排序方式: 共有46条查询结果,搜索用时 15 毫秒
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F. Perotti A. Della Ventura G. Villa L. Bassani C. Butler G. Di Cocco R.E. Baker J.N. Carter A.J. Dean 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,3(10-12)
The black hole candidate Cygnus X-1 was observed in the hard X ray - soft γ ray energy range by the MISO telescope on two different occasions: in September 1979 and May 1980. We have measured two hard X-ray states of the source: in 1979 the observed spectrum confirms the superlow state measured in the same period by the HEAO-3 satellite, while in 1980 the MISO X-ray data are consistent with the so called low state of Cygnus X-1. In both occasions, no γ -ray excess has been observed above 200 KeV. 相似文献
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Alan M. Levine Hale Bradt Edward H. Morgan Ron Remillard The MIT/GSFC ASM Team 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2006,38(12):2970-2975
Selected results from the Rossi X-ray Timing Explorer All-Sky Monitor are presented to illustrate the phenomenology of the light curves. The sensitivity to periodic intensity variations is indicated by the folded light curve of AM Her. The gray line between transient and persistent sources is emphasized. Light curves of a range of systems comprising black holes or neutron stars and low and high mass companion stars show that the behavior of these systems is often, but not always, characteristic. 相似文献
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G. Beskin A. Biryukov S. Karpov V. Plokhotnichenko V. Debur 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
General properties of accretion onto isolated stellar-mass black holes in the Galaxy are discussed. An analysis of plasma internal energy growth during the infall is performed. Adiabatic heating of collisionless accretion flow due to magnetic adiabatic invariant conservation is 25% more efficient than in the standard non-magnetized gas case. It is shown that magnetic field line reconnections in discrete current sheets lead to significant nonthermal electron component formation, which leads to a formation of a hard (UV, X-ray, up to gamma), highly variable spectral component in addition to the standard synchrotron optical component first derived by Shvartsman generated by thermal electrons in the magnetic field of the accretion flow. Properties of accretion flow emission variability are discussed. Observation results of two single black hole candidates – gravitational lens MACHO-1999-BLG-22 and radio-loud X-ray source with featureless optical spectrum J1942+10 – in optical band with high temporal resolution are presented and interpreted in the framework of the proposed model. 相似文献
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J.H. Swank 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2006,38(12):2959-2963
The prime scientific objectives of the Rossi X-ray Timing Explorer (RXTE) were the study of astrophysical compact objects: black holes (galactic and extragalactic), many types of neutron stars, and accreting white dwarfs. RXTE was successful in achieving its original observing objectives of large area and high time resolution observations with broadband (2–200 keV) spectra, scheduled flexibly enough to enable observations of targets of opportunity on any timescale greater than a few hours. These capabilities enabled qualitatively new discoveries about dynamical timescale phenomena related to neutron stars and black holes, phenomena which probe basic physics in the most extreme environments of gravity, density, and magnetic fields. RXTE has extended its lifetime by applying the proportional counter area selectively and maintains schedule flexibility by making use of the distribution of targets around the sky. Proposed future observations emphasize opportunity to discover and study additional millisecond pulsars, pursue the high frequency quasi-periodic oscillations in black hole transients, and connect high frequency phenomena with longer-term characteristics. RXTE will continue to strongly support, for both galactic and extragalactic targets, combining RXTE observations with other wavelengths (from IR to TeV) or with other capabilities, such as high spectral resolution. 相似文献
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R. Misra K.P. Harikrishnan G. Ambika A.K. Kembhavi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2006,38(12):2897-2900
The Black hole system GRS 1915+105 exhibits various types of long term variability. Here we show that this behavior can be explained in terms of a deterministic non-linear system. In particular, evidence is provided for a non-linear deterministic limit cycle origin of the low frequency QPO exhibited by this source. 相似文献
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D. Radhika A. Nandi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
We re-investigated the ‘spectro-temporal’ behavior of the source XTE J1859+226 in X-rays during its outburst phase in 1999, by analysing the RXTE PCA/HEXTE data in 2–150 keV spectral band. Detailed analysis shows that the source evolves through different spectral states during its entire outburst as indicated by the variation in the spectral and temporal characteristics. Although the evolution pattern of the outburst followed the typical q-shaped profile, we observed an absence of ‘canonical’ soft state and a weak presence of ‘secondary’ emission during the decay phase of the outburst. The broad-band spectra, modeled with high energy cutoff, shows that the fold-energy increases monotonically in the hard and hard-intermediate states followed by a random variation in the soft-intermediate state. We attempted to estimate the mass of the source based on the evolution of Quasi-Periodic Oscillation (QPO) frequencies during rising phase modeled with the propagating oscillatory shock solution, and from the correlation of photon index and QPO frequency. It is also observed that during multiple ejections (observed as radio flares) the QPO frequencies are not present in the power spectra and there is an absence of lag in the soft to hard photons. The disk flux increases along with a decrease in the high energy flux, implying the soft nature of the spectrum. These results are the ‘possible’ indication that the inner part of the disk (i.e., Comptonized corona), which could be responsible for the generation of QPO and for the non-thermal Comptonized component of the spectrum, is disrupted and the matter gets evacuated in the form of jet. We attempted to explain the complex behavior of ‘spectro-temporal’ properties of the source during the entire outburst and the nature of the disk-jet connection before, during and after the ejection events in the context of two different types of accreting flow material, in presence of magnetic field. 相似文献
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Tim Johannsen Dimitrios Psaltis 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
According to the no-hair theorem, astrophysical black holes are uniquely described by their mass and spin. In this paper, we review a new framework for testing the no-hair hypothesis with observations in the electromagnetic spectrum. The approach is formulated in terms of a Kerr-like spacetime containing a quadrupole moment that is independent of both mass and spin. If the no-hair theorem is correct, then any deviation from the Kerr metric quadrupole has to be zero. We show how upcoming VLBI imaging observations of Sgr A∗ as well as spectroscopic observations of iron lines from accreting black holes with IXO may lead to the first astrophysical test of the no-hair theorem. 相似文献
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Ken Ebisawa Toshihiro Kawaguchi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2006,38(12):2862-2866
Our current theoretical and observational understandings of the accretion disks around Galactic black-holes are reviewed. Historically, a simple phenomenological accretion disk model has been used to interpret X-ray observations. Although such a phenomenological interpretation is still useful, high quality X-ray data from contemporary instruments allow us to test more realistic accretion disk models. In a simple and ideal case, the standard optically thick accretion disk model is successful to explain observations, such that the inner disk radius is constant at three times the Schwarzschild radius over large luminosity variations. However, when disk luminosity is close to or exceeds the Eddington luminosity, the standard disk model breaks, and we have to consider the “slim disk” solution in which radial energy advection is dominant. Recent observations of Ultra-luminous X-ray sources (ULXs), which may not be explained by the standard disk model, strongly suggest the slim disk solution. We compare theoretical X-ray spectra from the slim disk with observed X-ray spectra of ULXs. We have found that the slim disk model is successful to explain ULX spectra, in terms of the massive stellar black-holes with several tens of solar mass and the super-Eddington mass accretion rates. In order to explain the large luminosities (>1040 ergs s−1) of ULXs, “intermediate black-holes” (>100M) are not required. Slim disks around massive stellar black-holes of up to several tens of solar mass would naturally explain the observed properties of ULXs. 相似文献