Examinando por Autor "Marchesini, E.J."

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    Optical spectroscopic observations of gamma-ray blazar candidates VIII: the 2016–2017 follow up campaign carried out at SPM, NOT, KPNO and SOAR telescopes
    (Astrophysics and Space Science, 2019-01-01) Marchesini, E.J.; Peña-Herazo, H.A.; Álvarez Crespo, N.; Ricci, F.; Negro, M.; Milisavljevic, D.; Massaro, F.; Masetti, N.; Landoni, M.; Chavushyan, V.; D’Abrusco, R.; Jiménez-Bailón, E.; La Franca, F.; Paggi, A.; Smith, H.A.; Tosti, G.
    The third Fermi source catalog lists 3033 γ-ray sources above 4 σ significance. More than 30% are classified as either unidentified/unassociated Gamma-ray sources (UGSs), with about 20% classified as Blazar candidates of uncertain types (BCUs). To confirm the blazar-like nature of candidate counterparts of UGSs and BCUs, we started in 2012 an optical spectroscopic follow up campaign. We report here the spectra of 36 targets with observations from the Observatorio Astronómico Nacional San Pedro Mártir, the Southern Astrophysical Research Observatory, the Kitt Peak National Observatory and the Northern Optical Telescope, between 2016 and 2017. We confirm the BL Lac nature of 23 sources, and the flat spectrum radio quasar nature of other 7 ones. We also provide redshift estimates for 19 out of these 30 confirmations, with only one being a lower limit due to spectral features ascribable to intervening systems along the line of sight. As in previous analyses, the largest fraction of now-classified BCUs belong to the class of BL Lac objects, that appear to be the most elusive class of active galactic nuclei. One of the BL Lacs identified in this work, associated with 3FGL J2213.6-4755, lies at a redshift of z> 1.529 , making it one of the few distant gamma-ray BL Lac objects.
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    Optical spectroscopic observations of gamma-ray blazar candidates. VII. Follow-up campaign in the southern hemisphere
    (Springer Netherlands, 2017-12) 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.
    Searching for low energy counterparts of γ-rays sources is one of the major challenges in modern γ-ray astronomy. In the third Fermi source catalog about 30% of detected sources are unidentified/unassociated Gamma-ray Sources (UGSs). We recently started an optical spectroscopic follow up campaign to confirm the blazar-like nature of candidates counterparts of UGSs. Here we report the spectra of 61 targets collected with the Southern Astrophysical Research Telescope (SOAR) between 2014 and the 2017. Our sample includes 33 potential counterparts of UGSs, selected on the basis of WISE colors, and 27 blazar candidates of uncertain type associated with gamma-ray sources of the last release of the Fermi catalog. We confirm the BZB nature of 20 sources lying within the positional uncertainty region of the UGSs. All the observed BCUs show blazar-like spectra, classified as 2 BZQs and 25 BZBs, for which we obtained 6 redshift estimates. Within the BCUs observations we report the redshift estimate for the BZB associated with, 3FGL J1106.4-3643 that is the second most distant BL Lac known to date, at z≥ 1.084. © 2017, Springer Science+Business Media B.V., part of Springer Nature.