共查询到20条相似文献，搜索用时 31 毫秒
1.
The rotational energy of a black hole surrounded by a torus is released through several channels. We have determined that a minor fraction of the energy is released in baryon-poor outflows from a differentially rotating open magnetic flux tube, and a major fraction of about eta/2 is released in gravitational radiation by the torus with angular velocity eta similar 0.2 to 0.5 relative to that of the black hole. We associate the energy emitted in baryon-poor outflows with gamma-ray bursts. The remaining fraction is released in torus winds, thermal emissions, and (conceivably) megaelectron-volt neutrino emissions. The emitted gravitational radiation can be detected by gravitational wave experiments and provides a method for identifying Kerr black holes in the Universe. 相似文献
2.
Mazzali PA Valenti S Della Valle M Chincarini G Sauer DN Benetti S Pian E Piran T D'Elia V Elias-Rosa N Margutti R Pasotti F Antonelli LA Bufano F Campana S Cappellaro E Covino S D'Avanzo P Fiore F Fugazza D Gilmozzi R Hunter D Maguire K Maiorano E Marziani P Masetti N Mirabel F Navasardyan H Nomoto K Palazzi E Pastorello A Panagia N Pellizza LJ Sari R Smartt S Tagliaferri G Tanaka M Taubenberger S Tominaga N Trundle C Turatto M 《Science (New York, N.Y.)》2008,321(5893):1185-1188
The only supernovae (SNe) to show gamma-ray bursts (GRBs) or early x-ray emission thus far are overenergetic, broad-lined type Ic SNe (hypernovae, HNe). Recently, SN 2008D has shown several unusual features: (i) weak x-ray flash (XRF), (ii) an early, narrow optical peak, (iii) disappearance of the broad lines typical of SN Ic HNe, and (iv) development of helium lines as in SNe Ib. Detailed analysis shows that SN 2008D was not a normal supernova: Its explosion energy (E approximately 6x10(51) erg) and ejected mass [ approximately 7 times the mass of the Sun (M(middle dot in circle))] are intermediate between normal SNe Ibc and HNe. We conclude that SN 2008D was originally a approximately 30 M(middle dot in circle) star. When it collapsed, a black hole formed and a weak, mildly relativistic jet was produced, which caused the XRF. SN 2008D is probably among the weakest explosions that produce relativistic jets. Inner engine activity appears to be present whenever massive stars collapse to black holes. 相似文献
3.
We report an extremely rapid mechanism for magnetic field amplification during the merger of a binary neutron star system. This has implications for the production of the short class of gamma-ray bursts, which recent observations suggest may originate in such mergers. In detailed magnetohydrodynamic simulations of the merger process, the fields are amplified by Kelvin-Helmholtz instabilities beyond magnetar field strength and may therefore represent the strongest magnetic fields in the universe. The amplification occurs in the shear layer that forms between the neutron stars and on a time scale of only 1 millisecond, that is, long before the remnant can collapse into a black hole. 相似文献
4.
Fermi LAT Collaboration Ackermann M Ajello M Ballet J Barbiellini G Bastieri D Belfiore A Bellazzini R Berenji B Blandford RD Bloom ED Bonamente E Borgland AW Bregeon J Brigida M Bruel P Buehler R Buson S Caliandro GA Cameron RA Caraveo PA Cavazzuti E Cecchi C Çelik Ö Charles E Chaty S Chekhtman A Cheung CC Chiang J Ciprini S Claus R Cohen-Tanugi J Corbel S Corbet RH Cutini S de Luca A den Hartog PR de Palma F Dermer CD Digel SW do Couto e Silva E Donato D Drell PS Drlica-Wagner A Dubois R 《Science (New York, N.Y.)》2012,335(6065):189-193
Gamma-ray binaries are stellar systems containing a neutron star or black hole, with gamma-ray emission produced by an interaction between the components. These systems are rare, even though binary evolution models predict dozens in our Galaxy. A search for gamma-ray binaries with the Fermi Large Area Telescope (LAT) shows that 1FGL J1018.6-5856 exhibits intensity and spectral modulation with a 16.6-day period. We identified a variable x-ray counterpart, which shows a sharp maximum coinciding with maximum gamma-ray emission, as well as an O6V((f)) star optical counterpart and a radio counterpart that is also apparently modulated on the orbital period. 1FGL J1018.6-5856 is thus a gamma-ray binary, and its detection suggests the presence of other fainter binaries in the Galaxy. 相似文献
5.
