Photometric and polarimetric studies of three W UMa-type binaries: FZ Ori,V407 Peg and LP UMa     

Vinod Prasad  J. C. Pandey  M. K. Patel  D. C. Srivastava 《Astrophysics and Space Science》2014,353(2):575-594

We present analyses of new optical photometric observations of three W UMa-type contact binaries FZ Ori, V407 Peg and LP UMa. Results from the first polarimetric observations of the FZ Ori and V407 Peg are also presented. The periods of FZ Ori, V407 Peg and LP UMa are derived to be 0.399986, 0.636884 and 0.309898 d, respectively. The O?C analyses indicate that the orbital periods of FZ Ori and LP UMa have increased with the rate of 2.28×10^?8 and 1.25×10^?6 d?yr^?1, respectively and which is explained by transfer of mass between the components. In addition to the secularly increasing rate of orbital period, it was found that the period of FZ Ori has varied in sinusoidal way with oscillation period of ～30.1 yr. The period of oscillations are most likely to be explained by the light-time effect due to the presence of a tertiary companion. Small asymmetries have been seen around the primary and secondary maxima of light curves of all three systems, which is probably due to the presence of cool/hot spots on the components. The light curves of all three systems are analysed by using Wilson-Devinney code (WD) and the fundamental parameters of these systems have been derived. The present analyses show that FZ Ori is a W-subtype, and V407 Peg and LP UMa are A-subtype of the W UMa-type contact binary systems. The polarimetric observations in B, V, R and I bands, yield average values of polarization to be 0.26±0.03, 0.22±0.02, 0.22±0.03 and 0.22±0.05 per cent for FZ Ori and 0.21±0.02, 0.29±0.03, 0.31±0.01 and 0.31±0.04 per cent for V407 Peg, respectively.  相似文献   

Magnetosonic waveguide model of solar wind flow tubes     

A. K. Srivastava  B. N. Dwivedi 《Journal of Astrophysics and Astronomy》2006,27(2-3):353-359

We consider solar wind flow tubes as a magnetosonic wave-guide. Assuming a symmetric expansion in edges of slab-modelled wave-guide, we study the propagation characteristics of magnetosonic wave in the solar wind flow tubes. We present the preliminary results and discuss their implications.  相似文献   

Three-colour photometry of GH pegasi     

R. K. Srivastava  T. D. Padalia 《Astrophysics and Space Science》1974,29(2):435-438

The geometrical elements of the system GH Pegasi and a slightly improved period of 2 _. ^d 556136 have been given.  相似文献   

Some anisotropic spatially-homogeneous cosmological models with electromagnetic field     

T. Singh  R. S. Srivastava 《Astrophysics and Space Science》1989,159(1):21-38

Considering Bianchi type-I metric, cosmological models of a perfect fluid with an electromagnetic field have been obtained, using a supplementary condition between the metric potentials. The four-current is either zero or space-like. The model has expanding and shearing but non-rotating fluid flow which is also geodetic. The requirement of positive conductivity imposes an additional restriction on the model. Various physical and mathematical properties of the model have been discussed.  相似文献   

Thermal convection instability of liquid metals in magneto-hydrodynamics     

Rama Singhal  Krishna M. Srivastava 《Astrophysics and Space Science》1983,89(1):33-51

The problem of thermal convection instability of a horizontal layer of magnetized fluid has been studied to occur crystal growing under the effect of horizontal temperature gradient. In the study, the problem has been reduced to an eigen-value problem for a stream function. The dispersion relations for low viscosity fluid and high viscosity fluid respectively have been discussed analytically and some numerical results have been obtained. It is shown that the critical Rayleigh number and other its related constants for low viscosity fluid (i.e., mercury) are much differ than the high viscosity fluid (i.e., glycerol).  相似文献   

Nonlinear electrostatic drift Kelvin-Helmholtz instability     

Avadhesh C. Sharma  Krishna M. Srivastava 《Astrophysics and Space Science》1993,200(1):107-116

Nonlinear analysis of electrostatic drift Kelvin-Helmholtz instability is performed. It is shown that the analysis leads to the propagation of the weakly nonlinear dispersive waves and the nonlinear behaviour is governed by the nonlinear Burger's equation.  相似文献   

Eclipsing binary system AV Hydrae     

J. B. Srivastava  C. D. Kandpal 《Astrophysics and Space Science》1981,76(1):173-186

The eclipsing binary AV Hya has been observed photoelectrically inU, B andV filters on 15 nights. The primary eclipse appeared to be total with a totality of 23 min duration. A modified period of 0^d.6 834 062 has been obtained. Geometrical elements could only be determined for partial transit case.  相似文献   

Anisotropic propagation of magnetogasdynamic sonic waves in conducting and radiating atmosphere     

B. G. Verma  R. C. Srivastava  A. H. Khan 《Astrophysics and Space Science》1983,91(2):289-297

The propagation of sonic discontinuity in conducting and radiating atmosphere has been discussed under the influence of magnetic field. The velocity of sonic wave and its termination into shock wave has been obtained. We have also obtained the critical time at which sonic wave terminates into shock wave. There is significant effect of magnetic field on sonic velocity and its termination into shock wave.  相似文献   

An analysis of the light changes of the eclipsing binary XY ceti in the frequency-domain     

Srivastava  R. K. 《Astrophysics and Space Science》1987,138(1):197-207

The photoelectric observations of the eclipsing binary XY Ceti presented by us (see Srivastava and Padalia, 1975) have been analysed by Okazaki (1978) and Ramellaet al. (1980). They presented different sets of elements from the same set of our observations. This necessitated us to obtain the elements of XY Ceti again employing recent method of determination of elements.The revised geometrical elements of the eclipsing binary XY Ceti have been obtained by the method of Fourier analysis of the light changes in the frequency-domain, which was developed by Kopal (1979). These have been compared with our earlier (Srivastava and Padalia, 1975) results obtained by employing Russell and Merrill's (1952) method. The revised absolute dimensions of XY Ceti have been obtained using the spectroscopic elements given by Popper (1971), and the newly derived geometrical elements. The Roche radii have been derived to discuss the evolution of the system. The secondary component lies reasonably near to the Main Sequence, while the primary component falls above it. The evolutionary discussion indicates that the system is a detached one.  相似文献   

An exact similarity solution in radiation magneto-gas-dynamics for the flows behind a spherical shock wave     

J. P. Vishwakarma  R. C. Srivastava  Arun Kumar 《Astrophysics and Space Science》1987,129(1):45-52

An exact similarity solution for a spherical magnetogasdynamic shock is obtained in the case when radiation energy, radiation pressure and radiative heat flux are important. The total energy of the shock wave increase with time. We have shown that due to the magnetic field the flow variables are considerably changed. Also, due to increases in radiation pressure number the radiation flux is increased.  相似文献