WISEHSPCAT ivo://nasa.heasarc/wisehspcat NASA/GSFC HEASARC Chang et al. 2026-04-24 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Blazar High Synchrotron Peaked blazars (HSPs) dominate the gamma-ray sky at energies larger than a few GeV, however only a few hundred blazars of this type have been catalogued so far. In this paper, the authors present the 2WHSP sample, the largest and most complete list of HSP blazars available to date, which is an expansion of the 1WHSP catalog (Arsioli et al. 2015, A&A, 579, A34) of gamma-ray source candidates away from the Galactic Plane. They cross-matched a number of multi-wavelength surveys (in the radio, infrared and X-ray bands) and applied selection criteria based on the radio to IR, and IR to X-ray spectral slopes. To ensure the selection of genuine HSPs, the authors examined the spectral energy distribution (SED) of each candidate and estimated the peak frequency of its synchrotron emission (nu<sub>peak</sub>) using the Agenzia Spaziale Italiana Science Data Center (ASDC) SED tool, including only sources with nu<sub>peak</sub> > 10<sup>15</sup> Hz (equivalent to nu<sub>peak</sub> > 4 eV). The authors have assembled the largest and most complete catalog of HSP blazars to date, which includes 1691 sources. A number of population properties, such as infrared colors, synchrotron peak, redshift distributions, and gamma-ray spectral properties, have been used to characterize the sample and maximize completeness. The authors also derived the radio log N - log S distribution. This catalog has already been used to provide seeds to discover new very high energy objects within Fermi-LAT data and to look for the counterparts of neutrino and ultra-high energy cosmic ray sources, showing its potential for the identification of promising high-energy gamma-ray sources and multi-messenger targets. This table comprises the 2WHSP catalog, a multi-frequency catalog of HSP. It contains 1691 sources, 288 of which are newly identified HSPs, 540 are previously known HSPs, 814 are HSP candidates, 45 are HSP blazars taken from the 2FHL catalog, and 4 from TeVCat (<a href="http://tevcat.uchicago.edu">http://tevcat.uchicago.edu</a>). This table was created by the HEASARC in February 2017 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/598/A17">CDS Catalog J/A+A/598/A17</a> file 2whsp.dat. This is a service provided by NASA HEASARC . 2017A&A...598A..17C https://heasarc.gsfc.nasa.gov/W3Browse/all/wisehspcat.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=wisehspcat& GET text/xml 180 99999 true 74.59791667 -86.73555556 0.0166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=wisehspcat GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_wisehspcat&Action=More+Options&Action=Parameter+Search&ConeAdd=1 WISE 0.0166666666666667 Gamma-ray Infrared public wisehspcat 2WHSP Catalog of High Synchrotron Peaked Blazars and Candidates name Designation of the Object (2WHSP JHHMMSS.s+DDMMSS) 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 log_nu_f_nu_limit Limit Flag for Synchrotron Peak Flux meta.code;phot.flux char nullable log_nu_f_nu Synchrotron Peak Flux log(erg/s/cm^2) phot.flux double nullable log_nu_f_nu_flag Flag [:] Indicates Uncertainty in Synchrotron Peak Flux meta.code;phot.flux char nullable redshift_limit Limit Flag for Redshift meta.code;src.redshift char nullable redshift Redshift src.redshift double nullable fermi_lat_detection Fermi Gamma-Ray Detection meta.id.cross char nullable gamma_ray_index Fermi Gamma-Ray Photon Index spect.index;em.gamma double nullable gamma_ray_index_error Uncertainty for Fermi Gamma-Ray Photon Index stat.error;spect.index;em.gamma double nullable bii Galactic Latitude degree pos.galactic.lat double nullable log_nu_peak_flag Flag [:] Indicates Uncertainty in Synchrotron Peak meta.code;em.freq char nullable twofhl_name 2FHL Source Designation (HHMM.m+DDd, J2000) meta.id.cross char nullable ref_redshift Reference Code [bcdefg] for Redshift meta.ref;src.redshift char nullable source_flag Flag [U] Indicates Source Is Uncertain Member of This Class of Object meta.code;src char nullable log_nu_peak Synchrotron Peak log(Hz) em.freq double nullable lii Galactic Longitude degree pos.galactic.lon double nullable figure_of_merit Figure of Merit meta.code double nullable log_nu_peak_limit Limit Flag for Synchrotron Peak meta.code;em.freq char nullable bzcat_object_type 5BZCat Object Type src.class char nullable redshift_flag Flag [:] Indicates Uncertainty in Redshift meta.code;src.redshift 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