Photoelectric Light Curves Research Articles

The Light Curve and the Orbital Period Variations of Binary System TT Andromedae

The first photoelectric light curve analysis of the TT And system in a broad band filter (400 - 700 nm) was carried out using the PHOEBE program. The absolute dimensions of the system are determined and its evolution is discussed. The most distinct feature of the system is a comparatively very low mass of the cooler component i.e. M2 = 0.26M⊙. Moreover, using the Observed-minus-Calculated data, the period changes of the system are studied, which reveal the presence of a third body orbiting the system with a period P3 = 63.89 yr, superimposed on which is a secular period increase, which is ascribed to mass transfer with a rate −7.60 × 10−12 M⊙ yr−1 from the cooler secondary component.

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

AbstractIn 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)

Photometric elements, apsidal motion, and the third body in the eclipsing binary V974 Cyg

We have derived the first photoelectric light curve of the eclipsing binary V974 Cyg from our own photoelectric observations. Analysis of the light curve has yielded the system’s photometric elements (r1 ≈ r2 = 0.1192, e = 0.058, L1 ≈ L2 = 0.486, and L3 = 0.028) and absolute parameters (M1 ≈ M2 = 2.2M⊙, Teff,1 ≈ Teff,2 = 9500 K, a = 15.0R⊙, distance d = 1.29 kpc, age log t = 8.0, t/tMS = 0.11). We have detected apsidal motion with the period Uobs = (1140 ± 170) yrs, and the presence of a third body in the system. The orbital parameters derived for the third body are P3 = 26.5 yrs, e3 = 0.78, and a3 sin i3 = 1.5 AU; and the lower limit for its mass is M3 > 0.58M⊙. The observed apsidal-motion rate is higher than is expected theoretically by a factor of 1.5. The axial rotation of the system’s components is not yet synchronized with the orbital motion, probably because V974 Cyg is relatively young and detached.

Physical parameters and orbit of the eclipsing binary BD +66 1663 = GSC 4479 412

We have obtained the first UBV(RI)C photoelectric light curves of the recently discovered eclipsing binary BD +66 1663 = GSC 4479 412 (P = 7.04d, V = 10.14). We have derived relative and absolute parameters of the binary, and analyzed the interstellar extinction towards the object. Though the star is located in the field of the young open cluster Be 59, we demonstrate that it is not a member.

The physical parameters and orbit of the eclipsing binary system GSC 4596 1254 = SAO 3282

We have obtained the first U BV R photoelectric light curves for a recently discovered eclipsing binary with a period of 9.33d and an appreciable eccentricity (e = 0.08). We have used these data to determine the photometric elements of the system for a model with two spherical stars with linear limb darkening. The high accuracy of the observations enabled determination of the absolute parameters of the components using available calibrations. The masses of the components are 1.28 and 1.08 M⊙, and their ages are two billion years. The present orientation of the orbital ellipse is unfavorable for studies of the apsidal rotation, which is essentially due to relativistic effects.

Detection of a tertiary companion in the eclipsing binary AD Andromeda

New orbital period variation of the eclipsing binary, AD Andromeda, was analyzed based on one CCD photometric times of minimum we have obtained and all available photoelectric and CCD values collected from the literatures. It is discovered that the orbital period of the binary shows a periodic oscillation with a period of 14.38 years and an amplitude of 0.0186 days. The periodic oscillation can be explained by the light-time effect via the presence of a tertiary component in a nearly circular orbit with a small eccentricity of e = 0.30 in the system. Based on the present analysis, it is estimated that the mass of the third body is no less than 1.76 ( ± 0.08 ) M ⊙ , and it should contribute light to the total system. Meanwhile, the photoelectric light curve obtained in yellow light by Ruciński [Ruciński, S.M., 1966. AcA 16, 307] was reanalyzed with the 2003 version of the W–D code. The results show that AD Andromeda is a detached eclipsing binary, and photometric solutions were computed. Based on the analysis, we obtained a small amount of third light in the system ( L 3 V ∼ 0.001 ) , which is too small for the contribution of the tertiary companion star. The low luminosity of the third companion may be explained in two possible ways, either: (1) the third companion might itself be a close double star consisting of two stars of 0.88 solar masses, or (2) it is a dark star such as a neutron star. We think the first possibility is a more likely one than a neutron star companion. New photometric and spectroscopic observations and a detailed investigation of those data are urgently required in the future.

