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We present the results of an identification campaign of unassociated sources from the Fermi Large Area Telescope 3FHL catalog. Out of 200 unidentified sources, we selected 110 sources for which archival Swift-XRT observations were…

High Energy Astrophysical Phenomena · Physics 2019-01-25 Amanpreet Kaur , Marco Ajello , Stefano Marchesi , Nicola Omodei

Blazars and in particular the subclass of high synchrotron peaked Active Galactic Nuclei are among the main targets for the present generation of Imaging Atmospheric Cherenkov Telescopes (IACTs) and will remain of great importance for very…

High Energy Astrophysical Phenomena · Physics 2020-01-08 G. Chiaro , M. Meyer , M. Di Mauro , D. Salvetti , G. La Mura , D. J. Thompson

Fermi-LAT LCR provide continuous and regularly-sampled gamma-ray light curves, spanning about 14 years, for a large sample of blazars. The log-normal flux distribution and linear RMS-Flux relation of the light curves for a few of Fermi…

High Energy Astrophysical Phenomena · Physics 2023-07-21 Na Wang , Ting-Feng Yi , Liang Wang , Li-Sheng Mao , Zhi-Yuan Pu , Gong-Ming Ning , Wei-Tian Huang , He Lu , Shun Zhang , Yu-Tong Chen , Liang Dong

A significant fraction (~30%) of the high-energy gamma-ray sources listed in the second Fermi LAT catalog (2FGL) are still of unknown origin, being not yet associated with counterparts at low energies. We recently developed a new…

High Energy Astrophysical Phenomena · Physics 2015-06-15 F. Massaro , R. D'Abrusco , A. Paggi , N. Masetti , M. Giroletti , G. Tosti , Howard A. Smith , S. Funk

A majority of blazars exhibit variable emission across the entire electromagnetic spectrum, observed over various time scales. In particular, discernible periodic patterns are detected in the $\gamma$-ray light curves of a few blazars, such…

High Energy Astrophysical Phenomena · Physics 2025-06-18 Alba Rico , A. Domínguez , P. Peñil , M. Ajello , S. Buson , S. Adhikari , M. Movahedifar

In preparation for GLAST, we have compiled a sample of blazar candidates to increase the pool of well studied AGN from which GLAST counterparts will be drawn. Sources were selected with our Figure of Merit (FoM) ranking; thus, they have…

The third catalog of active galactic nuclei (AGNs) detected by the Fermi Large Area Telescope (3LAC) is presented. It is based on the third catalog (3FGL,\cite{3FGL}) of sources detected with a test statistic greater than 25, using the…

High Energy Astrophysical Phenomena · Physics 2019-08-14 Dario Gasparrini , Benoit Lott , Sara Cutini , Stefano Ciprini , Elisabetta Cavazzuti

We present a large sample of 501 radio-selected BL Lac candidates from the combination of the Sloan Digital Sky Survey (SDSS) Data Release 5 optical spectroscopy and from the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) radio…

We present a catalogue of 233 BL Lacertae objects compiled through an extensive bibliographic search updated to mid-1995. A large fraction of the sources listed in the catalogue belongs to well-defined samples and can be used for…

Astrophysics · Physics 2015-06-24 Paolo Padovani , Paolo Giommi

Utilizing the latest and the most sensitive radio and optical catalogs, we completed a new blazar candidate catalog, Blazar Radio and Optical Survey (BROS), which includes 88,211 sources located at declination $\delta > -40^{\circ}$ and…

High Energy Astrophysical Phenomena · Physics 2020-08-04 Ryosuke Itoh , Yousuke Utsumi , Yoshiyuki Inoue , Kouji Ohta , Akihiro Doi , Tomoki Morokuma , Koji S. Kawabata , Yasuyuki T. Tanaka

We present Very Large Telescope optical spectroscopy of nine BL Lac objects of unknown redshift belonging to the list of optically selected radio loud BL Lacs candidates. We explore their spectroscopic properties and the possible link with…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-17 A. Sandrinelli , A. Treves , R. Falomo , E. P. Farina , L. Foschini , M. Landoni , B. Sbarufatti

We present the results of the Fermi-Large Area Telescope (LAT) light curve (LC) modelling of selected blazars: six flat spectrum radio quasars (FSRQs) and five BL Lacertae (BL Lacs). All objects have densely sampled and long-term LCs, over…

High Energy Astrophysical Phenomena · Physics 2021-12-06 Natalia Żywucka , Mariusz Tarnopolski , Volodymyr Marchenko , Javier Pascual-Granado

We study the ensemble optical variability of 276 FSRQs and 86 BL Lacs in the Palomar-QUEST Survey with the goal of searching for common fluctuation properties, examining the range of behavior across the sample, and characterizing the…

Cosmology and Nongalactic Astrophysics · Physics 2011-02-11 Anne Bauer , Charles Baltay , Paolo Coppi , Nancy Ellman , Jonathan Jerke , David Rabinowitz , Richard Scalzo

The exact location of the gamma-ray emitting region in blazars is still controversial. In order to attack this problem we present first results of a cross-correlation analysis between radio (11 cm to 0.8 mm wavelength, F-GAMMA program) and…

Despite the large number of discoveries made recently by Fermi, the origins of the so called unidentified gamma-ray sources remain unknown. The large number of these sources suggests that among them there could be a population that…

High Energy Astrophysical Phenomena · Physics 2015-06-04 F. Massaro , R. D'Abrusco , G. Tosti , M. Ajello , D. Gasparrini , J. E. Grindlay , Howard A. Smith

We present deep radio images at 1.4 GHz of a large and complete sample of BL Lacertae objects (BL Lacs) selected from the Deep X-ray Radio Blazar Survey (DXRBS). We have observed 24 northern sources with the Very Large Array (VLA) in both…

Astrophysics · Physics 2009-11-13 Hermine Landt , Hayley E. Bignall

Besides the neutrino source detected by IceCube, NGC 1068, the association of the IceCube-170922A neutrino with the blazar in a flaring state among several wavelengths (from radio up to high-energy (HE) gamma-rays), the site and mechanisms…

High Energy Astrophysical Phenomena · Physics 2023-08-29 Antonio Galván , Nissim Fraija , Edilberto Aguilar-Ruiz , Jose Antonio de Diego Onsurbe , Maria G. Dainotti

We present a sample of 723 optically selected BL Lac candidates from the SDSS DR7 spectroscopic database encompassing 8250 deg^2 of sky; our sample constitutes one of the largest uniform BL Lac samples yet derived. Each BL Lac candidate has…

We put forward a scenario where blazars are classified as flat-spectrum radio quasars, BL Lacs, low synchrotron, or high synchrotron peaked objects according to a varying combination of Doppler boosted radiation from the jet, emission from…

High Energy Astrophysical Phenomena · Physics 2012-05-04 P. Padovani , P. Giommi , G. Polenta , S. Turriziani , V. D'Elia , S. Piranomonte

The fourth-DR3 version (4FGL-DR3) of the Fermi/LAT catalogue of $\gamma$-ray sources contains $\sim$ 1000 objects at a galactic latitude |b| > 10$^{\circ}$ which are not identified with an optical counterpart (UGS). We performed a…

High Energy Astrophysical Phenomena · Physics 2024-02-20 Alberto Ulgiati , Simona Paiano , Aldo Treves , Renato Falomo , Boris Sbarufatti , Fabio Pintore , Thomas D. Russell , Giancarlo Cusumano