- ID:
- ivo://nasa.heasarc/ngc4649cxo
- Title:
- NGC 4649 Chandra X-Ray Discrete Source Catalog
- Short Name:
- NGC4649CXO
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The authors performed a Chandra X-ray observation of the X-ray bright E2 elliptical galaxy NGC 4649 (M 60). In addition to bright diffuse emission, they resolved 165 discrete sources, most of which are presumably low-mass X-ray binaries (LMXBs). As found in previous studies, the luminosity function of the resolved sources is well-fitted by a broken power law. In NGC 4697 and NGC 1553, the break luminosity was comparable to the Eddington luminosity of a 1.4 solar mass neutron star. One possible interpretation of this result is that those sources with luminosities above the break are accreting black holes and those below are mainly accreting neutron stars. The total X-ray spectrum of the resolved sources is well fitted by a hard power law. NGC 4649 was observed on 2000 April 20 on the ACIS-S3 CCD operated at a temperature of -120 C and with a frame time of 3.2 s. In addition to the S3 chip, the ACIS chips I2, I3, S1, S2, and S4 were also turned on for the duration of the observation. Although a number of serendipitous sources were seen on the other chips, the analysis of NGC 4649 in this paper was based on data from the S3 chip alone. The total exposure for the S3 chip was 36,780 s. The discrete X-ray source population on the ACIS S3 image was determined using a wavelet detection algorithm in the 0.3 - 10.0 keV band, and they were confirmed with a local cell detection method. The authors used the CIAO, WAVDETECT, and CELLDETECT programs. The high spatial resolution of Chandra implies that the sensitivity to point sources is not affected very strongly by the background. Thus, the source detection was done using the entire exposure of 36,780 s, including periods with background flares. The wavelet source detection significance threshold was set at 10<sup>-6</sup>, which implies that less than 1 false source (due to a statistical fluctuation in the background) would be detected in the entire S3 image. This significance threshold approximately corresponds to requiring that the source flux be determined to better than 3 sigma. This table was created by the HEASARC in April 2007 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/600/729">CDS catalog J/ApJ/600/729</a> file table1.dat. This is a service provided by NASA HEASARC .
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- ID:
- ivo://nasa.heasarc/ngc2516cxo
- Title:
- NGC 2516 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC2516CXO
- Date:
- 07 Mar 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/ngc1291cxo
- Title:
- NGC 1291 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC1291CXO
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains some of the results from a study of the X-ray binary (XRB) populations in the bulge and ring regions of the ring galaxy NGC 1291. Utilizing the four available Chandra observations totaling an effective exposure of 179 ks, the authors detect 169 X-ray point sources in the galaxy in the full band (0.3 - 8.0 keV) with a false-positive probability threshold of 10<sup>-6</sup> (implying approximately 2 false detections given the size of the image). Of these sources, 75 are in the bulge and 71 are in the ring. The authors report photometric properties of these sources in a point-source catalog. There are ~ 40% of the bulge sources and ~ 25% of the ring sources showing > 3-sigma long-term variability in their X-ray count rate. The X-ray colors suggest that a significant fraction of the bulge (~ 75%) and ring (~ 65%) sources are likely low-mass X-ray binaries (LMXBs). The spectra of the nuclear source indicate that it is a low-luminosity active galactic nucleus (AGN) with moderate obscuration; spectral variability is observed between individual observations. The authors construct 0.3-8.0 keV X-ray luminosity functions (XLFs) for the bulge and ring XRB populations, taking into account the detection incompleteness and background AGN contamination. They reach 90% completeness limits of ~ 1.5 x 10<sup>37</sup> and ~ 2.2 x 10<sup>37</sup> erg s<sup>-1</sup> for the bulge and ring populations, respectively. Both XLFs can be fit with a broken power-law model, and the shapes are consistent with those expected for populations dominated by LMXBs. In the paper, the authors perform detailed population synthesis modeling of the XRB populations in NGC 1291, which suggests that the observed combined XLF is dominated by an old LMXB population. They compare the bulge and ring XRB populations, and argue that the ring XRBs are associated with a younger stellar population than the bulge sources, based on the relative overdensity of X-ray sources in the ring, the generally harder X-ray color of the ring sources, the overabundance of luminous sources in the combined XLF, and the flatter shape of the ring XLF. This table was created by the HEASARC in May 2012 based on an electronic version of Table 2 from the reference paper obtained from the ApJ website. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc4214cxo
- Title:
- NGC 4214 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC4214CXO
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains a comprehensive X-ray point source catalog of the IAB(s)m galaxy NGC 4214 similar to the LMC, one of the nearest examples of a starburst galaxy with a substantial population of Wolf-Rayet stars, as part of the Chandra Local Volume Survey. The combined archival observations of this galaxy have an effective exposure time of 79 ks. When combined with the catalogs of sources in NGC 55 and NGC 2403 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 4214 was observed by the Chandra X-Ray Observatory using the ACIS-S array on three occasions for a total of 79 ks: <pre> Obs. ID Date Eff. Exposure time (ks) 2030 2001 Oct 16 25 4743 2004 Apr 03 26 5197 2004 Jul 30 28 </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 4214 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 116 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 116 high-significance (pns < 4 x 10<sup>-6</sup>) X-ray sources which were detected in NGC 4214. It does not include the 95 lower-significance sources in NGC 4214 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/ngc4649cx2
- Title:
- NGC 4649 Chandra X-Ray Point Source Catalog 2
- Short Name:
- NGC4649CX2
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- 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 D<sub>25</sub> ellipse. The observed 0.3-8.0 keV luminosities of these 501 sources range from 9.3 x 10<sup>36</sup> erg s<sup>-1</sup> to 5.4 x 10<sup>39</sup> erg s<sup>-1</sup>. The 90% detection completeness limit within the D<sub>25</sub> ellipse is 5.5 x 10<sup>37</sup> erg s<sup>-1</sup>. 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 D<sub>25</sub> ellipse). There are nine sources with luminosities greater than 10<sup>39</sup> erg s<sup>-1</sup>, 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 10<sup>38</sup> erg s<sup>-1</sup>. 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 D<sub>25</sub> 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 .
