Examinando por Autor "Getman, F."

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    GRAWITA: VLT Survey Telescope observations of the gravitational wave sources GW150914 and GW151226
    (Oxford University Press, 2018-02) Brocato, E.; Branchesi, M.; Cappellaro, E.; Covino, S.; Grado, A.; Greco, G.; Limatola, L.; Stratta, G.; Yang, S.; Campana, S.; D'Avanzo, P.; Getman, F.; Melandri, A.; Nicastro, L.; Palazzi, E.; Pian, E.; Piranomonte, S.; Pulone, L.; Rossi, A.; Tomasella, L.; Amati, L.; Antonelli, L.A.; Ascenzi, S.; Benetti, S.; Bulgarelli, A.; Capaccioli, M.; Cella, G.; Dadina, M.; De Cesare, G.; D'Elia, V.; Ghirlanda, G.; Ghisellini, G.; Giuffrida, G.; Iannicola, G.; Israel, G.; Lisi, M.; Longo, F.; Mapelli, M.; Marinoni, S.; Marrese, P.; Masetti, N.; Patricelli, B.; Possenti, A.; Radovich, M.; Razzano, M.; Salvaterra, R.; Schipani, P.; Spera, M.; Stamerra, A.; Stella, L.; Tagliaferri, G.; Testa, V.
    We report the results of deep optical follow-up surveys of the first two gravitational-wave sources, GW150914 and GW151226, done by the GRAvitationalWave Inaf TeAm Collaboration (GRAWITA). The VLT Survey Telescope (VST) responded promptly to the gravitational wave alerts sent by the LIGO and Virgo Collaborations, monitoring a region of 90 and 72 deg 2 for GW150914 and GW151226, respectively, and repeated the observations over nearly two months. Both surveys reached an average limiting magnitude of about 21 in the r band. The paper describes the VST observational strategy and two independent procedures developed to search for transient counterpart candidates in multi-epoch VST images. Several transients have been discovered but no candidates are recognized to be related to the gravitational wave events. Interestingly, among many contaminant supernovae, we find a possible correlation between the supernova VSTJ57.77559-59.13990 and GRB150827A detected by Fermi-GBM. The detection efficiency of VST observations for different types of electromagnetic counterparts of gravitational wave events is evaluated for the present and future follow-up surveys. © 2017 The Author(s).
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    Search for the optical counterpart of the GW170814 gravitational wave event with the VLT Survey Telescope
    (Oxford University Press, 2020-02) Grado, A.; Cappellaro, E.; Covino, S.; Getman, F.; Greco, G.; Limatola, L.; Yang, S.; Amati, L.; Benetti, S.; Branchesi, M.; Brocato, E.; Botticella, M.; Campana, S.; Cantiello, M.; Dadina, M.; Ammando, F. D; De Cesare, G.; D’Elia, V.; Della Valle, M.; Iodice, E.; Longo, G.; . Mapelli, M; Masetti, N.; Nicastro, L.; Palazzi, E.; Possenti, A.; Radovich, M.; Rossi, A.; Salvaterra, R.; Stella, L.; Stratta, G.; Testa, V.; Tomasella, L.
    We report on the search for the optical counterpart of the gravitational event GW170814, which was carried out with the VLT Survey Telescope (VST) by the GRAvitational Wave Inaf TeAm. Observations started 17.5 h after the Laser Interferometer Gravitational-wave Observatory (LIGO) and Virgo alert and we covered an area of 99 deg2 that encloses ∼ 77 per cent and ∼ 59 per cent of the initial and refined localization probability regions, respectively. A total of six epochs were secured over nearly two months. The survey reached an average limiting magnitude of 22 AB mag in the r band. After assuming the model described in Perna, Lazzati & Farr, that derives as possible optical counterpart of a BBH (binary black hole) event a transient source declining in about one day, we have computed a survey efficiency of about 5 per cent. This paper describes the VST observational strategy and the results obtained by our analysis pipelines developed to search for optical transients in multi-epoch images. We report the catalogue of the candidates with possible identifications based on light-curve fitting. We have identified two dozens of SNe, nine AGNs, and one QSO. Nineteen transients characterized by a single detection were not classified. We have restricted our analysis only to the candidates that fall into the refined localization map. None out of 39 left candidates could be positively associated with GW170814. This result implies that the possible emission of optical radiation from a BBH merger had to be fainter than r ∼ 22 (Loptical ∼ 1.4 × 1042 erg s−1) on a time interval ranging from a few hours up to two months after the gravitational wave event.
