Kyoko Watanabe

Repeated injections of energy in the first 600?ms of the giant flare of SGR?1806 - 20

The massive flare of 27 December 2004 from the soft γ-ray repeater SGRu20091806–20, a possible magnetar, saturated almost all γ-ray detectors, meaning that the profile of the pulse was poorly characterized. An accurate profile is essential to determine physically what was happening at the source. Here we report the unsaturated γ-ray profile for the first 600u2009ms of the flare, with a time resolution of 5.48u2009ms. The peak of the profile (of the order of 107u2009photonsu2009cm-2u2009s-1) was reached ∼50u2009ms after the onset of the flare, and was then followed by a gradual decrease with superposed oscillatory modulations possibly representing repeated energy injections with ∼60-ms intervals. The implied total energy is comparable to the stored magnetic energy in a magnetar (∼ 1047u2009erg) based on the dipole magnetic field intensity (∼ 1015u2009G), suggesting either that the energy release mechanism was extremely efficient or that the interior magnetic field is much stronger than the external dipole field.On December 27, 2004, plasma particle detectors on the GEOTAIL spacecraft detected an extremely strong signal of hard X-ray photons from the giant flare of SGR1806-20, a magnetar candidate. While practically all gamma-ray detectors on any satellites were saturated during the first ~500 ms interval after the onset, one of the particle detectors on GEOTAIL was not saturated and provided unique measurements of the hard X-ray intensity and the profile for the first 600 ms interval with 5.48 ms time resolution. After ~50 ms from the initial rapid onset, the peak photon flux (integrated above ~50 keV) reached the order of 10^7 photons sec^{-1} cm^{-2}. Assuming a blackbody spectrum with kT=175 keV, we estimate the peak energy flux to be 21 erg sec^{-1} cm^{-2} and the fluence (for 0-600 ms) to be 2.4 erg cm^{-2}. The implied energy release comparable to the magnetic energy stored in a magnetar (~10^{47} erg) suggests an extremely efficient energy release mechanism.

Development of faster front end electronics for the SciCRT detector at Sierra Negra, Mexico

The SciBar Cosmic ray telescope (SciCRT) is installed on the top of the Sierra Negra volcano with the main goal of observing solar neutrons to investigate the ion acceleration process during solar flares. Using scintillator bars as a medium to stop energetic particles, the SciCRT is capable of recording both energy deposited on the bars and direction of the incoming particles with high resolution. The original DAQ system was used in neutrino oscillation experiment (low event rate), therefore operation of the electronics on cosmic ray experiment is limited. To improve the SciCRT performance as a solar neutron telescope, development of custom made DAQ electronics is essential. Our first step onto this task was the design and construction of a new fast readout back-end board using SiTCP. The installation of this new system on Sierra Negra and its further improvement on the data acquisition for the detector will be analyzed on separate paper on this conference. The development of new front end electronics is the next stage of the upgrading process. To achieve this goal, we are developing new electronics applying the time over threshold (ToT) technique, using a FPGA to process the signal from one 64 channel multi anode photomutiplier tube (MAPMT). In this paper we will present the details of this new system and several tests performed to guarantee its proper operation to detect solar neutrons.

Sensitivity of the SciBar Cosmic Ray Telescope (SciCRT) to solar neutrons

The SciBar Cosmic Ray Telescope (SciCRT) is aimed to help elucidate the acceleration mechanism of high-energy ions that may produce neutrons at the Sun. It is a fully active scintillator tracker which consists of 14,848 plastic scintillator bars, originally constructed for accelerator neutrino oscillation experiments. The SciCRT; it has a huge detector volume compared with conventional Solar Neutron Telescopes (SNTs), e.g. 15 times larger than Mexico SNT. Furthermore, the SciCRT can measure the energy deposition of each particle as neutron ADC data which have not been registered before. Neutron ADC data provide us with a precise measurement of energies deposited at the detector. The SciCRT was deployed at the summit of Mt. Sierra Negra (4,600 m) and began to acquire data in September 2013. Then we partially upgraded the DAQ system developed originally for an accelerator experiment, as the readout rate of the DAQ system was significantly limited for our experiment. nThis paper highlights sensitivity numerical studies of solar neutrons that the SciCRT is able to register. At first, we focus in the accuracy to determine the spectrum power-law index, assuming an instantaneous emission of solar neutrons. This is required to determine the power-law index within an error of ±1.0 in order to discuss the efficiency of the acceleration. Then in the case of the fixed power-law index, we discuss the capability of discriminating three different lengths of emission times: 0 min, 5 min, and 8 min. Finally we evaluate whether it is possible to discriminate a different combination of these two parameters simultaneously. Thus, we show that data from the SciCRT will unlock the degeneracy problem amid the emission time and the energy spectrum of solar neutrons.

Current status of SciCRT experiment and its expected future performance

Solar neutron telescopes (SNT) were designed and installed on high mountains to study particle acceleration mechanisms in solar surface. Of these, SciBar cosmic ray telescope (SciCRT) is a brand new telescope installed on the top of the Sierra Negra volcano in eastern Mexico (

Detection efficiency of the Solar Neutron Telescopes located at high altitudes

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Development of a pattern recognition algorithm for particle identification on the SciCRT in the Sierra Negra Volcano Summit

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Upgrade of a data acquisition system for SciBar Cosmic Ray Telescope (SciCRT) at Mt. Sierra Negra, Mexico

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A Catalog of Suzaku/WAM Hard X-Ray Solar Flares

W) composed of roughly 15000 scintillator bars, capable of detecting solar particles with both high efficiency and energy resolution. SciCRT is also useful to study the anisotropy of galactic cosmic ray muons. The implementation of SciCRT as a cosmic ray telescope began on September 2013, with

11pSP-4 Project for observing solar neutrons by using the SciBar Detector XIV : Revised Particle Identification using mini-SciCR data at Mount Negra, Mexico

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11pSP-5 Project for observing solar neutrons by using the SciBar Detector XV : Progress of developing of new Back End Board for fast readout

of the complete detector operative. After that, further improvement of the operating conditions on the place were made in order to maintain a stable data acquisition on the severe atmospheric conditions on high mountain (4600 m). In July 2015 we partially upgrade the DAQ system, installing a