Evidence of Hot Spot Activity on BH Virginis

Photoelectric light curves of BH Vir in the UBVRI bands observed by Arévalo et al. in 1986 were analyzed by using the latest version of the Wilson–Devinney program and to investigate the photometric parameters and spot activity. Satisfactory fits were obtained by assuming a hot spot only on the secondary star. The results show that the temperature of the spotted region relative to the photosphere, $T_{\rm s}/T_{\rm ph}$, is 1.13$\pm$0.027. The active region tends to occur at low latitude (near 81$^{\circ}$). The results also show that the mass ratio obtained from the photoelectric light curves is $q=m_{2}/m_{1} =$ 0.971. It is close to the spectroscopic value of 0.968 obtained by Zhai et al. (1990). The photosphere temperature of the primary is $T_{1}=$ 5969$\pm$11 K. After checking of the activity pattern from 1953 to 1991, the activity cycle is estimated to be about 10 yr.

Light-Curve and Radial Velocity Study of the Contact Binary BD +42 2782

BD +42 2782 was recently discovered to be a variable star with a W UMa-type, eclipsing-binary light curve. We have obtained the first photoelectric light curves (RC, IC) and also the first radial velocity curves for this binary. These show the system to be a W UMa binary of the W type, with the less massive component eclipsed at primary minimum. The light and velocity curves have been analyzed in a consistent manner using the Wilson-Devinney synthetic light-curve code. The binary has an orbital inclination of 74°, a mass ratio of 0.48, a secondary component ~150 K hotter than the primary, and an overcontact fill-out factor of 34%. Absolute parameters of the component stars are M1 = 1.38 M⊙, R1 = 1.29 R⊙, L1 = 1.75 L⊙, and M2 = 0.67 M⊙, R2 = 0.95 R⊙, L2 = 1.05 L⊙, and the calculated distance is 124 ± 15 pc. Even when corrected for energy transfer between the two components, the more massive component is found to be underluminous for its mass. Several means to explain this are explored, but no completely satisfactory explanation is found.

BL Andromedae and GW Tauri: close binary stars in a key evolutionary stage

A photoelectric light curve of BL And is presented along with the first CCD light curve of GW Tau. Both objects are short-period eclipsing binaries and were observed in 2003 or 2004. Photometric elements were computed using the latest version of the Wilson-Van Hamme code. The results reveal that BL And is a semidetached system with the primary component filling its Roche lobe and the secondary one almost filling but still detached, while GW Tau is a marginal-contact binary system with a small degree of contact (f= 10.9 per cent) and a large temperature difference of about 3100 K. All available eclipse times, including new ones, were analysed for each system. It was found that the orbital period of BL And is decreasing at the rate of dP/dt=-2.36 x 10(-8) (+/- 0.09) d yr(-1) while that of GW Tau may be decreasing or oscillating. We think period decrease is more probable. The derived configuration and secular period decrease for BL And combined with the asymmetry of the light curve indicate that this system may evolve from the present semidetached phase into a contact stage, with mass transfer from the primary component to the secondary one through the L-1 point, or that it might just undergo the broken stage predicted by the theory of thermal relaxation oscillations. In contrast, GW Tau is a marginal-contact binary in poor thermal contact and may be at the beginning of the contact phase.

Light curve solution and orbital period analysis of the contact binary V842 Herculis

New photoelectric BV light curves were obtained for the neglected eclipsing binary V842 Her at the TUBITAK National Observatory (TUG) and studied for the first time in detail to determine the orbital parameters and geometry of the system. The solutions obtained simultaneously for the new light curves and the radial velocity curves in the literature by using the Wilson-Devinney code reveal a typical W-type contact system. The light curves exhibit the so-called O'Connell effect which the level of the primary maxima being higher than that of the secondary ones in both pass-bands. The O'Connell effect in the light curves is explained in terms of a dark-spot located on the more massive component which makes the more massive larger component slightly cooler than the less massive smaller one. The O – C diagram constructed for all available times of minima of V842 Her exhibits a cyclic character superimposed on a quadratic variation. The quadratic character yields a orbital period increase with a rate of dP /dt = 7.76 × 10–7 days yr–1 which can be attributed to the mass exchange/loss mechanism in the system. By assuming the presence of a gravitationally bound third body in the system, the analysis of the cyclic nature in the O – C diagram revealed a third body with mass of 0.4M⊙ orbiting around the eclipsing pair. The possibility of magnetic activity cycle effect as a cause for the observed cyclic variation in the O – C diagram was also discussed. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Deep, Low Mass Ratio Overcontact Binary Systems. III. CU Tauri and TV Muscae

