This table contains the results from an X-ray and optical analysis of 188 active galactic nuclei (AGN) identified from 497 hard X-ray (observed flux in the (2.0 - 8.0 keV) band > 2.7 x 10^-15 erg/cm²/s) sources in 20 Chandra fields (1.5 square degrees) forming part of the Chandra Multiwavelength Project (ChaMP). These medium-depth X-ray observations enable the detection of a representative subset of those sources responsible for the bulk of the 2 - 8 keV cosmic X-ray background. Brighter than the survey's optical spectroscopic limit, the authors achieve a reasonable degree of completeness (77% of X-ray sources with counterparts r' < 22.5 have been classified): broad emission-line AGNs (62%), narrow emission-line galaxies (24%), absorption-line galaxies (7%), stars (5%), or clusters (2%). To construct a pure AGN sample, the authors required the rest-frame 2.0-8.0 keV luminosity (uncorrected for intrinsic absorption) to exceed 10⁴² erg s^-1, thereby excluding any sources that may contain a significant stellar or hot ISM component. The most luminous known star-forming or elliptical galaxies attain at most L_X = 10⁴² erg s^-1. Since many of the traditional optical AGN signatures are not present in obscured sources, high X-ray luminosity becomes the authors' single discriminant for supermassive black hole accretion. They believe that almost all of the NELGs and ALGs harbor accreting SMBHs based on their X-ray luminosity. They find that 90% of the identified ChaMP sources have luminosities above this threshold. These selection criteria yield a sample of 188 AGNs from 20 Chandra fields with f(2-8 keV) > 2.7 x 10^-15 erg cm^-2 s^-1, r' < 22.5, and L_X > 10⁴² erg s^-1. The authors removed five objects identified as clusters based on their extended X-ray emission. This table was created by the HEASARC in March 2007 based on the CDS table J/ApJ/618/123, file table4.dat. This is a service provided by NASA HEASARC .

The maximum number density of Active Galactic Nuclei (AGNs), as deduced from X-ray studies, occurs at z >= 1, with lower luminosity objects peaking at smaller redshifts. Optical studies lead to a different evolutionary behaviour, with a number density peaking at z ~ 2 independently of the intrinsic luminosity, but this result is limited to active nuclei brighter than the host galaxy. A selection based on optical variability can detect low luminosity AGNs (LLAGNs), where the host galaxy light prevents the identification by non-stellar colours. The authors collected X-ray data in a field where there existed an optically-selected sample of "variable galaxies", i.e. variable objects with diffuse appearance, in order to investigate the X-ray and optical properties of the population of AGNs, particularly of low luminosity ones, where the host galaxy is visible. They observed a field of ~ 0.2 deg² in the Selected Area 57, for 67 ks with XMM-Newton. They correlated the list of detected X-ray sources with a photographic survey of SA 57, complete to B_J ~ 23 and with the available spectroscopic data. They obtained a catalog of 140 X-ray sources to limiting fluxes of 5 x 10^-16 and 2 x 10^-15 erg/cm²/s in the 0.5 - 2 keV and 2 - 10 keV bands, respectively, 98 of which are identified in the optical bands. The X-ray detection of part of the variability-selected candidates confirms their AGN nature. Diffuse variable objects populate the low luminosity side of the sample. Only 25/44 optically-selected QSOs are detected in X-rays. 15% of all QSOs in the field have X/O < 0.1. Additional information on the likely optical counterparts of 98 of the X-ray sources is available in the reference paper, e.g., in Table 3. This table was created by the HEASARC in September 2007 based on CDS table J/A+A/469/1211 file table2.dat. This is a service provided by NASA HEASARC .

