Examinando por Autor "Botticella, M."

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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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    Supernova rates from the SUDARE VST-OmegaCAM search: I. Rates per unit volume
    (EDP Sciences, 2015-12) Cappellaro, E.; Botticella, M.; Pignata, G.; Grado, A.; Greggio, L.; Limatola, L.; Vaccari, M.; Baruffolo, A.; Benetti, S.; Bufano, F.; Capaccioli, M.; Cascone, E.
    Aims.We describe the observing strategy, data reduction tools, and early results of a supernova (SN) search project, named SUDARE, conducted with the ESO VST telescope, which is aimed at measuring the rate of the different types of SNe in the redshift range 0.2 < z < 0:8. Methods. The search was performed in two of the best studied extragalactic fields, CDFS and COSMOS, for which a wealth of ancillary data are available in the literature or in public archives. We developed a pipeline for the data reduction and rapid identification of transients. As a result of the frequent monitoring of the two selected fields, we obtained light curve and colour information for the transients sources that were used to select and classify SNe by means of an especially developed tool. To accurately characterise the surveyed stellar population, we exploit public data and our own observations to measure the galaxy photometric redshifts and rest frame colours. Results. We obtained a final sample of 117 SNe, most of which are SN Ia (57%) with the remaining ones being core collapse events, of which 44% are type II, 22% type IIn and 34% type Ib/c. To link the transients, we built a catalogue of ∼1.3 × 105 galaxies in the redshift range 0 < z ≤ 1; with a limiting magnitude KAB= 23.5 mag. We measured the SN rate per unit volume for SN Ia and core collapse SNe in different bins of redshifts. The values are consistent with other measurements from the literature. Conclusions. The dispersion of the rate measurements for SNe-Ia is comparable to the scatter of the theoretical tracks for single degenerate (SD) and double degenerate (DD) binary systems models, therefore it is not possible to disentangle among the two different progenitor scenarios. However, among the three tested models (SD and the two flavours of DD that either have a steep DDC or a wide DDWdelay time distribution), the SD appears to give a better fit across the whole redshift range, whereas the DDC better matches the steep rise up to redshift ∼1.2. The DDW instead appears to be less favoured. Unlike recent claims, the core collapse SN rate is fully consistent with the prediction that is based on recent estimates of star formation history and standard progenitor mass range. © ESO 2015.