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Nearly one-third of the sources in the $Fermi$-LAT catalogs lack a lower energy counterpart, hence being referred as unidentified/unassociated gamma-ray sources (UGSs). In order to firmly classify them, dedicated multifrequency follow-up…

A significant fraction of all $\gamma$-ray sources detected by the Large Area Telescope aboard the \fer\ satellite is still lacking a low-energy counterpart. In addition, there is still a large population of $\gamma$-ray sources with…

We recently started a systematic search of low-energy counterparts of the unidentified gamma-ray sources (UGSs) listed in the Fermi-Large Area Telescope (LAT) First Source Catalog (1FGL) and the Fermi-LAT 2-Year Source Catalog (2FGL).} The…

High Energy Astrophysical Phenomena · Physics 2015-06-24 F. Massaro , M. Landoni , R. D'Abrusco , D. Milisavljevic , A. Paggi , N. Masetti , Howard A. Smith , G. Tosti

We study the $\gamma$-ray and broadband spectral energy distribution (SED) properties of a complete sample of 104 bright, radio-selected low-synchrotron peaked (LSP) blazars. Most of the sources have already been detected in the…

High Energy Astrophysical Phenomena · Physics 2018-08-08 B. Arsioli , G. Polenta

One of the main scientific objectives of the ongoing Fermi mission is unveiling the nature of the unidentified gamma-ray sources (UGSs). Despite the large improvements of Fermi in the localization of gamma-ray sources with respect to the…

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

A sample of 312 low-frequency peaked BL Lacertae objects (LBLs) and 694 flat spectrum radio quasars (FSRQs) with the parameters both redshift and $\gamma$-ray photon spectral index ($\Gamma _\gamma$) is compiled from the active galactic…

High Energy Astrophysical Phenomena · Physics 2025-03-31 S. Liang , W. G. Yang , Y. G. Zheng , S. J. Kang

For the duration of the Fermi Gamma-Ray Space Telescope's mission, approximately one-third of the point sources detected have been noted as "unassociated," meaning that they seem to have no known counterpart at any other…

High Energy Astrophysical Phenomena · Physics 2021-08-11 S. Bruzewski , F. K. Schinzel , G. B. Taylor , L. Petrov

Radio and gamma-ray emission from active galactic nuclei (AGN) are thought to share a common origin, related to the ejection phenomena in the vicinity of supermassive black holes. Thanks to its sensitivity, surveying capability, and broad…

Cosmology and Nongalactic Astrophysics · Physics 2010-01-29 M. Giroletti , A. Reimer , L. Fuhrmann , V. Pavlidou , J. L. Richards

We present the results of an all-sky radio survey between 5 and 9 GHz of the fields surrounding all unassociated gamma-ray objects listed in the Fermi Large Area Telescope Second Source Catalog (2FGL). The goal of these observations is to…

High Energy Astrophysical Phenomena · Physics 2015-03-12 Frank K. Schinzel , Leonid Petrov , Gregory B. Taylor , Elizabeth K. Mahony , Philip G. Edwards , Yuri Y. Kovalev

By combining high-sensitivity LOFAR 150MHz, uGMRT 400MHz and 1,250MHz, GMRT 610MHz, and VLA 5GHz data in the ELAIS-N1 field, we study the radio spectral properties of radio-detected star-forming galaxies (SFGs) at observer-frame frequencies…

We use the distributions of spectral indices of a large homogenous sample of Fermi-detected blazars to re-investigate the relationship between flat spectrum radio quasars (FSRQs) and subclasses of BL Lac objects (BL Lacs). We compute the…

High Energy Astrophysical Phenomena · Physics 2020-07-20 E. U. Iyida , F. C. Odo , A. E. Chukwude , A. A. Ubachukwu

In this study, we systematically studied the X-ray to GeV gamma-ray spectra of 61 {\it Fermi} Large Area Telescope (LAT) detected radio galaxies. We found an anticorrelation between peak frequency and peak luminosity in the high-energy…

High Energy Astrophysical Phenomena · Physics 2022-06-15 Yasushi Fukazawa , Hiroto Matake , Taishu Kayanoki , Yoshiyuki Inoue , Justin Finke

Searching for low energy counterparts of gamma-ray sources is one of the major challenges in modern gamma-ray astronomy. In the third Fermi source catalog about 30 % of detected sources are unidentified/unassociated Gamma-ray Sources…

Astrophysics of Galaxies · Physics 2019-03-26 Peña-Herazo , H. A. , Marchesini , E. J. , Álvarez Crespo , N. , Ricci , F. , Massaro , F. , Chavushyan , V. , Landoni , M. , Strader , J. , Chomiuk , L. , Cheung , C. C. , Masetti , N. , Jiménez-Bailón , E. , D'Abrusco , R. , Paggi , A. , Milisavljevic , D. , La Franca , F. , Smith , H. A. , Tosti , G.

We have recently proposed a new simplified scenario where blazars are classified as flat-spectrum radio quasars (FSRQs) or BL Lacs according to the prescriptions of unified schemes, and to a varying combination of Doppler boosted radiation…

High Energy Astrophysical Phenomena · Physics 2015-06-15 P. Giommi , P. Padovani , G. Polenta

We present a catalog of radio-loud candidate gamma-ray emitting blazars with WISE mid-infrared colors similar to the colors of confirmed gamma-ray blazars. The catalog is assembled from WISE sources detected in all four WISE filters, with…

High Energy Astrophysical Phenomena · Physics 2015-06-23 R. D'Abrusco , F. Massaro , A. Paggi , H. A. Smith , N. Masetti , M. Landoni , G. Tosti

The identification of low-energy counterparts for gamma-ray sources is one of the biggest challenge in modern gamma-ray astronomy. Recently, we developed and successfully applied a new association method to recognize gamma-ray blazar…

High Energy Astrophysical Phenomena · Physics 2015-06-04 F. Massaro , A. Paggi , R. D'Abrusco , G. Tosti

We have searched the archived, pointed ROSAT Position Sensitive Proportional Counter data for blazars by correlating the WGACAT X-ray database with several publicly available radio catalogs, restricting our candidate list to serendipitous…

Astrophysics · Physics 2008-11-26 H. Landt , P. Padovani , E. Perlman , P. Giommi , H. Bignall , A. Tzioumis

The parsec-scale radio properties of 232 active galactic nuclei (AGNs), most of which are blazars, detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope have been observed contemporaneously by the Very Long…

High Energy Astrophysical Phenomena · Physics 2015-06-11 J. D. Linford , G. B. Taylor , F. K. Schinzel

During a decade of the $Fermi$-Large Area Telescope (LAT) operation, thousands of blazars have been detected in the $\gamma$-ray band. However, there are still numbers of blazars that have not been detected in the $\gamma$-ray band. In this…

High Energy Astrophysical Phenomena · Physics 2021-08-18 Xue-Jiao Deng , Rui Xue , Ze-Rui Wang , Shao-Qiang Xi , Hu-Bing Xiao , Lei-Ming Du , Zhao-Hua Xie

Blazars are powerful, variable emitters from radio to gamma-ray wavelengths. Even though the general picture of synchrotron emission at low energies and inverse Compton at the high energy end is well established, many important aspects of…

High Energy Astrophysical Phenomena · Physics 2019-08-15 W. Max-Moerbeck , J. L. Richards , V. Pavlidou , T. J. Pearson , A. C. S. Readhead , T. Hovatta , O. G. King , R. Reeves