This table contains some of the results from the first X-ray study of Collinder 261 (Cr 261), which at an age of 7 Gyr is one of the oldest open clusters known in the Galaxy. This observation with the Chandra X-Ray Observatory was aimed at uncovering the close interacting binaries in Cr 261, and reached a limiting X-ray luminosity of L_X ~ 4 x 10²⁹ erg s^-1 (0.3-7 keV) for stars in the cluster. The authors detected 107 sources within the cluster half-mass radius r_h, and they estimate that among the sources with L_X >~ 10³⁰ erg s^-1, about 26 are associated with the cluster. They identify a mix of active binaries and candidate active binaries, candidate cataclysmic variables, and stars that have "straggled" from the main locus of CR 261 in the color-magnitude diagram. Based on a deep optical source catalog of the field, the authors estimate that Cr 261 has an approximate mass of 6500 M_sun, roughly the same as the old open cluster NGC 6791. The X-ray emissivity of Cr 261 is similar to that of other old open clusters, supporting the trend that they are more luminous in X-rays per unit mass than old populations of higher (globular clusters) and lower (the local neighborhood) stellar density. This implies that the dynamical destruction of binaries in the densest environments is not solely responsible for the observed differences in X-ray emissivity. Cr 261 was observed with the Advanced CCD Imaging Spectrometer (ACIS) on board Chandra starting 2009 November 9 14:50 UTC, for a total exposure time of 53.8 ks (ObsID 11308). The observation was made in Very Faint, Timed exposure mode, with a single frame exposure time of 3.2 s. Kharchenko et al. (2013, A&A, 558, A53) estimate that the radius of Cr 261 is ~ 14.1 arcminutes. This is considerably larger than a single ACIS chip (8 4 x 8 4 arcminute²) and therefore the authors placed the center of the cluster (J2000.0 RA = 12^h 38^m 06.0^s, Dec = -68^o 22' 01" according to Kharchenko et al. 2013) close to the I3 aimpoint so that a larger contiguous part of the cluster could be imaged (see Figure 1 in the reference paper). The CCDs used were I0, I1, I2, and I3 from the ACIS-I array, and S2 and S3 from the ACIS-S array. The authors limited the X-ray analysis to the data from chips I0, I1, I2, and I3. The S2 and S3 chips lie far from the I3 aimpoint, giving rise to large positional errors on any sources detected on them. Such large errors make it hard to identify optical counterparts, and thus to classify the sources. Source detection was done in soft (0.3-2.0 keV), hard (2-7 keV) and broad (0.3-7 keV) energy bands. The CIAO source detection routine wavdetect was run for eight wavelet scales ranging from 1.0 to 11.3 pixels. The wavdetect detection threshold (sigthresh) was set at 10^-7. The corresponding expected number of spurious detections per wavelet scale is 0.42 for all four ACIS chips combined, or 3.35 in total for all wavelet scales. The authors ran wavdetect for the three different energy bands and then cross-correlated the resulting source lists to obtain a master X-ray source list. They detected 113 distinct X-ray sources. To check if any real sources were missed, they ran wavdetect again with a detection threshold of 10^-6, which increased the expected total number of spurious detections to 33.5, and found a total of 151 distinct X-ray sources with more than two counts (0.3-7 keV) in this case. The positions of 7 of the extra 38 sources were found to match those of short-period binaries discovered by Mazur et al. (1995, MNRAS, 273, 59; see Section 3.4). Close, interacting binaries are plausible real X-ray sources, and indeed the expected number of chance alignments between the Chandra detections and the binaries in the Mazur catalog is very low, as discussed in Section 3.5 of the reference paper. It is therefore likely that at

Wide area X-ray and far-infrared surveys are a fundamental tool to investigate the link between AGN growth and star formation, especially in the low-redshift universe (z < 1). The Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) has covered 550 deg² in five far-infrared and sub-mm bands, 16 deg² of which have been presented in the Science Demonstration Phase (SDP) catalogue. The reference paper cited below introduces the XMM-Newton observations in the H-ATLAS SDP area, covering 7.1 deg² with flux limits of 2 x 10^-15, 6 x 10^-15, and 9 x 10^-15 erg/s/cm² in the 0.5-2, 0.5-8 and 2-8keV bands, respectively. The paper presents the source detection techniques and the "main" catalog, which includes 1700, 1582 and 814 sources detected by EMLDetect in the 0.5-8, 0.5-2 and 2-8keV bands, respectively; the number of unique sources is 1816. The authors extract spectra and derive fluxes from power-law fits for 398 sources with more than 40 counts in the 0.5-8 keV band. They compare the best-fit fluxes with those in the catalog, which were obtained assuming a common photon index Gamma of 1.7; the authors find no bulk difference between the fluxes, and a moderate dispersion s of 0.33 dex. Using wherever possible the fluxes from the spectral fits, the authors derive the 2-10 keV Log N-Log S distribution, which is consistent with a Euclidean distribution. Finally, they release the computer code for the tools which they developed for this project. Sources were detected with a two-stage process. With the first pass at low significance, the authors got a list of candidate detections; and on the second pass they raised the significance threshold and derived accurate source parameters. Between the two passes, and because the