Mutsumi Sugizaki

Relativistic jet activity from the tidal disruption of a star by a massive black hole

Supermassive black holes have powerful gravitational fields with strong gradients that can destroy stars that get too close, producing a bright flare in ultraviolet and X-ray spectral regions from stellar debris that forms an accretion disk around the black hole. The aftermath of this process may have been seen several times over the past two decades in the form of sparsely sampled, slowly fading emission from distant galaxies, but the onset of the stellar disruption event has not hitherto been observed. Here we report observations of a bright X-ray flare from the extragalactic transient Swift J164449.3+573451. This source increased in brightness in the X-ray band by a factor of at least 10,000 since 1990 and by a factor of at least 100 since early 2010. We conclude that we have captured the onset of relativistic jet activity from a supermassive black hole. A companion paper comes to similar conclusions on the basis of radio observations. This event is probably due to the tidal disruption of a star falling into a supermassive black hole, but the detailed behaviour differs from current theoretical models of such events.D. N. Burrows , J. A. Kennea , G. Ghisellini , V. Mangano , B. Zhang , K. L. Page , M. Eracleous , P. Romano , T. Sakamoto , A. D. Falcone , J. P. Osborne , S. Campana , A. P. Beardmore , A. A. Breeveld , M. M. Chester , R. Corbet , S. Covino , J. R. Cummings , P. D’Avanzo , V. D’Elia , P. Esposito , P. A. Evans , D. Fugazza, J. M. Gelbord , K. Hiroi , S. T. Holland , K. Y. Huang , M. Im, G. Israel , Y. Jeon , Y.-B. Jeon , N. Kawai , H. A. Krimm , P. Mészáros , H. Negoro , N. Omodei , W.K. Park , J. S. Perkins , M. Sugizaki , H.-I. Sung , G. Tagliaferri , E. Troja , Y. Ueda, Y. Urata, R. Usui , L. A. Antonelli , S. D. Barthelmy , G. Cusumano , P. Giommi , F. E. Marshall , A. Melandri , M. Perri , J. L. Racusin , B. Sbarufatti , M. H. Siegel , & N. Gehrels 21

Relativistic jet activity from the tidal disruption of a star by a massive black hole [Discovery of the onset of rapid accretion by a dormant massive black hole]

Supermassive black holes have powerful gravitational fields with strong gradients that can destroy stars that get too close, producing a bright flare in ultraviolet and X-ray spectral regions from stellar debris that forms an accretion disk around the black hole. The aftermath of this process may have been seen several times over the past two decades in the form of sparsely sampled, slowly fading emission from distant galaxies, but the onset of the stellar disruption event has not hitherto been observed. Here we report observations of a bright X-ray flare from the extragalactic transient Swift J164449.3+573451. This source increased in brightness in the X-ray band by a factor of at least 10,000 since 1990 and by a factor of at least 100 since early 2010. We conclude that we have captured the onset of relativistic jet activity from a supermassive black hole. A companion paper comes to similar conclusions on the basis of radio observations. This event is probably due to the tidal disruption of a star falling into a supermassive black hole, but the detailed behaviour differs from current theoretical models of such events.D. N. Burrows , J. A. Kennea , G. Ghisellini , V. Mangano , B. Zhang , K. L. Page , M. Eracleous , P. Romano , T. Sakamoto , A. D. Falcone , J. P. Osborne , S. Campana , A. P. Beardmore , A. A. Breeveld , M. M. Chester , R. Corbet , S. Covino , J. R. Cummings , P. D’Avanzo , V. D’Elia , P. Esposito , P. A. Evans , D. Fugazza, J. M. Gelbord , K. Hiroi , S. T. Holland , K. Y. Huang , M. Im, G. Israel , Y. Jeon , Y.-B. Jeon , N. Kawai , H. A. Krimm , P. Mészáros , H. Negoro , N. Omodei , W.K. Park , J. S. Perkins , M. Sugizaki , H.-I. Sung , G. Tagliaferri , E. Troja , Y. Ueda, Y. Urata, R. Usui , L. A. Antonelli , S. D. Barthelmy , G. Cusumano , P. Giommi , F. E. Marshall , A. Melandri , M. Perri , J. L. Racusin , B. Sbarufatti , M. H. Siegel , & N. Gehrels 21

The MAXI Mission on the ISS: Science and Instruments for Monitoring All-Sky X-Ray Images

The Monitor of All-sky X-ray Image (MAXI) mission is the first astronomical payload to be installed on the Japanese Experiment Module — Exposed Facility (JEM-EF or Kibo-EF) on the International Space Station. It has two types of X-ray slit cameras with wide FOVs and two kinds of X-ray detectors consisting of gas proportional counters covering the energy range of 2 to 30 keV and X-ray CCDs covering the energy range of 0.5 to 12 keV. MAXI will be more powerful than any previous X-ray All Sky Monitor payloads, being able to monitor hundreds of Active Galactic Nuclei. A realistic simulation under optimal observation conditions suggests that MAXI will provide all-sky images of X-ray sources of � 20 mCrab (� 7 � 10 � 10 erg cm � 2 s � 1 in the energy band of 2–30 keV) from observations during one ISS orbit (90 min), � 4.5 mCrab for one day, and � 2 mCrab for one week. The final detectability of MAXI could be � 0.2 mCrab for two years, which is comparable to the source confusion limit of the MAXI field of view (FOV). The MAXI objectives are: (1) to alert the community to X-ray novae and transient X-ray sources, (2) to monitor long-term variabilities of X-ray sources, (3) to stimulate multi-wavelength observations of variable objects, (4) to create unbiased X-ray source cataloges, and (5) to observe diffuse cosmic X-ray emissions, especially with better energy resolution for soft X-rays down to 0.5 keV.

