Agile Observations of the Gravitational-Wave Event GW150914

TAVANI, MARCOMARCOTAVANI0000-0003-2893-1459PITTORI, CarlottaCarlottaPITTORI0000-0001-6661-9779VERRECCHIA, FrancescoFrancescoVERRECCHIA0000-0003-3455-5082BULGARELLI, ANDREAANDREABULGARELLI0000-0001-6347-0649GIULIANI, ANDREAANDREAGIULIANI0000-0002-4315-1699Donnarumma, I.I.DonnarummaARGAN, ANDREAANDREAARGAN0000-0002-6230-665XTROIS, ALESSIOALESSIOTROIS0000-0002-3180-6002LUCARELLI, FabrizioFabrizioLUCARELLI0000-0002-6311-764XMarisaldi, M.M.Marisaldi0000-0002-4000-3789Monte, E. DelE. DelMonteEVANGELISTA, YURIYURIEVANGELISTA0000-0001-6096-6710FIORETTI, VALENTINAVALENTINAFIORETTI0000-0002-6082-5384Zoli, A.A.ZoliPIANO, GiovanniGiovanniPIANO0000-0002-9332-5319Munar-Adrover, P.P.Munar-AdroverANTONELLI, Lucio AngeloLucio AngeloANTONELLI0000-0002-5037-9034Barbiellini, G.G.BarbielliniCARAVEO, PATRIZIAPATRIZIACARAVEO0000-0003-2478-8018Cattaneo, P. W.P. W.CattaneoCosta, E.E.Costa0000-0002-9991-2709FEROCI, MARCOMARCOFEROCI0000-0002-7617-3421Ferrari, A.A.FerrariLongo, F.F.LongoMEREGHETTI, SandroSandroMEREGHETTI0000-0003-3259-7801MINERVINI, GABRIELEGABRIELEMINERVINI0000-0001-9778-6633Morselli, A.A.MorselliPACCIANI, LUIGILUIGIPACCIANI0000-0001-6897-5996PELLIZZONI, ALBERTO PAOLOALBERTO PAOLOPELLIZZONI0000-0002-4590-0040Picozza, P.P.PicozzaPILIA, MauraMauraPILIA0000-0001-7397-8091Rappoldi, A.A.RappoldiSabatini, S.S.SabatiniVERCELLONE, STEFANOSTEFANOVERCELLONE0000-0003-1163-1396VITTORINI, VALERIOVALERIOVITTORINI0000-0002-1208-8818Giommi, P.P.GiommiColafrancesco, S.S.ColafrancescoCARDILLO , MARTINAMARTINACARDILLO0000-0001-8877-3996Galli, M.M.GalliFUSCHINO, FABIOFABIOFUSCHINO0000-0003-2139-32992021-01-072021-01-0720162041-8205http://hdl.handle.net/20.500.12386/29528We report the results of an extensive search through the AGILE data for a gamma-ray counterpart to the LIGO gravitational-wave (GW) event GW150914. Currently in spinning mode, AGILE has the potential of cover 80% of the sky with its gamma-ray instrument, more than 100 times a day. It turns out that AGILE came within a minute of the event time of observing the accessible GW150914 localization region. Interestingly, the gamma-ray detector exposed ∼65% of this region during the 100 s time intervals centered at -100 and +300 s from the event time. We determine a 2σ flux upper limit in the band 50 MeV-10 GeV, UL = 1.9 × 10-8 erg cm-2 s-1, obtained ∼300 s after the event. The timing of this measurement is the fastest ever obtained for GW150914, and significantly constrains the electromagnetic emission of a possible high-energy counterpart. We also carried out a search for a gamma-ray precursor and delayed emission over five timescales ranging from minutes to days: in particular, we obtained an optimal exposure during the interval -150/-30 s. In all these observations, we do not detect a significant signal associated with GW150914. We do not reveal the weak transient source reported by Fermi-GBM 0.4 s after the event time. However, even though a gamma-ray counterpart of the GW150914 event was not detected, the prospects for future AGILE observations of GW sources are decidedly promising.STAMPAenAgile Observations of the Gravitational-Wave Event GW150914Article10.3847/2041-8205/825/1/L42-s2.0-84978516356000379366100004https://iopscience.iop.org/article/10.3847/2041-8205/825/1/L42016ApJ...825L...4TFIS/05 - ASTRONOMIA E ASTROFISICA