Related papers: Discovery, identification, and study of variabilit…
We used the data from the Fermi Gamma-ray Space Telescope to characterise the {\gamma}-ray flux variability of blazars on month-like time scales. Our sample consists of 1120 blazars of which 481 are flat spectrum radio quasars (FSRQs) and…
A probabilistic technique for the joint estimation of background and sources with the aim of detecting faint and extended celestial objects is described. Bayesian probability theory is applied to gain insight into the coexistence of…
We present some first results on the variability, polarization and general properties of radio sources selected in a blind survey at 20 GHz, the highest frequency at which a sensitive radio survey has been carried out over a large area of…
In this paper we present the Fermi All-sky Variability Analysis (FAVA), a tool to systematically study the variability of the gamma-ray sky measured by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. For each…
Following the discovery of the brightest high-energy neutrino sources in the sky, the further detection of fainter sources is more challenging. A natural solution is to combine fainter source candidates, and instead of individual…
In a recent paper, Romero et al. (1999) have presented the results of a positional correlation analysis of the low-latitude unidentified gamma-ray sources in the Third EGRET catalog with complete lists of galactic objects like supernova…
Ongoing deep surveys of galaxy luminosity functions, spectral energy distributions and backwards evolution models of star formation rates can be used to calculate the past history of intergalactic photon densities and, from them, the…
We have recently proposed a simplified scenario for blazars in which these sources are classified as flat-spectrum radio quasars or BL Lacs according to the prescriptions of unified schemes, and to a varying combination of Doppler boosted…
We established a sample of millimeter-wave and gamma-ray bright active galactic nuclei matching the WMAP catalog with the EGRET catalog, highest energy photons and the Fermi bright source list. We have monitored over 80 of these objects in…
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…
To fully exploit the scientific potential of the Fermi mission, we initiated the F-GAMMA program. Between 2007 and 2015 it was the prime provider of complementary multi-frequency monitoring in the radio regime. We quantify the radio…
Low-frequency radio surveys allow in-depth studies and new analyses of classes of sources previously known and characterised only in other bands. In recent years, low radio frequency observations of blazars have been available thanks to new…
The classification of gamma-ray-detected blazar candidates of uncertain type (BCU) is a relevant problem in extragalactic gamma-ray astronomy. Here we report the optical spectroscopic characterization, using two 3-4~m class telescopes,…
In recent years, the cross spectrum has received considerable attention as a means of characterising the variability of astronomical sources as a function of wavelength. While much has been written about the statistics of time and phase…
The availability of about a decade of uninterrupted sky monitoring by the Fermi satellite has made possible to study long-term quasi-periodicities for high-energy sources. It is therefore not a surprise that for several blazars in the…
Studying unidentified {\gamma}-ray sources is important as they may hide new discoveries. We conducted a multiwavelength analysis of 13 unidentified Fermi-LAT sources in the 3FGL catalog that have no known counterparts (Unidentified…
We present preliminary results of a campaign undertaken with different radio interferometers to observe a sample of the most variable unidentified EGRET sources. We expect to detect which of the possible counterparts of the gamma-ray…
Context:Blazars are the rarest and most powerful active galactic nuclei, playing a crucial and growing role in today multi-frequency and multi-messenger astrophysics. Current blazar catalogs, however, are incomplete and particularly…
We present the preliminary results from two new surveys of blazars that have direct implications on the GLAST detection of extragalactic sources from two different perspectives: microwave selection and a combined deep X-ray/radio selection.…
We present the results of a new model calculation of the gamma-ray background produced by unresolved blazars, using the second EGRET catalogue and taking account of flaring. These results are compared to the preliminary gamma-ray background…