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Swift XRT Counterparts to Unidentified 1FGL Sources
The authors have analyzed all the archival X-ray data of 134 unidentified (unID) gamma-ray sources listed in the first Fermi/LAT (1FGL) catalog and subsequently followed up by the Swift/XRT. They constructed the spectral energy distributions (SEDs) from radio to gamma-rays for each X-ray source detected, and tried to pick up unique objects that display anomalous spectral signatures. In these analyses, they target all the 1FGL unID sources, using updated data from the second Fermi/LAT (2FGL) catalog on the Large Area Telescope (LAT) position and spectra. In the reference paper, the authors discuss the X-ray identification results and the SEDs of all 134 sources observed with the Swift/XRT. The selection criteria for the Fermi sources were as follows: (1) categorized as unID sources in the 1FGL catalog, (2) localized at high Galactic latitude |b| > 10 degrees, (3) observational data were made public by October 2011, and (4) the positional center of the Swift FoV is within 12 arcminutes of the 1FGL sources. Among 630 unID sources listed in the 1FGL catalog, this selection yielded 134 sources which were analyzed in this study. This table contains the list of the positions and 0.3-10 keV count rates of 267 Swift XRT sources which were detected with a signal-to-noise ratio (SNR) of 3 or more within the Swift/XRT field of views (FoV) of 112 of the 134 1FGL unID gamma-ray sources, with 22 of the 1FGL sources having no detected Swift XRT sources in their FoVs. The Swift XRT images of all 134 unID gamma-ray sources, the positions of the significant XRT sources, and the 95% 1FGL and 2FGL error ellipses are shown in Figure 11 of the reference paper. This table was created by the HEASARC in September 2014 based on an electronic version of Table 4 from the reference paper which was obtained from the ApJS website. Some of the values for the name parameter in the HEASARC's implementation of this table were corrected in April 2018. This is a service provided by NASA HEASARC .
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Fermi 2FGL Unassociated Gamma-Ray Sources Possible Radio Identifications
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This table contains some of the results from an all-sky radio survey between 5- and 9-GHz of sky areas surrounding all unassociated gamma-ray objects listed in the Fermi Large Area Telescope (LAT) Second Source Catalog (2FGL). The goal of these observations is to find all new gamma-ray active galactic nucleus (AGN) associations with radio sources > 10 mJy at 8GHz. The authors observed with the Very Large Array (VLA) and the Australia Telescope Compact Array (ATCA) the areas around unassociated sources, providing localizations of weak radio point sources found in 2FGL fields at arcminute scales. They then followed up a subset of these with the Very Long Baseline Array (VLBA) and the Long Baseline Array (LBA) in order to confirm detections of radio emission on parsec-scales. The authors quantified association probabilities based on known statistics of source counts and assuming a uniform distribution of background sources. In total, they found 865 radio sources at arcsecond scales as candidates for association and detected 95 of 170 selected for follow-up observations at milliarcsecond resolution. Based on this, they obtained firm associations for 76 previously unknown gamma-ray AGNs. Comparison of these new AGN associations with the predictions from using the Wide-field Infrared Survey Explorer (WISE) color-color diagram shows that half of the associations are missed. The authors found that in 129 out of 588 gamma-ray sources observed at arcminute scales not a single radio continuum source was detected above their sensitivity limit within the 3-sigma gamma-ray localization. These "empty" fields were found to be particularly concentrated at low Galactic latitudes. The nature of these Galactic gamma-ray emitters is not yet determined. A list of 216 target fields were observed with the VLA. The instantaneous bandwidth was split into two parts, with one half centered at 5.0 GHz (4.5 - 5.5 GHz) and the other centered at 7.3 GHz (6.8 - 7.8 GHz). The observations were made on 2012 October 26 and 2012 November 3. See section 2.1 of the reference paper for more details. These data are included in this HEASARC table. During the first campaign with the ATCA from 2012 September 19-20, the authors observed 411 2FGL unassociated sources in a Declination range of -90 degrees to +10 degrees at 5.5 and 9 GHz. The details of this observing campaign and results have been reported by Petrov et al. (2013, MNRAS, 432, 1294: available at the HEASARC as the AT2FGLUS table). The authors detected a total of 424 point sources. In a second ATCA campaign on 2013 September 25-28, the authors re-observed sources that were detected at 5 GHz, but were not detected at 9 GHz. See section 2.2 of the reference paper for more details. These data are included in this