A 50 ks Chandra observation of the unidentified TeV source in Cygnus reported by the High Energy Gamma-Ray Astronomy (HEGRA) collaboration reveals no obvious diffuse X-ray counterpart. However, 240 pointlike X-ray sources are detected within or nearby the extended TeV J2032+4130 source region, of which at least 36 are massive stars and two may be radio emitters. That the HEGRA source is a composite, having as a counterpart the multiple pointlike X-ray sources that are observed, cannot be ruled out. Indeed, the distribution of pointlike X-ray sources appears nonuniform and concentrated broadly within the extent of the TeV source region. A hypothesis is offered for the origin of the very high energy gamma-ray emission in Cyg OB2 based on the local acceleration of TeV-range cosmic rays and the differential distribution of OB versus less massive stars in this association. The region of TeV J2032+4130 was observed by Chandra on 2004 July 12 for a total effective exposure time of 48,728 seconds using the Advanced CCD Imaging Specrometer imaging array (ACIS-I). The observation was centered on J2000.0 coordinates (RA, Dec) = )20 32 07.0, +41 30 30). This table contains the list of the 240 pointlike sources which were detected in the ACIS-I data and their 2MASS near-IR counterparts, if any are found within 3" of the X-ray sources. 130 (54%) of the 240 X-ray sources have 2MASS counterparts within these error radii. This table was created by the HEASARC in February 2007 based on the electronic version of Table 1 from the above reference which was obtained from the ApJ website. This is a service provided by NASA HEASARC .

The Gaia DR2 Source Catalogue contains positions and brightnesses for 1.693 billion stars, including distances and proper motions for more than 1.3 billion stars. For more details, see the Gaia documentation, particularly the Source Catalogue columns description.

This table contains a catalog of 1696 X-ray sources detected in the massive star-forming region (SFR) Cygnus OB2 and extracted from two archival Chandra observations of the center of the region. A deep source extraction routine, exploiting the low background rates of Chandra observations was employed to maximize the number of sources extracted. Observations at other wavelengths were used to identify low count-rate sources and remove likely spurious sources. Monte Carlo simulations were also used to assess the authenticity of these sources. X-ray spectra were fitted with thermal plasma models to characterize the objects and X-ray light curves were analyzed to determine their variability. The authors used a Bayesian technique to identify optical or near-IR counterparts for 1501 (89%) of our sources, using deep observations from the INT Photometric H-alpha Survey, the Two Micron All Sky Survey (2MASS), and the UKIRT Infrared Deep Sky Survey-Galactic Plane Survey. 755 (45%) of these objects have six-band r', H-alpha, i', J, H, and K optical and near-IR photometry. From an analysis of the Poisson false-source probabilities for each source they estimate that their X-ray catalog includes <1% of false sources, and an even lower fraction when only sources with optical or near-IR associations are considered. A Monte Carlo simulation of the Bayesian matching scheme allows this method to be compared to more simplified matching techniques and enables the various sources of error to be quantified. The catalog of 1696 objects presented here includes X-ray broad-band fluxes, spectral model fits, and optical and near-IR photometry in what is one of the largest X-ray catalogs of a single SFR to date. The high number of stellar X-ray sources detected from relatively shallow observations confirms the status and importance of Cygnus OB2 as one of our Galaxy's most massive SFRs. This table was created by the HEASARC in October 2009 based on electronic versions of Tables 2, 3 and 4 from the reference paper which were obtained from the CDS (their catalog J/ApJS/184/84 files table2.dat, table3.dat and table4.dat). This is a service provided by NASA HEASARC .

This table contains the main X-ray source catalog for the Chandra monitoring observations of the 16.5-Mpc distant elliptical galaxy, NGC 4649. The galaxy has been observed with Chandra ACIS-S3 in six separate pointings, reaching a total exposure of 299 ks. There are 501 X-ray sources detected in the 0.3-8.0 keV band in the merged observation or in one of the six individual observations; 399 sources are located within the D₂₅ ellipse. The observed 0.3-8.0 keV luminosities of these 501 sources range from 9.3 x 10³⁶ erg s^-1 to 5.4 x 10³⁹ erg s^-1. The 90% detection completeness limit within the D₂₅ ellipse is 5.5 x 10³⁷ erg s^-1. Based on the surface density of background active galactic nuclei (AGNs) and the detection completeness, we expect ~ 45 background AGNs among the catalog sources (~ 15 within the D₂₅ ellipse). There are nine sources with luminosities greater than 10³⁹ erg s^-1, which are candidates for ultraluminous X-ray sources. The nuclear source of NGC 4649 is a low-luminosity AGN, with an intrinsic 2.0-8.0 keV X-ray luminosity of 1.5 x 10³⁸ erg s^-1. The X-ray colors suggest that the majority of the catalog sources are low-mass X-ray binaries (LMXBs). The authors find that 164 of the 501 X-ray sources show long-term variability, indicating that they are accreting compact objects, and discover four transient candidates and another four potential transients. They also identify 173 X-ray sources (141 within the D₂₅ ellipse) that are associated with globular clusters (GCs) based on Hubble Space Telescope and ground-based data; these LMXBs tend to be hosted by red GCs. Although NGC 4649 has a much larger population of X-ray sources than the structurally similar early-type galaxies, NGC 3379 and NGC 4278, the X-ray source properties are comparable in all three systems. This HEASARC table contains the main Chandra source catalog of the basic properties of the 501 X-ray detected sources (Table 3 in the reference paper which includes both sources detected in the merged X-ray image as well as a number only detected in the individual observations), and also the information on source counts, hardness ratios and soft and hard X-ray colors in the merged observation for the same 501 X-ray detected sources (Table 4 in the reference paper). It does not contain the information on source counts, hardness ratios and soft and hard X-ray colors for these same sources in the six individual observations that were contained in Tables 5 - 10 of the reference paper. This table was created by the HEASARC in March 2013 based on the electronic version of Tables 3 and 4 from the reference paper which were obtained from the ApJS website.. This is a service provided by NASA HEASARC .

