Examinando por Autor "Masetti, Nicola"
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Ítem AGN candidates in the VVV near-IR galaxy catalogue(2023-04) Baravalle, Laura D.; Schmidt, Eduardo O.; Victoria Alonso M.; Pichel, Ana; Minniti, Dante; Rodríguez-Kamenetzky, Adriana R.; Masetti, Nicola; Villalon, Carolina; Smith, Leigh C.; Lucas, Philip W.The goal of this work is to search for Active Galactic Nuclei (AGN) in the Galactic disc at very low latitudes with |b| < 2◦. For this, we studied the five sources from the VVV near-infrared (IR) galaxy catalogue that have also WISE counterparts and present variability in the VIrac VAriable Classification Ensemble (VIVACE) catalogue. In the near-IR colour-colour diagrams, these objects have in general redder colours compared to the rest of the sources in the field. In the mid-IR ones, they are located in the AGN region, however, there is a source that presents the highest interstellar extinction and different mid-IR colours to be a young stellar object (YSO). We also studied the source variability using two different statistical methods. The fractional variability amplitude σrms ranges from 12.6 to 33.8, being in concordance with previous results found for type-1 AGNs. The slopes of the light curves are in the range (2.6-4.7) × 10-4 mag d-1, also in agreement with results reported on quasars variability. The combination of all these results suggest that four galaxies are type-1 AGN candidates, whereas the fifth source likely a YSO candidate. © 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.Ítem Bat AGN spectroscopic survey - IV. Near-infrared coronal lines, hidden broad lines and correlation with hard X-ray emission(Oxford University Press, 2017-05) Lamperti, Isabella; Koss, Michael; Trakhtenbrot, Benny; Schawinski, Kevin; Ricci, Claudio; Oh, Kyuseok; Landt, Hermine; Riffel, Rogério; Rodríguez-Ardila, Alberto; Gehrels, Neil; Harrison, Fiona; Masetti, Nicola; Mushotzky, Richard; Treister, Ezequiel; Ueda, Yoshihiro; Veilleux, Sylvain kWe provide a comprehensive census of the near-infrared (NIR, 0.8-2.4 µm) spectroscopic properties of 102 nearby (z < 0.075) active galactic nuclei (AGN), selected in the hard X-ray band (14-195 keV) from the Swift-Burst Alert Telescope survey. With the launch of the James Webb Space Telescope, this regime is of increasing importance for dusty and obscured AGN surveys. We measure black hole masses in 68 per cent (69/102) of the sample using broad emission lines (34/102) and/or the velocity dispersion of the Ca II triplet or the CO band-heads (46/102). We find that emission-line diagnostics in the NIR are ineffective at identifying bright, nearby AGN galaxies because [Fe II] 1.257 µm/Paβ and H2 2.12 µm/Brγ identify only 25 per cent (25/102) as AGN with significant overlap with star-forming galaxies and only 20 per cent of Seyfert 2 have detected coronal lines (6/30). We measure the coronal line emission in Seyfert 2 to be weaker than in Seyfert 1 of the same bolometric luminosity suggesting obscuration by the nuclear torus. We find that the correlation between the hard X-ray and the [Si VI] coronal line luminosity is significantly better than with the [O III] λ5007 luminosity. Finally, we find 3/29 galaxies (10 per cent) that are optically classified as Seyfert 2 show broad emission lines in the NIR. These AGN have the lowest levels of obscuration among the Seyfert 2s in our sample (log NH < 22.43 cm−2), and all show signs of galaxy-scale interactions or mergers suggesting that the optical broad emission lines are obscured by host galaxy dust. © 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical SocietyÍtem Multiwavelength monitoring of a very active dwarf nova AX J1549.8-5416 with an unusually high duty cycle(Oxford University Press, 2017-08) Zhang, Guobao; Gelfand, Joseph D.; Russell, David M.; Lewis, Fraser; Masetti, Nicola; Bernardini, Federico; Andruchow, Ileana; Zibecchi L.We present the results of our analysis of new optical, ultraviolet (UV) and X-ray observations of a highly variable source - AX J1549.8-5416. Both the detection of several fast rise, exponential decay outbursts in the optical light curve and the lack of He II emission lines in the optical spectra suggest AX J1549.8-5416 is a cataclysmic variable of the dwarf nova (DN) type. The multiwavelength analysis of three mini-outbursts and one normal outburst represent one of the most complete multiwavelength studies of a DN and help to refine the relationship between the X-ray, UV and optical emission in this system. We find that the UV emission is delayed with respect to the optical by 1.0 5.4 d during the rising phase of the outburst. The Xray emission is suppressed during the peak of the optical outburst and recovers during the end of the outburst. From our analysis of archival Swift, Chandra and XMM Newton observations of AX J1549.8-5416, we estimate this DN has a high duty cycle (∼50 per cent), suggesting a quiescent X-ray luminosity larger than 1032 erg s-1. We also find the X-ray and UV flux are roughly anticorrelated. Furthermore, we find that, at low X-ray fluxes, the X-ray spectrum is well described by a single temperature thermal plasma model, while at high X-ray fluxes, an isobaric cooling flow model also works. We find that the maximum temperature of the plasma in quiescence is significantly higher than that in outburst. © 2017 The Authors.