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تسجيل مستخدم جديدCALET Upper Limits on X-ray and Gamma-ray Counterparts of GW 151226
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We present upper limits in the hard X-ray and gamma-ray bands at the time of the LIGO gravitational-wave event GW 151226 derived from the CALorimetric Electron Telescope (CALET) observation. The main instrument of CALET, CALorimeter (CAL), observes gamma-rays from ~1 GeV up to 10 TeV with a field of view of ~2 sr. The CALET gamma-ray burst monitor (CGBM) views ~3 sr and ~2pi sr of the sky in the 7 keV - 1 MeV and the 40 keV - 20 MeV bands, respectively, by using two different scintillator-based instruments. The CGBM covered 32.5% and 49.1% of the GW 151226 sky localization probability in the 7 keV - 1 MeV and 40 keV - 20 MeV bands respectively. We place a 90% upper limit of 2 x 10^{-7} erg cm-2 s-1 in the 1 - 100 GeV band where CAL reaches 15% of the integrated LIGO probability (~1.1 sr). The CGBM 7 sigma upper limits are 1.0 x 10^{-6} erg cm-2 s-1 (7-500 keV) and 1.8 x 10^{-6} erg cm-2 s-1 (50-1000 keV) for one second exposure. Those upper limits correspond to the luminosity of 3-5 x 10^{49} erg s-1 which is significantly lower than typical short GRBs.
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We present results on searches for gamma-ray counterparts of the LIGO/Virgo gravitational-wave events using CALorimetric Electron Telescope ({sl CALET}) observations. The main instrument of {sl CALET}, CALorimeter (CAL), observes gamma-rays from $sim
1$ GeV up to 10 TeV with a field of view of nearly 2 sr. In addition, the {sl CALET} gamma-ray burst monitor (CGBM) views $sim$3 sr and $sim2pi$ sr of the sky in the 7 keV -- 1 MeV and the 40 keV -- 20 MeV bands, respectively, by using two different crystal scintillators. The {sl CALET} observations on the International Space Station started in October 2015, and here we report analyses of events associated with the following gravitational wave events: GW151226, GW170104, GW170608, GW170814 and GW170817. Although only upper limits on gamma-ray emission are obtained, they correspond to a luminosity of $10^{49}sim10^{53}$ erg s$^{-1}$ in the GeV energy band depending on the distance and the assumed time duration of each event, which is approximately the order of luminosity of typical short gamma-ray bursts. This implies there will be a favorable opportunity to detect high-energy gamma-ray emission in further observations if additional gravitational wave events with favorable geometry will occur within our field-of-view. We also show the sensitivity of {sl CALET} for gamma-ray transient events which is the order of $10^{-7}$~erg,cm$^{-2}$,s$^{-1}$ for an observation of 100~s duration.
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n in 25 minutes. No significant time variations on timescales of 1 s to 4 days were found in the GW error region. The $3sigma$ upper limits for the X-ray emission associated with the GW event in 2--20 keV were 9.5 $times 10^{-10}$, 2.3 $times 10^{-10}$, and 0.8 $times 10^{-10}$ ergs cm$^{-2}$ s$^{-1}$ for the time scale of $sim$ 1000 s, 1 day, and 10 days, respectively. If GW events are associated with short GRBs like GRB 050709, MAXI will be able to detect X-ray emissions from the source.
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