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SWBAT157M - Swift-BAT 157-Month All-Sky Hard X-Ray Survey

 HEASARC
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Overview

This catalog includes the hard X-ray sources detected in the first 157 months of observations with the Burst Alert Telescope (BAT) coded-mask imager on board the Swift observatory. The results of the 157 months survey catalog has been obtained using data from February 2007 to December 2017 and provide a uniform hard X-ray all-sky survey with a sensitivity of 8.40 x 10-12 erg/s/cm2 over 90% of the sky and 7.24 x 10-12 erg/s/cm2 over 50% of the sky in the 14-195 keV band. The exposure time in all sky ranges from ~ 15 Ms to ~ 35 Ms, where ~ 50% of the sky achieves an exposure time of ~ 22.8 Ms. The 157 months survey provides 1891 hard X-ray sources in the 14-195 keV band above the 4.8 sigma significance level, where 259 are new detections from the 105-month catalog of which 54 are previously known source in X-ray. The sources identification is mostly from NED and SIMBAD and the 157-month catalog reports for positive identification the counterpart R.A. and Dec and the alternative name. The sources are classified in 17 different classes as follows: 

 Class   Source Type                 Number of Sources
  0      Unknown                         221
  1      Galactic                          4
  2      Galaxy                           16
  3      Galaxy Cluster                   26
  4      Seyfert I                       446
  5      Seyfert II                      464
  6      Other AGN                       130
  7      Beamed AGN (Blazar/FSRQ)        192
  8      LINER                             7
  9      Cataclysmic Variable Star (CV)   81
 10      Pulsar                           27
 11      Supernova Remnant (SNR)           7
 12      Star                             26
 13      High Mass X-ray Binary (HMXB)   108
 14      Low Mass X-ray Binary (LMXB)    118
 15      Other X-ray Binary (XRB)         17
 16      Tidal Disruption Event            1
	 Total                          1891

The data reduction, analysis, and catalog generation of the Swift-BAT are conducted following the same procedures of the previous catalog survey (Tueller+ 2010, J/ApJS/1167/186, Baumgartner+ 2013, J/ApJS/207/19). The BAT survey data are collected into arrays (Detector Plane Histograms, DPHs) where the data are binned in ~ 300 s time interval and in 8 energy band channels (14-20, 20-24, 24-35, 35-50, 50-75, 75-100, 100- 197 150, and 150-195 keV) and 1 energy total band (14-195 keV). Three different mosaic images are created from the DPH dividing the sky in 6 regions. The first set has images created in 8 energy bands to span a contiguous time interval (snapshot). The second set has images co-adding data on a time period of a month. The third set is created in 8 energy bands by Crab-weighting the monthly images in each of the energy band with the following weights (Baumgartner+ 2013, J/ApJS/207/19): 27.000, 35.260, 22.700, 29.444, 21.272, 16.062, 8.449, 2.630. The benchmark Crab spectrum adopted is F(E) = 10.17E−2.15 photon cm2 s keV. The source detection algorithm uses the Crab-weighted mosaic images. For each source detected lightcurves and spectra are derived. The lightcurves are obtained from the snapshot images, the mosaic monthly images and the Crab-weighted mosaic images. The spectra are obtained from an additional set of mosaic images by adding all the snapshots for the 157 months period in 8-bands. All the analyses use HEASoft tools version 6.23, and the most recent BAT calibration database (updated on Oct. 3, 2017).

Data products are generated for each source detected and these are: three different lightcurves in FITS format obtained from the snapshot, monthly and Crab-weighted monthly mosaic images and the equivalent plots as GIF images; an 8-channel average spectrum in FITS obtained using all 157 months; and a GIF file showing the spectrum with the fit to the best parameter of the power-law model. The snapshot lightcurves report rates for the 8-energy band, the monthly and Crab-weighted monthly mosaic lightcurves reports rated for the 8-energy band and the total band 14-195 keV.

References

The 157-month Swift-BAT all-sky hard X-ray survey.
    Lien A., Hans Krimm, Craig Markwardt, Kyuseok Oh, Lea Marcotulli, Richard Mushotzky,
    Nicholas R. Collins, Scott Barthelmy, Wayne H. Baumgartner, S. Bradley Cenko,  Michael Koss,
    Sibasish Laha, Takanori Sakamoto, David Palmer, and Tyler Parsotan
    Submitted  2025ApJS

Provenance

This table was ingested by the HEASARC in February 2025 based upon the published 157-month catalog. The catalog is also available at https://swift.gsfc.nasa.gov/results/bs157mon/.

