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15171. Swift X-Ray Telescope Cluster Survey Catalog
ID:
ivo://nasa.heasarc/swxcscat
Title:
Swift X-Ray Telescope Cluster Survey Catalog
Short Name:
SWXCSCAT
Date:
25 Apr 2025
Publisher:
NASA/GSFC HEASARC
Description:
This table contains the Swift X-ray Cluster Survey (SWXCS) catalog obtained using archival data from the X-ray telescope (XRT) on board the Swift satellite acquired from 2005 February to 2012 November, extending the first release of the SWXCS. The catalog provides positions and soft X-ray fluxes for a flux-limited sample of X-ray group and cluster candidates. In Table 3 of the reference paper (available at the HEASARC as the linked table SWXCSOXID), when possible, optical counterparts are given for these candidates. The authors consider the fields with Galactic latitude |b| > 20 degrees so as to avoid regions of high H I column density. They discard all of the observations targeted at groups or clusters of galaxies, as well as particular extragalactic fields not suitable for searching for faint extended sources. The authors finally select ~ 3000 useful fields covering a total solid angle of ~ 400 deg<sup>2</sup>. They identify extended source candidates in the soft-band (0.5-2 keV) images of these fields using the software EXSdetect, which is specifically calibrated for the XRT data. Extensive simulations are used to evaluate contamination and completeness as a function of the source signal, allowing the authors to minimize the number of spurious detections and to robustly assess the selection function. The final catalog includes 263 candidate galaxy clusters and groups down to a flux limit of 7 x 10<sup>-15</sup> erg/cm<sup>2</sup>/s in the soft band (0.5 - 2.0 keV), and the log N - log S is in very good agreement with previous deep X-ray surveys. In the reference paper, the final list of sources is cross-correlated with published optical, X-ray, and Sunyaev-Zel'dovich catalogs of clusters. The authors find that 137 sources have been previously identified as clusters in the literature in independent surveys, while 126 are new detections. Currently, they have collected redshift information for 158 sources (60% of the entire sample). From the entire Swift XRT archive in the period 2005 February-2012 November, the authors have selected all the fields that can be used to build an unbiased, serendipitous X-ray cluster catalog. This table was created by the HEASARC in March 2015 based on an electronic version of Table 2 from the reference paper which was obtained from the CDS as their catalog J/ApJS/216/28 file table2.dat. This is a service provided by NASA HEASARC .
15172. Swift X-ray Telescope Cluster Survey. II.
ID:
ivo://CDS.VizieR/J/A+A/567/A89
Title:
Swift X-ray Telescope Cluster Survey. II.
Short Name:
J/A+A/567/A89
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a spectral analysis of a new, flux-limited sample of 72 X-ray selected clusters of galaxies identified with the X-ray Telescope (XRT) on board the Swift satellite down to a flux limit of ~10^-14^erg/s/cm2 (SWXCS). We carry out a detailed X-ray spectral analysis with the twofold aim of measuring redshifts and characterizing the properties of the intracluster medium (ICM) for the majority of the SWXCS sources. Optical counterparts and spectroscopic or photometric redshifts for some of the sources are obtained with a cross-correlation with the NASA/IPAC Extragalactic Database. Additional photometric redshifts are computed with a dedicated follow-up program with the Telescopio Nazionale Galileo and a cross-correlation with the SDSS. In addition, we also blindly search for the Hydrogen-like and He-like iron K_{alpha}_ emission line complex in the X-ray spectrum. We detect the iron emission lines in 35% of the sample, and hence obtain a robust measure of the X-ray redshift z_X_ with typical rms error 1-5%. We use z_X_ whenever the optical redshift is not available. Finally, for all the sources with measured redshift, background-subtracted spectra are fitted with a single-temperature mekal model to measure global temperature, X-ray luminosity and iron abundance of the ICM. We perform extensive spectral simulations to accounts for fitting bias, and to assess the robustness of our results. We derive a criterion to select reliable best-fit models and an empirical formula to account for fitting bias. The bias-corrected values are then used to investigate the scaling properties of the X-ray observables.
15173. Swift XRT Counterparts to Unidentified 1FGL Sources
ID:
ivo://nasa.heasarc/swxrt1fgl
Title:
Swift XRT Counterparts to Unidentified 1FGL Sources
Short Name:
SWXRT1FGL
Date:
25 Apr 2025
Publisher:
NASA/GSFC HEASARC
Description:
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 .
