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Register a new userSearch for Tens of MeV Neutrinos associated with Gamma-Ray Bursts in Super-Kamiokande
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A search for neutrinos produced in coincidence with Gamma-Ray Bursts(GRB) was conducted with the Super-Kamiokande (SK) detector. Between December 2008 and March 2017, the Gamma-ray Coordinates Network recorded 2208 GRBs that occurred during normal SK operation. Several time windows around each GRB were used to search for coincident neutrino events. No statistically significant signal in excess of the estimated backgrounds was detected. The $bar u_e$ fluence in the range from 8 MeV to 100 MeV in positron total energy for $bar u_e+prightarrow e^{+}+n$ was found to be less than $rm 5.07times10^5$ cm$^{-2}$ per GRB in 90% C.L. Upper bounds on the fluence as a function of neutrino energy were also obtained.
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We report the results from a search in Super-Kamiokande for neutrino signals coincident with the first detected gravitational wave events, GW150914 and GW151226, using a neutrino energy range from 3.5 MeV to 100 PeV. We searched for coincident neutrino events within a time window of $pm$500 seconds around the gravitational wave detection time. Four neutrino candidates are found for GW150914 and no candidates are found for GW151226. The remaining neutrino candidates are consistent with the expected background events. We calculated the 90% confidence level upper limits on the combined neutrino fluence for both gravitational wave events, which depends on event energy and topologies. Considering the upward going muon data set (1.6 GeV - 100 PeV) the neutrino fluence limit for each gravitational wave event is 14 - 37 (19 - 50) cm$^{-2}$ for muon neutrinos (muon antineutrinos), depending on the zenith angle of the event. In the other data sets, the combined fluence limits for both gravitational wave events range from 2.4$times 10^{4}$ to 7.0$times 10^{9}$ cm$^{-2}$.
We search for electron anti-neutrinos ($overline{ u}_e$) from long and short-duration gamma-ray bursts~(GRBs) using data taken by the KamLAND detector from August 2002 to June 2013. No statistically significant excess over the background level is found. We place the tightest upper limits on $overline{ u}_e$ fluence from GRBs below 7 MeV and place first constraints on the relation between $overline{ u}_e$ luminosity and effective temperature.
We report the results of a neutrino search in Super-Kamiokande for coincident signals with the first detected gravitational wave produced by a binary neutron star merger, GW170817, which was followed by a short gamma-ray burst, GRB170817A, and a kilonova/macronova. We searched for coincident neutrino events in the range from 3.5 MeV to $sim$100 PeV, in a time window $pm$500 seconds around the gravitational wave detection time, as well as during a 14-day period after the detection. No significant neutrino signal was observed for either time window. We calculated 90% confidence level upper limits on the neutrino fluence for GW170817. From the upward-going-muon events in the energy region above 1.6 GeV, the neutrino fluence limit is $16.0^{+0.7}_{-0.6}$ ($21.3^{+1.1}_{-0.8}$) cm$^{-2}$ for muon neutrinos (muon antineutrinos), with an error range of $pm5^{circ}$ around the zenith angle of NGC4993, and the energy spectrum is under the assumption of an index of $-2$. The fluence limit for neutrino energies less than 100 MeV, for which the emission mechanism would be different than for higher-energy neutrinos, is also calculated. It is $6.6 times 10^7$ cm$^{-2}$ for anti-electron neutrinos under the assumption of a Fermi-Dirac spectrum with average energy of 20 MeV.
The detection of six Fast Radio Bursts (FRBs) has recently been reported. FRBs are short duration ($sim$ 1 ms), highly dispersed radio pulses from astronomical sources. The physical interpretation for the FRBs remains unclear but is thought to involve highly compact objects at cosmological distance. It has been suggested that a fraction of FRBs could be physically associated with gamma-ray bursts (GRBs). Recent radio observations of GRBs have reported the detection of two highly dispersed short duration radio pulses using a 12 m radio telescope at 1.4 GHz. Motivated by this result, we have performed a systematic and sensitive search for FRBs associated with GRBs. We have observed five GRBs at 2.3 GHz using a 26 m radio telescope located at the Mount Pleasant Radio Observatory, Hobart. The radio telescope was automated to rapidly respond to Gamma-ray Coordination Network notifications from the Swift satellite and slew to the GRB position within $sim$ 140 s. The data were searched for pulses up to 5000 pc $rm cm^{-3}$ in dispersion measure and pulse widths ranging from 640 $rm mu$s to 25.60 ms. We did not detect any events $rm geq 6 sigma$. An in-depth statistical analysis of our data shows that events detected above $rm 5 sigma$ are consistent with thermal noise fluctuations only. A joint analysis of our data with previous experiments shows that previously claimed detections of FRBs from GRBs are unlikely to be astrophysical. Our results are in line with the lack of consistency noted between the recently presented FRB event rates and GRB event rates.
The result of a search for neutrino bursts from supernova explosions using the Super-Kamiokande detector is reported. Super-Kamiokande is sensitive to core-collapse supernova explosions via observation of their neutrino emissions. The expected number of events comprising such a burst is ~10^4 and the average energy of the neutrinos is in few tens of MeV range in the case of a core-collapse supernova explosion at the typical distance in our galaxy (10 kiloparsecs); this large signal means that the detection efficiency anywhere within our galaxy and well past the Magellanic Clouds is 100%. We examined a data set which was taken from May, 1996 to July, 2001 and from December, 2002 to October, 2005 corresponding to 2589.2 live days. However, there is no evidence of such a supernova explosion during the data-taking period. The 90% C.L. upper limit on the rate of core-collapse supernova explosions out to distances of 100 kiloparsecs is found to be 0.32 SN/year.
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