X-Ray Selected BL Lac Objects Catalog

X-Ray Selected BL Lac Objects Catalog XRAYSELBLL ivo://nasa.heasarc/xrayselbll NASA/GSFC HEASARC Kapanadze 2026-04-24 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov BL Lac This table contains a catalog of 312 X-ray selected BL Lacertae objects (XBLs), optically identified through the end of 2011. It contains the names from different surveys, equatorial coordinates, redshifts, multi-frequency flux values, and luminosities for each source. In the reference, the different characteristics of these XBLs are statistically investigated (redshift, radio/optical/X-ray luminosities, central black hole (BH) mass, synchrotron peak frequency, broadband spectral indices, optical flux variability). Their values were collected through an extensive bibliographic and database search or calculated by the author. The redshifts range from 0.031 to 0.702 with a maximum of the distribution at z = 0.223. The 1.4-GHz luminosities of XBLs log (nu * Lnu) ~ 39 - 42 (in units of erg s-1), while the optical V and X-ray (0.1-2.4 keV) bands show log (nu * Lnu) ~ 43 - 46 (same units). The XBL hosts are elliptical galaxies with effective radii reff = 3.26 - 25.40 kpc and ellipticities e = 0.04 - 0.52. Their R-band absolute magnitudes MR range from -21.11 mag to -24.86 mag with a mean value of -22.83 mag. The V - R indices of the hosts range from 0.61 to 1.52 and reveal a fourth-degree polynomial relationship with z that enabled the author to evaluate the redshifts of five sources whose V - R indices were determined from the observations, but whose redshifts values are either not found or not confirmed. The XBL nuclei show a wider range of 7.31 mag for MR, with the highest luminosity corresponding to MR = -27.24 mag. The masses of the central BHs are found in the interval log MBH = 7.39 - 9.30 (in units of solar masses), with the maximum of the distribution at log MBH/Msun = 8.30. The synchrotron peak frequencies are spread over the range log nupeak = 14.56 - 19.18 Hz, with a peak of the distribution at log nupeak = 16.60 Hz. The broad-band radio-to-optical (alpharo), optical-to-X-ray (alphaox), and radio-to-X-ray (alpharx) spectral indices are distributed in the intervals (0.17, 0.59), (0.56, 1.48), and (0.41, 0.75), respectively. In the optical energy range, the overall flux variability increases, on average, towards shorter wavelengths: Delta(m) = 1.22, 1.50, and 1.82 through the R, V, B bands of the Johnson-Cousins system, respectively. XBLs seem be optically less variable at intranight timescales compared to radio-selected BL Lacs (RBLs). This table was created by the HEASARC in June 2013 based on an electronic version of Table 2 from the reference paper which was obtained form the AJ web site. This is a service provided by NASA HEASARC . 2013AJ....145...31K https://heasarc.gsfc.nasa.gov/W3Browse/all/xrayselbll.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=xrayselbll& GET text/xml 180 99999 true 344.57916667 -55.42694444 0.0166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=xrayselbll GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_xrayselbll&Action=More+Options&Action=Parameter+Search&ConeAdd=1 GALAXY CATALOG 0.0166666666666667 X-ray Optical Radio public xrayselbll X-Ray Selected BL Lac Objects Catalog name Source Designation meta.id;meta.main char nullable alt_name_1 Alternative Source Designation #1 meta.id char nullable ra Right Ascension degree pos.eq.ra;meta.main double nullable dec Declination degree pos.eq.dec;meta.main double nullable redshift_limit Limit Flag for Redshift meta.code;src.redshift char nullable redshift Redshift src.redshift double nullable redshift_flag Flag [U] Indicates Uncertainty in Redshift meta.code;src.redshift char nullable fx X-Ray Flux erg/cm^2/s phot.flux;em.X-ray double nullable fx_flag Flag [f] Indicates 2-keV Flux meta.code;phot.flux;em.X-ray char nullable fx_over_f_rad Ratio of X-Ray Flux to Radio Flux erg/cm^2/s/Jy phot.flux.density;em.radio.750-1500MHz;em.X-ray;arith.ratio double nullable log_l_opt Logarithm of Optical Luminosity log(erg/s) phys.luminosity;em.opt double nullable log_lx Logarithm of X-Ray Luminosity log(erg/s) phys.luminosity;em.X-ray double nullable alt_name_3 Alternative Source Designation #3 meta.id char nullable log_lx_flag Flag [U] Indicates Uncertainty in Logarithm of X-Ray Luminosity meta.code;phys.luminosity;em.X-ray char nullable log_l_rad_limit Limit Flag for Logarithm of the Radio Luminosity meta.code;phys.luminosity;em.radio char nullable sample_ids Sample Identifier(s) meta.code char nullable bii Galactic Latitude degree pos.galactic.lat double nullable vmag_flag Flag [ceg] Indicates c=Derived from B Mag, e=Derived from Linear Flux, g=Average meta.code;phot.mag;em.opt.V char nullable log_lx_limit Limit Flag for Logarithm of X-Ray Luminosity meta.code;phys.luminosity;em.X-ray char nullable alt_name_4 Alternative Source Designation #4 meta.id char nullable log_l_opt_flag Flag [U] Indicates Uncertainty in Logarithm of Optical Luminosity meta.code;phys.luminosity;em.opt char nullable vmag V Band Magnitude mag phot.mag;em.opt.V double nullable lii Galactic Longitude degree pos.galactic.lon double nullable log_l_rad_flag Flag [U] Indicates Uncertainty in Logarithm of the Radio Luminosity meta.code;phys.luminosity;em.radio char nullable log_l_opt_limit Limit Flag for Logarithm of Optical Luminosity meta.code;phys.luminosity;em.opt char nullable f_rad Radio Flux Density mJy phot.flux.density;em.radio.750-1500MHz double nullable alt_name_2 Alternative Source Designation #2 meta.id char nullable log_l_rad Logarithm of the Radio Luminosity log(erg/s) phys.luminosity;em.radio double nullable f_rad_flag Flag [ab] Indicates Radio Frequency: a=5 GHz, b=843 MHz meta.code;phot.flux.density;em.radio.750-1500MHz char nullable refs_source Reference(s) meta.ref char 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