Parameters

Source_Number
The Swift-Bat Survey identification number, which is unique for each source in the catalog. The provided index is the same as in the 70-month and 105-month catalog. For the new detections, the index is assigned in the order of increasing right ascension.

Name
The Swift-BAT source designation (SWIFT JHHMM.m+DDMMA or SWIFT JHHMMSS.s+DDMMSS). For the sources that have been previously published (i.e., the 70-month and 105-month Swift-BAT catalog), the corresponding BAT name is used.

RA
The Right Ascension of the Swift-BAT source, given in J2000.0 decimal degrees.

Dec
The Declination of the Swift-BAT source, given in J2000.0 decimal degrees.

LII
The Galactic longitude of the Swift-BAT source. This parameter has been added by the HEASARC and is derived from the J2000.0 source position.

BII
The Galactic latitude of the Swift-BAT source. This parameter has been added by the HEASARC and is derived from the J2000.0 source position.

SNR
The signal-to-noise ratio. This is calculated as the ratio between the highest pixel value of the source from the total-band mosaic flux map and the local noise. The detection threshold is set to snr=4.8.

Ctrpart_Name
The counterpart source designation, based on well-known optical source or X-ray archival data (e.g., Swift-XRT, Chandra, and XMM-Newton).

Ctrpart_RA
The right ascension for the counterpart source, given in degrees for the J2000.0 epoch. This coordinate is taken from NED or SIMBAD. If no counterpart if known, the field is empty.

Ctrpart_Dec
The declination for the counterpart source, given in degrees for the J2000.0 epoch. This coordinate is taken from NED or SIMBAD. If no counterpart if known, the field is empty.

Flux
The Swift-BAT 14-195keV flux, in erg/s/cm2. The flux is calculated from the spectral fitting using the XSPEC pegpwrlw model. NOTE: The flux parameter is empty for the sources SWIFT J1628.4-4838, SWIFT J1740.6-2821B, SWIFT J1824.4-2442 because the flux could not be determined for these sources.

Flux_Lower
The lower 90%-confidence interval in flux, in units of erg/s/cm2. NOTE: The flux_lower parameter is empty when the value could not be determined.

Flux_Upper
The upper 90%-confidence interval in flux, in units of erg/s/cm2.

Spectral_Index
The spectral photon index computed from a power-law fit, using the XSPEC pegpwrlaw model (power-law with pegged normalization) to the eight-band BAT spectrum extracted for the source. NOTE: This parameter is empty when the value could not be determined.

Spectral_Index_Lower
The lower 90%-confidence interval in the spectral index. The 90%-confidence interval was calculated based on the error function, within XSPEC.

Spectral_Index_Upper
The lower 90%-confidence interval in the spectral index. The 90%-confidence interval was calculated based on the error function, within XSPEC.

Chi_Squared
The reduced chi squared of the spectral fit.

Redshift
The redshift of the source, taken from the online databases NED and SIMBAD or in a few cases, from the analysis of the optical data.

Log_Lx
The logarithm of Swift-BAT X-ray 14-195keV luminosity, in erg/s. The luminosities are computed using the flux and redshift, given in this catalog and assume the following cosmology: H0 = 70 km/s/Mpc, Omegam = 0.30, and OmegaLambda = 0.70. Luminosities are not given if the redshift value is missing.

Ctrpart_Flag
This parameter is a numerical value to indicate the method used to confirm or not the source identification of the BAT detection with the counterpart. The flags are as follows: 

     Flag
      0   Confirmed with X-ray imaging
      1   Old association held over from previous catalog
      2   No good hard X-ray source; soft X-ray source
      3   No X-ray source; source from another waveband
      4   Educated guess (unavailable/unchecked X-ray image or crowded region)
      5   No likely counterpart; BAT source on Galactic plane
      6   No likely counterpart; BAT source off Galactic plane
      7   No association assigned (unavailable/unchecked X-ray image or crowded region)

Ctrpart_Class
This parameter contains the classification numerical code of the counterpart. Sources are divided in 18 classes, and the numeric value ranges from 0 to 17.

Source_Type
The character string associated with the counterpart classification numerical value. These are shown in the table above.

Root_Filename
Records the root of the file names for the spectra and light curves associated with each source.

Contact Person

Questions regarding the SWBAT157M database table can be addressed to the HEASARC Help Desk.
Page Author: Browse Software Development Team
Last Modified: Monday, 10-Mar-2025 22:11:20 EDT