N. Kawai
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View article: Thermonuclear Superburst of MAXI J1752−457 Observed with NinjaSat and MAXI
Thermonuclear Superburst of MAXI J1752−457 Observed with NinjaSat and MAXI Open
An uncatalogued bright X-ray transient was detected with MAXI on 2024 November 9, named MAXI J1752−457. The NinjaSat X-ray observatory promptly observed the source from November 10 to 18, while the small angular separation from the Sun ham…
View article: Possible X-ray Cocoon Emission from GRB 050709
Possible X-ray Cocoon Emission from GRB 050709 Open
The detection of the short gamma-ray burst (SGRB) 050709 by the HETE-2 satellite opened a new window into understanding the nature of SGRBs, offering clues about their emission mechanism and progenitors, with the crucial aid of optical fol…
View article: Evolution of accretion disk structure of the black hole X-ray binary MAXI J1820+070 during the rebrightening phase
Evolution of accretion disk structure of the black hole X-ray binary MAXI J1820+070 during the rebrightening phase Open
To understand the evolution of global accretion disk structure in the “rebrightening” phase of MAXI J1820+070, we perform a comprehensive analysis of its near infrared/optical/UV to X-ray spectral energy distribution (SED) utilizing data o…
View article: The 2018 X-Ray and Radio Outburst of Magnetar XTE J1810-197
The 2018 X-Ray and Radio Outburst of Magnetar XTE J1810-197 Open
We present the earliest X-ray observations of the 2018 outburst of XTE. J1810-197, the first outburst since its 2003 discovery as the prototypical transient and radio-emitting anomalous X-ray pulsar (AXP). The Monitor of Allsky X-ray Image…
View article: EXTRAORDINARY LUMINOUS SOFT X-RAY TRANSIENT MAXI J0158–744 AS AN IGNITION OF A NOVA ON A VERY MASSIVE O-Ne WHITE DWARF
EXTRAORDINARY LUMINOUS SOFT X-RAY TRANSIENT MAXI J0158–744 AS AN IGNITION OF A NOVA ON A VERY MASSIVE O-Ne WHITE DWARF Open
We present the observation of an extraordinary luminous soft X-ray transient, MAXI J0158-744, by the Monitor of All-sky X-ray Image (MAXI) on 2011 November 11. This transient is characterized by a soft X-ray spectrum, a short duration (1.3…
View article: Optical and X-ray variations during five outbursts of Aql X-1 in 3.6 yr from 2016
Optical and X-ray variations during five outbursts of Aql X-1 in 3.6 yr from 2016 Open
We analysed optical/X-ray quasi-simultaneous light curves of Aql X-1, obtained by Monitor of All-sky X-ray Image, Zwicky Transient Facility, and Las Cumbres Observatory Global Telescope network in about 3.6 yr from 2016, for understanding …
View article: Optical and X-ray variations during 5 outbursts of Aql X-1 in 3.6 years from 2016
Optical and X-ray variations during 5 outbursts of Aql X-1 in 3.6 years from 2016 Open
We analyzed optical/X-ray quasi-simultaneous light curves of Aql X-1, obtained by MAXI (Monitor of All-sky X-ray Image), ZTF (Zwicky Transient Facility) and LCO (Las Cumbres Observatory) in about 3.6 years from 2016, for understanding elec…
View article: GRB 221009A: Discovery of an Exceptionally Rare Nearby and Energetic Gamma-Ray Burst
GRB 221009A: Discovery of an Exceptionally Rare Nearby and Energetic Gamma-Ray Burst Open
We report the discovery of the unusually bright long-duration gamma-ray burst (GRB), GRB 221009A, as observed by the Neil Gehrels Swift Observatory (Swift), Monitor of All-sky X-ray Image, and Neutron Star Interior Composition Explorer Mis…
View article: GRB 221009A: Discovery of an Exceptionally Rare Nearby and Energetic Gamma-Ray Burst
GRB 221009A: Discovery of an Exceptionally Rare Nearby and Energetic Gamma-Ray Burst Open
We report the discovery of the unusually bright long-duration gamma-ray burst (GRB), GRB 221009A, as observed by the Neil Gehrels Swift Observatory (Swift), Monitor of All-sky X-ray Image (MAXI), and Neutron Star Interior Composition Explo…
View article: Discovery of a new supergiant fast X-ray transient MAXI J0709−159 associated with the Be star LY Canis Majoris
Discovery of a new supergiant fast X-ray transient MAXI J0709−159 associated with the Be star LY Canis Majoris Open