F Ronning C Kim DL Feng DS Marshall AG Loeser LL Miller JN Eckstein I Bozovic Z Shen 《Science (New York, N.Y.)》1998,282(5396):2067-2072
An angle-resolved photoemission study is reported on Ca2CuO2Cl2, a parent compound of high-Tc superconductors. Analysis of the electron occupation probability, n(k), from the spectra shows a steep drop in spectral intensity across a contour that is close to the Fermi surface predicted by the band calculation. This analysis reveals a Fermi surface remnant, even though Ca2CuO2Cl2 is a Mott insulator. The lowest energy peak exhibits a dispersion with approximately the &cjs3539;coskxa - coskya&cjs3539; form along this remnant Fermi surface. Together with the data from Dy-doped Bi2Sr2CaCu2O8+delta, these results suggest that this d-wave-like dispersion of the insulator is the underlying reason for the pseudo gap in the underdoped regime. 相似文献
6.
Recent observations support the suggestion that short-duration gamma-ray bursts are produced by compact star mergers. The x-ray flares discovered in two short gamma-ray bursts last much longer than the previously proposed postmerger energy-release time scales. Here, we show that they can be produced by differentially rotating, millisecond pulsars after the mergers of binary neutron stars. The differential rotation leads to windup of interior poloidal magnetic fields and the resulting toroidal fields are strong enough to float up and break through the stellar surface. Magnetic reconnection-driven explosive events then occur, leading to multiple x-ray flares minutes after the original gamma-ray burst. 相似文献
7.
Champion DJ Ransom SM Lazarus P Camilo F Bassa C Kaspi VM Nice DJ Freire PC Stairs IH van Leeuwen J Stappers BW Cordes JM Hessels JW Lorimer DR Arzoumanian Z Backer DC Bhat ND Chatterjee S Cognard I Deneva JS Faucher-Giguère CA Gaensler BM Han J Jenet FA Kasian L Kondratiev VI Kramer M Lazio J McLaughlin MA Venkataraman A Vlemmings W 《Science (New York, N.Y.)》2008,320(5881):1309-1312
Binary pulsar systems are superb probes of stellar and binary evolution and the physics of extreme environments. In a survey with the Arecibo telescope, we have found PSR J1903+0327, a radio pulsar with a rotational period of 2.15 milliseconds in a highly eccentric (e = 0.44) 95-day orbit around a solar mass (M(middle dot in circle)) companion. Infrared observations identify a possible main-sequence companion star. Conventional binary stellar evolution models predict neither large orbital eccentricities nor main-sequence companions around millisecond pulsars. Alternative formation scenarios involve recycling a neutron star in a globular cluster, then ejecting it into the Galactic disk, or membership in a hierarchical triple system. A relativistic analysis of timing observations of the pulsar finds its mass to be 1.74 +/- 0.04 M solar symbol, an unusually high value. 相似文献
8.
Aharonian F Akhperjanian AG Aye KM Bazer-Bachi AR Beilicke M Benbow W Berge D Berghaus P Bernlöhr K Boisson C Bolz O Borrel V Braun I Breitling F Brown AM Bussons Gordo J Chadwick PM Chounet LM Cornils R Costamante L Degrange B Dickinson HJ Djannati-Ataï A Drury LO Dubus G Emmanoulopoulos D Espigat P Feinstein F Fleury P Fontaine G Fuchs Y Funk S Gallant YA Giebels B Gillessen S Glicenstein JF Goret P Hadjichristidis C Hauser M Heinzelmann G Henri G Hermann G Hinton JA Hofmann W Holleran M 《Science (New York, N.Y.)》2005,309(5735):746-749
X-ray binaries are composed of a normal star in orbit around a neutron star or stellar-mass black hole. Radio and x-ray observations have led to the presumption that some x-ray binaries called microquasars behave as scaled-down active galactic nuclei. Microquasars have resolved radio emission that is thought to arise from a relativistic outflow akin to active galactic nuclei jets, in which particles can be accelerated to large energies. Very high energy gamma-rays produced by the interactions of these particles have been observed from several active galactic nuclei. Using the High Energy Stereoscopic System, we find evidence for gamma-ray emission of >100 gigaelectron volts from a candidate microquasar, LS 5039, showing that particles are also accelerated to very high energies in these systems. 相似文献
9.
