SWIFTFT - Swift Serendipitous Survey in Deep XRT GRB Fields (SwiftFT)

Overview

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 = (c_H - c_S)/(c_H + c_S) where c_S and c_H 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 N_H 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.

Catalog Bibcode

2011A&A...528A.122P

References

The Swift serendipitous survey in deep XRT GRB fields (SwiftFT)
     Puccetti S., et al  <A&A 528, A122 (2011) >
    =2011A&A...528A.122P

Provenance

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.

Parameters

Source_Number
Unique numerical identifier for each entry in the SWIFTFT catalog.

Name
The unique IAU-style source designation in the form SWIFTFT JHHMMSS.s+DDMM.m.

RA
Right Ascension of the source. The position was originally given in J2000 coordinates with a precision of 0.0001 deg.

Dec
Declination of the source. The position was originally given in J2000 coordinates with a precision of 0.0001 deg.

LII
Galactic Longitude of the source. The HEASARC calculated this value by converting the J2000 position to Galactic coordinates.

BII
Galactic Latitude of the source. The HEASARC calculated this value by converting the J2000 position to Galactic coordinates.

Error_Radius_68
68% confidence radial position error, in degrees.

Error_Radius_90
90% confidence radial position error, in degrees.

X_Pixel_Pos
X pixel position of the source in the GRB deep field image.

Y_Pixel_Pos
Y pixel position of the source in the GRB deep field image.

Target_Name
XRT field target designation in GRB YYMMDD format. Burst sources are named for the date in which they were detected: if multiple bursts occur in one day, the first burst is given a suffix "A", the second "B", and so on.

Time
Start time of the first observation of the source.

End_Time
End time of the last observation of the source.

Exposure
Total exposure time on the source, given in seconds.

Count_Rate_0p3_10
The 0.3-10 keV count rate, or 90% upper limit, in count/s.

Count_Rate_0p3_10_Error
The one-sigma 0.3-10 keV count rate error in count/s. If count_rate_0p3_10 is an upper limit, this is set to -99.

Flux_0p5_10
The 0.5-10 keV flux, or 90% upper limit, in ergs/cm²/s.

Flux_0p5_10_Error
The one-sigma 0.5-10 keV flux error in erg/cm²/s. If flux_0p5_10 is an upper limit, this is set to -99.

ProbDet_0p3_10
The 0.3-10 keV detection probability.

SNR_0p3_10
The 0.3-10 keV signal-to-noise ratio.

Exposure_MapA
Total 1.5 keV exposure time for the source, given in seconds.

Count_Rate_0p3_3
The 0.3-3 keV count rate, or 90% upper limit, in count/s.

Count_Rate_0p3_3_Error
The one-sigma 0.3-3 keV count rate error in count/s. If count_rate_0p3_3 is an upper limit, this is set to -99.

Flux_0p5_2
The 0.5-2 keV flux, or 90% upper limit, in ergs/cm²/s.

Flux_0p5_2_Error
The one-sigma 0.5-2 keV flux error in ergs/cm²/s. If flux_0p5_2 is an upper limit, this is set to -99.

ProbDet_0p3_3
The 0.3-3 keV detection probability.

SNR_0p3_3
The 0.3-3 keV signal-to-noise ratio.

Exposure_MapB
Total 1.0 keV exposure time for the source, given in seconds.

Count_Rate_2_10
The 2-10 keV count rate, or 90% upper limit, in count/s.

Count_Rate_2_10_Error
The one-sigma 2-10 keV count rate error in count/s. If count_rate_2_10 is an upper limit, this is set to -99.

Flux_2_10
The 2-10 keV flux, or 90% upper limit, in ergs/cm²/s.

Flux_2_10_Error
The one-sigma 2-10 keV flux error in ergs/cm²/s. If flux_2_10 is an upper limit, this is set to -99.

ProbDet_2_10
The 2-10 keV detection probability.

SNR_2_10
The 2-10 keV signal-to-noise ratio.

Exposure_MapC
The 4.5 keV exposure time for the source, given in seconds.

Hardness_Ratio
The hardness ratio, defined as (Hard-Soft)/(Hard+Soft) where Hard is the 2-10 keV count rate and Soft is the 0.3-3 keV count rate. This parameter is set to -99 if either Hard or Soft counts are missing.

Hardness_Ratio_Error
The one-sigma hardness ratio error evaluated using the error propagation formulas from Bevington and Robinson, Data Reduction and Error Analysis for the Physical Sciences (1992; McGraw-Hill).

Offaxis
Distance from the field median center, given in arcmin.

Galactic_NH
The Galactic hydrogen column density in the direction of the source in cm^-2.

Contact Person

Questions regarding the SWIFTFT database table can be addressed to the HEASARC Help Desk.

Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:35:30 EDT