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PERIOD VARIATION STUDY OF THE NEGLECTED ALGOL ECLIPSING BINARY SYSTEM V346 CYGNIUS
PERIOD VARIATION STUDY OF THE NEGLECTED ALGOL ECLIPSING BINARY SYSTEM V346 CYGNIUS
Journal of The Korean Astronomical Society. 2014. May, 47(3): 99-104
Copyright © 2014, null
  • Received : February 24, 2014
  • Accepted : April 07, 2014
  • Published : May 20, 2014
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MAGDY HANNA

Abstract
We present the rst period variation study for the Algol eclipsing binary V346 Cyg by constructing the ( O-C ) residual diagram using all the available precise minima times. We conclude that the period variation can be explained by a sine-like variation due to the presence of a third body orbiting the binary in about 68.89±4.69 years, together with a long-term orbital period decrease ( dP/dt =−1.23×10 −7 day/yr) that can be interpreted to be due to slow mass loss from the δ -Scuti primary component. The sinusoidal variation may also be explained by using the the Applegate (1992) mechanism involving cyclic magnetic activity due to star-spots on the secondary component. The present preliminary solution needs more precise photometric observations to be confirmed.
Keywords
1. INTRODUCTION
The system V346 Cyg (HIP 100198, TYC 2684-1000-1, α 2000 = 20 h 19 m 24 s .7244, δ 2000 = +36° 20′ 24.2092, π = 2.57 (mas), and Sp. type A5 according to the SIMBAD database) is an eclipsing binary system. Its changeability was discovered by Beljawsky (1932), and confirmed by Parenago (1933) who determined the first three photographic times of minimum and suggested its Algol type configuration. Florja (1934) monitored the system visually covering the time interval from Aug 8, 1932 to Aug 31, 1933. From the observations, he derived 10 minima times and obtained the first linear ephemeris:
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Florja also combined his visual observations to those photographic minima given by Parenago and deduced the linear ephemeris:
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According to this ephemeris, he also obtained the first (mean) visual light curve for V346 Cyg.
The first photographic light curve was observed by Petrow (1946) who used the linear elements of Florja (1934) and deduced the linear elements:
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The system was recorded as a semi-detached Algol eclipsing binary by many authors (e.g., Brancewicz & Dworak 1980; Budding et al. 2004; Samus et al. 2004; Kim et al. 2005; Soydugan et al. 2006a,b), while it was mentioned as a detached system by the current SIMBAD database.
The system was partially observed photometrically in the B-passband by Kim et al. (2005). They used 2K CCD camera attached to 1.0m telescope of the Mt. Lemmon Optical Astronomy Observatory. Their observations were performed for six nights in November 2004, about 2 hours per night. They obtained some parts of the phase diagram, combined them to a primary minimum of depth 1 m .7, used the light curve solution of Surkova & Svechnikov (2004) and considered the semi-detached Algol binary configuration to apply the Wilson & Devinney (1971) code. They then concluded that the primary component of V346 Cyg has δ Scuti character.
As V346 Cyg is of maximum mag B = 11.8, and a relatively short period P = 2. d 743310 (Brancewicz & Dworak 1980), Budding (1984) has listed it among a relatively neglected group of binaries. Since then, many observers have monitored this system and determined about 20 photoelectric (pe) and CCD minima times. Later, the general properties of V346 Cyg were given by Soydugan et al. (2006b) and are listed in Table 1 . They deduced that the system is an eclipsing binary with pulsating component and A5+G4IV Sp. Type.
Physical Parameters of V346 Cyg in literature
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Physical Parameters of V346 Cyg in literature
The aim of the present paper is to discuss the possible mechanisms that could be causing the changes in the period of V346 Cyg and to determine the LITE due to the presence of a third body, as well as to apply the Applegate mechanism to test the magnetic activity which is nearly a common characteristic among late–type low–mass stars similar to our sun.
