- ID:
- ivo://nasa.heasarc/swxcscat
- Title:
- Swift X-Ray Telescope Cluster Survey Catalog
- Short Name:
- SWXCSCAT
- Date:
- 09 May 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 .
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- ID:
- ivo://nasa.heasarc/swxcsoxid
- Title:
- Swift X-Ray Telescope Cluster Survey Cross-Correlation Catalog
- Short Name:
- SWXCSOXID
- Date:
- 09 May 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the Swift X-ray Cluster Survey (SWXCS) table of cross-correlations of the X-ray galaxy cluster and group candidates with optical, X-ray and Sunyaev-Zel'dovich catalogs and optical follow-up. The SWXCS list of cluster candidates was 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 main catalog (available at the HEASARC as the linked table SWXCSCAT) provides positions and soft X-ray fluxes for a flux-limited sample of X-ray group and cluster candidates. The table herein (based on Table 3 of the reference paper) contains when possible, optical and other counterparts 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). The authors checked for counterparts in previous X-ray cluster surveys, in optical cluster surveys, and in the Planck SZ cluster survey. They simply assume a search radius of 2 arcminutes from the X-ray centroid, which has been shown to be an efficient criterion in Paper I. Nevertheless, they also inspected the area within 5 arcminutes from the X-ray centroid in order to investigate whether some possible identification is found at radii larger than 2 arcminutes. Counterparts at distances between 2 and 5 arcminutes are included when the optical or SZ corresponding source has a large uncertainty in its position. This is often the case for optical, sparse clusters, or for SZ cluster candidates. The authors list all of the counterparts associated with the SWXCS sources herein, and they include the measured redshift when available. In case of multiple counterparts, they list all of them. Except for a few cases where there are multiple counterparts with statistically inconsistent redshifts, the authors keep the counterpart with the smallest angular distance from the X-ray center. From optical surveys, the authors found 233 optical counterparts corresponding to 116 SWXCS sources. From X-ray surveys, they found 70 X-ray counterparts classified as clusters, corresponding to 36 SWXCS sources. Finally, for 15 SWXCS sources, they found 16 cluster counterparts detected via the SZ effect, 13 by Planck and 3 by the South Pole Telescope (SPT). The Planck sources are typically at larger distances from the X-ray centroid (between 1 and 3 arcminutes) because of the much larger position errors of Planck clusters. Overall, about half (137) of the 263 SWXCS sources were previously identified as groups or clusters of galaxies, while 126 SWXCS sources are new cluster and group candidates. The authors have collected spectroscopic or photometric redshifts for 130 of their sources. Moreover, to increase the number of available redshifts, they also searched in NED catalogs for single galaxies with published redshifts not associated with previously known clusters within a search radius of 7 arcseconds from the X-ray centroid of their sources. They find 50 galaxies with measured redshifts for 47 of their sources as a complement to the redshifts obtained from cluster counterparts. In 35 cases where the authors have both cluster and galaxy counterparts, the galaxy redshifts are consistent with those of clusters. In the 12 cases where no cluster counterpart is found, the authors tentatively assign the galaxy redshift to their X-ray source. This table was created by the HEASARC in March 2015 based on an electronic version of Table 3 from the reference paper which was obtained from the CDS as their catalog J/ApJS/216/28 file table3.dat. This is a service provided by NASA HEASARC .
- 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.
- ID:
- ivo://CDS.VizieR/J/ApJ/889/142
- Title:
- Swift/XRT and NICER timing study of MAXI J1820+070
- Short Name:
- J/ApJ/889/142
- Date:
- 03 Dec 2021 13:13:00
- Publisher:
- CDS
- Description:
- We present a detailed timing analysis of the bright black hole X-ray binary MAXI J1820+070 (ASASSN-18ey), during its first detected outburst lasting from 2018 March until 2019 October based on Swift/XRT window timing mode observations, corresponding UVOT data and NICER observations. The light curves clearly show four outbursts, with the source remaining in the hard state during its first outburst, while the rise of the second outburst corresponds with the transition to the soft state. A similar double outburst of GX339-4 has been observed in 2004. Here it is followed by two hard-state only outbursts. In many observations the power density spectra showed type-C quasi-periodic oscillations (QPOs) with characteristic frequencies below 1Hz, which suggests that the source stayed in a state of low effective accretion for large parts of its outburst. The absence of other types of QPOs hinders a precise determination of the state transitions, but from combining NICER and Swift/XRT data, we find that MAXI J1820+070 went from the hard-intermediate to the soft state in less than one day. The covariance ratios derived from NICER data show an increase toward lower energies, which indicate that the source should make a transition to the soft state. This transition finally took place, after MAXI J1820+070 stayed in the hard state at rather constant luminosity for about 116 days. The steepness of the increase of the covariance ratios is not correlated with the amount of rms variability and it does not show a monotonic evolution along the outburst.
