Related papers: A Search for Candidate TeV Emitters in the High-la…
1RXS J101015.9-311909 is a galaxy located at a redshift of z=0.14 hosting an active nucleus belonging to the class of bright BL Lac objects. Observations at high (HE, E > 100 MeV) and very high (VHE, E > 100 GeV) energies provide insights…
Recent observations with atmospheric Cherenkov telescope systems such as H.E.S.S. and MAGIC have revealed a large number of new sources of very-high-energy (VHE) gamma-rays from 100 GeV - 100 TeV, mostly concentrated along the Galactic…
The optical spectroscopic followup of 27 sources belonging to a sample of 30 high-energy objects selected by positionally cross correlating the first Fermi/LAT Catalog and the ROSAT All-Sky Survey Bright Source Catalog is presented here. It…
The high energy peaked BL Lac (HBL) object 1ES 0414+009 (z=0.287) is a distant very high-energy (VHE, E > 100 GeV) blazars with well-determined redshift. This source was detected with the High Energy Stereoscopic System (H.E.S.S.) between…
We report on Fermi Large Area Telescope (LAT) and multi-wavelength results on the recently-discovered very-high-energy (VHE, $E>$ 100 GeV) blazar S4 0954+65 ($z=0.368$) during an exceptionally bright optical flare in 2015 February. During…
The very high energy (VHE; >100 GeV) source HESS J0632+057 has been recently confirmed as a \gamma-ray binary, a subclass of the high mass X-ray binary (HMXB) population, through the detection of an orbital period of 321 days. We performed…
1ES 0414+009 (z = 0.287) is a distant high-frequency-peaked BL Lac object, and has long been considered a likely emitter of very-high energy (VHE, E>100 GeV) gamma-rays due to its high X-ray and radio flux. Observations in the VHE gamma-ray…
The HAWC (High Altitude Water Cherenkov) collaboration recently published their 2HWC catalog, listing 39 very high energy (VHE; >100~GeV) gamma-ray sources based on 507 days of observation. Among these, there are nineteen sources that are…
The observation of Very High Energy gamma rays (VHE, E > 100 GeV) led us to the identification of extremely energetic processes and particle acceleration sites both within our Galaxy and beyond. We expect that VHE facilities, like CTA, will…
The bright gamma-ray quasar 4C +55.17 is a distant source ($z = 0.896$) with a hard spectrum at GeV energies as observed by the Large Area Telescope (LAT) on board the {{\it Fermi}} satellite. This source is identified as a good source…
The synergy between the Fermi-LAT and ground-based Cherenkov telescope arrays gives us the opportunity for the first time to characterize the high-energy emission from blazars over 5 decades in energy, from 100 MeV to 10 TeV. In this study,…
Recently, a new method to constrain the distance of blazars with unknown redshift using combined observations in the GeV and TeV regimes has been developed, with the underlying assumption that the Very High Energy (VHE) spectrum corrected…
Very-high-energy astronomy studies the Universe at energies between 30 GeV and 100 TeV. The past decade has seen enormous progress in this field. There are now at least seven known sources of VHE photons. By studying these objects in the…
We report on our study of high-energy properties of two peculiar TeV emitters: the "extreme blazar" 1ES 0347-121 and the "extreme blazar candidate" HESS J1943+213 located near the Galactic Plane. Both objects are characterized by quiescent…
In any given 24-hour period, the Fermi-LAT detects photons with energies of order 100 GeV not associated with any known VHE emitter. The RA/Dec of these photons frequently falls into the field of view of VERITAS the following evening. A…
The past decade has seen a dramatic improvement in the quality of data available at both high (HE: 100 MeV to 100 GeV) and very high (VHE: 100 GeV to 100 TeV) gamma-ray energies. With three years of data from the Fermi Large Area Telescope…
We estimate the galaxy density along lines of sight to hard extragalactic gamma-ray sources by correlating source positions on the sky with a void catalog based on the Sloan Digital Sky Survey (SDSS). Extragalactic gamma-ray sources that…
The attenuation of very high energy (VHE) photons by the extragalactic background light (EBL) prevents the observation of high redshift flat spectrum radio quasars (FSRQs). However, the correlation of VHE spectral index with source redshift…
A new method to constrain the distance of blazars with unknown redshift using combined observations in the GeV and TeV regimes will be presented. The underlying assumption is that the Very High Energy (VHE) spectrum corrected for the…
We reconsider the emission properties of the BL Lac objects emitting in the high-energy gamma-ray band exploiting the new information in the MeV-GeV band obtained by the Large Area Telescope (LAT) onboard the Fermi Gamma-Ray Space Telescope…