HEASARC table. Follow-up observations of 149 targets selected from the VLA and ATCA surveys above -30 degrees Declination were conducted with the VLBA between 2013 Feb-Aug (VCS7 project; 4.128 - 4.608 and 7.392 - 7.872 GHz simultaneously) and in 2013 Jun-Dec (campaign S5272; 7.392 - 7.872 GHz only). See section 2.3 of the reference paper for more details. These data are NOT included in this HEASARC table. For sources with Declination below -30 degrees, the authors added 21 objects to the on-going LCS campaign being conducted using the LBA (Petrov et al. 2011, MNRAS, 414, 2528) in 2013 Mar-2013 Jun at 8.200 - 8.520 GHz. See section 2.4 of the reference paper for more details. These data are NOT included in this HEASARC table. This table was created by the HEASARC in May 2015 based on the union of CDS Catalog J/ApJS/217/4/ files table2.dat (the 148 'Category I' objects that were detected at 5.0/5.5 and/or 7.3/9.0 GHz within 2.7' of the 2FGL counterpart localization), table3.dat (the 501 'Category II' objects that were detected at 5.0/5.5 and/or 7.3/9.0 GHz between 2.7' and 6.5' of the 2FGL counterpart localization) and table4.dat (the 216
The Seven-Year Swift-XRT Point Source Catalog (1SWXRT)
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This table contains the 1SWXRT catalog of point sources detected by X-ray Telescope (XRT) on board of the Swift satellite during the first seven years of operation (Jan 2005 - Dec 2011). Swift is a NASA mission with international participation dedicated to gamma-ray burst study. It carries three instruments. The BAT is the large field of view instrument and operates in the 10-300 keV energy band; and two narrow field instruments, XRT and UVOT, that operate in the X-ray and UV/optical regime, respectively. The seven-year Swift-XRT point source catalog (1SWXRT) was built using all the observations performed by Swift-XRT in PC observing mode with an exposure longer than 500 s. The total number of observations considered is 35011, for an overall exposure time of ~140 Ms. Different observations with same pointing were not merged, but analyzed separately, thus retaining information about the variability of the catalogued sources. Most of the observations have short exposures. In fact, ~18% have texp < 1 ks and ~77% have texp < 5 ks. Only 7% of the observations have an exposure time > 10 ks, which are mostly (but not exclusively) fields associated with GRBs. The catalog was generated by running the detection algorithm in the XIMAGE package version 4.4.1 that locates the point sources using a sliding-cell method. The average background intensity is estimated in several small square boxes uniformly located within the image. The position and intensity of each detected source are calculated in a box whose size maximizes the signal-to-noise ratio. For each detection the catalog reports three count rates in the 0.3-3 (Soft), and 2-10 (Hard), and 0.3-10 (Full) keV energy bands. Each are corrected for dead times and vignetting using exposure maps and for the PSF. Hardness ratios are calculated using the three energy band and defined as HR = (cH - cS)/(cH + cS) where cS and cH are the count rates in the S(oft) and H(ard) bands, respectively. The catalog was cleaned from spurious and extended sources by visual inspection of all the observations. Count rates in the three bands were converted to 0.5-10, 0.5-2, and 2-10 keV observed fluxes, respectively. For the fluxes these energy bands were adopted to easy comparison with other X-ray catalogs (Watson, M. G. et al. 2009, A&A, 493, 339; Evans, I. N. et al. 2010, ApJ, 189, 37). The count rate to flux conversion was made using an absorbed power-law. The absorption is the Galactic hydrogen column density in the direction of the source and the photon spectral index has been estimated through the hardness ratio. Each row in the catalog is a detection not a unique source since the analysis was done by observation. Since multiple observations have covered the same part of the sky, a source may be detected more than once. The total number of detections is 84979 with an estimated 36000 unique sources as reported in the D'Elia et al. paper. The number of unique sources is derived by considering as one source all detections that have their positions within 12 arcsec. However, the catalog does not have a marker to identify all detections of a unique source. This database table was created by the HEASARC in November 2021 based on the electronic version available from the ASI Data Center https://www.asdc.asi.it/1swxrt/ and published in the Astronomy and Astrophysics Journal. This catalog is also available as CDS catalog J/A+A/551/A142. The HEASARC added the id_number parameter, a counter to numerically identify each detection in the catalog (since the names of the detections are not unique), . Note that there is a discrepancy in the number of detections in the electronic version which has 84979 records and the number of detections reported in the paper (84992). This is a service provided by NASA HEASARC .