Ítem Optical Spectroscopic Observations of Gamma-Ray Blazar Candidates. XII. Follow-up Observations from SOAR, Blanco, NTT, and OAN-SPM(American Astronomical Society, 2023-03) García-Pérez, Abigail; Peña-Herazo, Harold A.; Massaro, Francesco; Chavushyan, Vahram; D’abrusco, Raffaele; Masetti, Nicola; Landoni, Marco; Franca, Fabio La; Patiño-Álvarez, Víctor M.; Amaya-Almazán, Raúl A.; Milisavljevic, Dan; Paggi, Alessandro; Ricci, Federica; Jiménez-Bailón, Elena; Smith, Howard A.Roughly one third of the sources in the Fermi-LAT catalogs are listed as unidentified/unassociated γ-ray sources (UGS), i.e., they lack a low-energy counterpart. In addition, there is a growing population of blazars of uncertain type (BCUs). Spectroscopic observations are crucial to confirm the blazar nature of the UGSs candidate counterparts and BCUs. Hence, in 2013 we started an optical spectroscopic campaign to carry out the identifications and classifications. In this paper, as a continuation of the campaign we report the spectra of 39 sources: the sample comprises 37 sources classified as BCUs, one source classified as a BL Lac in the Fourth Source Catalog of the Fermi-LAT (4FGL), and one source classified as UGS. We classify 19 of the sources in the sample as BL Lacs, 13 as blazars with nonnegligible host-galaxy emission, six as Flat Spectrum Radio Quasars, and one as a normal elliptical galaxy. The source listed as BL Lac in the 4FGL seems to be a blazar with nonnegligible host-galaxy emission in our observations, most likely due to an ongoing quiescent state. We classified the UGS source as a BL Lac. Six out of the 39 sources were previously reported in the campaign; in general, both the classifications and redshifts are in agreement, except for one of them with no redshift reported before. Altogether, we provided reliable redshift estimates to 21 out of the 39 sources. Finally, we describe the statistics of the data collected in our campaign so far. © 2023. The Author(s). Published by the American Astronomical Society.Ítem The Highly Energetic Expansion of SN2010bh Associated with GRB100316D(2012) Bufano, Filomena; Pian, Elena; Sollerman, Jesper; Benetti, Stefano; Pignata, Giuliano; Valenti, Stefano; Covino, Stefano; D’Avanzo, Paolo; Malesani, Daniele; Enrico, Cappellaro; Della Valle, Massimo; Fynbo, Johan; Hjorth, Jens; Mazzali, Paolo A.; Reichart, Daniel E.; Starling, Rhaana L. C.; Turatto, Massimo; Vergani, Susanna D.; Wiersema, Klass; Amati, Lorenzo; Bersier, David; Campana, Sergio; Cano, Zach; Castro-Tirado, Alberto J.; Chincarini, Guido; D’Elia, Valerio; de Ugarte, Antonio; Postigo, Deng, Jinsong; Ferrero, Patrizia; Alexei V., Filippenko; Goldoni, Paolo; Gorosabel, Javier; Greiner, Jochen; Hammer, Francois; Jakobsson, Pall; Kaper, Lex; Kawabata, Koji S.; Klose, Sylvio; Levan, Andrew J.; Maeda, Keiichi; Masetti, Nicola; Milvang-Jensen, Bo; Mirabel, Felix I.; Moller, Palle; Nomoto, Ken’ichi; Palazzi, Eliana; Piranomonte, Silvia; Salvaterra, Ruben; Stratta, Giulia; Tagliaferri, Gianpiero; Tanaka, Masaomi; Tanvir, Nial R.; Wijers, Ralph A.M.J.Ítem Two New Catalogs of Blazar Candidates in the WISE Infrared Sky(Astrophysical Journal, Supplement Series, 2019) D’Abrusco, Raffaele; Álvarez Crespo, Nuria; Massaro, Francesco; Campana, Riccardo; Chavushyan, Vahram; Landoni, Marco; La Franca, Fabio; Masetti, Nicola; Milisavljevic, Dan; Paggi, Alessandro; Ricci, Federica; Smith, Howard A.We present two catalogs of radio-loud candidate blazars whose Wide-Field Infrared Survey Explorer (WISE) mid-infrared colors are selected to be consistent with the colors of confirmed γ-ray-emitting blazars. The first catalog is the improved and expanded release of the WISE Blazar-like Radio-Loud Sources (WIBRaLS) catalog presented by D’Abrusco et al. It includes sources detected in all four WISE filters, spatially cross-matched with radio sources in one of three radio surveys and radio-loud based on their q22 spectral parameter. WIBRaLS2 includes 9541 sources classified as BL Lacs, flat-spectrum radio quasars, or mixed candidates based on their WISE colors. The second catalog, called KDEBLLACS, based on a new selection technique, contains 5579 candidate BL Lacs extracted from the population of WISE sources detected in the first three WISE passbands ([3.4], [4.6], and [12]) only, whose mid-infrared colors are similar to those of confirmed, γ-ray BL Lacs. Members of KDBLLACS are also required to have a radio counterpart and be radio-loud based on the parameter q12, defined similarly to the q22 used for the WIBRaLS2. We describe the properties of these catalogs and compare them with the largest samples of confirmed and candidate blazars in the literature. We cross-match the two new catalogs with the most recent catalogs of γ-ray sources detected by the Fermi Large Area Telescope. Since spectroscopic observations of candidate blazars from the first WIBRaLS catalog within the uncertainty regions of γ-ray unassociated sources confirmed that ∼90% of these candidates are blazars, we anticipate that these new catalogs will again play an important role in the identification of the γ-ray sky.