Very-long-baseline interferometry observations have revealed a bright, compact radio component near the center of the expanding shell of supernova 1986J. The component, not present in earlier images, has an inverted radio spectrum different from that of the shell. Such an inversion has not been seen in the spectrum of any other supernova. The new component is likely radio emission associated either with accretion onto a black hole or with the nebula formed around an energetic young neutron star in the center of SN 1986J, which would directly link either a black hole or a neutron star to a modern supernova. 相似文献
10.
Schilling G 《Science (New York, N.Y.)》2000,290(5493):926-927
Most astrophysicists puzzling over what causes gamma ray bursts--short, intense explosions of high-energy photons that occur deep in space--now agree that the answer is a hypernova, the blast of energy released when a supermassive star collapses into a black hole. Two papers in this issue of Science (pp. 953 and 955), reporting on new x-ray observations of two gamma ray bursts, argue that the hypernova model tells only half of the story. On its way to becoming a black hole, the authors propose, the supermassive star actually collapses twice. 相似文献
11.
MC Lonergan 《Science (New York, N.Y.)》1997,278(5346):2103-2106
Although in principle semiconductor-metal (Schottky) diodes should be tunable by changing the work function of the metal, such flexibility cannot be achieved in a single device and in practice is often limited by interfacial states that cause Fermi-level pinning. A tunable diode is reported based on a hybrid inorganic-organic, n-indium phosphide&cjs3539;poly- (pyrrole)&cjs3539;nonaqueous electrolyte architecture. By electrochemically manipulating the work function of the conjugated polymer poly(pyrrole), the turn-on voltage (more precisely, the forward bias potential required to pass a particular current) of the diode can be continuously and actively tuned by more than 0.6 volt. The work highlights a distinguishing feature of conjugated polymers relative to more traditional semiconductor materials, namely, the ability of dopant ions to permeate conjugated polymers, thereby enabling electrochemical manipulation. 相似文献
12.
KS Thorne 《Science (New York, N.Y.)》2012,337(6094):536-538
Numerical simulations have revealed two types of physical structures, made from curved spacetime, that are attached to black holes: tendexes, which stretch or squeeze anything they encounter, and vortexes, which twist adjacent inertial frames relative to each other. When black holes collide, their tendexes and vortexes interact and oscillate (a form of nonlinear dynamics of curved spacetime). These oscillations generate gravitational waves, which can give kicks up to 4000 kilometers per second to the merged black hole. The gravitational waves encode details of the spacetime dynamics and will soon be observed and studied by the Laser Interferometer Gravitational Wave Observatory and its international partners. 相似文献
13.
A new computer code can solve Einstein's equations of general relativity for the dynamical evolution of a relativistic star cluster. The cluster may contain a large number of stars that move in a strong gravitational field at speeds approaching the speed of light. Unstable star clusters undergo catastrophic collapse to black holes. The collapse of an unstable cluster to a supermassive black hole at the center of a galaxy may explain the origin of quasars and active galactic nuclei. By means of a supercomputer simulation and color graphics, the whole process can be viewed in real time on a movie screen. 相似文献
14.
Margon B 《Science (New York, N.Y.)》1982,215(4530):247-252
A variety of recent optical, radio, and x-ray observation have confirmed the hypothesis that the peculiar star SS 433 is ejecting two narrow, opposed, highly collimated jets of matter at one-quarter the speed of light. This unique behavior is probably driven by mass exchange between a relatively normal star and a compact companion, either a neutron star or a black hole. However, numerous details regarding the energetics, radiation, acceleration, and collimation of the jets remain to be understood. This phenomenon may well be a miniature example of similar collimated ejection of gas by active extragalactic objects such as quasars and radio galaxies. 相似文献
15.