Fermi LAT Sources Refined Associations Catalog
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The Fermi-Large Area Telescope (LAT) First Source Catalog (1FGL: Abdo et al. 2010, ApJS, 188, 405) was released in 2010 February and the Fermi-LAT 2-Year Source Catalog (2FGL: Nolan et al. 2012, ApJS, 199, 31) appeared in 2012 April, based on data from 24 months of operations. Since they were released, many follow up observations of unidentified gamma-ray sources have been performed and new procedures for associating gamma-ray sources with potential counterparts at other wavelengths have been developed. In the reference paper, the authors review and characterize all of the associations as published in the 1FGL and 2FGL catalogs on the basis of multi-frequency archival observations. In particular, they locate 177 spectra for the low-energy counterparts that were not listed in the previous Fermi catalogs, and in addition they present new spectroscopic observations of eight gamma-ray blazar candidates. Based on their investigations, the authors introduce a new counterpart category of "candidate associations" and propose a refined classification for the candidate low-energy counterparts of the Fermi sources. They compare the 1FGL-assigned counterparts with those listed in 2FGL to determine which unassociated sources became associated in later releases of the Fermi catalogs. The authors also search for potential counterparts to all of the remaining unassociated Fermi sources. Finally, they prepare a refined and merged list of all of the associations of 1FGL plus 2FGL that includes 2219 unique Fermi objects. This is the most comprehensive and systematic study of all the associations collected for the gamma-ray sources available to the date of this study. The authors conclude that 80% of the Fermi sources have at least one known plausible gamma-ray emitter within their positional uncertainty regions. This table was created by the HEASARC in May 2015 based on CDS Catalog J/ApJS/217/2 file table4.dat. This is a service provided by NASA HEASARC .
AT20G/Fermi 1FGL Source Catalog
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The high-frequency radio sky, like the gamma-ray sky surveyed by the Fermi satellite, is dominated by flat-spectrum radio quasars and BL Lac objects at bright flux levels. To investigate the relationship between radio and gamma-ray emission in extragalactic sources, the authors have cross-matched the Australia Telescope 20-GHz survey catalog (AT20G: Murphy et al. 2010, MNRAS, 402, 2403, available as a HEASARC Browse table) with the Fermi-LAT 1-year Point Source Catalog (1FGL: Abdo et al. 2010, ApJS, 188, 405, also available as the HEASARC Browse table FERMILPSC). The 6.0 sr of sky covered by both catalogs (Declination < 0 degrees, |b| > 1.5 degrees) contains 5890 AT20G radio sources and 604 1FGL gamma-ray sources. The AT20G source positions are accurate to within ~1 arcsec and, after excluding known Galactic sources, 43% of Fermi 1FGL sources have an AT20G source within the 95% Fermi confidence ellipse. Monte Carlo tests imply that at least 95% of these matches are genuine associations. Only five gamma-ray sources (1% of the Fermi catalog) have more than one AT20G counterpart in the Fermi error box. The AT20G matches also generally support the active galactic nucleus (AGN) associations in the First LAT AGN Catalog. The authors find a trend of increasing gamma-ray flux density with 20 GHz radio flux density. The Fermi detection rate of AT20G sources is close to 100% for the brightest 20 GHz sources, decreasing to 20% at 1 Jy, and to roughly 1% at 100 mJy. Eight of the matched AT20G sources have no association listed in 1FGL and are presented here as potential gamma-ray AGNs for the first time. The authors also identify an alternative AGN counterpart to one 1FGL source. The percentage of Fermi sources with AT20G detections decreases toward the Galactic plane, suggesting that the 1FGL catalog contains at least 50 Galactic gamma-ray sources in the southern hemisphere that are yet to be identified. This table contains the complete list of all 233 Fermi-AT20G matches. This table was created by the HEASARC in August 2010 based on the electronic version of Table 4 obtained from the ApJ web site. This is a service provided by NASA HEASARC .