This table combines the published X-ray source catalogs of the high galactic latitude (|b| > 10^o), Kawamuro et 2018, and the low galactic latitude (|b| < 10^o), Hori et al. 2018, based on 7 years of MAXI Gas Slit Camera (GSC) data from 2009 August 13 to 2016 July 31. The low galactic latitude catalog contains 221 sources with a significance threshold > 6.5 sigma. The low galactic faintest source has a flux of 5.2 x 10^-12 erg cm^-2 s^-1 (or an intensity of 0.43 mCrab) in the 4-10 keV band. The high galactic latitude catalog contains 686 sources detected at significances >= 6.5 sigma in the 4-10 keV band. The high galactic 4-10 keV sensitivity reaches ~0.48 mCrab, or ~5.9 x 10^-12 erg cm^-2 s^-1, over half of the survey area. The same data-screening criteria were applied to obtain the low and high galactic catalogs. In their papers the authors describe the detection method, the statistical quantities derived for each source and their variability. To derive a counterpart, each source was cross-matched with the Swift/BAT 105-month catalog (BAT105; Oh et al. 2018), the Uhuru fourth catalog (4U; Forman et al. 1978), the RXTE All-Sky Monitor long-term observed source table (XTEASMLONG16), Meta-Catalog of X-Ray Detected Clusters of Galaxies (MCXC; Piffaretti et al. 2011), the XMM-Newton Slew Survey Catalog (XMMSL217), and the ROSAT All-Sky Survey Bright Source Catalog (1RXS; Voges et al. 1999). Seven of the sources in the low galactic latitudes were detected by binning the data differently (source numbers 215-221 in the catalog named 73-day sources), and, similarly, four of the sources in the high galactic latitude catalog named transient sources. The parameters in the combined table include the source name (3MAXI), the position and its error, the detection significances and fluxes in the 4-10 keV, 3-4 keV bands and 10-20 keV bands the hardness ratios (HR1: 3-4 keV, 4-10 keV and HR2: 4-10 keV, 10-20 keV), excess variance in the 4-10 keV lightcurve and information on the likely counterpart. The high galactic catalogs also reports the flux in the 3-10 keV, an additional hardness (HR3: 3-10 keV and 10-20 keV) and an additional parameter representing variability. The hardness ratios are defined as H-S/H+S were S and H are the soft- and hard-band fluxes, respectively. This table was created by the HEASARC in April 2021. It is a combination of the 7-year low- and high-latitude MAXI source catalogs published on ApJS. The data for the low-galactic latitude and the high-galactic latitude were downloaded from the ApJS electronic version of the Hori et al. 2018 ApJS 235,7 and Kawamuro et al. 2018 ApJS 238,33 papers respectively. The low-latitude data included in this table are from tables 4, 5, 6, 7 of the Hori paper that report the X-ray sources detected (214 sources, table 4), their possible identification (table 5), the transient sources discovered binning the data on 73 days period (7 sources, table 5) and their identification (table 6). The high-latitude data included in this table are from the tables 1,2,3 of the Kawamuro paper that report the X-ray sources detected (682 sources in table 1), their identifications (table 2), and the transient sources (4 sources in table 3). The low and high galactic latitude source catalogs provide for each individual source similar parameters for the X-ray properties with the high-latitude having three additional parameters, specifically, the flux in the 3-10 keV energy range, the 3-10/10-20-keV hardness ratio, and a time variability test. These parameters are kept in the HEASARC combined table and set to "blank" values for the low-latitude sources. The four sources in the high-latitude catalog named transient sources have only fluxes in the 4-10 keV band and no other fluxes in the other energy bands or the hardness ratio are reported. The HEASARC combined table includes a field to identify whether the source is from the

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 10³⁵ erg s^-1 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:

 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 

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^-6 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^-6) 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^-6 < pns < 1.0 x 10^-3, some of which are likely to be genuine X-ray sources. This is a service provided by NASA HEASARC .

