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IBISCAT - Fifth IBIS/ISGRI Soft Gamma-Ray Survey Catalog

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Overview

This table contains an all-sky soft gamma-ray source catalog based on IBIS observations performed during the first 1000 orbits of INTEGRAL. The database for the construction of the source list consists of all good-quality data available, from the launch of INTEGRAL in 2002, up to the end of 2010. This corresponds to ~ 110 Ms of scientific public observations, with a concentrated coverage on the Galactic Plane and extragalactic deep exposures. This new catalog includes 939 sources above a 4.5-sigma significance threshold detected in the 17-100 keV energy band, of which 120 sources represent previously undiscovered soft gamma-ray emitters. The source positions are determined, mean fluxes are provided in two main energy bands, and these are both reported together with the overall source exposure. Indicative levels of variability are provided, and outburst times and durations are given for transient sources. In the reference paper, a comparison is made with previous IBIS catalogs and catalogs from other similar missions.

Catalog Bibcode

2016ApJS..223...15B

References

The IBIS soft gamma-ray sky after 1000 INTEGRAL orbits.
    Bird A.J., Bazzano A.,  Malizia A., Fiocchi M., Sguera V., Bassani L.,
    Hill A.B., Ubertini P., Winkler C.
    <Astrophys. J. Suppl. 223, 15-15 (2016)>
    =2016ApJS..223...15B

Provenance

This database table, the Fifth IBIS/ISGRI source catalog, was ingested by the HEASARC in September 2016 based on the machine-readable version of Table 2 of the above-cited paper, which was obtained from the CDS website. It replaced the previous (fourth) version.

Parameters

Name
The standard designation for the source. Sources discovered by INTEGRAL have been given names using the IGR prefix.

New_Flag
This flag parameter is set to 'N' to indicate that the specified source is one of the ~300 new detections added since the fourth catalog.

RA
The Right Ascension of the high-energy source in the selected equinox. This was given in J2000.0 coordinates and to a precision of 0.001 degrees in the original table. The astrometric coordinates of the source positions were extracted from the mosaics by the barycentering routines built into SExtractor 2.5. In almost all cases, the position for a source was extracted from the map yielding the highest source significance. In a few cases, primarily for blended sources, other maps were chosen in order to minimize the interference of other sources. Simultaneous fitting of multiple Gaussian PSFs was used in the most difficult cases - these sources are indicated as blended in the blend_flag parameter.

Dec
The Declination of the high-energy source in the selected equinox. This was given in J2000.0 coordinates and to a precision of 0.001 degrees in the original table. The astrometric coordinates of the source positions were extracted from the mosaics by the barycentering routines built into SExtractor 2.5. In almost all cases, the position for a source was extracted from the map yielding the highest source significance. In a few cases, primarily for blended sources, other maps were chosen in order to minimize the interference of other sources. Simultaneous fitting of multiple Gaussian PSFs was used in the most difficult cases - these sources are indicated as blended in the blend_flag parameter.

LII
The Galactic Longitude of the high-energy source.

BII
The Galactic Latitude of the high-energy source.

Error_Radius
The positional error of the high-energy source, in arcseconds, expressed as the radius of the 90% confidence circle. This was given as arcminutes with a precision of 0.01 arcminutes in the original table. The point source location error of IBIS is highly dependent upon the significance of the source detected (Gros et al. 2003, A&A, 411, L179; Scaringi et al. 2010, A&A, 516, 75). The authors use the formulation of Gros et al. (2003), combined with the significance of the detection used to locate the source, in order to define an error on the source position. The source localization errors quoted are for the 90% confidence limit.

SB_Flux_Limit
This parameter is set to '<' if the associated soft-band flux of the particular source is an upper limit rather than a detection.

SB_Flux
The time-averaged flux of the high-energy source over the whole data set in the soft energy band (20 - 40 keV), in units of milliCrab (mCrab). Appropriate conversion factors for this band are 10 mCrab = 7.57 x 10-11 erg/cm2/s = 1.71 x 10-3 photons/cm2/s. This information is provided for compatibility with past catalogs and as a general reference value.

SB_Flux_Error
The uncertainty in the time-averaged 20 - 40 keV flux, in mCrab.

HB_Flux_Limit
This parameter is set to '<' if the associated hard-band flux of the particular source is an upper limit rather than a detection.

HB_Flux
The time-averaged flux of the high-energy source over the whole data set in the hard energy band (40 - 100 keV), in units of milliCrab (mCrab). Appropriate conversion factors for this band are 10 mCrab = 9.42 x 10-11 erg/cm2/s = 9.67 x 10-4 photons/cm2/s. This information is provided for compatibility with past catalogs and as a general reference value.

HB_Flux_Error
The uncertainty in the time-averaged 40 - 100 keV Flux, in mCrab.

