Examinando por Autor "Strader, J."

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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.
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    SOAR/Goodman Spectroscopic Assessment of Candidate Counterparts of the LIGO/Virgo Event GW190814
    (IOP Publishing Ltd, 2022-04-01) Tucker, D.L.; Wiesner, M.P.; Allam, S.S.; Soares-Santos, M.; Bom, C.R.; Butner, M.; Garcia, A.; Morgan, R.; Olivares, E. F.; Palmese, A.; Santana-Silva, L.; Shrivastava, A.; Annis, J.; García-Bellido, J.; Gill, M.S.S.; Herner, K.; Kilpatrick, C.D.; Makler, M.; Sherman, N.; Amara, A.; Lin, H.; Smith, M.; Swann, E.; Arcavi, I.; Bachmann, T.G.; Bechtol, K.; Berlfein, F.; Briceño, C.; Brout, D.; Butler, R.E.; Cartier, R.; Casares, J.; Chen, H.-Y.; Conselice, C.; Contreras, C.; Cook, E.; Cooke, J.; Dage, K.; D'Andrea, C.; Davis, T.M.; De Carvalho, R.; Diehl, H.T.; Dietrich, J.P.; Doctor, Z.; Drlica-Wagner, A.; Drout, M.; Farr, B.; Finley, D.A.; Fishbach, M.; Foley, R.J.; Förster-Burón, F.; Fosalba, P.; Friedel, D.; Frieman, J.; Frohmaier, C.; Gruendl, R.A.; Hartley, W.G.; Hiramatsu, D.; Holz, D.E.; Howell, D.A.; Kawash, A.; Kessler, R.; Kuropatkin, N.; Lahav, O.; Lundgren, A.; Lundquist, M.; Malik, U.; Mann, A.W.; Marriner, J.; Marshall, J.L.; Martínez-Vázquez, C.E.; McCully, C.; Menanteau, F.; Meza, N.; Narayan, G.; Neilsen, E.; Nicolaou, C.; Nichol, R.; Paz-Chinchón, F.; Pereira, M.E.S.; Pineda, J.; Points, S.; Quirola-Vásquez, J.; Rembold, S.; Rest, A.; Rodriguez, Ó.; Romer, A.K.; Sako, M.; Salim, S.; Scolnic, D.; Smith, J.A.; Strader, J.; Sullivan, M.; Swanson, M.E.C.; Thomas, D.; Valenti, S.; Varga, T.N.; Walker, A.R.; Weller, J.; Wood, M.L.; Yanny, B.; Zenteno, A.; Aguena, M.; Andrade-Oliveira, F.; Bertin, E.; Brooks, D.; Burke, D.L.; Rosell, A. Carnero; Kind, M. Carrasco; Carretero, J.; Costanzi, M.; Da Costa, L.N.; De Vicente, J.; Desai, S.; Everett, S.; Ferrero, I.; Flaugher, B.; Gaztanaga, E.; Gerdes, D.W.; Gruen, D.; Gschwend, J.; Gutierrez, G.; Hinton, S.R.; Hollowood, D.L.; Honscheid, K.; James, D.J.; Kuehn, K.; Lima, M.; Maia, M.A.G.; Miquel, R.; Ogando, R.L.C.; Pieres, A.; Plazas Malagón, A.A.; Rodriguez-Monroy, M.; Sanchez, E.; Scarpine, V.; Schubnell, M.; Serrano, S.; Sevilla-Noarbe, I.; Suchyta, E.; Tarle, G.; To, C.; Zhang, Y.
    On 2019 August 14 at 21:10:39 UTC, the LIGO/Virgo Collaboration (LVC) detected a possible neutron star-black hole merger (NSBH), the first ever identified. An extensive search for an optical counterpart of this event, designated GW190814, was undertaken using the Dark Energy Camera on the 4 m Victor M. Blanco Telescope at the Cerro Tololo Inter-American Observatory. Target of Opportunity interrupts were issued on eight separate nights to observe 11 candidates using the 4.1 m Southern Astrophysical Research (SOAR) telescope's Goodman High Throughput Spectrograph in order to assess whether any of these transients was likely to be an optical counterpart of the possible NSBH merger. Here, we describe the process of observing with SOAR, the analysis of our spectra, our spectroscopic typing methodology, and our resultant conclusion that none of the candidates corresponded to the gravitational wave merger event but were all instead other transients. Finally, we describe the lessons learned from this effort. Application of these lessons will be critical for a successful community spectroscopic follow-up program for LVC observing run 4 (O4) and beyond. © 2022. The Author(s). Published by the American Astronomical Society.
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    The gamma-ray blazar quest: new optical spectra, state of art and future perspectives
    (Springer Netherlands, 2016-10) Massaro, F.; Álvarez Crespo, N.; D’Abrusco, R.; Landoni, M.; Masetti, N.; Ricci, F.; Milisavljevic, D.; Paggi, A.; Chavushyan, V.; Jiménez-Bailón, E.; Patiño-Álvarez, V.; Strader, J.; Chomiuk, L.; La Franca, F.; Smith, Howard A.; Tosti, G.
    We recently developed a procedure to recognize γ -ray blazar candidates within the positional uncertainty regions of the unidentified/unassociated γ -ray sources (UGSs). Such procedure was based on the discovery that Fermi blazars show peculiar infrared colors. However, to confirm the real nature of the selected candidates, optical spectroscopic data are necessary. Thus, we performed an extensive archival search for spectra available in the literature in parallel with an optical spectroscopic campaign aimed to reveal and confirm the nature of the selected γ -ray blazar candidates. Here, we first search for optical spectra of a selected sample of γ -ray blazar candidates that can be potential counterparts of UGSs using the Sloan Digital Sky Survey (SDSS DR12). This search enables us to update the archival search carried out to date. We also describe the state-of-art and the future perspectives of our campaign to discover previously unknown γ -ray blazars.