Fermi LAT High-Energy Source Catalog (1FHL)
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This table contains the catalog of gamma-ray sources at energies above 10 GeV based on data from the Large Area Telescope (LAT) accumulated during the first 3 years of the Fermi Gamma-ray Space Telescope mission. The first Fermi-LAT catalog of > 10 GeV sources (1FHL) has 514 sources. For each source, the authors present location, spectrum, a measure of variability,and associations with cataloged sources at other wavelengths. They found that 449 (87%) could be associated with known sources, of which 393 (76% of the 1FHL sources) are active galactic nuclei. Of the 27 sources associated with known pulsars, they find 20 (12) to have significant pulsations in the range > 10 GeV (> 25 GeV). In this work, the authors also report that, at energies above 10 GeV, unresolved sources account for 27% +/- 8% of the isotropic gamma-ray background, while the unresolved Galactic population contributes only at the few percent level to the Galactic diffuse background. The authors also highlight the subset of the 1FHL sources that are the best candidates for detection at energies above 50 - 100 GeV with current and future ground-based gamma-ray observatories. The time interval analyzed here is from the beginning of Fermi LAT science operations on 2008 August 4 (MET 239557447) to 2011 August 1 (MET 333849586), covering very nearly 3 years. In this work, the authors analyze gamma rays with energies in the range 10-500 GeV. To limit the contamination from gamma rays produced by cosmic-ray interactions in the upper atmosphere, gamma rays with zenith angles greater than 105 degrees were excluded. To further reduce the residual gamma rays from the upper atmosphere only data for time periods when the spacecraft rocking angle was less than 52 degrees were considered. See Section 2 of the reference paper for further explanations. This table was created by the HEASARC in April 2015 based on CDS Catalog J/ApJS/209/34/ files table3.dat and table7.dat. This is a service provided by NASA HEASARC .
Swift Serendipitous Survey in Deep XRT GRB Fields (SwiftFT)
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This table contains the SwiftFT catalog of point sources detected by the X-ray Telescope (XRT) on board the Swift satellite in observations centered on gamma-ray bursts (GRBs) during the first four years of operation (Jan 2005 - Dec 2008). Swift is a NASA mission with international participation dedicated to the gamma-ray burst study. It carries three instruments. The BAT is the large field of view instrument and operates in the 10-300 keV energy band; and two narrow field instruments, XRT and UVOT, that operate in the X-ray and UV/optical regime, respectively. The catalog was derived including pointing positions of the 374 fields centered on the GRBs covering a total area of ~32.55 square degrees. Since GRBs are distributed randomly in the sky, the survey covers totally unrelated parts of the sky, and is highly uniform courtesy of the XRT's stable point spread function and small vignetting correction factors. The observations for a particular field were merged together and the source search analysis was restricted to a circular area of 10 arcmin radius centered in the median of the individual observation aim points. The total exposure considering all the fields is of 36.8 Ms, with ~32% of the fields having more than 100 ks exposure time, and ~28% with exposure time in the range 50-100 ks. The catalog was generated by running the detection algorithm in the XIMAGE package version 4.4.1 that locates the point sources using a sliding-cell method. The average background intensity is estimated in several small square boxes uniformly located within the image. The position and intensity of each detected source are calculated in a box whose size maximizes the signal-to-noise ratio. The detect algorithm was run separately in the following three energy bands: 0.3-3 (Soft), 2-10 (Hard), and 0.3-10 (Full) keV. For each detections the three count rates in the soft, hard, and full bands are all corrected for dead times and vignetting using exposure maps and for the PSF. Hardness ratios are calculated using the three energy band and defined as HR = (cH - cS)/(cH + cS) where cS and cH are the count rates in the S(oft) and H(ard) bands, respectively. The