15174. Swift XRT follow-up of LIGO/Virgo GW triggers
ID:
ivo://CDS.VizieR/J/ApJS/245/15
Title:
Swift XRT follow-up of LIGO/Virgo GW triggers
Short Name:
J/ApJS/245/15
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Neil Gehrels Swift Observatory carried out prompt searches for gravitational-wave (GW) events detected by the LIGO/Virgo Collaboration (LVC) during the second observing run ("O2"). Swift performed extensive tiling of eight LVC triggers, two of which had very low false-alarm rates (GW170814 and the epochal GW170817), indicating a high confidence of being astrophysical in origin; the latter was the first GW event to have an electromagnetic counterpart detected. In this paper we describe the follow-up performed during O2 and the results of our searches. No GW electromagnetic counterparts were detected; this result is expected, as GW170817 remained the only astrophysical event containing at least one neutron star after LVC's later retraction of some events. A number of X-ray sources were detected, with the majority of identified sources being active galactic nuclei. We discuss the detection rate of transient X-ray sources and their implications in the O2 tiling searches. Finally, we describe the lessons learned during O2 and how these are being used to improve the Swift follow-up of GW events. In particular, we simulate a population of gamma-ray burst afterglows to evaluate our source ranking system's ability to differentiate them from unrelated and uncataloged X-ray sources. We find that ~60%-70% of afterglows whose jets are oriented toward Earth will be given high rank (i.e., "interesting" designation) by the completion of our second follow-up phase (assuming that their location in the sky was observed), but that this fraction can be increased to nearly 100% by performing a third follow-up observation of sources exhibiting fading behavior.
15175. Swift XRT Instrument Log
ID:
ivo://nasa.heasarc/swiftxrlog
Title:
Swift XRT Instrument Log
Short Name:
SwiftXRT
Date:
25 Apr 2025
Publisher:
NASA/GSFC HEASARC
Description:
The XRT runs only one type of configuration mode/window in a given time interval. The table therefore contains for a given time interval a single record that describes one configuration. A new record is generated when the following is changing within an observation: new operating mode , new pointing mode, or new window configuration. This database table is generated by the Swift Data Center. During operation, it is updated on daily basis. This is a service provided by NASA HEASARC .
15176. Swift-XRT long GRB durations
ID:
ivo://CDS.VizieR/J/ApJ/800/16
Title:
Swift-XRT long GRB durations
Short Name:
J/ApJ/800/16
Date:
21 Oct 2021
Publisher:
CDS
Description:
The discovery of a number of gamma-ray bursts (GRBs) with duration exceeding 1000s has opened the debate on whether these bursts form a new class of sources, the so-called ultra-long GRBs, or if they are rather the tail of the distribution of the standard long GRB duration. Using the long GRB sample detected by Swift, we investigate the statistical properties of long GRBs and compare them with the ultra-long burst properties. We compute the burst duration of long GRBs using the start epoch of the so-called "steep decay" phase detected with Swift/XRT. We discuss also the differences observed in their spectral properties. We find that ultra-long GRBs are statistically different from the standard long GRBs with typical burst duration less than 100-500s, for which a Wolf-Rayet star progenitor is usually invoked. Together with the presence of a thermal emission component we interpret this result as indication that the usual long GRB progenitor scenario cannot explain the extreme duration of ultra-long GRBs, their energetics, as well as the mass reservoir and size that can feed the central engine for such a long time.
15177. Swift-XRT observations of GRBs
ID:
ivo://CDS.VizieR/J/MNRAS/397/1177
Title:
Swift-XRT observations of GRBs
Short Name:
J/MNRAS/397/1177
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a homogeneous X-ray analysis of all 318 Gamma Ray Bursts detected by the X-ray Telescope on the Swift satellite up to 2008 July 23; this represents the largest sample of X-ray GRB data published to date. In Sections 2-3 we detail the methods which the Swift-XRT team has developed to produce the enhanced positions, light curves, hardness ratios and spectra presented in this paper. Software using these methods continues to create such products for all new GRBs observed by the Swift-XRT. We also detail web-based tools allowing users to create these products for any object observed by the XRT, not just GRBs. In Sections 4-6 we present the results of our analysis of GRBs, including probability distribution functions of the temporal and spectral properties of the sample. We demonstrate evidence for a consistent underlying behaviour which can produce a range of light curve morphologies, and attempt to interpret this behaviour in the framework of external forward shock emission. We find several difficulties, in particular that reconciliation of our data with the forward shock model requires energy injection to continue for days to weeks.
