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RISS 인기검색어
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- 저자 : Malu, S. (검색결과 3 건)
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ASAS J083241+2332.4: A NEW EXTREME LOW MASS RATIO OVERCONTACT BINARY SYSTEM
Sriram, K.,Malu, S.,Choi, C. S.,Vivekananda Rao, P. American Astronomical Society 2016 The Astronomical journal Vol.151 No.3
<P>We present the R-and V-band CCD photometry and H alpha line studies of an overcontact binary ASAS J083241+2332.4. The light curves exhibit totality along with a trace of the O'Connell effect. The photometric solution indicates that this system falls into the category of extreme low-mass ratio overcontact binaries with a mass ratio, q similar to 0.06. Although a trace of the O' Connell effect is observed, constancy of the H alpha line along various phases suggest that a relatively higher magnetic activity is needed for it to show a prominent fill-in effect. The study of O-C variations reveals that the period of the binary shows a secular increase at the rate of dP/dt similar to 0.0765 s years(-1), which is superimposed by a low, but significant, sinusoidal modulation with a period of similar to 8.25 years. Assuming that the sinusoidal variation is due to the presence of a third body, orbital elements have been derived. There exist three other similar systems, SX Crv, V857 Her, and E53, which have extremely low mass ratios and we conclude that ASAS J083241+2332.4 resembles SX Crv in many respects. Theoretical studies indicate that at a critical mass ratio range, q(critical) = 0.07-0.09, overcontact binaries should merge and form a fast rotating star, but it has been suggested that q(critical) can continue to fall up to 0.05 depending on the primary's mass and structure. Moreover, the obtained fill-out factors (50%-70%) indicate that mass loss is considerable and hydrodynamical simulations advocate that mass loss from L-2 is mandatory for a successful merging process. Comprehensively, the results indicate that ASAS J083241+2332.4 is at a stage of merger. The pivotal role played by the subtle nature of the derived mass ratio in forming a rapidly rotating star has been discussed.</P>
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A Study of the<i>Kepler K2</i>Variable EPIC 211957146 Exhibiting a Variable O’ Connell Effect
Sriram, K.,Malu, S.,Choi, C. S.,Rao, P. Vivekananda American Astronomical Society 2017 The Astronomical journal Vol.153 No.5
<P>We present the multi-band photometric and spectroscopic study of an over-contact binary system, EPIC 211957146. The light curves exhibit a variable O' Connell effect, confirmed from our observational data and the Kepler K2 data. The best photometric solution incorporating a dark spot over the primary component unveils that the system has a low-mass ratio (q similar to 0.17) and a high inclination (i similar to 85 degrees). To confirm the solution and constrain the uncertainty, Monte-Carlo simulations are performed and the results are reported. Based on the O-C diagram analysis, we see that the variable shows a period increase at the rate of dP/dt similar to 1.06. x. 10(-6) days yr(-1), which is higher than the theoretically predicted value. Presence of a third body having a period of similar to 16.23 years is evident from the O-C diagram. No filled-in effect is observed in the Ha line, while the effect is vividly present in the Na line. From the Kepler K2 data, we found that the primary and secondary minima exhibit an anti-correlated O-C variation followed by an erratic behavior. This is possibly caused by the longitudinal motion of the spot, and hence, we set a lower limit of similar to 40 days for the spot modulation. We also observe a possibly associated photometric difference in the primary depth by comparing our light curves with Kepler K2 normalized light curves. This system has a low-mass ratio and a high fill-out factor, and, theoretically, such a physical configuration would lead to a merger.</P>
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