A Model for Contact Binary EP Andromedae

Manzoori, Davood

doi:10.1071/as11003

Cited by 7 publications

(6 citation statements)

References 51 publications

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“…Table 3 lists the light-curve sets for EP And analyzed in this paper and the standard deviations (σ) of a single observation. Although the binary parameters have been reported by Pribulla et al (2001) and Manzoori (2012), their solutions with q <1.0 do not correspond to our high-precision observations of 2008, showing a total eclipse at primary minimum and hence implying q >1.0. To resolve this confusion, we analyzed the light curves of EP And in a manner similar to that for the overcontact systems AR Boo (Lee et al 2009c) and GW Cep (Lee et al 2010) using the so-called q-search procedure.…”

Section: New Long-term Ccd Photometrycontrasting

confidence: 90%

“…From a quadratic least-squares fit, they reported a period increase with a rate of +1.16×10 −7 d yr −1 . Recently, Manzoori (2012) claimed that two periodicities of 41.2 yr and 11.7 yr, superimposed on the upward parabolic variation, exist in the timing residuals. As the first step for ephemeris computations, we applied a periodogram analysis to the complete dataset using the PERIOD04 program (Lenz & Breger 2005).…”

Section: Orbital Period Studymentioning

confidence: 99%

“…Since the discovery of its variability by Strohmeier et al (1955), EP And (TYC 2827-17-1, GSC 2827-17, 2MASS J01422933+4445424; V =+11.90, B-V =+0.57) has been the topic of several investigations, but its properties are relatively poorly known compared to other shortperiod binaries. Most recently, Manzoori (2012) reviewed the observational history of the system and presented the first comprehensive photometric study. The author analyzed the photometric data from both the AAVSO (American Association of Variable Stars Observers) International Database 1 and the WASP (Wide Angle Search for Planets) public archive (Butters et al 2010), and concluded that EP And is an A-type (defined observationally by Binnendijk 1970) overcontact binary with a mass ratio of q=0.395, an orbital inclination of i=81 • .5, a temperature difference between the components of ∆T =120 K, and a fill-out factor of f = 16.6 %.…”

Section: Introductionmentioning

confidence: 99%

“…In order to obtain a unique set of photometric solutions and to examine whether the Manzoori's (2012) suggestion is appropriate for the orbital period change, we have studied in detail the long-term photometric behavior of EP And from all available data. Our results from both the light-curve synthesis and the orbital period study show that EP And is probably a multiple system.…”

Section: Introductionmentioning

confidence: 99%

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The Eclipsing System Ep Andromedae and Its Circumbinary Companions

Lee

Hinse

Park

2013

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We present new long-term CCD photometry for EP And acquired during the period 2007 to 2012. The light curves display total eclipses at primary minima and seasonto-season light variability. Our synthesis for all available light curves indicates that the eclipsing pair is a W-type overcontact binary with parameters of q=2.578, i=83 • .3, ∆T =27 K, f =28 %, and l 3 =2∼3 %. The asymmetric light curves in 2007 were satisfactorily modeled by a cool spot on either of the eclipsing components from a magnetic dynamo. Including our 95 timing measurements, a total of 414 times of minimum light spanning about 82 yr were used for a period study. A detailed analysis of the eclipse timing diagram revealed that the orbital period of EP And has varied as a combination of an upward-opening parabola and two periodic variations, with cycle lengths of P 3 =44.6 yr and P 4 =1.834 yr and semi-amplitudes of K 3 =0.0100 d and K 4 =0.0039 d, respectively. The observed period increase at a fractional rate of +1.39×10 −10 is in excellent agreement with that calculated from the W-D code and can be plausibly explained by some combination of mass transfer from the primary to the secondary star and angular momentum loss due to magnetic braking. The most reasonable explanation for both cycles is a pair of light-travel-time effects driven by the possible existence of a third and fourth component with projected masses of M 3 =0.25 M ⊙ and M 4 =0.90 M ⊙ . The more massive companion could be revealed using high-resolution spectroscopic data extending over the course of a few years and could also be a binary itself. It is possible that the circumbinary objects may have played an important role in the formation and evolution of the eclipsing pair, which would cause it to have a short initial orbital period and thus evolve into an overcontact configuration by angular momentum loss. Subject headings: binaries: close -binaries: eclipsing -stars: individual (EP Andromedae) -stars: spots 3. LIGHT-CURVE SYNTHESIS AND ABSOLUTE DIMENSIONS As shown in Figure 1, our observations display a typical light curve of an overcontact system and a flat bottom at primary minimum, indicating that the smaller primary star is totally occulted by the secondary. This would mean that EP And belongs to the W-type of W UMa stars. On the contrary, Pribulla et al. (2001) and Manzoori (2012) analyzed their BV light curves and both the AAVSO and WASP datasets, respectively, and classified the binary system as a member of the A-type category with the mass ratios of 0.34 and 0.395. The light curves of 2008 present equal light levels at the quadratures (Max I and Max II) within about 0.002 mag, while those of 2007 show the O'Connell effect with Max I brighter than Max II by about 0.014, 0.011, and 0.009 mag for the B, V , and R bandpasses, respectively. The effect is usually interpreted as spot activity on the component stars and the seasonal light variations most likely arise from the variability of the spots with time presumably produced by a magnetic dynamo.

