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.
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.
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.
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 .
SWIRE/Chandra Lockman Hole Field X-Ray Source Catalog
Short Name:
SWIRELHCXO
Date:
09 May 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 .
We report a moderate-depth (70ks), contiguous 0.7deg^2^ 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 (logN_H_>23) subset. Chandra has detected 775 X-ray sources to a limiting broadband (0.3-8keV) flux ~4x10^-16^erg/cm^2^/s. We present the X-ray catalog, fluxes, hardness ratios, and multi-wavelength fluxes. The logN versus logS 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 24um detections. There are four optical-only X-ray sources and four with no visible optical/IR counterpart. The very deep (~2.7uJy rms) VLA data yield 251 (>4{sigma}) radio counterparts, 44% of the X-ray sources in the field. More than 40% of the X-ray sources in the VLA field are radio-loud using the classical definition, RL. The majority of these are red and relatively faint in the optical so that the use of RL to select those AGNs with the strongest radio emission becomes questionable. Using the 24um to radio flux ratio (q_24_) 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. We conclude that q_24_ is a more reliable indicator of radio-loudness. Use of RL should be confined to the optically selected type 1 AGN.
The Spitzer Wide-area InfraRed Extragalactic survey (SWIRE; Lonsdale et al., 2003PASP..115..897L) Version 1.0 data products release includes an image atlas and a source catalogs from the first of the 6 SWIRE fields to be observed by Spitzer, the ELAIS-N1 field. The release includes both Spitzer IRAC and MIPS mid/far-infrared data products and also Ug'r'i'Z optical data covering the same regions of the sky from the Isaac Newton Telescope (INT) Wide-Field Survey (WFS; McMahon et al., 2001NewAR..45...97M; Gonzalez-Solares et al., 2004, MNRAS, in press). The Version 1.0 SWIRE ELAIS-N1 Source Catalogs have three parts: (1) a catalog including IRAC and MIPS 24{mu}m sources which have been band-merged together. The Spitzer source list has been positionally matched to the optical source list and we report optical position and 5-band magnitude data for each successful match. This catalog contains only sources lying with the region which has full coverage in all four IRAC bands; (2) a 70{mu}m catalog; and (3) a 160{mu}m catalog. The longer wavelength catalogs have not been band-merged with the IRAC+24{mu}m catalog or the optical source list at this time because of complex source confusion issues. The two MIPS-Ge catalogs cover the full area scanned by each MIPS-array, except for areas of low coverage around each edge, and are not restricted to the full IRAC coverage area. All data are available at http://data.spitzer.caltech.edu/popular/swire/20041027_enhanced_v1_EN1
Main data on the IR-peakers sample in the SWIRE ELAIS-S1 field. For each IR-peak galaxy, we report R band magnitude (AB units, from the ESIS survey, Berta et al., 2006A&A...451..881B), Spitzer SWIRE fluxes (Lonsdale et al., 2003PASP..115..897L, 2004ApJS..154...54L), photometric redshift (based on Hyper-z fit, Bolzonella et al., 2000A&A...363..476B), the stellar mass and its minimal-maximal range. The stellar mass estimate is based on mixed stellar population (MSP) synthesis (Berta et al., 2004A&A...418..913B). The minimal and maximal stellar masses are obtained by exploring the SFH-extinction parameter space with the Adaptive Simulated Annealing algorithm (Ingber et al., 2001, http://www.ingber.com/asa01_lecture.pdf). See the paper associated to these data for more details.
We present the SWIRE Photometric Redshift Catalogue 1025119 redshifts of unprecedented reliability and of accuracy comparable with or better than previous work. Our methodology is based on fixed galaxy and quasi-stellar object templates applied to data at 0.36-4.5um, and on a set of four infrared emission templates fitted to infrared excess data at 3.6-170um. The galaxy templates are initially empirical, but are given greater physical validity by fitting star formation histories to them, which also allows us to estimate stellar masses.