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    Spectroscopic identification of r-process nucleosynthesis in a double neutron-star merger
    (Nature Publishing Group, 2017-11) Pian, E.; D'Avanzo, P.; Benetti, S.; Branchesi, M.; Brocato, Campana S.; Cappellaro, E.; Covino, S.; D'Elia, V.; Fynbo, J.P.U.; Getman, F.; Ghirlanda, G.; Ghisellini, G.; Grado, A.; Greco, G.; Hjorth, J.; Kouveliotou, C.; Levan, A.; Limatola, L.; Malesani, D.; Mazzali, P.A.; Melandri, A.; Møller, P.; Nicastro, L.; Palazzi, E.; Piranomonte, S.; Rossi, A.; Salafia, O.S.; Selsing, J.; Stratta, G.; Tanaka, M.; Tanvir, N.R.; Tomasella, L.; Watson, D.; Yang, S.; Amati, L.; Antonelli, L.A.; Ascenzi, S.; Bernardini, M.G.; Boër, M.; Bufano, F.; Bulgarelli, A.; Capaccioli, M.; Casella, P.; Castro-Tirado, A.J.; Chassande-Mottin, E.; Ciolfi, R.; Copperwheat, C.M.; Dadina, M.; De Cesare, G.; Di Paola, A.; Fan, Y.Z.; Gendre, B.; Giuffrida, G.; Giunta, A.; Hunt, L.K.; Israel, G.L.; Jin, Z.-P.; Kasliwal, M.M.; Klose, S.; Lisi, M.; Longo, F.; Maiorano, E.; Mapelli, M.; Masetti, N.; Nava, L.; Patricelli, B.; Perley, D.; Pescalli, A.; Piran, T.; Possenti, A.; Pulone, L.; Razzano, M.; Salvaterra, R.; Schipani, P.; Spera, M.; Stamerra, A.; Stella, L.; Tagliaferri, G.; Testa, V.; Troja, E.; Turatto, M.; Vergani, S.D.; Vergani, D.
    The merger of two neutron stars is predicted to give rise to three major detectable phenomena: a short burst of γ-rays, a gravitational-wave signal, and a transient optical-near-infrared source powered by the synthesis of large amounts of very heavy elements via rapid neutron capture (the r-process)1-3. Such transients, named 'macronovae' or 'kilonovae'4-7, are believed to be centres of production of rare elements such as gold and platinum8. The most compelling evidence so far for a kilonova was a very faint near-infrared rebrightening in the afterglow of a short γ-ray burst9,10 at redshift z = 0.356, although findings indicating bluer events have been reported11. Here we report the spectral identification and describe the physical properties of a bright kilonova associated with the gravitational-wave source12 GW170817 and γ-ray burst13,14 GRB 170817A associated with a galaxy at a distance of 40 megaparsecs from Earth. Using a series of spectra from ground-based observatories covering the wavelength range from the ultraviolet to the near-infrared, we find that the kilonova is characterized by rapidly expanding ejecta with spectral features similar to those predicted by current models15,16. The ejecta is optically thick early on, with a velocity of about 0.2 times light speed, and reaches a radius of about 50 astronomical units in only 1.5 days. As the ejecta expands, broad absorption-like lines appear on the spectral continuum, indicating atomic species produced by nucleosynthesis that occurs in the post-merger fast-moving dynamical ejecta and in two slower (0.05 times light speed) wind regions. Comparison with spectral models suggests that the merger ejected 0.03 to 0.05 solar masses of material, including high-opacity lanthanides. © 2017 Macmillan Publishers Limited, part of Springer Nature.