second pass needs an input catalog, they identified the sources detected in more than one band. In the first pass, the SAS wavelet detection program ewavelet was run separately on each of the 0.5-2, 2-8 and 0.5-8 keV images of the entire mosaic, with a significance threshold of 4 sigma and the default wavelet scales (minimum 2 pixels, maximum 8 pixels, with a pixel size of 4). All parameters in this catalog which were derived from ewavelet have been given a prefix of 'wav' in this HEASARC representation so as to distinguish them from the parameters derived using EMLDetect. In the second pass, the authors used the SAS EMLDetect program to validate the detections, refine the coordinates and obtain maximum-likelihood estimates of the source counts, count rates and fluxes. The EMLDetect minimum likelihood was set at L = 4.6, as in Ranalli et al. (2013, A&A, 555, A42), which corresponds to a false-detection probability of 1.01 x 10^-2. Together with the 4-sigma threshold for ewavelet, for the final catalog this yields a joint significance between 4 sigma and 5 sigma, but which cannot be further constrained without simulations. This table contains the X-ray sources which were detected in the 7.1 deg² XMM-Newton observations of the H-ATLAS field. The 1816 sources which were detected by both programs were presented in the main table in the reference paper (and are included in this HEASARC table where they are indicated by a value of the source_sample parameter of 'main'), while the 234 sources which were only detected by ewavelet were presented in the supplementary table in the reference paper (and are included in this HEASARC table where they are indicated by a value of the source_sample parameter of 'supp'). The same parameters were present in both the main and supplementary tables in the reference paper, but those parameters which came from EMLDetect are empty for the sources in the supplementary table. The parameters obtained using ewavelet (those parameters with the 'wav' prefix in their names) containing the source properties (counts, count rates, fluxes, exposure times, background, wavelet detection scale and source

This table contains some of the results from an in-depth study of low-mass X-ray binaries (LMXBs) detected in the nearby lenticular galaxy NGC 3115 using the Megasecond Chandra X-ray Visionary Project observation (total exposure time 1.1 Ms). In total the authors found 136 candidate LMXBs in the field and 49 in globular clusters (GCs) above 2-sigma detection, with 0.3-8 keV luminosity L_X ~ 10³⁶ - 10³⁹ erg s^-1. Other than 13 transient candidates, the sources overall have less long-term variability at higher luminosity, at least at L_X >~ 2 x 10³⁷ erg s^-1. In order to identify the nature and spectral state of these sources, the authors compared their collective spectral properties based on single-component models (a simple power law or a multicolor disk) with the spectral evolution seen in representative Galactic LMXBs. The authors found that in the L_X vs. photon index Gamma_PL and L_X versus disk temperature kT_MCD plots, most of their sources fall on a narrow track in which the spectral shape hardens with increasing luminosity below L_X ~ 7 x 10³⁷ erg s^-1, but is relatively constant (Gamma_PL ~ 1.5 or kT_MCD ~ 1.5 keV) above this luminosity, which is similar to the spectral evolution of Galactic neutron star (NS) LMXBs in the soft state in the Chandra bandpass. Therefore, the authors identified the track as the NS LMXB soft-state track and suggested sources with L_X <~ 10³⁷ erg s^-1 as atolls in the soft state and those with L_X >~ 10³⁷ erg s^-1 as Z sources. Ten other sources (five are transients) displayed significantly softer spectra and are probably black hole X-ray binaries in the thermal state. One of them (a persistent source) is in a metal-poor GC. The 11 Chandra observations of NGC 3115 are listed in Table 1 of the reference paper. They were made during three epochs: one in 2001,two in 2010, and nine in 2012. All observations used the imaging array of the AXAF CCD Imaging Spectrometer (ACIS). This table contains the properties of the 482 detected point sources in the merged and single Chandra ACIS observations of NGC 3115 above a 2-sigma threshold and after eliminating a number of spurious sources associated with bright streaks on the ACIS-S1 chip and (in one case) on a CCD edge. 469 of these sources (indicated by values of obs_flag = '0') have a single entry in this table, based on their properties as derived from all of the available Chandra data for that position. There are 13 transient sources (having obs_flag = 'h') for which an additional entry is provided referring to their properties in the "high state", and based on the combination of their high-state observations, as shown in Figures 3(a) - 3(d) in the reference paper. For source number 198, there is a second additional entry provided referring to its properties in the "low state", and based on the combination of its low-state observations, as shown in Figure 3(c) in the reference paper. Thus, there are 496 entries (rows) in this table, i.e., 482 + 13 + 1. This table was created by the HEASARC in August 2015 based on the union of the machine-readable versions of Table 3 (the master source catalog) and Table 4 (the source counts, fluxes and hardness ratios in the merged observations) that were obtained from the ApJ web site. It does not contain the source counts and fluxes in the individual observations which were given in Table 5 of the reference paper. This is a service provided by NASA HEASARC .