- ID:
- ivo://nasa.heasarc/skyview/swiftxrt
- Title:
- Swift XRT Combined Intensity Images
- Short Name:
- SWIFTXRT
- Date:
- 09 May 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The Swift XRT (<a href="https://ads.harvard.edu/abs/2005SSRv..120..165B">Burrows et al 2005, SSRv, 120, 165</a>) is a sensitive, broad-band (0.2 - 10 keV) X-ray imager with an effective area of about 125 cm**2 at 1.5 keV. The 600 x 600 pixel CCD at the focus provides a 23.6' x 23.6' field of view with a pixel scale of 2.36". The point spread function is 18" (HPD) at 1.5 keV. <p> These XRT surveys represent the data from the first 12.5 years of Swift X-ray observations. They include all data taken in photon counting mode. A total of just over 8% of the sky has some non-zero exposure. The fraction of sky exposed as a function of the exposure is given in the following table: <table border> <tr><th>Exposure</th><td>>0</td> <td>10</td> <td>30</td> <td>100</td> <td>300</td> <td>1000</td> <td>3000</td> <td>1000</td> <td>30000</td> <td>100000</td><td>300000</td></tr> <tr><th>Coverage</th> <td> 8.42 </td><td> 8.37 </td><td> 8.29 </td><td> 7.67 </td><td> 7.29 </td><td> 5.68 </td> <td> 3.40 </td><td> 1.26 </td><td> 0.35 </td><td> 0.044 </td><td> 0.00118</td></th> </table> The individual exposure and counts maps have been combined into a Hierarchical Progressive Survey (HiPS) where the data are stored in tiles in the HEALPix projection at a number of different resulutions. The highest resolution pixels (HEALPix order 17) have a size of roughly 1.6". Data are also stored at lower resolutions at factors of 1/2, 1/4, 1/8, 1/16, and 1/32, and in an all sky image with a resolution 1/256 of the higest resolution. An intensity map has been created as the ratio of the counts and exposure maps. <p> These surveys combine the basic count and exposure maps provided as standard products in the Swift XRT archive in obsid/xrt/products/*xpc_(sk|ex).img.gz. The surveys were created as follows: <ul> <li>All of the exposure maps available in the archive in mid-May 2017 were combined using the CDS-developed Hipsgen tool. This includes 129,063 observations for which both count and exposure files were found in PC mode. Three exposures where there was a counts map but no exposure map were ignored. A few exposure files had more than one exposure extension. 1,082 files had two extensions and 1 file had 3 extensions. The 1084 HDUs in extensions were extracted as separate files and included in the total exposure. The value of 0 was given to the Hipsgen software as the null value for the FITS files. This caused the CDS software to treat such pixels as missing rather than 0 exposure. <li> The counts data was extracted from the counts maps for each observation using <i>SkyView</i> developed software. For any pixel in which a count was recorded, the corresponding exposure file was checked and if there was any exposure (in any of the associated extensions), then the count was retained. If there was no exposure in any of the extensions of the corresponding exposure file, the counts in the pixel were omitted. Once a count was accepted, the overlap between the counts map pixel and the pixels of the corresponding HiPS tile (or tiles) was computed. Each count was then assigned entirely to a single pixel in the HiPS tile randomly but with the destination pixel probabilities weighted by area of the overlap. Thus if several pixels were found in a given counts map pixel they might be assigned to different pixels in the output image. The HiPS pixels (~1.6") used were of substantially higher resolution than the XRT resolution of 18" and somewhat higher than the counts map resolution of 2.36". <p> A total of 183,750,428 photons were extracted from the counts maps while 15,226 were rejected as being from pixels with 0 exposure. There were 501 pixels which required special treatment as straddling the boundaries of the HEALPix projection. <li> The resulting counts tiles were then clipped using the exposure tiles that had been previously generated. Basically this transferred the coverage of the exposure tiles to the counts tiles. Any counts pixel where the corresponding exposure pixel was a NaN was changed to a NaN to indicate that there was no coverage in this region. <p> During the clipping process 137,730 HiPS level 8 were clipped (of 786,432 over the entire sky). There were 12,236 tiles for which there was some exposure but no counts found. During the clipping process 2 photons were found on pixels where there was no corresponding exposure in the exposure tiles. This can happen when the pixel assignment process noted above shifts a photon just outside the exposed region but should be -- as it was -- rare. These photons were deleted. <li> After creating the clipped level 8 counts maps, level 7 to 3 tiles and an all sky map where generated by averaging pixels 2x2 to decrease each level. When adding the four pixels in the level N map together only pixels whose value was not NaN were considered. <li> Finally an intensity map was created by dividing the counts tiles by the exposure tiles. To eliminate gross fluctuations due to rare counts in regions with very low exposure, only regions with exposure > 1 second were retained. A total of 30 photons were deleted due to this criterion. </ul> <p> Note that while any sampler may in principle be used with these data, the Spline sampler may give unexpected results. The spline computation propogates NaNs thought the image and means that even occasional NaNs can corrupt the output image completely. NaNs are very common in this dataset. Also, if the region straddles a boundary in the HEALPix projection, the size of the requested input region is likely to exceed memory limits since the HiPS data are considered a single very large image. Provenance: Data generated from public images at HEASARC archive. This is a service of NASA HEASARC.
