Kazuo Hiroi

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.

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

AbstractWe present the first unbiased source catalog of the Monitor of All-sky X-ray Image (MAXI) mission athigh Galactic latitudes (|b|>10 ◦ ), produced from the first 7-month data (2009 September 1 to 2010 March31) of the Gas Slit Camera in the 4–10 keV band. We develop an analysis procedure to detect faint sourcesfrom the MAXI data, utilizing a maximum likelihood image fitting method, where the image response,background, and detailed observational conditions are taken into account. The catalog consists of 143X-ray sources above 7 sigma significance level with a limiting sensitivity of ∼ 1.5×10 −11 ergs cm −2 s −1 (1.2 mCrab) in the 4–10 keV band. Among them, we identify 38 Galactic/LMC/SMC objects, 48 galaxyclusters, 39 Seyfert galaxies, 12 blazars, and 1 galaxy. Other 4 sources are confused with multiple objects,and one remains unidentified. The log N - log S relation of extragalactic objects is in a good agreementwith the HEAO-1 A-2 result, although the list of the brightest AGNs in the entire sky has significantlychanged since that in 30 years ago.Key words:catalogs — surveys — galaxies: active — X-rays: galaxies1. INTRODUCTIONAll-sky X-ray surveys are powerful tools to investigatethe whole populations of active and hot phenomena inthe universe at the brightest flux end. The strong X-ray emitters include Galactic objects such as active stars,SNRs, pulsars, CVs, low mass and high mass X-ray bi-naries (with a neutron star or a black hole as the pri-mary), and extragalactic objects, mainly active galacticnuclei (AGNs; Seyfert galaxies and blazars) and clustersof galaxies. The source catalog consisting of a statisticallywell-defined sample detected from an unbiased survey isa primary product on which many subsequent studies arebased. For extragalactic populations, in particular, theseresults define the “local” sample in the present universe,the end point of their cosmological evolution. Thus, toestablish the statistical properties of bright X-ray sourcesusing the best quality data over the entire sky has alwaysbeen a key issue in high energy astrophysics.Past all-sky X-ray surveys indeed brought valuable in-formation on the X-ray source populations. In the softX-ray band, the ROSAT mission conducted an all-sky sur-vey in the 0.1–2.4 keV band, producing the ROSAT All-Sky Survey (RASS) Bright Source Catalog (BSC; Voges

Revisit of Local X-Ray Luminosity Function of Active Galactic Nuclei with the MAXI Extragalactic Survey

We construct a new X-ray (2--10 keV) luminosity function of Compton-thin active galactic nuclei (AGNs) in the local universe, using the first MAXI/GSC source catalog surveyed in the 4--10 keV band. The sample consists of 37 non-blazar AGNs at

Spectral Evolution of a New X-Ray Transient MAXI J0556−332 Observed by MAXI, Swift, and RXTE

z=0.002-0.2

Bright X-Ray Flares from the BL Lac Object Markarian 421, Detected with MAXI in 2010 January and February

, whose identification is highly (

A spectral study of the black hole candidate XTE J1752-223 in the high/soft state with MAXI, Suzaku, and Swift

>97%

Spectroscopic Observations of the WZ Sge-Type Dwarf Nova GW Librae during its 2007 Superoutburst

) complete. We confirm the trend that the fraction of absorbed AGNs with

Large X-ray flares on stars detected with MAXI/GSC: A universal correlation between the duration of a flare and its X-ray luminosity

N_{\rm H} > 10^{22}