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111.
D. P. Kjurkchieva D. V. Marchev S. Zola 《Monthly notices of the Royal Astronomical Society》2007,382(2):835-839
High-resolution spectroscopic observations around the Hα line of the binary star QX Cas covering the whole orbital period are presented. Our radial velocity solution, the first ever determined, requires an eccentric orbit with the following orbital parameters: eccentricity, e = 0.22 ± 0.01 ; longitude of periastron, ω= 45°± 5° ; semi-amplitudes of the radial velocity curves of the primary and secondary stars, K 1 sin i = 125.8 ± 0.9 km s−1 and K 2 sin i = 144.8 ± 1.1 km s−1 ; gamma velocity, V 0 = 65.1 ± 0.5 km s−1 ; and mass ratio, q = 0.869 ± 0.013 . The corresponding lower limits of the masses of the components and their separation are , and a sin i = 31.34 ± 0.48 R⊙ . 相似文献
112.
J. Martí D. Pérez-Ramírez P. Luque-Escamilla J. L. Garrido J. M. Paredes A. Muñoz-Arjonilla J. R. Sánchez-Sutil 《Astrophysics and Space Science》2007,309(1-4):309-313
We report and shortly discuss here the observational work carried out in order to test the possibility that two previously
detected radio sources, in the vicinity of the well known microquasar Cygnus X-3, could be hot spot tracers of interaction
between its relativistic jet and the interstellar medium (ISM). The motivation behind this search is in part justified considering
recent theoretical models of high energy γ-ray emission which strongly rely on the interaction sites of galactic relativistic jets with nearby ISM clouds.
The results presented in this paper include an improved radio exploration of the several arc-minute field around Cygnus X-3
using the Very Large Array (VLA), as well as deep near infrared (NIR) imaging with the Calar Alto 3.5 m telescope. We anticipate
here that our observations do not appear to support the initial hot spot hypothesis. Instead, the resulting images suggest
that the two radio sources, originally believed to be hot spot candidates, are most likely background or foreground objects. 相似文献
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Daniel Malmberg Francesca De Angeli Melvyn B. Davies Ross P. Church Dougal Mackey Mark I. Wilkinson 《Monthly notices of the Royal Astronomical Society》2007,378(3):1207-1216
The stars that populate the solar neighbourhood were formed in stellar clusters. Through N -body simulations of these clusters, we measure the rate of close encounters between stars. By monitoring the interaction histories of each star, we investigate the singleton fraction in the solar neighbourhood. A singleton is a star which formed as a single star, has never experienced any close encounters with other stars or binaries, or undergone an exchange encounter with a binary. We find that, of the stars which formed as single stars, a significant fraction is not singletons once the clusters have dispersed. If some of these stars had planetary systems, with properties similar to those of the Solar System, the planets' orbits may have been perturbed by the effects of close encounters with other stars or the effects of a companion star within a binary. Such perturbations can lead to strong planet–planet interactions which eject several planets, leaving the remaining planets on eccentric orbits. Some of the single stars exchange into binaries. Most of these binaries are broken up via subsequent interactions within the cluster, but some remain intact beyond the lifetime of the cluster. The properties of these binaries are similar to those of the observed binary systems containing extrasolar planets. Thus, dynamical processes in young stellar clusters will alter significantly any population of Solar System-like planetary systems. In addition, beginning with a population of planetary systems exactly resembling the Solar System around single stars, dynamical encounters in young stellar clusters may produce at least some of the extrasolar planetary systems observed in the solar neighbourhood. 相似文献
116.
Rebecca G. Martin J. E. Pringle Christopher A. Tout 《Monthly notices of the Royal Astronomical Society》2007,381(4):1617-1624
We consider the shape of an accretion disc whose outer regions are misaligned with the spin axis of a central black hole and calculate the steady state form of the warped disc in the case where the viscosity and surface densities are power laws in the distance from the central black hole. We discuss the shape of the resulting disc in both the frame of the black hole and that of the outer disc. We note that some parts of the disc and also any companion star maybe shadowed from the central regions by the warp. We compute the torque on the black hole caused by the Lense–Thirring precession, and hence compute the alignment and precession time-scales. We generalize the case with viscosity and hence surface density independent of radius to more realistic density distributions for which the surface density is a decreasing function of radius. We find that the alignment time-scale does not change greatly but the precession time-scale is more sensitive. We also determine the effect on this time-scale if we truncate the disc. For a given truncation radius, the time-scales are less affected for more sharply falling density distributions. 相似文献
117.
Roland Walter 《Astrophysics and Space Science》2007,309(1-4):5-9
INTEGRAL is operational since more than three years and producing high quality data that allows to detect fainter new hard
X-ray sources. The new sources, identified until now, are mostly active galactic nuclei and absorbed or transient high mass
X-ray binaries. TeV emission could be expected from the new high mass X-ray binaries accreting dense clumps of stellar wind.
INTEGRAL sources with TeV counterparts are discussed.
Based on observations with INTEGRAL, an ESA project with instruments and science data centre funded by ESA member states (especially
the PI countries: Denmark, France, Germany, Italy, Switzerland, Spain), Czech Republic and Poland, and with the participation
of Russia and the USA. 相似文献
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120.
M. L. Pretorius C. Knigge D. O'Donoghue J. P. Henry I. M. Gioia C. R. Mullis 《Monthly notices of the Royal Astronomical Society》2007,382(3):1279-1288
We use the ROSAT North Ecliptic Pole (NEP) survey to construct a small, but purely X-ray flux-limited sample of cataclysmic variable stars (CVs). The sample includes only four systems, two of which (RX J1715.6+6856 and RX J1831.7+6511) are new discoveries. We present time-resolved spectroscopy of the new CVs and measure orbital periods of 1.64 ± 0.02 and 4.01 ± 0.03 h for RX J1715.6+6856 and RX J1831.7+6511, respectively. We also estimate distances for all the CVs in our sample, based mainly on their apparent brightness in the infrared. The space density of the CV population represented by our small sample is 1.1+2.3 −0.7 × 10−5 pc−3 . We can also place upper limits on the space density of any subpopulation of CVs too faint to be included in the NEP survey. In particular, we show that if the overall space density of CVs is as high as 2 × 10−4 pc−3 (as has been predicted theoretically), the vast majority of CVs must be fainter than L X ≃ 2 × 1029 erg s−1 . 相似文献