Winding sense of galaxies around the local supercluster

We present an analysis of the winding sense(S and Z-shapes) of 1 621 field galaxies that have radial velocity between 3 000 km s-1 and 5 000 km s-1.The preferred alignments of S-and Z-shaped galaxies are studied using chi-square,autocorrelation and Fourier series tests.We classify all the galaxies into 32 subsamples and notice a good agreement between the position angle(PA) distribution of the S-and Zshaped galaxies.The homogeneous distribution of the S-and Z-shaped galaxies is more noticeable for the late-...     

First photometric study of the eclipsing binary PS Persei

CCD photometric observations of the eclipsing binary PS Persei (PS Per) were obtained on two consecutive days in 2009.The 2003 version of the WilsonDevinney code was used to analyze the first complete light curves in the V and R bands.It is found that PS Per is a short-period Algol-type binary with the less massive component completely filling its inner critical Roche lobe.The mass ratio of q=0.518 and the orbital inclination of i=89.86° are obtained.In addition,based on all available times of primary light...     

Solar sail time-optimal interplanetary transfer trajectory design

The fuel consumption associated with some interplanetary transfer trajectories using chemical propulsion is not affordable. A solar sail is a method of propulsion that does not consume fuel. Transfer time is one of the most pressing problems of solar sail transfer trajectory design. This paper investigates the time-optimal interplanetary transfer trajectories to a circular orbit of given inclination and radius. The optimal control law is derived from the principle of maximization. An indirect method is used...     

Photometric analysis of V30 of open cluster NGC 7789

We present the photometric solutions of the variable star V30 that is in the foreground of intermediate open cluster NGC 7789.The observations were done in the V passband using the 2 m telescope at the IUCAA-Girawali Observatory in India.The analysis is done using the Wilson-Devinney Code (2003) and the fitted light curve is presented.The photometric solutions reveal a W-subtype contact configuration.The photometric mass ratio is found to be 0.395 and the absolute masses and radii for the components are ded...     

On pulsar-driven mass ejection in low-mass X-ray binaries

There is accumulating evidence for mass ejection in low-mass X-ray binaries(LMXBs)driven by radio pulsar activity during X-ray quiescence.We consider the condition for mass ejection by comparing the radiation pressure from a millisecond pulsar,and the gas pressure at the inner Lagrange point or at the surrounding accretion disk.We calculate the critical spin period of the pulsar below which mass ejection is allowed.Combining with the evolution of the mass transfer rate,we present constraints on the orbital ...     

CCD photometry of W UMa-type contact binaries in the old open cluster Berkeley 39

We present the combined BVI multicolor photometric solutions of seven EW variables in the old open cluster Berkeley 39.The observations were carried out in the B and V passbands from the 2 m telescope at the IUCAA-Girawali Observatory in India.The analysis is done using the 2003 version of the Wilson-Devinney code and the fitted light curves are presented.The light curves appear to be symmetric in all the passbands.The photometric solutions suggest that the variables are W-type systems.The new ephemeris ind...     

Relations between integrated and monochromatic luminosities of flat-spectrum radio quasars

We employ a sample of 362 flat-spectrum radio quasars (FSRQs) to calculate their integrated luminosities by integrating the spectral energy distribution (SED) constructed with multi-band (radio,IR,optical,UV and X-ray) data.We compare these luminosities with those estimated from monochromatic luminosities by multiplying them by the conventional bolometric correction factors.Our analysis shows that the integrated luminosities calculated from the SED are much larger than the bolometric luminosities estimated ...     

Strange star candidates revised within a quark model with chiral mass scaling

We calculate the properties of static strange stars using a quark model with chiral mass scaling.The results are characterized by a large maximum mass (～ 1.6 M) and radius (～10 km).Together with a broad collection of modern neutron star models,we discuss some recent astrophysical observational data that could shed new light on the possible presence of strange quark matter in compact stars.We conclude that none of the present astrophysical observations can prove or confute the existence of strange stars.     

A note on the discovery of a 2M_⊙ pulsar

It is conventionally thought that the state equation of dense matter softens and thus cannot result in high maximum mass if pulsars are quark stars and that a recently discovered 2M⊙ pulsar (PSR J1614-2230) may make pulsars unlikely to be quark stars. However, this standard point of view would be revisited and updated if quark clustering could occur in cold quark matter because of the strong coupling be- tween quarks at realistic baryon densities in compact stars. It can be argued that the state equation of...     

Dark halos acting as chaos controllers in asymmetric triaxial galaxy models

We study the regular or chaotic character of orbits in a 3D dynamical model,describing a triaxial galaxy surrounded by a spherical dark halo component.Our numerical experiments suggest that the percentage of chaotic orbits decreases exponentially as the mass of the dark halo increases.A linear increase of the percentage of the chaotic orbits was observed as the scale length of the halo component increases. In order to distinguish between regular and chaotic motion,we chose to use the total angular momentum ...