Examinando por Autor "Marchesini, EJ"

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    Looking for blazars in a sample of unidentified high-energy emitting Fermi sources
    (EDP SCIENCES, 2016-11) Marchesini, EJ; Masetti, N; Chavushyan, V; Cellone, SA; Andruchow, I; Bassani, L; Bazzano, A; Jimenez-Bailon, E; Landi, R; Malizia, A; Palazzi, E; Patino-Alvarez, V; Rodriguez-Castillo, GA; Stephen, JB; Ubertini, P
    Context. Based on their overwhelming dominance among associated Fermi gamma-ray catalogue sources, it is expected that a large fraction of the unidentified Fermi objects are blazars. Through crossmatching between the positions of unidentified gamma-ray sources from the First Fermi Catalog of gamma-ray sources emitting above 10 GeV (1FHL) and the ROSAT and Swift/XRT catalogues of X-ray objects and between pointed XRT observations, a sample of 36 potential associations was found in previous works with less than 15 arcsec of positional off set. One-third of them have recently been classified; the remainder, though believed to belong to the blazar class, still lack spectroscopic classifications. Aims. We study the optical spectrum of the putative counterparts of these unidentified gamma-ray sources in order to find their redshifts and to determine their nature and main spectral characteristics. Methods. An observational campaign was carried out on the putative counterparts of 13 1FHL sources using medium-resolution optical spectroscopy from the Osservatorio Astronomico di Bologna in Loiano, Italy; the Telescopio Nazionale Galileo and the Nordic Optical Telescope, both in the Canary Islands, Spain; and the Observatorio Astronomico Nacional San Pedro Martir in Baja California, Mexico. Results. We were able to classify 14 new objects based on their continuum shapes and spectral features. Conclusions. Twelve new blazars were found, along with one new quasar and one new narrow line Seyfert 1 (NLS1) to be potentially associated with the 1FHL sources of our sample. Redshifts or lower limits were obtained when possible alongside central black hole mass and luminosity estimates for the NLS1 and the quasar.
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    Ítem
    RADIO-WEAK BL LAC OBJECTS IN THE FERMI ERA
    (ASTROPHYSICAL JOURNAL, 834 (2):10.3847/1538-4357/834/2/113 JAN 6 201, 2017-01) Massaro, F; Marchesini, EJ; D'Abrusco, R; Masetti, N; Andruchow, I; Smith, HA
    The existence of "radio-weak BL Lac objects" (RWBLs) has been an open question, and has remained unsolved since the discovery that quasars could be radio-quiet or radio-loud. Recently, several groups identified RWBL candidates, mostly found while searching for low-energy counterparts of the unidentified or. unassociated gammaray sources listed in the Fermi catalogs. Confirming RWBLs is a challenging task since they could be confused with white dwarfs (WDs) or weak. emission. line quasars (WELQs) when there are not sufficient data to precisely draw their broadband spectral energy distribution, and their classification is mainly based on a featureless optical spectra. Motivated by the recent discovery that Fermi BL Lacs appear to have very peculiar mid-IR emission, we show that it is possible to distinguish between WDs, WELQs, and BL Lacs using the [3.4]-[4.6]-[12] mu m color-color plot built using the WISE magnitudes when the optical spectrum is available. On the basis of this analysis, we identify WISE J064459.38 + 603131 and WISE J141046.00 + 740511.2 as the first two genuine RWBLs, both potentially associated with Fermi sources. Finally, to strengthen our identification of these objects as true RWBLs, we present multifrequency observations for these two candidates to show that their spectral behavior is indeed consistent with that. of the BL Lac population.