排序方式: 共有18条查询结果,搜索用时 31 毫秒
1.
P. G. Jonker M. van der Klis C. Kouveliotou M. Méndez W. H. G. Lewin T. Belloni 《Monthly notices of the Royal Astronomical Society》2003,346(2):684-688
We have observed the eclipsing low-mass X-ray binary MS 1603.6+2600 with Chandra for 7 ks. The X-ray spectrum is well fit with a single absorbed power law with an index of ∼2. We find a clear sinusoidal modulation in the X-ray light curve with a period of 1.7 ± 0.2 h , consistent with the period of 1.85 h found before. However, no (partial) eclipses were found. We argue that if the X-ray flare observed in earlier X-ray observations was a type I X-ray burst, then the source can only be an accretion disc corona source at a distance of ∼11–24 kpc (implying a height above the Galactic disc of ∼8–17 kpc). It has also been proposed in the literature that MS 1603.76+2600 is a dipper at ∼75 kpc. We argue that, in this dipper scenario, the observed optical properties of MS 1603.6+2600 are difficult to reconcile with the optical properties one would expect on the basis of comparisons with other high-inclination, low-mass X-ray binaries, unless the X-ray flare was not a type I X-ray burst. In that case, the source can be a nearby soft X-ray transient accreting at a quiescent rate, as was proposed by Hakala et al., or a high-inclination source at ∼15–20 kpc. 相似文献
2.
Hurley K Strohmayer T Li P Kouveliotou C Woods P van Paradijs J Murakami T Hartmann D Smith I Ando M Yoshida A Sugizaki M 《The Astrophysical journal》2000,528(1):L21-L23
We present a 2-10 keV ASCA observation of the field around the soft gamma repeater SGR 1627-41. A quiescent X-ray source, whose position is consistent both with that of a recently discovered BeppoSAX X-ray source and with the Interplanetary Network localization for this soft gamma repeater, was detected in this observation. In 2-10 keV X-rays, the spectrum of the X-ray source may be fit equally well by a power-law, blackbody, or bremsstrahlung function, with unabsorbed flux approximately 5x10-12 ergs cm-2 s-1. We do not confirm a continuation of a fading trend in the flux, and we find no evidence for periodicity, both of which were noted in the earlier BeppoSAX observations. 相似文献
3.
4.
S. D. Barthelmy P. Butterworth T. L. Cline N. Gehrels G. J. Fishman C. Kouveliotou C. A. Meegan 《Astrophysics and Space Science》1995,231(1-2):235-238
The celestial coordinates of gamma-ray burst sources observed with BATSE on GRO are automatically determined and distributed in real time to members of the global scientific community. These data are now being used by more than 20 operations to enable searches for associated transients in a variety of other wavelength or energy regimes to identify the burst source objects. The minimum total delay time from the onset of a burst to the receipt of its coordinates by distant experimenters can be under 4 sec, less than the duration of a typical GRB, and the maximum total delay is 7 sec, or longer, depending on the distribution method. Some improvements to the BACODINE system and a summary of the follow-up observations made by some of the sites are given. 相似文献
5.
Stefanie Wachter Chryssa Kouveliotou Sandeep Patel Don Figer Peter Woods 《Astrophysics and Space Science》2007,308(1-4):67-71
Both Anomalous X-ray Pulsars (AXPs) and Soft Gamma Repeaters (SGRs) are thought to be manifestations of magnetars. However, the specific physical characteristics that differentiate the two classes of objects remain unclear. There is some evidence that the progenitors of these sources and/or the environment in which they form might influence the type of phenomena the resulting magnetar displays. Several of the AXPs appear to be associated with supernova remnants, while embedded clusters of massive stars have been found in the immediate vicinity of some SGRs. Since both AXPs and SGRs are distributed close to the Galactic plane, high extinction makes studies in the optical difficult. We present early results from our Spitzer program aimed at probing the environmental factors that might contribute to the difference in the observed characteristics between AXPs and SGRs. 相似文献
6.
R. A. Stathakis B. J. Boyle D. H. Jones M. S. Bessell T. J. Galama Lisa M. Germany M. Hartley D. M. James C. Kouveliotou I. J. Lewis Q. A. Parker K. S. Russell E. M. Sadler C. G. Tinney J. van Paradijs P. M. Vreeswijk 《Monthly notices of the Royal Astronomical Society》2000,314(4):807-814
Supernova 1998bw holds the record for the most energetic Type Ic explosion, one of the brightest radio supernovae and probably the first supernova associated with a γ -ray burst. In this paper we present spectral observations of SN 1998bw observed in a cooperative monitoring campaign using the Anglo-Australian Telescope, the UK Schmidt Telescope and the Siding Springs Observatories 2.3-m telescope. We investigate the evolution of the spectrum between 7 and 94 d after V -band maximum in comparison with well-studied examples of Type Ic SNe in order to quantify the unusual properties of this supernova event. Though the early spectra differ greatly from observations of classical Ic supernovae (SNe), we find that the evolution from the photospheric to nebular phases is slow but otherwise typical. The spectra differ predominantly in the extensive line blending and blanketing which has been attributed to the high velocity of the ejecta. We find that by day 19, the absorption line minima blueshifts are 10–50 per cent higher than other SNe and on day 94 emission lines are 45 per cent broader, as expected if the progenitor had a massive envelope. However, it is difficult to explain the extent of line blanketing entirely by line broadening, and we argue that an additional contribution from other species is present, indicating unusual relative abundances or physical conditions in the envelope. 相似文献
7.
