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101.
Results from simultaneous spectral and photometric monitoring of the Herbig Ae star CQ Tau in the neighborhood of the Hα and
resonance sodium doublet Na I D lines are presented. It is shown that the inner structure of the accretion disk of CQ Tau
is nonuniform and consists of two regions with quite different kinematic characteristics. Region I is characterized by relative
stability and a smooth long-term variation in the velocity of the gas along the line of sight. Region II is distinguished
by the highest velocities and a variability in their maximum values over time scales from a few days to 700 days. The dust
clouds which produse the star’s brightness minima may also be the source of cold gas and contribute to the observed spectral
variability. We assume that region I of the disk coincides with the accretion disk of the star. The kinematic differences
in region II may be caused by dissipation of circumstellar dust clouds which, moving in elongated orbits, are able to approach
the star quite closely.
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Translated from Astrofizika, Vol. 50, No. 1, pp. 39–55 (February 2007). 相似文献
102.
103.
104.
C. Brocksopp J. C. A. Miller-Jones R. P. Fender B. W. Stappers 《Monthly notices of the Royal Astronomical Society》2007,378(3):1111-1117
XTE J1748−288 is a black hole X-ray transient which went into outburst in 1998 June. The X-ray light curves showed canonical morphologies, with minor variations on the 'fast rise exponential decay' profile. The radio source, however, reached an unusually high flux density of over 600 mJy. This high radio flux was accompanied by an exceptional (>20 per cent) fractional linear polarization, the variability of which was anticorrelated with the flux density. We use this variability to discuss possible depolarization mechanisms and to predict the underlying behaviour of the (unresolved) core/jet components. 相似文献
105.
T. Shahbaz C. A. Watson H. Hernandez-Peralta 《Monthly notices of the Royal Astronomical Society》2007,376(4):1886-1888
We report the discovery of a periodic modulation in the optical lightcurve of the candidate ultracompact X-ray binary 4U 1822−000. Using time-resolved optical photometry taken with the William Herschel Telescope we find evidence for a sinusoidal modulation with a semi-amplitude of 8 per cent and a period of 191 min, which is most likely close to the true orbital period of the binary. Using the van Paradijs & McClintock relation for the absolute magnitude and the distance modulus allowing for interstellar reddening, we estimate the distance to 4U 1822−000 to be 6.3 kpc. The long orbital period casts severe doubts on the ultracompact nature of 4U 1822−000. 相似文献
106.
107.
R. Cornelisse R. Wijnands J. Homan 《Monthly notices of the Royal Astronomical Society》2007,380(4):1637-1641
We observed the neutron star X-ray transient 2S 1803−245 in quiescence with the X-ray satellite XMM–Newton , but did not detect it. An analysis of the X-ray bursts observed during the 1998 outburst of 2S 1803−245 gives an upper limit to the distance of ≤7.3 kpc, leading to an upper limit on the quiescent 0.5–10 keV X-ray luminosity of ≤2.8 × 1032 erg s−1 (3σ). Since the expected orbital period of 2S 1803−245 is several hours, this limit is not much higher than those observed for the quiescent black hole transients with similar orbital periods. 相似文献
108.
109.
What is the origin of the soft excess in active galactic nuclei? 总被引:1,自引:0,他引:1
Magorzata A. Sobolewska Chris Done 《Monthly notices of the Royal Astronomical Society》2007,374(1):150-158
110.