- ID:
- ivo://nasa.heasarc/ngc2403cx2
- Title:
- NGC 2403 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC2403CX2
- Date:
- 07 Mar 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/ngc2024cxo
- Title:
- NGC 2024 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC2024CXO
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The NGC 2024 Chandra X-Ray Point Source Catalog contains the results of a sensitive 76 ks Chandra observation of the young stellar cluster in NGC 2024, lying at a distance of ~415 pc in the Orion B giant molecular cloud. Previous infrared observations have shown that this remarkable cluster contains several hundred embedded young stars, most of which are still surrounded by circumstellar disks. Thus, it presents a rare opportunity to study X-ray activity in a large sample of optically invisible protostars and classical T Tauri stars (CTTSs) undergoing accretion. Chandra detected 283 X-ray sources, of which 248 were identified with counterparts at other wavelengths, mostly in the near-infrared. Astrometric registration of Chandra images against the Two Micron All Sky Survey (2MASS) resulted in positional offsets of ~0.25" near field center, yielding high confidence identifications of infrared counterparts. The Chandra detections are characterized by hard, heavily absorbed spectra and specular variability. Spectral analysis of more than 100 of the brightest X-ray sources yields a mean V-band extinction of ~10.5 magnitudes and typical plasma energies <kT> ~ 3 keV. Chandra detected all but one of a sample of 27 classical T Tauri stars (CTTSs) identified from previous near- and mid-infrared photometry, and their X-ray and bolometric luminosities are correlated. IRS 2b, which is thought to be a massive embedded late O or early B star that may be the ionizing source of NGC 2024, is detected as an X-ray source. Seven millimeter-bright cores (FIR 1-7) in NGC 2024 that may be protostellar were not detected, with the possible exception of faint emission near the unusual core FIR 4. This table was created by the HEASARC in January 2007 based on CDS table J/ApJ/598/375/table1.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc2808cxo
- Title:
- NGC 2808 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC2808CXO
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the sources detected in a Chandra X-ray observation of the Galactic globular cluster NGC 2808, as well as the corresponding XMM-Newton data for those sources which have XMM-Newton X-ray counterparts. Using new Chandra X-ray observations and existing XMM-Newton X-ray and Hubble Space Telescope far-ultraviolet observations, the authors aim to detect and identify the faint X-ray sources belonging to NGC 2808 in order to understand their role in the evolution of globular clusters. The authors classify the X-ray sources associated with the cluster by analysing their colors and variability. Previous observations with XMM-Newton and far-ultraviolet observations with Hubble are re-investigated to help identify the Chandra sources associated with the cluster. The authors compare their results to population synthesis models and observations of other Galactic globular clusters. NGC 2808 was observed with the Chandra X-ray Observatory Advanced CCD Imaging Spectrometer-Imager (ACIS-I) on 2007 June 19-21 (28 months after the XMM-Newton observation referred to the reference paper) for two distinct exposures of 46 and 11 kiloseconds. The authors detect 113 sources, of which 16 fall inside the half-mass radius of NGC 2808 and are concentrated towards the cluster core. This table was created by the HEASARC in February 2009 based on the electronic version of Table 1 from the paper which was obtained from the CDS (their catalog J/A+A/490/641 file table1.dat). This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc6334cxo
- Title:
- NGC 6334 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC6334CXO
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The full stellar population of NGC 6334, one of the most spectacular regions of massive star formation in the nearby Galaxy, has not been well sampled in past studies. The authors have analyzed a mosaic of two Chandra X-ray Observatory images of the region using sensitive data analysis methods, giving a list of 1607 faint X-ray sources with arcsecond positions and approximate line-of-sight absorption. About 95% of these are expected to be cluster members, most lower mass pre-main-sequence stars. Extrapolating to low X-ray levels, the total stellar population is estimated to be 20,000 - 30,000 pre-main-sequence stars. The X-ray sources show a complicated spatial pattern with ~10 distinct star clusters. The heavily obscured clusters are mostly associated with previously known far-infrared sources and radio H II regions. The lightly obscured clusters are mostly newly identified in the X-ray images. Dozens of likely OB stars are found, both in clusters and dispersed throughout the region, suggesting that star formation in the complex has proceeded over millions of years. A number of extraordinarily heavily absorbed X-ray sources are associated with the active regions of star formation. This table was created by the HEASARC in August 2009 based on the electronic version of table 1 from the above reference which were obtained from the AJ web site. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc55cxo
- Title:
- NGC 55 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC55CXO
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains a comprehensive X-ray point source catalog of the SB(s)m galaxy NGC 55, a member of the nearby Sculptor group of galaxies, as part of the Chandra Local Volume Survey. The combined archival observations of this galaxy have an effective exposure time of 56.5 ks. When combined with the catalogs of sources in NGC 2403 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 55 was observed by the Chandra X-Ray Observatory on 2001 September 11 for 47 ks using the ACIS-I array (Obs. ID 2255), and on 2004 June 29 for 9.5 ks using the ACIS-I array (Obs. ID 4744). 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 55 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 55 contains 154 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 154 high-significance (pns < 4 x 10<sup>-6</sup>) X-ray sources which were detected in NGC 55. It does not include the 76 lower-significance sources in NGC 55 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 .