15178. Swift/XRT obs. of unidentified IBIS sources
ID:
ivo://CDS.VizieR/J/MNRAS/403/945
Title:
Swift/XRT obs. of unidentified IBIS sources
Short Name:
J/MNRAS/403/945
Date:
21 Oct 2021
Publisher:
CDS
Description:
The most recent IBIS/ISGRI survey, i.e. the fourth one, lists 723 hard X-ray sources, many still unidentified, i.e. lacking an X-ray counterpart or simply not studied at lower energies, i.e. below 10keV. In order to overcome this lack of X-ray information, we cross-correlated the list of IBIS sources included in the fourth IBIS catalogue with the Swift/X-ray Telescope (XRT) data archive, finding a sample of 20 objects, not yet reported in the literature, for which XRT data could help in the search for the X-ray and hence optical counterpart and/or, for the first time, in the study of the source spectral and variability properties below 10keV. 16 of these objects are new INTEGRAL detections, while four were already listed in the third survey but not yet observed in X-rays.
15179. Swift-XRT Point Source Catalog (2SXPS)
ID:
ivo://nasa.heasarc/swift2sxps
Title:
Swift-XRT Point Source Catalog (2SXPS)
Short Name:
SWIFT2SXPS
Date:
25 Apr 2025
Publisher:
NASA/GSFC HEASARC
Description:
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: <pre> Data included 2005 Jan 01 - 2018 August 01 Sky coverage 3,790 square degrees Typical Sensitivity (0.3-10 keV) 2x10<sup>-13</sup> erg cm<sup>-2</sup> s<sup>-1</sup> (observations) 4x10<sup>-14</sup> erg cm<sup>-2</sup> s<sup>-1</sup> (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% </pre> 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: <pre> 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 </pre> 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 the hardness ratio. Look-up tables containing (HR1, HR2, NH, photon index) and (HR1, HR2, NH, kT) are pre-calculated for the power-law and APEC models. If the source HR1 and HR2 are close to the values in the table, spectral parameters are derived by interpolating the HR1 and HR2 in the look-up tables that are close to the HR1 and HR2 of the source. The parameters starting with "fit" have been derived from fitting an actual source spectrum in XSPEC and they are only available for the brightest sources (>50 net counts, and at least one detection in a single observation). The parameters fields starting with "pow" and "apec" report the values from the 'best' of these methods. The parameters "which_pow" and "which_apec" indicates which of the three methods are reported. The catalog also includes flags derived from the cross-correlated with other source catalogs. The catalogs and their reference sources are as follows: <pre> * AllWISE: <a href="https://wise2.ipac.caltech.edu/docs/release/allwise/">https://wise2.ipac.caltech.edu/docs/release/allwise/</a> * ROSAT HRI: <a href="https://heasarc.gsfc.nasa.gov/docs/rosat/rra/RRA.html">https://heasarc.gsfc.nasa.gov/docs/rosat/rra/RRA.html</a> * SDSS Quasar Catalog DR14: Paris et al., 2018, A&A, 613, 51 (<a href="https://www.sdss.org/dr14/algorithms/qso_catalog/">https://www.sdss.org/dr14/algorithms/qso_catalog/</a>) * 2MASS: Skrutskie et al., 2006, AJ, 131, 1163 * 2CSC: accessed via the CSCView Tool at <a href="https://cxc.harvard.edu/csc/about.html">https://cxc.harvard.edu/csc/about.html</a> (1CSC paper: Evans et al., 2010, ApJS, 189, 37) * 1SWXRT: Evans et al., 2014, ApJS, 210,8 * 1SXPS: D'Elia et al., 2013, A&A, 551, 142 * 2RXS: Boller et al., 2016, A&A, 588, 103 * 3XMM-DR8: <a href="http://xmmssc.irap.omp.eu/Catalogue/3XMM-DR8/3XMM_DR8.html">http://xmmssc.irap.omp.eu/Catalogue/3XMM-DR8/3XMM_DR8.html</a> (3XMM paper: Rosen, Webb, Watson et al., 2016, A&A, 590, 1) * 3XMM Stack: Traulsen et al., 2019, A&A, 642, 77 * SwiftFT: Puccetti et al. 2011, A&A,528, A122 * XMM SL2: Saxton et al., 2008, A&A 480, 611 * XRTGRB: Evans et al, 2009, MNRAS, 397, 1177 (<a href="https://www.swift.ac.uk/xrt_positions">https://www.swift.ac.uk/xrt_positions</a>) * USNOB1: Monet et al., 2003, AJ, 125, 984 </pre> The 2SXPS paper (Evans et al. 2020 ApJS, 247,54) describes in detail the methodology of stacking images, background modeling, point spread function mapping, stray light detection and corrections, data filtering techniques and processing. The 2SXPS catalog has a dedicated website at <a href="https://www.swift.ac.uk/2SXPS">https://www.swift.ac.uk/2SXPS</a>. This database table was created by the HEASARC in November 20201 based on the electronic version delivered to the HEASARC by the Leicester University. The catalog has a dedicated website at <a href="https://www.swift.ac.uk/2SXPS">https://www.swift.ac.uk/2SXPS</a>. The version available from the HEASARC corresponds to the catalog designated as "All" on the Leicester website. This is a service provided by NASA HEASARC .
