created in March 2010 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/468/49">CDS catalog J/A+A/468/49</a> file table2.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/m31cfcxo
- Title:
- M 31 Central Field Chandra HRI X-Ray Point Source Catalog
- Short Name:
- M31CFCXO
- Date:
- 02 May 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The central field of the Andromeda galaxy (M 31) was monitored from 2006 to 2012 using the Chandra HRC-I detector (about 0.1 - 10 keV energy range) with the main aim of detecting X-rays from optical novae. The authors present a systematic analysis of all X-ray sources found in the 41 nova monitoring observations, along with 23 M 31 central field HRC-I observations available from the Chandra data archive starting in December 1999. Based on these observations, they studied the X-ray long-term variability of the source population and especially of the X-ray binaries in M31. The authors created a catalog of sources detected in the 64 available observations that adds up to a total exposure time of about 1 Ms. To study the variability, they developed a processing pipeline to derive long-term Chandra HRC-I light curves for each source over the 13 years of observations, and also searched for extended X-ray sources in the merged images. This table contains the point-source catalog of 318 X-ray sources with detailed long-term variability information, 28 of which are published for the first time. The spatial and temporal resolution of the catalog allows the authors to classify 115 X-ray binary candidates showing high X-ray variability or even outbursts, as well as 14 globular cluster X-ray binary candidates showing no significant variability. The analysis may suggest that outburst sources are less frequent in globular clusters than in the field of M 31. Seven supernova remnants (not included in the point-source catalog) were detected, one of which is a new candidate, and also the first X-rays from a known radio supernova remnant were resolved. In addition to 33 known optical nova/X-ray source correlations, the authors discovered one previously unknown super-soft X-ray outburst and several new nova candidates. A large sample of detailed long-term X-ray light curves of sources in the M31 central field has been obtained in this study (see Appendix B.1 of the reference paper), which helps in understanding the X-ray population of our neighboring spiral galaxy M 31. Based on all the available Chandra HRC-I observations (see Table A.1 in the reference paper for the complete list), a source catalog has been created (available in this HEASARC table) and the energy flux of each source in every individual observation derived (these are not available in this HEASARC table, but are obtainable at the CDS: for more details, see the files <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A%2BA/555/A65/ReadMe">https://cdsarc.cds.unistra.fr/ftp/cats/J/A%2BA/555/A65/ReadMe</a> and <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J_A%2BA/555/A65/table2.dat.gz">https://cdsarc.cds.unistra.fr/ftp/cats/J_A%2BA/555/A65/table2.dat.gz</a>). One thing to be aware of is that, in the latter file, upper limits are denoted by a '>' symbol rather than the more usual '<' symbol!). These fluxes were calculated assuming a generic power law spectrum and Galactic foreground absorption for each source. This table was created by the HEASARC in August 2013 based on the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/555/A65">CDS catalog J/A+A/555/A65</a> files table1.dat and xcorr.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/m31cxoxray
- Title:
- M 31 Central Region Chandra X-Ray Point Source Catalog
- Short Name:
- Chan/M31
- Date:
- 02 May 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table countains the M 31 Central Region Catalog of Chandra X-Ray Point Sources. It is based on Chandra observations of the central region of M 31. By combining eight Chandra ACIS-I observations which were taken between 1999 and 2001, the authors have identified 204 X-ray sources within the central ~17'x17' region of M 31, with a detection limit of ~2x10<sup>35</sup> erg/s. Of these 204 X-ray sources, 22 are identified with globular clusters, two with supernova remnants, nine with planetary nebulae, and nine with supersoft sources. By comparing individual images, about 50% of the sources were found to be variable on timescales of months. The authors also found 13 transients, with light curves showing a variety of shapes. They also extracted the energy spectra of the 20 brightest sources; they can be well fitted by a single power law with a mean photon index of 1.8. The spectral shapes of 12 sources were variable, suggesting that they went through state changes. All sources in the catalog have S/N > 2.5 and only five have S/N < 3.0. The detection limit for the sources varies across the image due to the variation of exposure time, background, and instrumental PSF, and is highest near the edges, where the PSF broadens rapidly and the exposure time is lowest. Over the inner 4' of the field, the detection limit is 2.1 x 10<sup>-4</sup> ct/s, which is equivalent to an X-ray luminosity of about 2 x 10<sup>35</sup> erg/s. Additional information about optical identifications and cross-correlated ROSAT X-ray sources not provided in this HEASARC table is available in the published paper (Tables 4 and 5) and/or the CDS at <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/577/738/">https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/577/738/</a> (table4.dat & table5.dat). This table was created by the HEASARC in October 2004 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/577/738/table2">CDS Catalog J/ApJ/577/738/table2</a>.dat. This is a service provided by NASA HEASARC .