Mészáros P 《Science (New York, N.Y.)》2001,291(5501):79-84
Gamma-ray bursts (GRBs) are sudden, intense flashes of gamma rays that, for a few blinding seconds, light up in an otherwise fairly dark gamma-ray sky. They are detected at the rate of about once a day, and while they are on, they outshine every other gamma-ray source in the sky, including the sun. Major advances have been made in the last 3 or 4 years, including the discovery of slowly fading x-ray, optical, and radio afterglows of GRBs, the identification of host galaxies at cosmological distances, and evidence showing that many GRBs are associated with star-forming regions and possibly supernovae. Progress has been made in understanding how the GRB and afterglow radiation arises in terms of a relativistic fireball shock model. These advances have opened new vistas and questions on the nature of the central engine, the identity of their progenitors, the effects of the environment, and their possible gravitational wave, cosmic ray, and neutrino luminosity. The debates on these issues indicate that GRBs remain among the most mysterious puzzles in astrophysics. 相似文献
16.
We determined some basic properties of stars that produce spectacular gamma-ray bursts at the end of their lives. We assumed that accretion of the outer portion of the stellar core by a central black hole fuels the prompt emission and that fall-back and accretion of the stellar envelope later produce the plateau in the x-ray light curve seen in some bursts. Using x-ray data for three bursts, we estimated the radius of the stellar core to be approximately (1 - 3) x 10(10) cm and that of the stellar envelope to be approximately (1 - 2) x 10(11) cm. The density profile in the envelope is fairly shallow, with rho approximately r(-2) (where rho is density and r is distance from the center of the explosion). The rotation speeds of the core and envelope are approximately 0.05 and approximately 0.2 of the local Keplerian speed, respectively. 相似文献
17.
The Density of Hydrous Magmatic Liquids 总被引：2，自引：0，他引：2
Density measurements on several hydrous (相似文献
18.
One of the major astronomical discoveries of the last two decades was the detection of luminous x-ray binary star systems in which gravitational energy from accretion is released by the emission of x-ray photons, which have energies in the range of 0.1 to 10 kiloelectron volts. Recent observations have shown that some of these binary sources also emit photons in the energy range of 10(12) electron volts and above. Such sources contain a rotating neutron star that is accreting matter from a companion. Techniques to detect such radiation are ground-based, simple, and inexpensive. Four binary sources (Hercules X-1, 4U0115+63, Vela X-1, and Cygnus X-3) have been observed by at least two independent groups. Although the discovery of such very high energy "gamma-ray binaries" was not theoretically anticipated, models have now been proposed that attempt to explain the behavior of one or more of the sources. The implications of these observations is that a significant portion of the more energetic cosmic rays observed on Earth may arise from the action of similar sources within the galaxy during the past few million years. 相似文献
19.
Aharonian F Akhperjanian AG Bazer-Bachi AR Beilicke M Benbow W Berge D Bernlöhr K Boisson C Bolz O Borrel V Braun I Brown AM Bühler R Büsching I Carrigan S Chadwick PM Chounet LM Coignet G Cornils R Costamante L Degrange B Dickinson HJ Djannati-Ataï A Drury LO Dubus G Egberts K Emmanoulopoulos D Espigat P Feinstein F Ferrero E Fiasson A Fontaine G Funk S Funk S Füssling M Gallant YA Giebels B Glicenstein JF Goret P Hadjichristidis C Hauser D Hauser M Heinzelmann G Henri G Hermann G Hinton JA 《Science (New York, N.Y.)》2006,314(5804):1424-1427
The detection of fast variations of the tera-electron volt (TeV) (10(12) eV) gamma-ray flux, on time scales of days, from the nearby radio galaxy M87 is reported. These variations are about 10 times as fast as those observed in any other wave band and imply a very compact emission region with a dimension similar to the Schwarzschild radius of the central black hole. We thus can exclude several other sites and processes of the gamma-ray production. The observations confirm that TeV gamma rays are emitted by extragalactic sources other than blazars, where jets are not relativistically beamed toward the observer. 相似文献
20.