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Section: New Long-term Ccd Photometrycontrasting

confidence: 90%

Section: Orbital Period Studymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Eclipsing System Ep Andromedae and Its Circumbinary Companions

Lee

Hinse

Park

2013

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“…Additionally, the length of the obtained cyclic period seems to be too long as to be interpreted as a magnetic activity cycle. For example, this period for the sun is 11 yr, for U Sge 9.5 yr (Manzoori 2007), for U Cep 16.4 yr (Manzoori 2008), for Algol 32 yr (Soderhjelm 1980), for UV Leo 24.3 yr (Manzoori 2012a), for SW Cyg 27.9 yr (Manzoori 2007), for RT And 11.9 yr (Manzoori 2009), for EP And 11.72 yr (Manzoori 2012b). …”

Section: Magnetic Activity Cyclementioning

confidence: 98%

Light and period study of the ecipsing binary system TW Andromedae

Manzoori

2014

Astron Nachr

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Photoelectric light curve (LC) solutions of the close binary system TW And were obtained using the PHOEBE program (version 0.31a). Absolute parameters of the stellar components were then determined, enabling us to discuss the structure and evolutionary status of TW And. The configuration of the system based on the LCs solutions indicates that the secondary component is slightly detached from its critical Roche surface. In addition, times of minima data ("O -C curve") were analyzed. Apart from an almost parabolic variation of the general trend of the O -C data, indicative of a secular increase in the orbital period with a rate 0.032 s yr −1 , which was attributed to a mass transfer with a rate of Δm2 = −1.10×10−10 M yr −1 . Additionally, a sinusoidal variation with a period of 52.75 ± 1.80 yr, modulating the orbital period, was found, which we attribute to a third body orbiting the system.

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Analysis of the photoelectric light curve and the orbital period variations of the binary system UU Andromedae

2015

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In this work, the analysis of the photoelectric light curve (LC) in the broad‐band filter (400–700 nm) for the UU And system was carried out using the PHOEBE program (vers. 0.31a). The absolute dimensions of the system are determined and its evolution is discussed. Moreover, the period changes of the system are studied using updated O – C data, which shows a cyclic change with a period of Pmod = 18 yr. This was attributed to a magnetic activity cycle operating in this system. In addition to the cyclic change, a long‐term secular variation due to mass transfer from the secondary to the primary component with a rate of 6.17×10–9 M⊙ yr–1 was also detected. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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A Model for Contact Binary EP Andromedae

Cited by 7 publications

References 51 publications

The Eclipsing System Ep Andromedae and Its Circumbinary Companions

The Eclipsing System Ep Andromedae and Its Circumbinary Companions

Light and period study of the ecipsing binary system TW Andromedae

Analysis of the photoelectric light curve and the orbital period variations of the binary system UU Andromedae

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