D. M. Palmer T. L. Cline J. G. Laros K. Hurley G. J. Fishman C. Kouveliotou 《Astrophysics and Space Science》1995,231(1-2):315-318
Very Large Array (VLA) radio observations of precisely-located GRB error boxes have been performed to search for fading and quiescent emission associated with -ray bursts. These observations were made as quickly as 23 hours and as late as 13 years after the time of the burst. Our measurements presented here have found GRB error boxes to be empty of sources to the 80 µJy level ( = 3.6 cm) at 9 months, to 1 mJy (20 cm) at 9 days, and probably to 5 mJy (20 cm) at 23 hours after the bursts. 相似文献
8.
C. B. Luginbuhl F. J. Vrba R. Hudec D. Hartmann K. Hurley M. Boër M. Niel M. Sommer C. Kouveliotou C. Meegan G. Fishman 《Astrophysics and Space Science》1995,231(1-2):289-292
We present preliminary results from deep optical searches of small (5 arcmin2) GRB error boxes determined using the Third Interplanetary Network (IPN3). Two of these fields also have been found to have historical OT events located within the IPN3 error boxes. We compare the preliminary results of these searches to those reported for the larger IPN1 error boxes. The small size of the IPN3 error boxes should allow a test of the hypothesis suggested by the IPN1 study that there are excess QSOs associated with the GRB fields. 相似文献
9.
R. S. Priddey N. R. Tanvir A. J. Levan A. S. Fruchter C. Kouveliotou I. A. Smith R. A. M. J. Wijers 《Monthly notices of the Royal Astronomical Society》2006,369(3):1189-1195
We present millimetre (mm) and submillimetre (submm) photometry of a sample of five host galaxies of gamma-ray bursts (GRBs), obtained using the Max Planck Millimetre Bolometer (MAMBO2) array and Submillimetre Common-User Bolometer Array (SCUBA). These observations were obtained as part of an ongoing project to investigate the status of GRBs as indicators of star formation. Our targets include two of the most unusual GRB host galaxies, selected as likely candidate submm galaxies: the extremely red ( R − K ≈ 5) host of GRB 030115, and the extremely faint ( R > 29.5) host of GRB 020124. Neither of these galaxies is detected, but the deep upper limits for GRB 030115 impose constraints on its spectral energy distribution, requiring a warmer dust temperature than is commonly adopted for submillimetre galaxies (SMGs).
As a framework for interpreting these data, and for predicting the results of forthcoming submm surveys of Swift -derived host samples, we model the expected flux and redshift distributions based on luminosity functions of both submm galaxies and GRBs, assuming a direct proportionality between the GRB rate density and the global star formation rate density. We derive the effects of possible sources of uncertainty in these assumptions, including (1) introducing an anticorrelation between GRB rate and the global average metallicity, and (2) varying the dust temperature. 相似文献
As a framework for interpreting these data, and for predicting the results of forthcoming submm surveys of Swift -derived host samples, we model the expected flux and redshift distributions based on luminosity functions of both submm galaxies and GRBs, assuming a direct proportionality between the GRB rate density and the global star formation rate density. We derive the effects of possible sources of uncertainty in these assumptions, including (1) introducing an anticorrelation between GRB rate and the global average metallicity, and (2) varying the dust temperature. 相似文献
10.
K.-I. Nishikawa C. B. Hededal P. E. Hardee G. J. Fishman C. Kouveliotou Y. Mizuno 《Astrophysics and Space Science》2007,307(1-3):319-323
We have applied numerical simulations and modeling to the particle acceleration, magnetic field generation, and emission from
relativistic shocks. We investigate the nonlinear stage of theWeibel instability and compare our simulations with the observed
gamma-ray burst emission. In collisionless shocks, plasma waves and their associated instabilities (e.g., the Weibel, Buneman
and other two-stream instabilities) are responsible for particle (electron, positron, and ion) acceleration and magnetic field
generation. 3-D relativistic electromagnetic particle (REMP) simulations with three different electron-positron jet velocity
distributions and also with an electron-ion plasma have been performed and show shock processes including spatial and temporal
evolution of shocks in unmagnetized ambient plasmas. The growth time and nonlinear saturation levels depend on the initial
jet parallel velocity distributions. Simulations show that the Weibel instability created in the collisionless shocks accelerates
jet and ambient particles both perpendicular and parallel to the jet propagation direction. The nonlinear fluctuation amplitude
of densities, currents, electric, and magnetic fields in the electron-positron shocks are larger for smaller jet Lorentz factor.
This comes from the fact that the growth time of the Weibel instability is proportional to the square of the jet Lorentz factor.
We have performed simulations with broad Lorentz factor distribution of jet electrons and positrons, which is assumed to be
created by photon annihilation. Simulation results with this broad distribution show that the Weibel instability is excited
continuously by the wide-range of jet Lorentz factor from lower to higher values. In all simulations the Weibel instability
is responsible for generating and amplifying magnetic fields perpendicular to the jet propagation direction, and contributes
to the electron’s (positron’s) transverse deflection behind the jet head. This small scale magnetic field structure contributes
to the generation of “jitter” radiation from deflected electrons (positrons), which is different from synchrotron radiation
in uniform magnetic fields. The jitter radiation resulting from small scale magnetic field structures may be important for
understanding the complex time structure and spectral evolution observed in gamma-ray bursts or other astrophysical sources
containing relativistic jets and relativistic collisionless shocks. The detailed studies of shock microscopic process evolution
may provide some insights into early and later GRB afterglows. 相似文献