2. PERIOD VARIATION STUDY
No period variation studies of this system have been conducted till now. An essential method to study the period variation in eclipsing binary systems is the analysis of the O – C diagram, by the use of minima times determined throughout the observational history of the binary. For this purpose, a total of 71 minima times are gathered and listed in the self-explanatory Table 4 . We construct the O – C diagram ( Figure 1 ) by using Kreiner’s (2004a) light elements:
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Times of minima
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REFERENCES: [1] Parenago, P. P. 1933, PZ, 4, 134 [2] Florja, N. 1934, PZ, 4, 383 [3] Petrow, A. A. 1946, PZ, 6, 207 [4] Whitney, B. S. 1959, AJ, 64, 258 [5] Szczepanowska, A. 1956, AcA, 6, 144 [6] Szczepanowska, A. 1959, AcA, 9, 46 [7] Paschke, A., & Brát, L. 2013 [8] OEJV, Brno Contr., 34, 2007 [9] Agerer, F., & Hübscher, J. 2003, IBVS, 5484 [10] Cook, J. M., et al. 2005, IBVS, 5636 [11] Hübscher, J., et al. 2006, IBVS, 5731 [12] Diethelm, R. 2007, IBVS, 5781 [13] Sipahi, E., et al. 2009, IBVS, 5904 [14] Samolyk, G. 2010, JAAVSO, 28, 1 [15] Hübscher, J., & Monninger, G. 2006, IBVS, 5959
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Raw O – C diagram for V346 Cyg based on Kreiner’s ephemeris (upper panel). The individual observations are shown as dots. The size of the dot is proportional to the statistical weight assigned to the minima (visual - 1; photographic - 3; photoelectric & CCD measurement - 10). The lower panel represents the residuals after the subtraction of the solution.
For minima time detection, we used the last 18 photoelectric and CCD minima of Table 4 (the upward branch of Figure 1 ) starting from JD 24 48500.6600, and obtained the new linear ephemeris:
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with standard deviation SD =0.0039, and regression r = 0.955. All the linear elements given by various authors, together with the linear elements obtained in this work are listed in Table 2 .
The ephemerids of V346 Cyg found by different authors
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† Light elements from the last 18 pe and CCD minima times. ‡ Light elements obtained from the solution approach of section IIa.
The ( O – C ) diagram of V346 Cyg ( Figure 1 ) shows a sine-like variation which is usually attributed to be a result of light time effect (LITE) caused by the presence of a third body orbiting the binary system, or it may be a result of cyclic magnetic activity due to star spot(s) on the late G4 Sp. type secondary component of the binary. Beside this, the semi-detached Algol type configuration usually suggests a transfer of matter from the less massive evolved component to the more massive primary one. However, this does not agree with the system under study as we shall see below.
To analyze the O – C diagram we use the standard approach (Mayer 1990) assuming that the time of minima follow a quadratic ephemeris and are modulated by LITE (Irwin 1959). The time of mid eclipse is computed as follows:
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where e 3 , ω 3 , ν , a 12 sin i and c are the eccentricity, longitude of the periastron, true anomaly of the binary orbit around the center of mass of the triple system, projected semi-major axis, and the speed of light, respectively. We used the weighted least squares computer programme written by Zasche et al. (2009). We exclude the first three photographic (pg) minima (listed in Table 4 ) due to the big gap (≈ 34 years) between them and the other data. We gave weights 1, 3 and 10 for visual (v), pg, and photoelectric (pe) &CCD minima, respectively.
The quadratic ephemeris of the minima is captured by the first three terms of Equation (6), and shown by the dashed line in Figure 1 , while the solid line fit represents the LITE. The lower panel in Figure 1 shows the residuals after the subtraction of the solution.
- 2.1. Mass Loss
Many semi-detached Algol binary systems exhibit either long–term parabolic increase or decrease in their orbital periods during their evolution depending on whether the process of matter transfer is conservative or non-conservative; for examples see Hanna & Amin (2013). However, in case of binaries that show orbital period decrease many authors, e.g., Kreiner et al. (1994b) and Pribulla (1998) have attributed such orbital period decrease to non–conservative mass loss from the primary component.
As one can see from the obtained quadratic term coefficient of Equation (6) (see Table 2 or 3 ), there is a decreasing parabolic long{term evolution of the orbital period represented by the dashed line in Figure 1 . It may be identified as a period decrease caused by slow mass loss dP=dt = −9.27 × −10 day=cycle (= −1.23 × 10 −7 day=yr ≃ 1 Second=Century) from the more massive δ Scuti pulsating primary component.
A light–time effect solution and the corresponding ephemeris of the binary system V346 Cyg
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A light–time effect solution and the corresponding ephemeris of the binary system V346 Cyg
- 2.2. Third Body Hypothesis
The O – C residuals show a sine-like variation with an amplitude ≃ 0 d .068±0.01. This value is above the lower limit, 0 d .030, suggested by Frieboes-Conde and Herczeg (1973) for detecting a third component orbiting a close binary system. Anyhow, the LITE due to the presence of the third body is clearly visible in the upper panel of Figure 2 after the removal of the parabola. The residuals are also presented in the lower panel of Figure 2 . In this analysis we have considered the physical parameters obtained by Soydugan et al. (2006b) (see Table 1 ). The final solution of the orbital parameters are listed in Table 3 . The solution shows a third body of mass M 3 = 1.45 M that can be observed photometrically.
