CALET UPPER LIMITS ON X-RAY AND GAMMA-RAY COUNTERPARTS OF GW151226

We present upper limits in the hard X-ray and gamma-ray bands at the time of the Laser Interferometer Gravitational-wave Observatory (LIGO) gravitational-wave event GW151226 derived from the CALorimetric Electron Telescope (CALET) observation. The main instrument of CALET, CALorimeter (CAL), observes gammarays from similar to 1 GeV up to 10 TeV with a field of view of similar to 2 sr. The CALET gamma-ray burst monitor (CGBM) views similar to 3 sr and similar to 2 pi 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 GW151226 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 (similar to 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 a 1 s 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.