MAXI observations of GRBs

Abstract

Monitor of all-sky image (MAXI) Gas Slit Camera (GSC) detects gamma-ray bursts (GRBs) including the bursts with soft spectra, such as X-ray flashes (XRFs). MAXI/GSC is sensitive to the energy range from 2 to 30 keV. This energy range is lower than other currently operating instruments which is capable of detecting GRBs. Since the beginning of the MAXI operation on August 15, 2009, GSC observed 35 GRBs up to the middle of 2013. One third of them are also observed by other satellites. The rest of them show a trend to have soft spectra and low fluxes. Because of the contribution of those XRFs, the MAXI GRB rate is about three times higher than those expected from the BATSE log N - log P distribution. When we compare it to the observational results of the Wide-field X-ray Monitor on the High Energy Transient Explorer 2, which covers the the same energy range to that of MAXI/GSC, we find a possibility that many of MAXI bursts are XRFs with Epeak lower than 20 keV. We discuss the source of soft GRBs observed only by MAXI. The MAXI log N - log S distribution suggests that the MAXI XRFs distribute in closer distance than hard GRBs. Since the distributions of the hardness of galactic stellar flares and X-ray bursts overlap with those of MAXI GRBs, we discuss a possibility of a confusion of those galactic transients with the MAXI GRB samples.

12 figures

References in corpus (27)

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• The MAXI Mission on the ISS: Science and Instruments for Monitoring All Sky X-Ray Images
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• The luminosity function and the rate of Swift's Gamma Ray Bursts
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• The Cosmic Rate, Luminosity Function and Intrinsic Correlations of Long GRBs
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• In-Orbit Performance of MAXI Gas Slit Camera (GSC) on ISS
• A Redshift Determination for XRF 020903: First Spectroscopic Observations of an X-Ray Flash
• Global Properties of X-Ray Flashes and X-Ray-Rich Gamma-Ray Bursts Observed by Swift
• Afterglow Observations Shed New Light on the Nature of X-ray Flashes
• Solid-state Slit Camera (SSC) on Board MAXI
• Detailed optical and near-infrared polarimetry, spectroscopy and broadband photometry of the afterglow of GRB 091018: Polarisation evolution
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• A Spectacular Radio Flare from XRF 050416a at 40 days and Implications for the Nature of X-ray Flashes
• Simulations on High-z Long Gamma-Ray Burst Rate
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• Discovery of a New X-Ray Burst/Millisecond Accreting Pulsar HETE J1900.1-2455
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• Testing unified models for the origin of ultrahigh-energy cosmic rays and neutrinos: Multimessenger approaches with x-ray observations
• The Possible Electromagnetic Counterparts of the First High-Probability NSBH Merger LIGO/Virgo S190814bv
• X-ray upper limits of GW151226 with MAXI
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