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CCD Photometry, Roche Modeling and Evolutionary History of the W UMa-type Eclipsing Binary TYC 01664-0110-1

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Alton K. B. , Stępień K.

Acta Astronomica

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2016

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tom Vol. 66, No. 3

357--379

EN

TYC 01664-0110-1 (ASAS J212915+1604.9), a W UMa-type variable system (P=0.282962 d), was first detected over 17 years ago by the ROTSE-I telescope. Photometric data (B, V and Ic) collected at UnderOak Observatory (UO) resulted in five new times-of-minima for this variable star which were used to establish a revised linear ephemeris. No published radial velocity (RV) data are available for this system. However, since this W UMa binary undergoes a total eclipse, Roche modeling based on the Wilson-Devinney (W-D) code yielded a well-constrained photometric value for M2/M1 (q=0.356±0.001). There is a suggestion from ROTSE-I (1999) and ASAS survey data (2003, 2005, and 2008) that the secondary maximum is more variable than the primary one probably due to the so-called O'Connell effect. However, peak asymmetry in light curves (LC) from 2015 was barely evident during quadrature. Therefore, W-D model fits of these most recent data did not yield any substantive improvement with the addition of spot(s). Using the evolutionary model of cool close binaries we searched for a possible progenitor of TYC 01664-0110-1. The best fit is obtained if the initial binary has an orbital period between 3.3-3.8 d and component masses between 1.0-1.1 M⊙ and 0.30-0.35 M⊙. The model progenitor needs about 10 Gyr to attain the presently observed parameters of the variable. Its period slowly increases and the mass ratio decreases. According to the model predictions TYC 01664-0110-1 will go through the common envelope (CE) phase in the future, followed by merging of both components or formation of a double degenerate. Due to its apparent brightness (mV,max≈10.9 mag) and unique properties, the star is an excellent target for spectroscopic investigation of any possible deviations from a simple static model of a contact binary.

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Roche Modeling and Evolutionary History of Six Low Mass Contact Binary Systems

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Alton K. B. , Stępień K.

Acta Astronomica

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2021

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tom Vol. 71, No. 2

123--161

EN

We describe six eclipsing binary systems that were first detected by the ROTSE-I telescope and ultimately shown to be low mass contact binaries (LMCB). New photometric data (B, V and Ic) acquired from V473 Cam, PV Com, EI CVn, V2790 Ori, V2802 Ori and PS Vir were used to calculate an orbital period for each system along with updated ephemerides. All systems were subject to secular changes in orbital period with evidence for a third gravitationally bound body in V473 Cam, EI CVn, V2790 Ori, and PS Vir. Since a total eclipse is observed in all six systems, Roche modeling based on the Wilson-Devinney (WD) code yielded in each case a well-constrained photometric value for the mass ratio. Potential progenitors of these LMCBs were evaluated using an evolutionary model of cool close binaries. The best fits were obtained when the initial detached binaries have orbital periods ranging from 2.70 d to 3.71 d, total masses between 1.36 M and 1.53 M with mass ratios ranging from 2.34 to 4.04. The model progenitors require between 7.75-10.9 Gyr to attain the presently observed orbital period and physical attributes. Collectively, the models show that about half of orbital periods will increase in the future leading to a common envelope resulting from the evolutionary expansion of the accretor whereas the other half will decrease resulting in the overflow of the outer critical Roche surface and an ultimate merger.

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CCD Photometry, Light Curve Deconvolution, Period Analysis and Evolutionary Status of the HADS Variable V524 And

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Alton K. B. , Stępień K.

Acta Astronomica

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2019

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tom Vol. 69, No. 3

283--304

EN

New multi-color BVIc CCD photometric data of V524 And, a pulsating variable long considered to be an SX Phe-type subdwarf system were acquired during 2018. Deconvolution of precise time-series light curve data was accomplished using discrete Fourier transformation and revealed a mean fundamental mode f0 of oscillation at 10.583 d-1 along with four other harmonics from 2f0 to 5f0. Following successive pre-whitening of each residual signal, no other statistically significant frequency shared by all band-passes was resolved. Potential period changes over time were evaluated using four new times-of-maximum light derived from the present study along with other values reported in the literature. Photometric data collected during the ROTSE-I (1999) and SuperWASP (2007-2008) surveys combined with CCD-derived V-mag data acquired from the AAVSO archives produced an additional sixty-six times-of-maximum measurements. Corresponding residuals from the observed minus calculated values indicate very little change in the primary pulsation period since 1999. However, a far more interesting finding from this secular analysis suggests an underlying sinusoidal-like variation of PB=6.41 yr consistent with a putative binary partner that may be a brown dwarf (M<0.07 M☉). An investigation with PARSEC models for generating stellar tracks and isochrones provided further insight into the evolutionary status and physical character of V524 And. This intrinsic variable associated with the Galactic disk has an estimated mass around 2 M☉ with near-solar metallicity. These characteristics point to V524 And being a Population I HADS with an age approaching 1 Gyr rather than an SX Phe-type variable.

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Roche Modeling and Evolutionary History of Multiple Low Mass Contact Binary Systems

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Alton K. B. , Stępień K.

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tom Vol. 68, No. 4

449--482

EN

The Northern Sky Variable Survey (NSVS) has been a rich source of variable stars many of which have only been studied to a limited extent. Herein we describe five eclipsing binary systems that were first detected by the ROTSE-I telescope and ultimately shown to be low mass contact binaries. Photometric data (B, V and Ic) acquired from MU Cnc (NSVS 10133793, TYC 1397-1030-1), V596 Peg (NSVS 6225359, GSC 2765-0348), TYC 1597-2327-1 (NSVS 11082150), GSC 2723-2376 (NSVS 8849526) and GSC 4946-0765 (NSVS 13176410) were used to calculate an orbital period for each system along with new linear ephemerides. Except for MU Cnc, the limited number of time-of-minimum values precluded the characterization of any long-term period change. Since a total eclipse is observed with all five systems, Roche modeling based on the Wilson-Devinney W-D code yielded in each instance a well-constrained photometric value for the mass ratio. Using the evolutionary model of cool close binaries we searched for possible progenitors of the investigated binaries. The best fit is obtained if the initial binaries have orbital periods from the interval between 2.4–3.4 d, total masses between 6% and 9% higher than presently observed and mass ratios between 2.2 and 3.3. The model progenitors need between 7.5–10 Gyr to attain the presently observed parameters of the variables. The present periods of three models slowly increase with simultaneous mass ratio decrease, which suggests the formation of the common envelope in the future. However, in four other models the period decreases and the model computations predict the ultimate overflow of the outer Roche lobe.

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CCD Photometry, Light Curve Modeling and Period Analysis of the Overcontact Eclipsing Binary BN Ari

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Alton K. B. , Nelson R. H. , Boyd D. R. S.

Acta Astronomica

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2018

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tom Vol. 68, No. 2

159--181

EN

We present photometric and spectroscopic data of BN Ari, a totally eclipsing variable star. 15 new times-of-minimum have been determined. These along with other published eclipse timings were used to update the linear ephemeris and evaluate changes in orbital periodicity. Radial velocity data along with a definitive classification spectrum are reported for the first time. Simultaneous modeling of multicolor light curves and radial velocity data was accomplished using the Wilson-Devinney code with optimization by differential corrections. The weight of evidence from evaluating both the eclipse timing differences and light curve modeling indicates that BN Ari is most likely a triple system.