- ID:
- ivo://nasa.heasarc/swxrt1fgl
- Title:
- Swift XRT Counterparts to Unidentified 1FGL Sources
- Short Name:
- SWXRT1FGL
- Date:
- 09 May 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 .
- 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.
21288. Swift XRT Instrument Log
- ID:
- ivo://nasa.heasarc/swiftxrlog
- Title:
- Swift XRT Instrument Log
- Short Name:
- SwiftXRT
- Date:
- 09 May 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 .
- ID:
- ivo://CDS.VizieR/J/ApJ/768/47
- Title:
- Swift/XRT 0.2-10keV observations of SN2009ip
- Short Name:
- J/ApJ/768/47
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Some supernovae (SNe) show evidence for mass-loss events taking place prior to their explosions. Measuring their pre-outburst mass-loss rates provides essential information regarding the mechanisms that are responsible for these events. Here we present XMM-Newton and Swift X-ray observations taken after the latest, and presumably the final, outburst of SN 2009ip. We use these observations as well as new near-infrared and visible-light spectra and published radio and visible-light observations to put six independent order-of-magnitude constraints on the mass-loss rate of the SN progenitor prior to the explosion. Our methods utilize the X-ray luminosity, the bound-free absorption, the H{alpha} luminosity, the SN rise time, free-free absorption, and the bolometric luminosity of the outburst detected prior to the explosion. Assuming spherical mass loss with a wind-density profile, we estimate that the effective mass-loss rate from the progenitor was between 10^-3^ and 10^-2^M_{sun}_/yr, over a few years prior to the explosion, with a velocity of ~10^3^km/s. This mass-loss rate corresponds to a total circumstellar matter (CSM) mass of ~0.04M_{sun}_, within 6x10^15^cm of the SN. We note that the mass-loss rate estimate based on the H{alpha} luminosity is higher by an order of magnitude. This can be explained if the narrow-line H{alpha} component is generated at radii larger than the shock radius, or if the CSM has an aspherical geometry. We discuss simple geometries which are consistent with our results.
- ID:
- ivo://CDS.VizieR/J/ApJ/808/144
- Title:
- Swift/XRT 0.5-10keV obs. of MAXI J1659-152
- Short Name:
- J/ApJ/808/144
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an energy dependent X-ray variability study of the 2010 outburst of the black hole X-ray binary MAXI J1659-152 with the Swift X-ray Telescope (XRT). The broadband noise components and the quasi-periodic oscillations (QPO) observed in the power spectra show a strong and varied energy dependence. Combining Swift XRT data with data from the Rossi X-ray Timing Explorer, we report, for the first time, an rms spectrum (fractional rms amplitude as a function of energy) of these components in the 0.5-30keV energy range. We find that the strength of the low-frequency component (<0.1Hz) decreases with energy, contrary to the higher frequency components (>0.1Hz) whose strengths increase with energy. In the context of the propagating fluctuations model for X-ray variability, we suggest that the low-frequency component originates in the accretion disk (which dominates emission below ~2keV) and the higher frequency components are formed in the hot flow (which dominates emission above ~2keV). As the properties of the QPO suggest that it may have a different driving mechanism, we investigate the Lense-Thirring precession of the hot flow as a candidate model. We also report on the QPO coherence evolution for the first time in the energy band below 2keV. While there are strong indications that the QPO is less coherent at energies below 2keV than above 2keV, the coherence increases with intensity similar to what is observed at energies above 2keV in other black hole X-ray binaries.