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LITE solution made after the removal of a parabola (upper panel) and residuals (lower panel) for V346 Cyg.
- 2.3. Magnetic Activity
Magnetic activities seen in low–mass late–type stars may produce cyclic period variation because of their rapid rotation and outer convective layers (Richards & Albright 1993). Changes of the magnetic field distribution result in changes of angular momentum distribution. Gravitational quadrupole coupling produces changes in the internal structure of the active star which results in a period variation.
Zavala et al. (2002) studied the cause of period changes for the Algol binary WW Cyg whose orbital period undergoes a 56 yr cyclic variation with an amplitude ≈ 0.02 days. In their study they rejected the hypotheses of mass transfer, mass loss, apsidal motion, and the gravitational in uence of an unseen companion as causes for these changes. They invoked the Applegate (1992) model which involves variations of the subsurface magnetic field. Such subsurface magnetic field may be compared to solar activity cycles. The model can give a plausible explanation of the observed cyclic period variations of such late type active stars.
Star-spots are expected to be present on the cooler member i.e., the secondary less massive star (Sp. Type G4IV) was considered as the active component when applying the Applegate (1992) mechanism. For more details about the mechanism see Applegate and Patterson (1987), Applegate (1992) and references therein.
To compute the amplitude of the period oscillation of V346 Cyg shown in Figure 1 , one could use the following equation (Rovithis-Livaniou et al. 2000),
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as Δ P = 2.33 × 10 −5 with Pcycle = 25162 days. Thus, the rate of period variation is found to be Δ P/P = 8:491 × 10 −6 ≃ 10 −5 , which is in agreement to the amplitude proposed by Lanza and Rodonò (1999) for Algols.
Following Lanza & Rodonò (2002),
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the variation in the quadrupole moment can be estimated to be Δ Q = 4.7 × 10 51 g · cm 2 for the secondary evolved late type component; where M is the mass of the active star and the separation a between both components can be determined with the Kepler’s third low,
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Assuming conservation of the orbital angular momentum, Lanza and Rodonó (1999, 2004) have argued that magnetic variation could be detectable if the quadrupole moment Δ Q is of the order 10 51 −10 52 g cm 2 for Algol–type binaries, which indicating that the obtained Δ Q value of the secondary component of V346 Cyg is a typical value for the close binaries. Therefore, the magnetic activity proposed by Applegate is a possible mechanism to explain the cyclic variation of V346 Cyg. However, it is worth pointing out that the conservative angular momentum assumption for the system is in contrast to the result obtained in section IIa which concerns the loss of matter out of the system. In addition, magnetic activity cycle of about 70 years is considerably longer than expected in such low mass solar type stars in comparison to our sun.
- 2.4.δScuti Light Time Effect
Soydugan et al. (2006a) performed a study by considering a sample of 20 eclipsing binary systems with δ –Scuti type primaries. They discovered that there is a possible linear relation among the pulsation periods of the primaries and the orbital periods of the system governed by P puls = 0.020(2) P orb – 0.005(8). It is clearly seen that the longer the orbital period systems have longer pulsational periods. Also, they indicated and reported that the orbital motion of the pulsating component around the center-of-mass of the binary produces a light time effect, hence the observed period of variation will decrease and increase. They suggested that this effect is very small for the short period systems. However, more similar systems with δ –Scuti component have to be studied in order to confirm their new detection.
3. DISCUSSION
Pribulla (1998) derived the efficiency of mass transfer and mass outflow in close binaries. He concluded that, in case of conservative mass transfer the relative period change is
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where q is the mass ratio and m is the total mass M 1 + M 2 . And, if the matter is being transferred from the less to the more massive component, the period increases and the efficiency of the mass transfer is
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i.e., the efficiency of this process is zero if the mass ratio is unity. In other words, the efficiency of transferring matter from the less to the more massive component monotonically decreases for increasing mass ratio. Accordingly, for V346 Cyg in which high mass ratio ( q = 0:78, Soydugan et al. 2006b) is seen, the efficiency of the transfer of matter from the secondary to the primary massive star is low.