15180. SWIRE/Chandra Lockman Hole Field X-Ray Source Catalog
ID:
ivo://nasa.heasarc/swirelhcxo
Title:
SWIRE/Chandra Lockman Hole Field X-Ray Source Catalog
Short Name:
SWIRELHCXO
Date:
25 Apr 2025
Publisher:
NASA/GSFC HEASARC
Description:
The authors have carried out a moderate-depth (70 ks), contiguous 0.7 square degrees Chandra survey in the Lockman Hole Field of the Spitzer/SWIRE Legacy Survey coincident with a completed, ultra-deep VLA survey with deep optical and near-infrared imaging in-hand. The primary motivation is to distinguish starburst galaxies and active galactic nuclei (AGNs), including the significant, highly obscured (log N<sub>H</sub> > 23 cm<sup>-2</sup>) subset. Chandra has detected 775 X-ray sources to a limiting broadband (0.3 - 8 keV) flux of ~4 x 10<sup>-16</sup> erg cm<sup>-2</sup> s<sup>-1</sup>. This table contains the X-ray catalog, fluxes, hardness ratios, and multi-wavelength fluxes. The log N versus log S agrees with those of previous surveys covering similar flux ranges. The Chandra and Spitzer flux limits are well matched: 771 (99%) of the X-ray sources have infrared (IR) or optical counterparts, and 333 have MIPS 24-micron detections. There are four optical-only X-ray sources and four with no visible optical/IR counterpart. The very deep (~2.7 microJansky rms) VLA data yield 251 (> 4 sigma) radio counterparts, 44% of the X-ray sources in the field. The authors confirm that the tendency for lower X-ray flux sources to be harder is primarily due to absorption. As expected, there is no correlation between observed IR and X-ray fluxes. Optically bright, type 1, and red AGNs lie in distinct regions of the IR versus X-ray flux plots, demonstrating the wide range of spectral energy distributions in this sample and providing the potential for classification/source selection. Many optically bright sources, which lie outside the AGN region in the optical versus X-ray plots (f<sub>r</sub>/f<sub>x</sub> > 10), lie inside the region predicted for red AGNs in IR versus X-ray plots, consistent with the presence of an active nucleus. More than 40% of the X-ray sources in the VLA field are radio-loud using the classical definition of R<sub>L</sub>. The majority of these are red and relatively faint in the optical so that the use of R<sub>L</sub> to select those AGNs with the strongest radio emission becomes questionable. Using the 24-micron to radio flux ratio (q<sub>24</sub>) instead results in 13 of the 147 AGNs with sufficient data being classified as radio-loud, in good agreement with the ~10% expected for broad-lined AGNs based on optical surveys. The authors conclude that q<sub>24</sub> is a more reliable indicator of radio-loudness. Use of R<sub>L</sub> should be confined to the optically selected type 1 AGN. This table was created by the HEASARC in December 2009 based on the machine-readable versions of Tables 3, 4 and 7 from the reference paper which was obtained from the Astrophysical Journal web site. This is a service provided by NASA HEASARC .

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