• Stefano Ciroi

      Articles written in Journal of Astrophysics and Astronomy

    • Optical Counterparts of Undetermined Type 𝛾-Ray Active Galactic Nuclei with Blazar-Like Spectral Energy Distributions

      Giovanni La Mura Graziano Chiaro Stefano Ciroi Piero Rafanelli David Salvetti Marco Berton Valentina Cracco Fermi-LAT collaboration

      More Details Abstract Fulltext PDF

      During its first four years of scientific observations, the Fermi Large Area Telescope (Fermi-LAT) detected 3033 𝛾-ray sources above a 4𝜎 significance level. Although most of the extra-galactic sources are active galactic nuclei (AGN) of the blazar class, other families of AGNs are observed too, while a still high fraction of detections (∼30%) remains with uncertain association or classification. According to the currently accepted interpretation, the AGN 𝛾-ray emission arises from inverse Compton (IC) scattering of low energy photons by relativistic particles confined in a jet, which, in the case of blazars, is oriented very close to our line-of-sight. Taking advantage of data from radio and X-ray wavelengths, which we expect to be produced together with 𝛾-rays, providing a much better source localization potential, we focused our attention on a sample of 𝛾-ray Blazar Candidates of Undetermined type (BCUs), starting a campaign of optical spectroscopic observations. The main aims of our investigation include a census of the AGN families that contribute to 𝛾-ray emission and a study of their redshift distribution, with the subsequent implications on the intrinsic source power. We furthermore analyze which 𝛾-ray properties can better constrain the nature of the source, thus helping in the study of objects not yet associated with a reliable low frequency counterpart. Here we report on the instruments and techniques used to identify the optical counterparts of 𝛾-ray sources, we give an overview on the status of our work, and we discuss the implications of a large scale study of 𝛾-ray emitting AGNs.

  • Journal of Astrophysics and Astronomy | News

    • Continuous Article Publication

      Posted on January 27, 2016

      Since January 2016, the Journal of Astrophysics and Astronomy has moved to Continuous Article Publishing (CAP) mode. This means that each accepted article is being published immediately online with DOI and article citation ID with starting page number 1. Articles are also visible in Web of Science immediately. All these have helped shorten the publication time and have improved the visibility of the articles.

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

© 2017-2019 Indian Academy of Sciences, Bengaluru.