catalog was cleaned of spurious and extended sources by visual inspection of all the observations. Count rates in the three bands were converted into flux in the 0.5-10, 0.5-2, and 2-10 keV energy bands, respectively. The flux was estimated using a power law spectrum with photon spectral index of 1.8 and a Galactic NH of 3.3 x 1020 cm-2. Each row in the catalog is a unique source. The detections from the soft, hard, and full bands were merged into a single catalog using a matching radius of 6 arcsec and retaining detection with a significance level of being spurious <= 2 x 10-5 in at least one band. There are 9387 total entries in the catalog. The SWIFTFT acronym honors both the Swift satellite and the memory of Francesca Tamburelli who made numerous crucial contributions to the development of the Swift-XRT data reduction software. This database table was created by the HEASARC in November 2021 based on the electronic version available from the ASI Data Center https://www.asdc.asi.it/xrtgrbdeep_cat/ and published in the Astronomy and Astrophysics Journal. This catalog is also available as the CDS catalog J/A+A/528/A122. The HEASARC added the source_number parameter, a counter to numerically identify each source in the catalog, as well as Galactic coordinates and changed the source name from SWIFTFTJHHMMSS.s+DDMM.m to SWIFTFT JHHMMSS.s+DDMM.m, adding a space between the catalog prefix and the formatted J2000 coordinates. This is a service provided by NASA HEASARC .
Swift Simultaneous UV, Optical, and X-Ray Observed Quasar Catalog
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The authors have compiled a catalog of optically selected quasars with simultaneous observations in UV/optical and X-ray bands by the Swift Gamma-ray Burst Explorer. Objects in this catalog are identified by matching the Swift pointings with the Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5) quasar catalog. The final catalog contains 843 objects, among which 637 have both Ultraviolet Optical Telescope (UVOT) and X-Ray Telescope (XRT) observations and 354 of which are detected by both instruments. The overall X-ray detection rate is ~ 60% which rises to ~ 85% among sources with at least 10 ks of XRT exposure time. The authors construct the time-averaged spectral energy distribution (SED) for each of the 354 quasars using UVOT photometric measurements and XRT spectra. From model fits to these SEDs, they find that the big blue bump contributes about ~ 0.3 dex to the quasar luminosity. The authors re-visit the alphaox - L2500A relation by selecting a clean sample with only Type 1 radio-quiet quasars; the dispersion of this relation is reduced by at least 15% compared with studies that use non-simultaneous UV/optical and X-ray data. They find only a weak correlation between Lbol/LEdd and alphaUV. They do not find significant correlations between alphax and alphaox, alphaox and alphaUV, and alphax and log L(0.3-10 keV). The correlations between alphaUV and alphax, alphaox and alphax, alphaox and alphaUV, Lbol/LEdd and alphax, and Lbol/LEdd and alphaox are stronger among low-redshift quasars, indicating that these correlations are likely driven by the changes of SED shape with accretion state. This quasar sample was compiled in the following steps: 1. Candidate objects for the catalog were selected as any SDSS DR5 quasar that lie within 20 arcminutes of the center of the Swift FOV in any pointing from launch through 2008 June. 2. XRT data were processed to obtain X-ray count rates, spectra, and spectral parameters. 3. UVOT data were processed to obtain UV and optical photometry. 4. UVOT photometry were supplemented with measurements at other wavelengths from published catalogs. 5. Quasar SEDs were constructed. 6. Additional parameters were calculated based on the SEDs of each quasar. The raw sample is constructed by matching 3.5 years Swift pointings and the SDSS DR5 quasar catalog and contains 1034 objects. This HEASARC version of this catalog contains all 1034 objects in the "raw" catalog. To select only the 843 objects in the "final" catalog, the user should specify catalog_flag = 1 in any searches of this table. This table was created by the HEASARC in August 2012 based on an electronic version of Table 8 from the reference paper which was obtained from the ApJS web site. This is a service provided by NASA HEASARC .
