BeppoSAX High-Energy Large Area Survey (HELLAS) X-Ray Source Catalog

BeppoSAX High-Energy Large Area Survey (HELLAS) X-Ray Source Catalog SAXHELLAS ivo://nasa.heasarc/saxhellas NASA/GSFC HEASARC Fiore et al. 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source The BeppoSAX High Energy Large Area Survey (HELLAS) has surveyed about 85 deg2 of sky in the 4.5 - 10 keV band down to a flux of 4 - 5 x 10-14 erg/cm2/s using 142 high Galactic latitude (|b| > 20o) observations made by the BeppoSAX Medium Energy Concentrator Spectrometer (MECS). The source surface density of 16.9 +/- 6.4 deg2 at the survey limit corresponds to a resolved fraction of the 5 - 10 keV X-ray background (XRB) of the order of 20-30 per cent. Hardness ratio analysis indicates that the spectra of a substantial fraction of the HELLAS sources (at least one-third) are harder than a alphaE = 0.6 power law. This hardness may be caused by large absorbing columns. The hardness ratio analysis also indicates that many HELLAS sources may have a spectrum more complex than a single absorbed power law. A soft component, superimposed on a strongly cut-off power law, is likely to be present in several sources. There is no overlap among the 142 fields used and, wherever possible, multiple observations of the same field have been merged in one single pointing to increase the sensitivity. Fields were selected among public data (such as that of March 1999) and the authors' proprietary data. Fields centered on bright extended sources and bright Galactic sources were excluded from the survey, as were fields close to the Large Magellanic Cloud (LMC), Small Magellanic Cloud (SMC) and M 33. Most of the fields have exposures between 30 and 100 ks, and 20 fields have an exposure higher than 80 ks (see Fig. 1 of reference paper). Sources were detected in images accumulated between 4.5 and 10 keV. Source count rates in four bands (1.3 - 10 keV, total or T; 1.3 - 2.5 keV, low band or L; 2.5 - 4.5 keV, middle band or M; 4.5 - 10 keV, high band or H) were extracted and corrected for the energy-dependent vignetting and for the MECS PSF. The count rates were converted to fluxes using a conversion factor of 7.8 x 10-11 erg cm-2 s-1 (5 - 10 keV flux) per one '3 ECS count' (4.5 - 10 keV) appropriate for a power-law spectrum with alphaE = 0:6. The factor is not strongly sensitive to the spectral shape, owing to the narrow band: thus, for alphaE = 0.4 and 0.8 it is 8.1 and 7.6 x 10-11 erg cm-2 s-1, respectively. A conversion factor of 9:9 x 10-11 erg cm-2 s-1 per one '3 MECS count' has been used for sources under the 550 micron (µm) beryllium strongback supporting the MECS window to account for the reduced detector sensitivity. This table was created by the HEASARC in July 2014 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/327/771">CDS Catalog J/MNRAS/327/771</a> file table2.dat. This is a service provided by NASA HEASARC . 2001MNRAS.327..771F https://heasarc.gsfc.nasa.gov/W3Browse/all/saxhellas.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=saxhellas& GET text/xml 180 99999 true 95.98583333 -69.35361111 0.0333333333333333 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=saxhellas GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_saxhellas&Action=More+Options&Action=Parameter+Search&ConeAdd=1 BEPPOSAX 0.0333333333333333 X-ray public saxhellas BeppoSAX High-Energy Large Area Survey (HELLAS) X-Ray Source Cat name Source Designation meta.id;meta.main char nullable ra Right Ascension degree pos.eq.ra;meta.main double nullable dec Declination degree pos.eq.dec;meta.main double nullable off_axis Off-Axis Angle arcmin instr.offset double nullable flux Flux at 5-10 keV erg/s/cm^2 phot.flux;em.X-ray.medium double nullable snr Signal-to-Noise Ratio stat.snr;phot.flux;em.X-ray.medium double nullable softness_ratio Softness Ratio, S-H/S+H phot.flux;arith.ratio;em.X-ray double nullable softness_ratio_error RMS Uncertainty in Softness Ratio stat.error;phot.flux;arith.ratio;em.X-ray double nullable lii Galactic Longitude degree pos.galactic.lon double nullable hardness_ratio_2_flag Flag [bc] Indicates Note Concerning Hardness Ratio 2 meta.code;phot.flux;arith.ratio;em.X-ray.medium char nullable softness_ratio_flag Flag [b] Indicates Note Concerning Softness Ratio meta.code;phot.flux;arith.ratio;em.X-ray char nullable bii Galactic Latitude degree pos.galactic.lat double nullable hardness_ratio_2_error RMS Uncertainty in Hardness Ratio 2 stat.error;phot.flux;arith.ratio;em.X-ray.medium double nullable hellas_id HELLAS Identification Number meta.id char nullable hardness_ratio_1 Hardness Ratio 1, HR1=(M-L)/(M+L) phot.flux;arith.ratio;em.X-ray double nullable hardness_ratio_2 Hardness Ratio 2, HR2=(H-M)/(H+M) phot.flux;arith.ratio;em.X-ray.medium double nullable hardness_ratio_1_flag Flag [bc] Indicates Note Concerning Hardness Ratio 1 meta.code;phot.flux;arith.ratio;em.X-ray char nullable hardness_ratio_1_error RMS Uncertainty Hardness Ratio 1 stat.error;phot.flux;arith.ratio;em.X-ray double nullable "__x_ra_dec" System unit vector column double nullable "__y_ra_dec" System unit vector column double nullable "__z_ra_dec" System unit vector column double nullable "__row" System index column char nullable