Gas Slit Camera (GSC) onboard MAXI on ISS

The Gas Slit Camera (GSC) is an X-ray instrument on the MAXI (Monitor of All-sky X-ray Image) mission on the International Space Station. It is designed to scan the entire sky every 92-minute orbital period in the 2‐30 keV band and to achieve the highest sensitivity among the X-ray all-sky monitors ever flown so far. The GSC employs large-area position-sensitive proportional counters with the total detector area of 5350 cm 2 . The on-board data processor has functions to format telemetry data as well as to control the high voltage of the proportional counters to protect them from the particle irradiation. The paper describes the instruments, on-board data processing, telemetry data formats, and performance specifications expected from the ground calibration tests.

In-Orbit Performance of MAXI Gas Slit Camera (GSC) on ISS

We report the in-orbit performance of the Gas Slit Camera (GSC) on the MAXI (Monitor of All-sky X-ray Image) mission carried on the International Space Station (ISS). Its commissioning operation started on August 8, 2009, confirmed the basic performances of the effective area in the energy band of 2--30 keV, the spatial resolution of the slit-and-slat collimator and detector with 1.5 degree FWHM, the source visibility of 40-150 seconds for each scan cycle, and the sky coverage of 85% per 92-minute orbital period and 95% per day. The gas gains and read-out amplifier gains have been stable within 1%. The background rate is consistent with the past X-ray experiments operated at the similar low-earth orbit if its relation with the geomagnetic cutoff rigidity is extrapolated to the high latitude. We also present the status of the in-orbit operation and the calibration of the effective area and the energy response matrix using Crab-nebula data.

Astro-E hard x-ray detector

Astro-E is the x-ray satellite to be launched in the year 2000 by Inst. of Space & Astronautical Science. This report deals with the design and expected performance of the hard x-ray detector (HXD), one of the 3 experiments aboard Astro- E. The HXD is a combination of GSO/BGO well-type phoswich counters and silicon PIN diodes: the two combined will cover a wide energy band of 10 - 700 keV. The detector is characterized by its low background of approximately 10-5/s/cm2/keV and its sensitivity higher than any past missions between a few 10 keV and several 100 keV. Combined with the other 2 experiments, a micro-calorimeter array (XRS) and 4 CCD arrays (XIS), both with x-ray mirrors, the mission will cover the soft and hard x-ray range at a highest sensitivity.

THE ACCRETION DISK AND IONIZED ABSORBER OF THE 9.7 hr DIPPING BLACK HOLE BINARY MAXI J1305–704

We report the results from X-ray studies of the newly discovered black hole candidate MAXI J1305–704 based on Suzaku and Swift observations in the low/hard and high/soft states, respectively. The long Suzaku observation shows two types of clear absorption dips, both of which recur on a dip interval of 9.74 ± 0.04 hr, which we identify with the orbital period. There is also partially ionized absorption in the nondip (persistent) emission in both the high/soft state and, very unusually, the low/hard state. However, this absorption (in both states) has substantially lower ionization than that seen in other high inclination systems, where the material forms a homogeneous disk wind. Here instead the absorption is most likely associated with clumpy, compact structures associated with the dipping material, which we see uniquely in this source likely because we view it at a very large inclination angle. A large inclination angle is also favored, together with a low black hole mass, to explain the high disk temperature seen in the fairly low luminosity high/soft state, as Doppler boosting enhances the disk temperature at high inclination. The disk radius inferred from these data is significantly smaller than that of the soft component seen in the low/hard state, supporting models where the disk is truncated at low luminosities. We find, however, that the lack of variability power on timescales of ~50 s in the Suzaku low/hard state data is difficult to explain, even with a low-mass black hole.

A PROPELLER-EFFECT INTERPRETATION OF MAXI/GSC LIGHT CURVES OF 4U 1608–52 AND Aql X-1 AND APPLICATION TO XTE J1701–462

We present the luminosity dwell-time distributions during the hard states of two low-mass X-ray binaries containing a neutron star (NS), 4U 1608?52 and Aql X-1, observed with MAXI/GSC. The luminosity distributions show a steep cutoff on the low-luminosity side at ~1.0 ? 1036?erg?s?1 in both sources. The cutoff implies a rapid luminosity decrease in their outburst decay phases and this decrease can be interpreted as being due to the propeller effect. We estimate the surface magnetic field of 4U 1608?52 to be (0.5-1.6) ? 108?G and Aql X-1 to be (0.6-1.9) ? 108?G from the cutoff luminosity and apply the same propeller mechanism to the similar rapid luminosity decrease observed in the transient Z source, XTE J1701?462, with RXTE/ASM. Assuming that the spin period of the NS is on the order of milliseconds, the observed cutoff luminosity implies a surface magnetic field on the order of 109?G.

Discovery of a Cyclotron Resonance Feature in the X-Ray Spectrum of GX 304−1 with RXTE and Suzaku during Outbursts Detected by MAXI in 2010

We report the discovery of a cyclotron resonance scattering feature (CRSF) in the X-ray spectrum of GX 304-1, obtained by RXTE and Suzaku during major outbursts detected by MAXI in 2010. The peak intensity in August reached 600 mCrab in the 2-20 keV band, which is the highest ever observed from this source. The RXTE observations on more than twenty occasions and one Suzaku observation revealed a spectral absorption feature at around 54 keV, which is the first CRSF detection from this source. The estimated strength of surface magnetic field,

The First MAXI/GSC Catalog in the High Galactic-Latitude Sky

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