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We report the detection of two new gamma-ray sources in the Fermi-LAT sky (Pass 8) at energies higher than 20 GeV, and confirmed at lower energies, using a source detection tool based on the Minimum Spanning Tree algorithm. One of these…

High Energy Astrophysical Phenomena · Physics 2017-01-25 R. Campana , A. Maselli , E. Bernieri , E. Massaro

Blazars are radio-loud active galactic nuclei well known for their non thermal emission spanning a wide range of frequencies. The Roma-BZCAT is, to date, the most comprehensive list of these sources. We performed the cross-match of several…

High Energy Astrophysical Phenomena · Physics 2015-05-04 A. Maselli , F. Massaro , R. D'Abrusco , G. Cusumano , V. La Parola , A. Segreto , G. Tosti

We compare the gamma-ray photon flux variability of northern blazars in the Fermi/LAT First Source Catalog with 37 GHz radio flux density curves from the Metsahovi quasar monitoring program. We find that the relationship between…

High Energy Astrophysical Phenomena · Physics 2011-10-25 J. Leon-Tavares , E. Valtaoja , M. Tornikoski , A. Lahteenmaki , E. Nieppola

We place new constraints on the contribution of blazars to the large-scale isotropic gamma-ray background (IGRB) by jointly analyzing the measured source count distribution (logN-logS) of blazars and the measured intensity and anisotropy of…

Cosmology and Nongalactic Astrophysics · Physics 2013-03-12 Alessandro Cuoco , Eiichiro Komatsu , Jennifer Siegal-Gaskins

The Fermi-LAT DR1 and DR2 4FGL catalogues feature more than 5000 gamma-ray sources of which about one fourth are not associated with already known objects, and approximately one third are associated with blazars of uncertain nature. We…

High Energy Astrophysical Phenomena · Physics 2021-06-30 S. Germani , G. Tosti , . Lubrano , S. Cutini , I. Mereu , A. Berretta

The radio properties of blazars detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope have been observed as part of the VLBA Imaging and Polarimetry Survey (VIPS). This large, flux-limited sample of active…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-20 J. D. Linford , G. B. Taylor , R. Romani , S. E. Healey , J. F. Helmboldt , A. C. S. Readhead , R. Reeves , J. Richards , G. Cotter

We present simultaneous Planck, Swift, Fermi, and ground-based data for 105 blazars belonging to three samples with flux limits in the soft X-ray, hard X-ray, and gamma-ray bands. Our unique data set has allowed us to demonstrate that the…

Revealing the nature of unassociated high-energy (> 100 MeV) gamma-ray sources remains a challenge 35 years after their discovery. Of the 934 gamma-ray sources at high Galactic latitude (|b| > 15 degrees) in the First Fermi-LAT catalogue…

High Energy Astrophysical Phenomena · Physics 2010-11-25 N. Mirabal , D. Nieto , S. Pardo

The one-point function (i.e., the isotropic flux distribution) is a complementary method to (anisotropic) two-point correlations in searches for a gamma-ray dark matter annihilation signature. Using analytical models of structure formation…

Cosmology and Nongalactic Astrophysics · Physics 2015-12-02 Michael R. Feyereisen , Shin'ichiro Ando , Samuel K. Lee

Determining redshifts for BL Lacertae (BL Lac) objects using the traditional spectroscopic method is challenging due to the absence of strong emission lines in their optical spectra. We employ the photometric dropout technique to determine…

High Energy Astrophysical Phenomena · Physics 2017-01-04 A. Kaur , A. Rau , M. Ajello , J. Greiner , D. H. Hartmann , V. S. Paliya , A. Dominguez , J. Bolmer , P. Schady

Gamma-ray searches for new physics such as dark matter are often driven by investigating the composition of the extragalactic gamma-ray background (EGB). Classic approaches to EGB decomposition manifest in resolving individual point sources…

High Energy Astrophysical Phenomena · Physics 2018-10-31 Hannes-S. Zechlin , Silvia Manconi , Fiorenza Donato

The latest determination of the extragalactic gamma-ray background (EGRB) radiation by Fermi is compared with the theoretical prediction of the blazar component by Inoue & Totani (2009; hereafter IT09). The Fermi EGRB spectrum is in…

High Energy Astrophysical Phenomena · Physics 2010-01-05 Yoshiyuki Inoue , Tomonori Totani , Susumu Inoue , Masakazu A. R. Kobayashi , Jun Kataoka , Rie Sato

Flux distribution is an important tool to understand the variability processes in active galactic nuclei. We now have available a great deal of observational evidences pointing towards the presence of log-normal components in the high…

High Energy Astrophysical Phenomena · Physics 2018-12-18 Carlo Romoli , Nachiketa Chakraborty , Daniela Dorner , Andrew M. Taylor , Michael Blank

In this letter, we introduce a new method of image stacking to directly study the undetected but possible gamma-ray point sources. Applying the method to the Australia Telescope 20 GHz Survey (AT20G) sources which have not been detected by…

High Energy Astrophysical Phenomena · Physics 2015-05-20 Ming Zhou , Jiancheng Wang , Xiaoyan Gao

We present the results of the \textit{Fermi}-LAT 10-years-long light curves (LCs) modeling of selected blazars: six flat spectrum radio quasars (FSRQs) and five BL Lacertae (BL Lacs), examined in 7-, 10-, and 14-day binning. The LCs and…

High Energy Astrophysical Phenomena · Physics 2021-09-24 Mariusz Tarnopolski , Natalia Żywucka , Volodymyr Marchenko , Javier Pascual-Granado

We construct a large sample of gamma-ray blazars with low-frequency radio data using the recent released TGSS AD1 catalog at 150 MHz. The radio/gamma connections of blazars are compared from 143 GHz to 150 MHz. The radio flux density at all…

High Energy Astrophysical Phenomena · Physics 2018-12-26 Xu-Liang Fan , Qingwen Wu

In this study, we conducted a systematic analysis of long-term Fermi-LAT \gamma-ray data for a sample of blazars, including FSRQs, BL\,Lacs, and BCUs, to investigate their $\gamma$-ray variability. We focused on light curves binned in 3-,…

We investigate the blazar contribution to the cumulative neutrino intensity assuming a generic relationship between neutrino and gamma-ray luminosities, $L_{\nu}\propto (L_{\rm ph})^{\gamma_{\rm lw}}$. Using the gamma-ray luminosity…

High Energy Astrophysical Phenomena · Physics 2020-02-13 Chengchao Yuan , Kohta Murase , Peter Mészáros

Aiming to delineate the physical framework of blazars, we present an effective method to estimate four important parameters based on the idea proposed by \citet{BK95}, including the upper limit of central black hole mass $M$, the Doppler…

High Energy Astrophysical Phenomena · Physics 2022-02-02 Zhiyuan Pei , Junhui Fan , Jianghe Yang , Danyi Huang , Ziyan Li

The origin of the diffuse gamma-ray background (DGRB), the one that remains after subtracting all individual sources from observed gamma-ray sky, is unknown. The DGRB possibly encompasses contributions from different source populations such…

High Energy Astrophysical Phenomena · Physics 2023-05-02 Saqib Hussain , Rafael Alves Batista , Elisabete M. de Gouveia Dal Pino , Klaus Dolag