This database table contains the slightly revised contents of the detailed Tables 2A - 2G from the General Gamma-Ray Source Catalog of Macomb & Gehrels (1999). It lists details of all known gamma-ray observations within the energy range from 50 keV to ~1 TeV for 314 discrete gamma-ray sources that were listed in Tables 2A - 2G of the published version of this catalog, including all 310 sources listed in the published Summary Table 1, together with 4 sources (2CG 054+01, A0620-00, GX 340+0, and H1822-000) that were listed only in Table 2 of the published catalog but were (presumably accidentally) omitted from Table 1. The positions for the sources in the present database were taken from Table 1 of the General Gamma-Ray Source Catalog. Thus, this table is essentially a compilation of gamma-ray observations of discrete sources as known to the authors as of early 1999. There is another HEASARC database table called the Gamma-Ray Source Summary Catalog (Macomb & Gehrels 1999) or MGGAMMACAT that contains the summary information on these sources that was given in Table 1 of the General Gamma-Ray Source Catalog. As noted above, this is a slightly revised version compared to the published Tables 2A - 2G. The known differences between the HEASARC and published versions are discussed in the HEASARC_Version section of the help documentation. This database table was created by the HEASARC in March 2002 based upon machine-readable versions of Tables 2A-2G of the Macomb & Gehrels (1999) General Gamma-Ray Source Catalog that were supplied by the authors. One duplicate entry was removed from this table in June 2019. This is a service provided by NASA HEASARC .

This table lists some of the properties of the discrete X-ray sources detected in the authors' monitoring program of the globular cluster (GC)-rich elliptical galaxy, NGC 4278, observed with Chandra ACIS-S in six separate pointings, resulting in a co-added exposure of 458 ks. From this deep observation, 236 sources have been detected within the region overlapped by all observations, 180 of which lie within the D₂₅ ellipse angular diameter of the galaxy. These 236 sources range in X-ray luminosity L_X from 3.5 x 10³⁶ erg s^-1 (with 3-sigma upper limit <= 1 x 10³⁷ erg s^-1) to ~2 x 10⁴⁰ erg s^-1, including the central nuclear source which has been classified as a LINER. From optical data, 39 X-ray sources have been determined to be coincident with a GC, these sources tend to have high X-ray luminosity, with 10 of these sources exhibiting L_X > 1 x 10³⁸ erg s^-1. From X-ray source photometry, it has been determined that the majority of the 236 point sources that have well-constrained colors have values that are consistent with typical low-mass X-ray binary spectra, with 29 of the sources expected to be background objects from the log N-log S relation. There are 103 sources in this population that exhibit long-term variability, indicating that they are accreting compact objects. Three of these sources have been identified as transient candidates, with a further three possible transients. Spectral variations have also been identified in the majority of the source population, where a diverse range of variability has been identified, indicating that there are many different source classes located within this galaxy. This HEASARC table contains the master source list (Table 3 of the reference paper) and the X-ray properties of the sources in the co-added observations (Table 4 of the reference paper), but not the X-ray properties of the sources in the 6 individual observations (Tables 5-10 of the reference paper). The details of the six individual pointings used in this study, e.g., the Chandra ObsIDs, dates, exposure times and cleaned exposure times, are given in Table 1 of the reference paper, and repeated here:

 Obs. No.OBSID Date Exposure (s) Cleaned Exposure (s) 1 4741 2005 Feb 3 37462.0 37264.5 2 7077 2006 Mar 16 110303.8 107736.7 3 7078 2006 Jul 25 51433.2 48076.2 4 7079 2006 Oct 24 105071.7 102504.6 5 7081 2007 Feb 20 110724.0 107564.5 6 7080 2007 Apr 20 55824.8 54837.5 Total Co-added 470819.5 457984.0 

Notes. The pointing OBSID 7181 was taken before OBSID 7080, so to maintain the time sequence of the exposures these observation numbers have been labeled as above in the reference paper. The details of the energy bands and X-ray colors used in this study are given in Table 2 of the reference paper, and repeated here:

 Band/Color Energy Range/Definition Broad (B) 0.3-8 keV Soft (S) 0.3-2.5 keV Hard (H) 2.5-8 keV Soft 1 (S1) 0.3-0.9 keV Soft 2 (S2) 0.9-2.5 keV Conventional broad (Bc) 0.5-8 keV Conventional soft (Sc) 0.5-2 keV Conventional hard (Hc) 2-8 keV Hardness ratio HR (Hc-Sc)/(Hc+Sc) X-ray color C21 -log(S2) + log(S1) = log(S1/S2) X-ray color C32 -log(H) + log(S2) = log(S2/H) 

This table was created by the HEASARC in April 2009 based on machine-readable versions of Tables 3 and 4 from the reference paper which were obtained from the ApJ web site. This is a service provided by NASA HEASARC .