A non-main-sequence secondary in SY Cancri     

Robert Connon Smith  Otto Mehes  Dave Vande Putte  Nigel A. Hawkins 《Monthly notices of the Royal Astronomical Society》2005,360(1):364-374

Simultaneous spectroscopic and photometric observations of the Z Cam type dwarf nova SY Cancri were used to obtain absolute flux calibrations. A comparison of the photometric calibration with a wide-slit spectrophotometric calibration showed that either method is equally satisfactory. A radial velocity study of the secondary star, made using the far-red Na  i doublet, yielded a semi-amplitude of   K ₂= 127 ± 23 km s⁻¹  . Taking the published value of  86 ± 9 km s⁻¹  for K ₁ gives a mass ratio of   q = M ₂/ M ₁= 0.68 ± 0.14  ; this is very different from the value of  1.13 ± 0.35  quoted in the literature. Using the new lower mass ratio, and constraining the mass of the white dwarf to be within reasonable limits, then leads to a mass for the secondary star that is substantially less than would be expected for its orbital period if it satisfied a main-sequence mass–radius relationship. We find a spectral type of M0 that is consistent with that expected for a main-sequence star of the low mass we have found. However, in order to fill its Roche lobe, the secondary must be significantly larger than a main-sequence star of that mass and spectral type. The secondary is definitely not a normal main-sequence star.  相似文献   

High-resolution spectroscopy of the high galactic latitude RV Tauri star CE Virginis     

N. Kameswara Rao  Bacham E. Reddy 《Monthly notices of the Royal Astronomical Society》2005,357(1):235-241

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A non-adiabatic analysis for axisymmetric pulsations of magnetic stars     

Hideyuki Saio 《Monthly notices of the Royal Astronomical Society》2005,360(3):1022-1032

This paper presents the results of a non-adiabatic analysis for axisymmetric non-radial pulsations including the effect of a dipole magnetic field. Convection is assumed to be suppressed in the stellar envelope, and the diffusion approximation is used to radiative transport. As in a previous adiabatic analysis, the eigenfunctions are expanded in a series of spherical harmonics. The analysis is applied to a  1.9-M_⊙  , main-sequence model  (log  T _eff= 3.913)  . The presence of a magnetic field always stabilizes low-order acoustic modes. All the low-order modes of the model that are excited by the κ-mechanism in the He  ii ionization zone in the absence of a magnetic field are found to be stabilized if the polar strength of the dipole magnetic field is larger than about 1 kG. For high-order p modes, on the other hand, distorted dipole and quadrupole modes excited by the κ-mechanism in the H ionization zone remain overstable, even in the presence of a strong magnetic field. It is found, however, that all the distorted radial high-order modes are stabilized by the effect of the magnetic field. Thus, our non-adiabatic analysis suggests that distorted dipole modes and distorted quadrupole modes are most likely excited in rapidly oscillating Ap stars. The latitudinal amplitude dependence is found to be in reasonable agreement with the observationally determined one for HR 3831. Finally, the expected amplitude of magnetic perturbations at the surface is found to be very small.  相似文献   

Candidate extrasolar planet transits discovered in the Microlensing Observations in Astrophysics-I Galactic bulge data     

F. Abe  I. A. Bond  Y. Furuta  J. B. Hearnshaw  P. M. Kilmartin  Y. Kurata  K. Masuda  Y. Matsubara  Y. Muraki  S. Noda  K. Okajima  N. J. Rattenbury  T. Sako  D. J. Sullivan  T. Sumi  P. Tristram  J. N. Wood  T. Yanagisawa  P. C. M. Yock 《Monthly notices of the Royal Astronomical Society》2005,364(1):325-334

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XMM–Newton observations of three short-period polars: V347 Pav, GG Leo and EU UMa     

Gavin Ramsay  Mark Cropper  K. O. Mason  F. A. Córdova  W. Priedhorsky 《Monthly notices of the Royal Astronomical Society》2004,347(1):95-100

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Photometry of V1062 Tau: low states, short outbursts and period switching     

Y. M. Lipkin  E. M. Leibowitz  M. Orio 《Monthly notices of the Royal Astronomical Society》2004,349(4):1323-1330

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Observations of the pulsating subdwarf B star Feige 48: Constraints on evolution and companions     

《Monthly notices of the Royal Astronomical Society》2004,348(4):1164-1174

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Stokes imaging, Doppler mapping and Roche tomography of the AM Herculis system V834 Cen   总被引：1，自引：0，他引：1  

Stephen B. Potter  E. Romero-Colmenero  C. A. Watson  D. A. H. Buckley  A. Phillips 《Monthly notices of the Royal Astronomical Society》2004,348(1):316-324

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The investigation of nova-like variable MV Lyr during the 1999–2001 years     

N. A. Katysheva  S. Yu. Shugarov  E. P. Pavlenko  P. V. Abolmasov 《Journal of Astrophysics and Astronomy》2002,23(1-2):15-18

A peculiar nova-like MV Lyr was investigated. The CCD-observations of MV Lyr were continued in Crimea during the outbursts and quiescent states. Last year its behavior became non-typical for “anti-dwarf novae”. The length of its first deep minimum was 10 years. A modern state is characterized by very strong outbursts and very often changes of the stages. The periods 0. ^d 128 and 0. ^d 136 were obtained for 1998 and 1999 years accordingly. Possibly, a relation between the photometric period and the brightness exists.  相似文献   

Anomalous Behavior of the Linear Polarization of the Herbig Ae Star WW Vul during the 1997 Minimum     

D. N. Shakhovskoi 《Astrophysics》2002,45(4):426-431

In the course of photopolarimetric monitoring of the Herbig Ae star WW Vul, an unusual variation of linear polarization upon energence from a deep minimum was recorded, which cannot be explained by the standard mechanism for such objects (UX Ori stars): a variable contribution of radiation scattered by circumstellar dust. An analysis of possible causes of the anomalous behavior of polarization shows that it was most likely due to the presence of aligned, aspherical dust grains in the dust cloud crossing the line of sight at that time.  相似文献