We report on the discovery of a new supergiant fast X-ray transient (SFXT), MAXI J0709−159, and its identification with LY CMa (also known as HD 54786). On 2022 January 25, a new flaring X-ray object, named MAXI J0709−159, was detected by …
View article: Multiwavelength observations of the black hole X-ray binary MAXI J1820+070 in the rebrightening phase
Multiwavelength observations of the black hole X-ray binary MAXI J1820+070 in the rebrightening phase Open
We report the results of quasi-simultaneous multiwavelength (near-infrared, optical, UV, and X-ray) observations of the Galactic X-ray black hole binary MAXI J1820+070 performed in 2019 May 10–13, ∼60 d after the onset of the first rebrigh…
View article: The evaluation of school children's altered consciousness by intervention of 'Shokuiku (food and nutrition education)' program integrated with school lunch menu using local cuisine 'Seigaku-mochi' in Chiba, Japan
The evaluation of school children's altered consciousness by intervention of 'Shokuiku (food and nutrition education)' program integrated with school lunch menu using local cuisine 'Seigaku-mochi' in Chiba, Japan Open
We evaluated the effect of Shokuiku (Japanese style food education) intervention program, unifying the lecture on the soul and history of traditional cuisine 'Seigaku-mochi' of Chiba-prefecture, and school lunch using it for 4th to 6th-gra…
View article: Development and Validation of an Analytical Method for Simultaneous Determination of Perfluoroalkyl Acids in Drinking Water by Liquid Chromatography/Tandem Mass Spectrometry
Development and Validation of an Analytical Method for Simultaneous Determination of Perfluoroalkyl Acids in Drinking Water by Liquid Chromatography/Tandem Mass Spectrometry Open
The environmental presence and drinking water contamination of per- and polyfluoroalkyl substances (PFAS) have been reported since the early 2000s. This study seeks to develop a liquid chromatography/tandem mass spectrometry analytical met…
View article: Gravitational wave physics and astronomy in the nascent era
Gravitational wave physics and astronomy in the nascent era Open
The detections of gravitational waves (GW) by the LIGO/Virgo collaborations provide various possibilities for both physics and astronomy. We are quite sure that GW observations will develop a lot, both in precision and in number, thanks to…
View article: PETREL: Platform for Extra and Terrestrial Remote Examination with LCTF
PETREL: Platform for Extra and Terrestrial Remote Examination with LCTF Open
A small satellite ”PETREL” for UV astronomy and remote sensing with ”tunable” multi-spectral cameras conducted by an academia-industrial collaboration is presented. This project was originally proposed by an astronomer who desired a satell…
View article: Deep Modeling of Quasar Variability
Deep Modeling of Quasar Variability Open
Quasars have long been known as intrinsically variable sources, but the physical mechanism underlying the temporal optical/UV variability is still not well understood. We propose a novel nonparametric method for modeling and forecasting th…
View article: Overview of KAGRA : KAGRA science
Overview of KAGRA : KAGRA science Open
KAGRA is a newly build gravitational-wave observatory, a laser interferometer\nwith 3 km arm length, located in Kamioka, Gifu, Japan. In this paper in the\nseries of KAGRA-featured articles, we discuss the science targets of KAGRA\nproject…
View article: Kojima-1Lb Is a Mildly Cold Neptune around the Brightest Microlensing Host Star
Kojima-1Lb Is a Mildly Cold Neptune around the Brightest Microlensing Host Star Open
We report the analysis of additional multiband photometry and spectroscopy and new adaptive optics (AO) imaging of the nearby planetary microlensing event TCP J05074264+2447555 (Kojima-1), which was discovered toward the Galactic anticente…
View article: Okayama Astrophysical Observatory Wide-Field Camera
Okayama Astrophysical Observatory Wide-Field Camera Open
