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Photometric study of eclipsing binaries in the Large Magellanic Cloud--I.W UMa type binaries in the Large Magellanic Cloud

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Research in Astronomy and Astrophysics 2011年第2期11卷 175-180页

作者： Devarapalli Shanti Priya kandulapati sriram Pasagada Vivekananda Rao Department of Astronomy Osmania University Korea Astronomy and Space Science Institute

Eclipsing binaries are among the most important sources of information on stellar parameters like radii,masses,luminosities,*** present the analysis of six W UMa systems discovered in the Large Magellanic Cloud using ... 详细信息

关键词： binaries: eclipsing -- binaries: close

Photometric study of W UMa type binaries in the old open cluster Berkeley 39

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Research in Astronomy and Astrophysics 2009年第10期9卷 1149-1154页

作者： kandulapati sriram Yellapragada Ravi Kiron Pasagada Vivekananda Rao Department of Astronomy Osmania University

The study of W UMa binary systems gives a wealth of information about their nature as well as their parent bodies （if any）, like clusters. In this paper, we present the I passband photometric solutions of four W UMa binaries in the open cluster Berkeley 39 using the latest version of the W-D program. The result shows that two binary systems are W-subtype W UMa binary systems and the other two systems are H-subtype W UMa binary systems. No third body has been found in any of the four systems. We found a correlation between the period and mass-ratio as well as temperature and mass-ratio for the respective variables, which is similar to the relationship between mass ratio and total mass of the contact binaries as shown by van＇t Veer and Li et al.

关键词： binaries eclipsing -- binaries close

Photometric study of an eclipsing binary in the field of M37

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Research in Astronomy and Astrophysics 2014年第9期14卷 1166-1172页

作者： Devarapalli Shanti Priya kandulapati sriram Pasagada Vivekananda Rao Department of Astronomy Osmania University Hyderabad 500 007 India

CCD photometric observations with B and V passbands were performed on the contact binary V3 in the field of open cluster M37. The solutions were obtained for data from both B and V passbands along with R passband given by Hartman et al. using the Wilson-Devinney code. The positive O＇Connell effect was observed in all the three passbands and its associated cool spot parameters were derived. The results indicate that the spot parameters have not shown any significant variability during the last four years. The spot radius was found to be 40° and located close to the equator of the secondary component. The absolute parameters of the system were derived using the empirical relations given by Gazeas et al.

关键词： binaries: eclipsing -- binaries: close

A truncated accretion disk in the galactic black hole candidate source H1743–322

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Research in Astronomy and Astrophysics 2009年第8期9卷 901-910页

作者： kandulapati sriram Vivek Kumar Agrawal Arikkala Raghurama Rao Department of Astronomy Osmania University Department of Astronomy and Astrophysics Tata Institute of Fundamental Research Indian Space Research Organization

To investigate the geometry of the accretion disk in the source H1743-322, we have carried out a detailed X-ray temporal and spectral study using RXTE pointed observations. We have selected all data pertaining to the Steep Power Law （SPL） state during the 2003 outburst of this source. We find anti-correlated hard X-ray lags in three of the observations and the changes in the spectral and timing parameters （like the QPO frequency） confirm the idea of a truncated accretion disk in this source, Compiling data from similar observations of other sources, we find a correlation between the fractional change in the QPO frequency and the observed delay. We suggest that these observations indicate a definite size scale in the inner accretion disk （the radius of the truncated disk） and we explain the observed correlation using various disk parameters like Compton cooling time scale, viscous time scale etc..

关键词： accretion, accretion disk -- binaries close -- stars individual (H1743-322)-- X-rays binaries

Photometric study of an eclipsing binary in Praesepe

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Research in Astronomy and Astrophysics 2013年第4期13卷 465-470页

作者： Devarapalli Shanti Priya kandulapati sriram Pasagada Vivekananda Rao Department of Astronomy Osmania University Korea Astronomy and Space Science Institute

We present CCD photometric observations of an eclipsing binary in the direction of the open cluster Praesepe using the 2 m telescope at IUCAA Girawali Observatory, India. Though the system was classified as an eclipsing binary by Pepper et al., detailed investigations have been lacking. The photometric solutions using the Wilson-Devinney code suggest that it is a W-type W UMa system and, interestingly, the system parameters are similar to another contact binary system SW Lac.

关键词： binaries: eclipsing - binaries: close -open clusters: Praesepe

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

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Research in Astronomy and Astrophysics 2011年第12期11卷 1469-1481页

作者： Yellapragada Ravi Kiron kandulapati sriram Pasagada Vivekananda Rao Department of Astronomy Osmania University Korea Astronomy and Space Science Institute

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 indicates that the orbital periods of the studied variables have not changed during the timespan of observations. Revised orbital period, absolute mass, radius and luminosity of the respective variables are presented. The absolute physical parameters of the variables follow the trend of field EW stars. Comparing the results obtained with the other theoretical works, we suggest that there is an excess loss of mass and angular momentum in these systems which may be due to their short period and relatively young age, possibly due to the presence of a third component or the initial detached period being less than 2 d.

关键词： binaries -- eclipsing: contact: W UMa stars

Photometric analysis of V30 of open cluster NGC 7789

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Research in Astronomy and Astrophysics 2011年第9期11卷 1067-1073页

作者： Yellapragada Ravi Kiron kandulapati sriram Pasagada Vivekananda Rao Department of Astronomy Osmania UniversityHyderabad 500 007India Korea Astronomy and Space Science Institute Hwaam 61-1YuseongDaejeon 305-348Republic of Korea

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 deduced as 1.25Ms and 0.97Rs for the primary and 0.49Ms and 0.93Rs for the secondary, respectively. No signature of third light is found in the system.

关键词： stars binaries eclipsing -- binaries contact