Keck II spectroscopy of mHz quasi-periodic oscillations in Hercules X-1     

K. O'Brien  Keith Horne  B. Boroson †  M. Still ‡  R. Gomer  J.B. Oke  P. Boyd  S.D. Vrtilek 《Monthly notices of the Royal Astronomical Society》2001,326(3):1067-1075

We present Keck II spectroscopy of optical mHz quasi-periodic oscillations (QPOs) in the light curve of the X-ray pulsar binary Hercules X-1. In the power spectrum it appears as 'peaked noise', with a coherency ∼2, a central frequency of 35 mHz and a peak-to-peak amplitude of 5 per cent. However, the dynamic power spectrum shows it to be an intermittent QPO, with a lifetime of ∼100 s, as expected if the lifetime of the orbiting material is equal to the thermal time-scale of the inner disc. We have decomposed the spectral time series into constant and variable components and used blackbody fits to the resulting spectra to characterize the spectrum of the QPO variability and constrain possible production sites. We find that the spectrum of the QPO is best fitted by a small hot region, possibly the inner regions of the accretion disc, where the ballistic accretion stream impacts on to the disc. The lack of any excess power around the QPO frequency in the X-ray power spectrum, created using simultaneous light curves from RXTE , implies that the QPO is not simply reprocessed X-ray variability.  相似文献   

Erratum: The spectrum of BAL QSO 03 + 308: intrinsic variability and line-locking stability     

E.Y. Vilkoviskij  M.J. Irwin 《Monthly notices of the Royal Astronomical Society》2001,326(1):416-416

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The 2dF Galaxy Redshift Survey: the b_J-band galaxy luminosity function and survey selection function     

Peder Norberg  Shaun Cole  Carlton M. Baugh  Carlos S. Frenk  Ivan Baldry  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Matthew Colless  Chris Collins  Warrick Couch  Nicholas J. G. Cross  Gavin Dalton  Roberto De Propris  Simon P. Driver  George Efstathiou  Richard S. Ellis  Karl Glazebrook  Carole Jackson  Ofer Lahav  Ian Lewis  Stuart Lumsden  Steve Maddox  Darren Madgwick  John A. Peacock  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2002,336(3):907-931

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A complete relativistic ionized accretion disc in Cygnus X-1     

A.J. Young †  A.C. Fabian  R.R. Ross  Y. Tanaka 《Monthly notices of the Royal Astronomical Society》2001,325(3):1045-1052

The galactic black hole candidate Cygnus X-1 is observed to be in one of two X-ray spectral states: either the low/hard (low soft X-ray flux and a flat power-law tail) or high/soft (high blackbody-like soft X-ray flux and a steep power-law tail) state. The physical origin of these two states is unclear. We present here a model of an ionized accretion disc, the spectrum of which is blurred by relativistic effects, and fit it to the ASCA , Ginga and EXOSAT data of Cygnus X-1 in both spectral states. We confirm that relativistic blurring provides a much better fit to the low/hard state data and, contrary to some previous results, find the data of both states to be consistent with an ionized thin accretion disc with a reflected fraction of unity extending to the innermost stable circular orbit around the black hole. Our model is an alternative to those that, in the low/hard state, require the accretion disc to be truncated at a few tens of Schwarzschild radii, within which there is a Thomson-thin, hot accretion flow. We suggest a mechanism that may cause the changes in spectral state.  相似文献   

Infrared photometry of AGB stars     

T. Le Berter  N. Epchtein  F. Guglielmo  P. Le Sidaner 《Astrophysics and Space Science》1994,217(1-2):105-116

The goal of this article is to show that, if one avoids star forming regions, mass-losing AGB stars can generally be selected from the data that will be provided by the near-infrared surveys which are presently considered. Also, if IRAS data are available, the separation between carbon-rich and oxygen-rich stars can be operated by their positions in infrared colour diagrams. In extragalactic systems, red supergiants can be discriminated from AGB stars by their luminosities.based on observations obtained with the ESO 1-m telescope  相似文献   

Testing the line-driven disc wind model: time-resolved ultraviolet spectroscopy of IX Vel and V3885 Sgr     

L. E. Hartley  J. E. Drew  K. S. Long  C. Knigge  D. Proga 《Monthly notices of the Royal Astronomical Society》2002,332(1):127-143

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A normal and superoutburst study of the eclipsing SU UMa star: DV Ursae Majoris     

Daisaku Nogami  †  Taichi Kato  Hajime Baba  Rudolf Novák  J. J. Lockley  M. Somers 《Monthly notices of the Royal Astronomical Society》2001,322(1):79-84

We report on time-resolved photometry carried out during the 1995 short outburst and the 1997 long outburst in the eclipsing dwarf nova DV UMa. The revised orbital period is 0.0858526172 (67) d. We detected gigantic superhumps with an amplitude of ∼0.6 mag in the mid-phase of the 1997 outburst, revealing the SU UMa nature of DV UMa. The superhump period is 0.0887 (4) d. The superhumps became less clear during the late phase of the superoutburst, and we found two possible periods of 0.0885 (15) and 0.0764 (15). During both outbursts, the eclipse was wide and shallow near the maximum, and then became narrower and deeper, which is qualitatively well explained by the current disc instability theory.  相似文献   

Extremely weak reflection features in the X-ray spectrum of XTE J1118+480: possible evidence for X-ray-emitting jets?     

J. M. Miller  D. R. Ballantyne  A. C. Fabian  W. H. G. Lewin 《Monthly notices of the Royal Astronomical Society》2002,335(4):865-870

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The bivariate brightness function of galaxies and a demonstration of the impact of surface brightness selection effects on luminosity function estimations     

Nicholas Cross  Simon P. Driver 《Monthly notices of the Royal Astronomical Society》2002,329(3):579-587

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Reflection at large distance from the central engine in Seyferts     

Julien Malzac  Pierre-Olivier Petrucci 《Monthly notices of the Royal Astronomical Society》2002,336(4):1209-1216

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