LONG-TERM PHOTOMETRIC ANALYSIS OF THE ACTIVE W UMa-TYPE SYSTEM TU BOOTIS

Coughlin, Jeffrey L.; Dale, H. A.; Williamon, R. M.

doi:10.1088/0004-6256/136/3/1089

Cited by 13 publications

(12 citation statements)

References 25 publications

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“…Live version of the data can be downloaded from http://www.inasan.ru/∼malkov/CEV/ APPENDIX A: DISCUSSION OF SELECTED BINARIES TU Boo may be classified as a contact W UMa of Asubtype because the primary minimum is a transit. The asymmetry of light curves was detected by several authors (Niarchos et al 1996;Coughlin et al 2008). Niarchos et al (1996) found the light curve solution with WD program using spotted model for contact configuration.…”

Section: Discussionmentioning

confidence: 99%

“…Moreover, their solution with spots shows that the less massive and smaller secondary is hotter than the primary. According to Coughlin et al (2008) TU Boo is a marginal contact system with both components almost filling their critical lobes. They supposed the mass transfer from secondary to primary which is supported by an increased period.…”

Section: Appendix B: Application Of the Classification Algorithmmentioning

confidence: 99%

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Assessment of evolutionary status of eclipsing binaries using light-curve parameters and spectral classification

Avvakumova

Malkov

2014

Monthly Notices of the Royal Astronomical Society

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We have developed a procedure for the classification of eclipsing binaries from their light-curve parameters and spectral type. The procedure was tested on more than 1000 systems with known classification, and its efficiency was estimated for every evolutionary status we use. The procedure was applied to about 4700 binaries with no classification, and the vast majority of them was classified successfully. Systems of relatively rare evolutionary classes were detected in that process, as well as systems with unusual and/or contradictory parameters. Also, for 50 previously unclassified cluster binaries evolutionary classes were identified. These stars can serve as tracers for age and distance estimation of their parent stellar systems. The procedure proved itself as fast, flexible and effective enough to be applied to large ground based and space born surveys, containing tens of thousands of eclipsing binaries.

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Section: Discussionmentioning

confidence: 99%

Section: Appendix B: Application Of the Classification Algorithmmentioning

confidence: 99%

Assessment of evolutionary status of eclipsing binaries using light-curve parameters and spectral classification

Avvakumova

Malkov

2014

Monthly Notices of the Royal Astronomical Society

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“…The temperature of its spotfree part may be higher than the secondary's temperature but the apparent surface averaged temperature is lower. W UMa-type stars have a very high level of chromosphericcoronal activity (Cruddace & Dupree 1984;Rucinski 1985;Vilhu & Walter 1987;Stȩpień et al 2001) and variations of the light curve, observed on time scales of decades, indicate that they also possess dark starspots covering a variable fraction of the stellar surface (Gazeas, Niarchos & Gradoula 2006;Coughlin, Dale & Williamon 2008). Perhaps the most extreme example of light curve variability due to a variable coverage by spots can be seen in Rucinski & Paczynski (2002).…”

Section: The W-type Phenomenon and Photospheric Starspotsmentioning

confidence: 99%

Large-scale circulations and energy transport in contact binaries

Stępień

2009

Monthly Notices of the Royal Astronomical Society

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A hydrodynamic model for the energy transport between the components of a contact binary is presented. Energy is transported by a large‐scale, steady circulation carrying high entropy matter from the primary to secondary component. The circulation is driven by the baroclinic structure of the common envelope, which is a direct consequence of the non‐uniform heating at the inner critical Roche lobes due to unequal emergent energy fluxes of the components. The mass stream flowing around the secondary is bound to the equatorial region by the Coriolis force and its width is determined primarily by the flow velocity. Its bottom is separated from the underlying secondary's convection zone by a radiative transition layer acting as an insulator. For a typically observed degree of contact the heat capacity of the stream matter is much larger than radiative losses during its flow around the secondary. As a result, its effective temperature and entropy decrease very little before it returns to the primary. The existence of the stream changes insignificantly specific entropies of both convective envelopes and sizes of the components. Substantial oversize of the secondaries, required by the Roche geometry, cannot be explained in this way. The situation can, however, be explained by assuming that the primary is a main‐sequence star whereas the secondary is in an advanced evolutionary stage with hydrogen depleted in its core. Such a configuration is reached past mass transfer with mass ratio reversal. Good agreement with observations is demonstrated by model calculations applied to actual W UMa‐type binaries. In particular, a presence of the equatorial bulge moving with a relative velocity of 10–30 km s−! around both components of AW UMa is accounted for.

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“…As the two components of FO Hya are in a state of over-contact, we take the most likely cause of the period change as the transfer of mass between the components. The amount of mass transfer, dm is related to the change in period, dP, for a system of total mass, M via (Coughlin et al, 2008;Yang and Liu, 2003).…”

Section: Period Analysismentioning

confidence: 99%

BVRI photometric and polarimetric studies of W UMa type eclipsing binary FO Hydra

Prasad¹,

Pandey²,

Patel³

et al. 2013

New Astronomy

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h i g h l i g h t s " We present analysis of optical photometric and polarimetric observations of contact binary system FO Hydra (FO Hya). " The computed period of the system is 0.469556 ± 0.000003 days. " An O-C curve analysis indicates an increase in its period by 5.77 Â 10 -8 day yr À1 . " The photometric light curves are analyzed using Wilson-Devinney code (WD). " In this analysis we have taken up, presumably for the first time, the polarimetric studies of FO Hya, and obtain the mean values of degree of polarization and polarization position angle. a b s t r a c tWe present analysis of optical photometric and polarimetric observations of contact binary system FO Hydra (FO Hya). The computed period of the system is 0.469556 ± 0.000003 days. An O-C curve analysis indicates an increase in its period by 5.77 Â 10 À8 day yr À1 . The photometric light curves are analyzed using Wilson-Devinney code (WD). The present analysis shows that FO Hya is a B-subtype of W UMa type contact binary. The radii and mass of primary and secondary components are found, respectively, to be R 1 = 1.62 ± 0.03 R and R 2 = 0.91 ± 0.02 R , and M 1 = 1.31 ± 0.07 M and M 2 = 0.31 ± 0.11 M . The light curve shape shows small asymmetries around the primary and secondary maxima. This may be due to the presence of dark spots on the components. The polarimetric observations yield average values of its polarization to be 0.18 ± 0.03, 0.15 ± 0.03, 0.17 ± 0.02 and 0.15 ± 0.02% in B, V, R and I bands, respectively. These values are appreciably lower than the typical polarization of W UMa type binaries. We have discussed the possible sources of the observed polarization but in order to arrive at definitive answer to this more phase locked observations are needed.

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LONG-TERM PHOTOMETRIC ANALYSIS OF THE ACTIVE W UMa-TYPE SYSTEM TU BOOTIS

Cited by 13 publications

References 25 publications

Assessment of evolutionary status of eclipsing binaries using light-curve parameters and spectral classification

Assessment of evolutionary status of eclipsing binaries using light-curve parameters and spectral classification

Large-scale circulations and energy transport in contact binaries

BVRI photometric and polarimetric studies of W UMa type eclipsing binary FO Hydra

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