Extremely Luminous X-Ray Source Candidates Catalog
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Using Chandra archive data, the authors conducted a thorough survey of luminous X-ray sources. They directly analyzed about 9400 Chandra ACIS observations and cross-correlated the detected X-ray sources with 77,000 galaxies within a distance of 250 Mpc. The final catalog includes 119 unique luminous X-ray source candidates with LX > 3 x 1040 erg/s from 93 galaxies or 41 HLX candidates with LX > 1 x 1041 erg/s from 35 galaxies. The authors derive a moderate contamination rate due to foreground or background sources. In the reference paper, they also cross-correlate the catalog with FIRST, perform variability and periodicity tests, and analyze one HLX candidate in particular. This catalog could be a starting point to perform follow-up observations. In order to know whether an X-ray source falls within a particular galaxy, for each galaxy, the authors collected its center's RA, Dec, distance, and D25 isophotal info, which includes major axis length, minor axis length, and the position angle of the major axis from the PGC2003 Catalog (Paturel et al. 2003, A&A, 412, 45), which includes the full RC3 catalog and has all of the necessary parameters except for distance. The authors restricted the minimum major axis length to be 10 arcseconds, and collected their distances from NED as much as possible. Their final sample includes 77,000 galaxies within 250 Mpc. The authors used all of the Chandra ACIS data in TE mode that were released before 2014, which includes 9400 ObsIDs. A roughly linear relation between the flux and count rate derived by PIMMS 4.6b was established assuming a power-law spectral shape and galactic foreground extinction (Kalberla et al. 2005, A&A, 440, 775). Any source with a PIMMS luminosity larger than 5 x 1039 erg s-1 would be recalculated by the CIAO script model flux assuming a power-law index of 1.7 in the 0.3 - 8.0 keV energy band. After the recalculation, 1,809 X-ray sources with Lx > 3 x 1040 erg s-1 falling within 640 D25 contours covered by 905 ObsIDs were picked out. A large fraction of the 1,809 sources are galactic nuclei and some of them are repeated. Only off-nuclear sources are considered in this paper. In addition, the centers of the galaxies given by PGC2003 are not necessarily precise and the specific environments of the 1,809 sources are different. Therefore, the authors visually checked the Chandra and DSS images simultaneously, since two-band inspection can help to exclude the nuclear sources, bright knots, and extended sources. X-ray sources with clear DSS features would be dropped because, for a source with a visual magnitude <20 and a distance >30 Mpc, its absolute magnitude would be brighter than -12.4, which is beyond the limit of the brightest star clusters. This table was created by the HEASARC in February 2017 based on CDS Catalog J/ApJS/222/12 file table1.dat, the list of very luminous X-ray source candidates found within the D25 ellipses of Chandra ACIS-observed PGC2003 galaxies lying within 250 Mpc. Some of the values for the name parameter in the HEASARC's implementation of this table were corrected in April 2018. This is a service provided by NASA HEASARC .