We report on the development of a wide-field near-infrared (0.9–2.5$\, \mu$m) camera built as a renewal of the existing classical Cassegrain 0.91 m telescope at Okayama Astrophysical Observatory. The optics system was replaced with fast hy…
View article: Near-infrared polarimetric study of near-Earth object 252P/LINEAR: an implication of scattered light from the evolved dust particles
Near-infrared polarimetric study of near-Earth object 252P/LINEAR: an implication of scattered light from the evolved dust particles Open
Context. Comets undergo resurfacing due to solar radiation, while their primordial interiors remain unchanged. Multi-epoch observations of comets enable us to characterize a change in sublimation pattern as a function of heliocentric dista…
View article: 6U CubeSat for Ultraviolet Time-Domain Astronomy
6U CubeSat for Ultraviolet Time-Domain Astronomy Open
A wide-field ultraviolet observatory for time-domain astronomy utilizing 6U CubeSat is presented. Ultraviolet waveband is one of the unexplored fields in astronomy. Potential targets are short duration transient sources in UV-band: early-p…
View article: The fast, luminous ultraviolet transient AT2018cow: extreme supernova, or disruption of a star by an intermediate-mass black hole?
The fast, luminous ultraviolet transient AT2018cow: extreme supernova, or disruption of a star by an intermediate-mass black hole? Open
Wide-field optical surveys have begun to uncover large samples of fast (trise ≲ 5 d), luminous (Mpeak < -18), blue transients. While commonly attributed to the breakout of a supernova shock into a dense wind, the great distances to the …
View article: X-Ray, Optical, and Near-infrared Monitoring of the New X-Ray Transient MAXI J1820+070 in the Low/Hard State
X-Ray, Optical, and Near-infrared Monitoring of the New X-Ray Transient MAXI J1820+070 in the Low/Hard State Open
We report X-ray, optical, and near-infrared monitoring of the new X-ray transient MAXI J1820+070 discovered with MAXI on 2018 March 11. Its X-ray intensity reached ∼2 crab at 2–20 keV at the end of March, and then gradually decreased until…
View article: J-GEM follow-up observations of the gravitational wave source GW151226
J-GEM follow-up observations of the gravitational wave source GW151226 Open
We report the results of optical–infrared follow-up observations of the gravitational wave (GW) event GW151226 detected by the Advanced LIGO in the framework of J-GEM (Japanese collaboration for Gravitational wave ElectroMagnetic follow-up…
View article: Discovery and state transitions of the new Galactic black hole candidate MAXI J1535−571
Discovery and state transitions of the new Galactic black hole candidate MAXI J1535−571 Open
We report on the detection and subsequent X-ray monitoring of the new Galactic black hole candidate MAXI J1535−571 with the Gas Slit Camera onboard Monitor of All-sky X-ray Image (MAXI/GSC). After the discovery on 2017 September 2, made in…
View article: Late engine activity of GRB 161017A revealed by early optical observations
Late engine activity of GRB 161017A revealed by early optical observations Open
The long gamma-ray burst GRB 161017A was detected by Fermi and Swift, and its afterglow was observed by the MITSuME 50 cm optical telescope promptly, about 50 s after the burst. Early optical observations revealed that the optical light cu…
View article: Conceptual design of a wide-field near UV transient survey in a 6U CubeSat
Conceptual design of a wide-field near UV transient survey in a 6U CubeSat Open
A conceptual design of a wide-field near UV transient survey in a 6U CubeSat is presented. Ultraviolet is one of the frontier in the transient astronomy. To open up the discovery region, we are developing a 6U CubeSat for transient explora…
View article: MAXI upper limits of the electromagnetic counterpart of GW170817
MAXI upper limits of the electromagnetic counterpart of GW170817 Open
We report on the Monitor of All-sky X-ray Image (MAXI) observation of the gravitational-wave (GW) event GW170817 and the electromagnetic counterpart of GW170817. GW170817 is a binary neutron star coalescence candidate detected by the Advan…