This table contains some of the results from the first X-ray study of Collinder 261 (Cr 261), which at an age of 7 Gyr is one of the oldest open clusters known in the Galaxy. This observation with the Chandra X-Ray Observatory was aimed at uncovering the close interacting binaries in Cr 261, and reached a limiting X-ray luminosity of L_X ~ 4 x 10²⁹ erg s^-1 (0.3-7 keV) for stars in the cluster. The authors detected 107 sources within the cluster half-mass radius r_h, and they estimate that among the sources with L_X >~ 10³⁰ erg s^-1, about 26 are associated with the cluster. They identify a mix of active binaries and candidate active binaries, candidate cataclysmic variables, and stars that have "straggled" from the main locus of CR 261 in the color-magnitude diagram. Based on a deep optical source catalog of the field, the authors estimate that Cr 261 has an approximate mass of 6500 M_sun, roughly the same as the old open cluster NGC 6791. The X-ray emissivity of Cr 261 is similar to that of other old open clusters, supporting the trend that they are more luminous in X-rays per unit mass than old populations of higher (globular clusters) and lower (the local neighborhood) stellar density. This implies that the dynamical destruction of binaries in the densest environments is not solely responsible for the observed differences in X-ray emissivity. Cr 261 was observed with the Advanced CCD Imaging Spectrometer (ACIS) on board Chandra starting 2009 November 9 14:50 UTC, for a total exposure time of 53.8 ks (ObsID 11308). The observation was made in Very Faint, Timed exposure mode, with a single frame exposure time of 3.2 s. Kharchenko et al. (2013, A&A, 558, A53) estimate that the radius of Cr 261 is ~ 14.1 arcminutes. This is considerably larger than a single ACIS chip (8 4 x 8 4 arcminute²) and therefore the authors placed the center of the cluster (J2000.0 RA = 12^h 38^m 06.0^s, Dec = -68^o 22' 01" according to Kharchenko et al. 2013) close to the I3 aimpoint so that a larger contiguous part of the cluster could be imaged (see Figure 1 in the reference paper). The CCDs used were I0, I1, I2, and I3 from the ACIS-I array, and S2 and S3 from the ACIS-S array. The authors limited the X-ray analysis to the data from chips I0, I1, I2, and I3. The S2 and S3 chips lie far from the I3 aimpoint, giving rise to large positional errors on any sources detected on them. Such large errors make it hard to identify optical counterparts, and thus to classify the sources. The authors retrieved optical images of Cr 261 in the B and V bands from the ESO public archive. These data were taken as part of the ESO Imaging Survey (EIS; program ID 164.O-0561). The observations of Cr 261 were made using the Wide Field Imager (WFI), mounted on the 2.2 m MPG/ESO telescope at La Silla, Chile. After correcting the X-ray source positions for the (almost negligible) boresight correction (0.06 =/- 0.07 arcseconds in RA and 0.09 +/- 0.08 arcseconds in Dec), the authors matched their X-ray source list with the entire optical source list, using 95% match radii. For 89 unique X-ray sources, they found 124 optical matches; of the latter, 104 are present in both the V and B images, while for 20 there is only a V or B detection. The authors also inspected the area around each X-ray source in the WFI images by eye, and discovered that five more X-ray sources have candidate optical counterparts that are saturated and therefore missing from their optical catalog. Finally, they added to the list of candidate counterparts six optical sources that lay just outside the 95% match radius, but inside the 3-sigma radius. In total, 98 of the 151 unique X-ray sources were thus matched to one or more optical sources. This HEASARC table contains the list of the 135 optical counterparts to 98 of the 151 X-ray sources from Table 2 of the reference paper.