Source_Type
The astrophysical type(s) of the high-energy source. Up to 4 types may be given: these follow the convention of Liu et al. (2007, A&A, 469, 807), wherever possible. The following abbreviations have been used:

          A = Atoll source (neutron star);
        AGN = Active galactic nuclei;
        AXP = Anomalous X-ray pulsar;
          B = Burster (neutron star);
         Be = B-type emission-line star;
         BH = Black hole (confirmed mass evaluation);
        BHC = Black hole candidate;
         BL = broad line;
    Cluster = Cluster of galaxies;
         CV = Cataclysmic variable;
          D = Dipping source;
         DN = Dwarf Nova;
          G = Globular Cluster X-ray source;
        GRB = Gamma-Ray Burst;
       HMXB = High-mass X-ray binary;
         IP = Intermediate Polar;
       LMXB = Low-mass X-ray binary;
          M = Microquasar;
  Mol Cloud = Molecular cloud;
         NL = narrow line;
         NS = Neutron Star;
          P = Polar;
        PSR = Radio pulsar;
        PWN = Pulsar wind nebula;
        QSO = Quasar;
         RG = Radio Galaxy;
       SFXT = Supergiant Fast X-ray Transient;
         SG = Supergiant;
        SGR = Soft gamma-ray repeater;
        SNR = Supernova remnant;
         Sy = Seyfert galaxy;
       Symb = Symbiotic star;
          T = Transient source;
         XB = Galactic X-ray binary;
      XBONG = X-ray bright, optically normal galaxy;
         XP = X-ray pulsar;
          Z = Z-type source (neutron star)
  

Variability_Flag
The relevance of the time-averaged fluxes diminishes as the data set increases and the average time of activity for many of the sources is much shorter than the on-source exposure. The "bursticity" parameter contains a flag which indicates the presence of source variability in the 20-40 keV band. A value of 'Y' indicates a bursticity of > 1.1, i.e., a 10% increase in significance can be obtained by selecting a subset of the data. A flag value of 'YY' indicates a bursticity of > 4, i.e., a 400% increase in significance, indicating a strongly variable source. However, it should be noted that the flux and significance values may derive from different energy bands and/or subsets of the data, and may initially appear contradictory.

Significance
The maximum significance of the high-energy source in a single map. This is given since it provides the best indication of the robustness of the source detection. However, it should be noted that the flux and significance values may derive from different energy bands and/or subsets of the data, and may initially appear contradictory.

Exposure
The corrected on-source exposure time, in seconds (s), given to a precision of 100 seconds. This is the total effective exposure on the source after all filtering of the data has been carried out. This parameter was given in kiloseconds (ks) in the original, as-published table.

Alt_Name
An alternative designation for the source.

Low_Signif_Flag
This flag parameter is set to "WARN" to indicates that the detection is subject to a higher false positive rate (FPR) due to its lower significance or shorter duration (see Section 2.4 of the reference paper for more details). Overall, the authors estimate the FPR in this catalog is < 25% for sources detected between 4.5 and 4.8 sigma in persistent maps, < 1% for sources detected above 4.8 sigma in persistent maps, and (pessimistically) 1% for sources detected via the bursticity method. Thus, they anticipate ~ 30 false positives in a catalog of 939 sources, i.e., 3.5%.

Blend_Flag
This flag parameter is set to "BLEND" to indicate that the source was blended and that simultaneous fitting of multiple Gaussian PSFs was required. The source positions determined by such simultaneous fitting are considered reliable, but other measured values (flux, significance) may be contaminated by nearby source(s) and may be unreliable.

Galcent_Flag
This flag parameter is set to "GCFLAG1" or "GCFLAG2" to indicate the source is in the Galactic Center (GC) region and may suffer from confusion. The central 4 degrees x 2 degrees region of the Galaxy represents a challenging area for the INTEGRAL/IBIS map analysis (see Figure 6 in the reference paper). The presence of unresolved sources (and presumably many sources below the formal detection threshold creating a non-uniform background) means that the maps in this area are dominated by systematic effects and the usual statistical limits for source discovery do not apply. As a consequence, the authors were extremely conservative in this region, and in fact all the GC sources listed are already present in the INTEGRAL Reference Catalog (IRC). Because of the complex and unresolved source distribution, the data quality for these sources may be lower than for isolated sources away from the Galactic Center. A value of GCFLAG1 means that the source lies within the GC box, and is detected by the authors' standard methods. Furthermore, the source is sufficiently resolved that they can estimate the flux and position from their maps; nevertheless they expect that the detection may be affected by nearby unresolved faint sources and the quantitative data should be treated with caution. A value of GCFLAG2 means that there is clear evidence of emission from the source position in one or more of our maps, but it lies within an unresolved emission region. Therefore, the authors cannot unambiguously attribute the emission to the source, and they therefore supply the IRC position only. The fluxes are almost certainly contaminated by emission from nearby unresolved sources, or indeed resolved ones. Using this approach, there are 23 sources falling within the Galactic Center zone, of which 11 have GCFLAG2 values.

Comments
A brief commentary indicates the detection method for each source: here the term "persistent" means that the source detection is optimized in a mosaic of all of the data, but the detection may actually derive from a number of outbursts or flares, but no single outburst optimizes the detection. For sources detected during an outburst, the MJD and duration are indicated.

Class
The HEASARC Browse object classification, based on the value of the source_type parameter (typically the most specific part).


Contact Person

Questions regarding the IBISCAT database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 7-Sep-2016