Swift-XRT Point Source Catalog (2SXPS)
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This table contains the second Swift X-ray Point Source (2SXPS) catalog of detections by the Swift X-ray Telescope (XRT) used in Photon Counting (PC) mode in the 0.3-10 keV energy range. Swift is a NASA mission with international participation dedicated to the gamma-ray burst study. It carries three instruments. The BAT is the large field-of-view instrument and operates in the 10-300 keV energy band; and two narrow field instruments, XRT and UVOT, that operate in the X-ray and UV/optical regime, respectively. The overall 2SXPS catalog characteristics are as follows: 
 Data included 2005 Jan 01 - 2018 August 01 Sky coverage 3,790 square degrees Typical Sensitivity (0.3-10 keV) 2x10-13 erg cm-2 s-1 (observations) 4x10-14 erg cm-2 s-1 (stacked images) Typical position error 5.6" (90% confidence radius, including systematics) Detections 1,091,058 Unique sources 206,335 Variable sources 82,324 Uncatalogued sources 78,100 False positive rate Flag=Good 0.3% Flag=Good/Reasonable 1% Flag=Good/Reasonable/Poor <10%
This catalog enhances the 1SXPS catalogue (Evans, P. A., et al. 2014, ApJS, 210, 8) in different ways. The 2SXPS catalog uses an improved Point Spread Function (PSF) and pile-up models, a better source detection pipeline that includes a technique to model the effects of stray light, and tests to automatically avoid diffuse emission and ~six years more data. The results are that the 2SXPS catalog contains 50% more temporal coverage than 1SXPS, a sky coverage of 3790 square deg almost double compare to the 1SXPS (1905 square Degree) and ~30% more sources compared to the 1SXPS. The Swift XRT observations were filtered to remove times when: a) data were contaminated by scattered light from the daylight side of the Earth; b) the on-board astrometry derived from the images obtained by the Swift UV/Optical telescope was unreliable; and c) observations with less than 100s of PC mode. The 127519 observations included in the catalog provide a total usable exposure is 266.5 Ms. A Swift observation is a collection of snapshots and the source detection algorithm was run on individual observation as well as on stacked images. The latter were generated on a grid of 2,300x2,300 pixels (~ 90'x90') to ensure that every overlap between observations is in at least one stacked image. A total of 14628 stacked images were generated. Each record corresponds to a unique source which characteristics are described with 230 parameters. The catalog reports for each source rates in four energy band (0.3-10.keV, 0.3-1. keV, 1-2 keV and 3-10 keV), background rates, variability for each energy band, two hardness ratio, peak rate and several spectral parameters. The hardness ratios are defined as follows: 
 HR1 = (M-S)/(M+S) where M and S are the medium (1-2 keV) and soft (0.3-1 keV) band count rates HR2 = (H-M)/(H+M) where H and M are the hard (2-10 keV) and medium (1-2 keV) band count rates
and they are calculated using all observations. The peak rate is determined using three different timescale: the count rate considering all the observations (see parameters rates in this database), the count rate in each observation (not reported in this database) and the count rate in each snapshot (not reported in this database). The peak rate is the rate +/- error from the timescale which has the highest 1-sigma lower-limit on the count rate. Spectral parameters and source flux are estimated using three different methods for two spectral models, a power-law and APEC (see Smith et al., 2001, ApJL, 556, L91). Not all sources have values for all three methods. The parameters starting with "fix" are defined for every source and uses fixed spectral model parameters: a photon index of 1.7 for a power-law model, a temperature of kT=1keV for the APEC model and for both models uses the Galactic absorption listed in the parameter "nh". The parameters starting "intr" have been inferred from
XMM-Newton XAssist Source List
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This database table contains the latest XMM-Newton XAssist source list. XAssist is a NASA-funded project for the automation of X-ray astrophysics, with emphasis on galaxies. It is capable of data reprocessing, source detection, and preliminary spatial, temporal, and spectral analysis for all sources with sufficient counts. The bulk of the system is written in Python, which in turn drives underlying software to process the XMM-Newton data. Pipelines running on XMM-Newton observations of galaxies have generated the source list which comprises this HEASARC table. The pipeline also includes fields requested by users for various projects, most notably observations of a sample of quasars and several deep field observations have been processed. Note that the pipline processing is completely automated; therefore, users should visually inspect the results of any queries. This table was first created by the HEASARC in July 2005 based on the XMM source list available at the XAssist website. In December 2012, the HEASARC switched over to using the "pipeline5" XMM source list. It is updated on a weekly basis when and if the XAssist source list file at https://asd.gsfc.nasa.gov/xassist/pipeline5/xmm/master_srclist.csv is updated. This is a service provided by NASA HEASARC .
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