A δ Scuti variable (sometimes termed dwarf Cepheid) is a variable star which exhibits variations in its luminosity due to both radial and non-radial pulsations of the star’s surface. Recent infrared and radio observations show that the prototypical Cepheid, δ Cephei, is undergoing mass loss (Marengo et al. 2010; Mathews et al. 2012). Neilson (2013) reported that this result was surprising and raises important questions about the role pulsation and mass loss in these stars. It is worthy to note that this result has been obtained for classical Cepheids. However, δ Scuti stars are, in general, main sequence or slightly evolved post main-sequence stars with masses between 1.4 and 3 M . They are located near the bottom part of the classical Cepheid instability strip and are burning hydrogen either in a convective core, or in a shell outside the H-depleted core (Guzik 2000; Soydugan et al. 2006a). This may be explanation for the coefficient of the quadratic term in Equation (6) being negative implying the unexpected direction of flow of matter (from the primary to the secondary less massive component which filling its Roche lobe). The interpretation of this contradiction may be due to:
  • 1. Inaccuracy in specifying the evolutionary status of this system and the system is not specifically semi-detached, i.e., the secondary component is pre-contact its Roche lobe limit and the matter escape from the system isotropically from theδScuti primary component obeying the non–conservative assumption case. Also, in his catalogue of classical Algol–Type binaries, Budding (1984) reported that the high mass ratioqsd= 0.78 for V346 Cygni as a semi–detached system suggests faulty solution.
  • 2. Data is not enough and more minima times are needed.
  • 3. Mass transfers from theδScuti primary pulsating star to the secondary component, even if partial.
4. CONCLUSIONS
The period variation study of V346 Cyg leads us to the following conclusions:
  • 1. The nonexistence of the apsidal motion in the system V346 Cyg is confirmed by the 0.5 secondary minimum phase position (see, Florja 1934).
  • 2. If the secular period decrease exists, it needs mass flow (in the case of conservative mass transfer) from the more massive primary component, filling its Roche lobe, to the less massive secondary component. This is not valid for the system configuration as recorded by various authors. (e.g., Kim et al. 2005; Soydugan et al. 2006a,b). Instead one may consider mass transfer and/or loss from theδScuti primary component.
  • 3. Beside the secular decrease due to mass transfer and/or loss from V346 Cyg, the sine-like variation seen in theO – Cdiagram may also be attributed to:
  • (a) LITE due to the presence of a third body of mass 1.45M☉orbiting the binary with about 69 years period and orbital eccentricitye3≃ 0.69,
  • (b) a magnetic activity cycling due to star spots on the late type secondary star, or
  • (c) LITE due to the orbital motion of the pulsating component around the center-of-mass of the binary suggested before by Soydugan et al. (2006). However, this cause seems to be disfavoured until new evidence is obtained supporting their new detection.
Finally, it can be concluded that the O – C residual diagram shows a long term orbital period decrease superimposed on a sine{like variation behavior which may be interpreted as a result of periodic or cyclic variation due to the presence of a third body or star spots on the late type secondary star, respectively. However more precise minima times and high dispersion spectroscopic observation are needed in order to confirm the results obtained for this elusive Algol V346 Cyg.
Acknowledgements
This paper has made use of the STDF N5217, ASRT and Kottamia Center of Scientific Excellence for Astronomy and Space Sciences (KCSE ASSc). We acknowledge using NASA ADS and the O-C gateway database. Thanks go to Dr. Petr Zasche for the use of his program concerning the determination of the LITE due to the third body.
References
Applegate J. H. , Patterson J. 1987 Magnetic Activity, Tides, and Orbital Period Changes in Close Binaries ApJ 322 L99 - 99    DOI : 10.1086/185044
Applegate J. H. 1992 A Mechanism for Orbital Period Modulation in Close Binaries ApJ 385 621 -    DOI : 10.1086/170967
