Chandra Bulge Field X-Ray Point Source Catalog

Chandra Bulge Field X-Ray Point Source Catalog CBFGRXECXO ivo://nasa.heasarc/cbfgrxecxo NASA/GSFC HEASARC Morihana et al. 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source Apparently diffuse X-ray emission has been known to exist along the central quarter of the Galactic Plane since the beginning of X-ray astronomy; this is referred to as the Galactic Ridge X-ray emission (GRXE). Recent deep X-ray observations have shown that numerous X-ray point sources account for a large fraction of the GRXE in the hard band (2 - 8 keV). However, the nature of these sources is poorly understood. Using the deepest X-ray observations made in the Chandra bulge field, the authors present the result of a coherent photometric and spectroscopic analysis of individual X-ray point sources for the purpose of constraining their nature and deriving their fractional contributions to the hard-band continuum and Fe K line emission of the GRXE. Based on the X-ray color-color diagram, they divided the point sources into three groups: A (hard), B (soft and broad spectrum), and C (soft and peaked spectrum). The group A sources are further decomposed spectrally into thermal and non-thermal sources with different fractions in different flux ranges. From their X-ray properties, the authors speculate that the group A non-thermal sources are mostly active galactic nuclei and the thermal sources are mostly white dwarf (WD) binaries such as magnetic and non-magnetic cataclysmic variables (CVs), pre-CVs, and symbiotic stars, whereas the group B and C sources are X-ray active stars in flares and quiescence, respectively. In the log N - log S curve of the 2 - 8 keV band, the group A non-thermal sources are dominant above ~10-14 erg/cm2/s, which is gradually taken over by Galactic sources in the fainter flux ranges. The Fe K-alpha emission is mostly from the group A thermal (WD binaries) and the group B (X-ray active stars) sources. The authors retrieved 10 archived data sets of the Chandra bulge field (CBF) taken with the Advanced CCD Imaging Spectrometer-I (ACIS-I; 0.5 - 8.0 keV energy band with a spectral resolution of ~280 eV for the full width at half-maximum at 5.9keV) array on board Chandra. The observations were carried out from 2008 May to August with a total exposure time of ~900 ks. The authors first extracted point-source candidates using the wavdetect algorithm in the CIAO package. They set the significance threshold at 2.5 x 10-5, implying that one false positive detection would be expected at every 4 x 104 trials. As a result, 2596 source candidates were found. The number of their source candidates is nearly the same as that found by Revnivtsev et al.(2009, A&A, 507, 1211) in the same region. To select significant point sources from the candidates, the authors examined their validity based on their photometric significance (PS) and the probability of no source (PB). The PS is defined as the background-subtracted source counts (Cnet) divided by its background counts normalized by the area. PB is the probability that the source is attributable to a background fluctuation, assuming Poisson statistics. The authors recognized a source to be valid if it satisfied both these criteria: PS >= 1.0 and PB <= 1.0 x 10-2. As a result, they obtained 2002 valid point sources. This table was created by the HEASARC in December 2014 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/766/14">CDS catalog J/ApJ/766/14</a> file table2.dat. This is a service provided by NASA HEASARC . 2013ApJ...766...14M https://heasarc.gsfc.nasa.gov/W3Browse/all/cbfgrxecxo.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=cbfgrxecxo& GET text/xml 180 99999 true 267.82653 -29.739104 0.0166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=cbfgrxecxo GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_cbfgrxecxo&Action=More+Options&Action=Parameter+Search&ConeAdd=1 CHANDRA 0.0166666666666667 X-ray public cbfgrxecxo Chandra Bulge Field X-Ray Point Source Catalog source_number Sequential Identification Number for Each Source in Catalog meta.id;src short nullable name Chandra Source Designation (CXOU JHHMMSS.ss+DDMMSS.s; J2000) meta.id;meta.main char nullable off_axis Off-Axis Angle arcmin instr.offset double nullable ra Right Ascension degree pos.eq.ra;meta.main double nullable dec Declination degree pos.eq.dec;meta.main double nullable error_radius Positional Uncertainty arcsec stat.error;pos double nullable fb_counts Estimated Net 0.5-8 keV Counts ct phot;em.X-ray double nullable hb_counts Estimated Net Hard 2-8 keV Counts ct phot;em.X-ray.medium double nullable exposure Effective Exposure Time s time.duration;obs.exposure 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 lii Galactic Longitude degree pos.galactic.lon double nullable significance_limit Limit Flag for Photometric Significance meta.code char nullable fb_counts_error Uncertainty in Estimated Net 0.5-8 keV Counts ct stat.error;phot;em.X-ray double nullable log_bck_prob Logarithm of Probability That Net Counts Are Solely from Background stat.probability double nullable median_energy Background-Corrected Median Photon Energy keV phys.energy double nullable source_anomaly_flag Flag [g] Indicates Source Anomaly meta.code;src char nullable significance Photometric Significance stat.likelihood double nullable q1_quantile_value The q_1 Quantile Value stat.param double nullable var_flag Flag [abc] Indicates Variability Characterization meta.code;src.var char nullable psf_fraction Fraction of PSF Enclosed in Extraction Region instr.det.psf double nullable bck_counts Background 0.5-8 keV Counts ct phot;instr.background;em.X-ray double nullable fb_flux Photometric 0.5-8 keV Flux Estimate erg/s/cm^2 phot.flux;em.X-ray double nullable bii Galactic Latitude degree pos.galactic.lat double nullable q2_quantile_value The q_2 Quantile Value stat.param double nullable