Beljawaky S. 1932 Neun Neue Veränderliche Sterne im Cygnus PZ 34 23 -
Brancewicz H. K. , Dworak T. Z. 1980 A Catalogue of Parameters for Eclipsing Binaries AcA 30 501 -
Budding E. 1984 A Catalogue of Classical Evolved AlgolType Binary Candidate Stars BICDS 27 91 -
Budding E. , Erdem A. , Çiçek C. , Bulut I. , Soydugan F. , Soydugan E. , Bakis V. , Demircan O. 2004 Catalogue of Algol Type Binary Stars A&A 417 263 -    DOI : 10.1051/0004-6361:20034135
Florja N. 1934 Die Systemkonstanten der Neuen Bedeckungsveranderlichen AZ Vulpeculae und V346 Cygni und der Lichtwechsel von V360 Cygni PZ 4 283 -
Frieboes-Conde H. , Herczeg T. 1973 Period Variations of Fourteen Eclipsing Binaries with Possible Light-Time-Effect A&AS 12 1 -
Guzik J. A. , Ibanoglu C. 2000 NATO Sci. C, Mathematical and Pysycal Sciences, Variable Stars as Essential Astrophysical Tools Klouwer Dordecht vsea conf. Introduction to Asteroseismology of d Scuti Stars 544 213 -
Hanna M. A. , Amin S. M. 2013 Orbital Period Variation Study of the Algol Eclipsing Binary DI Pegasi JKAS 46 15 -
Irwin J. B. 1959 Standard Light-Time Curves AJ 64 149 -    DOI : 10.1086/107913
Kim S.-L. , Lee J. W. , Kang Y. B. , Koo J.-R. , Mkr-tichian D. E. 2005 Discovery of a Short-Periodic Pulsating Component in the Algol-Type Eclipsing Binary System V346 Cyg IBVS 5628 -
Kreiner J. M. 2004 Up-to-date Linear Elements of Eclipsing Binaries AcA 54 207 -
Kreiner J. M. 2004 Physical Parameters of Components in Close Binary Systems: III AcA 54 299 -
Lanza A. F. , Rodonó M. 1999 Orbital Period Modulation and Quadrupole Moment Changes in Magnetically Active Close Binaries A&A 349 887 -
Lanza A. F. , Rodonò M. 2004 Magnetic Activity and Dynamics of Close Binaries AN 325 393 -
Mayer P. 1990 Eclipsing Binaries with Light-Time Effect BAICz 41 231 -
Marengo M. , Evans N. R. , Barmby P. , Matthews L. D. , Bono G. , Welch D. L. , Romaniello M. , Huelsman D. , Su K. Y. L. , Fazio G. G. 2010 An Infrared Nebula Associated with δ Cephei: Evidence of Mass Loss? ApJ 725 2392 -    DOI : 10.1088/0004-637X/725/2/2392
Matthews L. D. , Marengo M. , Evans N. R. , Bono G. 2012 New Evidence for Mass Loss from δ Cephei from H I 21 cm Line Observations ApJ 744 53 -    DOI : 10.1088/0004-637X/744/1/53
Neilson H. R. 2014 Pulsation and Mass Loss Across the HR Diagram: From OB Stars to Cepheids to Red Super-giants Proceedings IAU Symposium (301) 205 -
Parenago P. P. 1933 Bestätigung der von Balanowsky, Bel-jawsky und Neujmin Entdeckten Veränderlichen Sterne PZ 4 134 -
Petrow A. A. 1946 V346 Cygni PZ 6 207 -
Paschke A. , Brát L. 2013 Sekce pozorovatelu prom-ěnných hvězd http://var.astro.cz/ocgate
Pribulla T. 1998 Efficiency of Mass Transfer and Outflow in Close Binaries CoSka 28 101 -
Richards M. T. , Albright G. E. 1993 Evidence of Mag-netic Activity in Short-Period Algol Binaries ApJS 88 199 -    DOI : 10.1086/191821
Rovithis-Livaniou H. , Kranidiotis A. N. , Rovithis P. , Athanassiades G. 2000 Study of the Period Changes of X Trianguli A&A 354 904 -
Samus N. N. , Durlevich O. V. 2004 Combined Gen-eral Catalog of Variable Stars (GCVS4.2, 2004 Ed.)
Soydugan E. , Ibanoglu C. , Soydugan F. , Akan M. C. , Demircan O. 2006 The Connection between the Pulsa-tional and Orbital Periods for Eclipsing Binary Systems MNRAS 366 1289 -    DOI : 10.1111/j.1365-2966.2005.09889.x
Soydugan E. , Soydugan F. , Demircan O. , Ibanoglu C. 2006 A Catalogue of Close Binaries Located in the δ Scuti Region of the Cepheid Instability Strip MNRAS 370 2024 -
Surkova L. P. , Svechnikov M. A. 2004 Semi-Detached Eclipsing Binaries (Surkova+ 2004) yCat 5115 0 -
Wilson R. E. , Devinney E. J. 1971 Realization of Ac-curate Close Binary Light Curves: Application to MR Cygni ApJ 166 605 -    DOI : 10.1086/150986
Wood D. B. , Forbes J. E. 1963 Ephemerides of Eclipsing Stars AJ 68 257 -    DOI : 10.1086/108949
Zasche P. , Liakos A. , Niarchos P. , Wolf M. , Manimanis V. , Gazeas K. 2009 Period Changes in Six Contact Binaries: WZ And, V803 Aql, DF Hya, PY Lyr, FZ Ori, and AH Tau NA 14 121 -    DOI : 10.1016/j.newast.2008.06.002
Zavala R. T. , McNamara B. J. , Harrison T. E. 2002 The Origin of Cyclic Period Changes in Close Binaries: The Case of the Algol Binary WW Cygni AJ 123 450 -    DOI : 10.1086/338084