New CCD photometric light curves in the B and V bands of the neglected W UMa - type eclipsing variable star CU Tauri are presented. The O'Connell effect in the V light curve obtained in 2001 by Yang and Liu was about Delta V = +0.015, but it vanished in our 2004 observations. The variations in the levels of bothminima were seen. Our two epochs of light minimum and others compiled from the literature were used for the period study. It is shown that the types of some eclipse times were incorrect and the values of the period obtained by previous investigators were aliases that prevented formation of a plausible O - C curve. A new linear ephemeris was derived, and it is discovered that the orbital period of CU Tau shows a continuous decrease at a rate of dP/dt = - 1.81 x 10(-6) days yr(-1). The present symmetric light curves were solved with the 2003 version of the Wilson-Devinney (W-D) code. Both our solutions and those derived by Yang and Liu reveal that CU Tau is a deep ( f = 50.1% +/- 3.2%), low mass ratio (q = 0.1770 +/- 0.0017) overcontact binary system. Meanwhile, the photoelectric light curves in the B, V, R, and I bands of TV Muscae published by Hilditch and coworkers were reanalyzed with the 2003 version of the W-D code. It is shown that the low mass ratio binary turns out to be a deep overcontact system with f = 74.3% +/- 11.3%. A period analysis with all collected times of light minimum revealed a combination of a long-term period decrease (dP/dt = - 2.16 x 10(-7) days yr(-1)) and a possible cyclic change with a period of 29.1 yr. The rapid long-term period decreases of both systems can be explained as a combination of the mass transfer from the more massive component to the less massive one and the angular momentum loss due to mass outflow from the L2 point. In that way, the overcontact degrees of the two systems will become deeper as their periods decrease, and finally they will evolve into a single rapid-rotation star. However, for CU Tau, the rate of the secular period decrease is very large when compared with the other systems of the same type. This suggests that the long-term period decrease may be part of a long-period periodic change, which we need more data to check.

The Unique Binary Star α Coronae Borealis

We present a new photoelectric light curve of α Coronae Borealis. The derived rate of apsidal motion differs from the theoretical prediction. A possible solution of the problem is suggested.

Analysis of photoelectric light curves of V448 CYG taking the Roche geometry into account

Three-color photoelectric UBV light curves of the close binary system V448 Cyg obtained at the Abastumani Astrophysical Observatory are analyzed using a new code by Djurasevi. A new value for the ratio of the masses of the components, which is the fundamental parameter for determining the absolute elements of the system, has recently been published. The parameters obtained in our analysis differ substantially from those published previously because the new mass ratio has been employed. The location of the components of V448 Cyg on a mass-logg plot shows that this system, similarly to XZ Cep and V382 Cyg, is in a phase subsequent to a rapid transfer of mass.

Photometric Studies of the Near‐Contact Binary AX Draconis

ABSTRACTWe have obtained CCD photometric observations of the near‐contact binary AX Dra during two observing seasons from 2001 March through May and from 2003 April and May. From these measurements, the seasonal light curves of AX Dra for 2001 and 2003 were compiled, and a total of 13 new timings of minimum light were calculated. An analysis of the resulting O - C diagram reveals evidence for a periodic change with a semiamplitude of 0.0061 days and a period of 56.1 yr, but this conclusion depends entirely on the photographic plate estimates around 1960. Our light curves display the conventional O’Connell effect and small‐scale year‐to‐year light variability. If these light variations are produced by a stellar spot, a cool‐model spot on the secondary star satisfies both seasonal light curves quite well. The same representation applies to the only other published photoelectric light curves.

A Photometric Analysis and Spot Activity of BH Virginis

BH Virginis is a short-period eclipsing binary with two solar-type components. The photoelectric light curves in $UBVRI$, observed by Scaltriti et al. (1985), and in the $B$ and 5125 Å bands, observed by Hoffmann (1982), were analyzed by using the 1992 version Wilson–Devinney program to investigate the activity of spots. The results show that there was a small cool spotted active region on the secondary star in 1984. The position and area of the active region in 1984 are remarkably similar to those in 1991. The distortion waves in the light curves observed by Hoffmann (1982) can be fitted satisfactorily with two hot-spot active regions: one is on the primary star, and the other is on the secondary component. The mass ratio $q = m_{2} / m_{1}$, obtained from photoelectric light curves, is inside the range of 0.965–0.971. It is close to the spectroscopic value of 0.968 obtained by Zhai et al. (1990). To study the physical cause of the variations and the distortions in the light curve of BH Vir, the photoelectric observations in $BV$ observed by Koch (1967) were re-analyzed based on a new spot model with an assumption of one cool spot active region on the primary star and two cool spot active regions on the secondary star. The fit of the new spot model to the observations is better than that of our former result (Xiang et al. 2000). The present results suggest that BH Vir may have an active cycle with a period of 7–10 years.

Study on spot activity of BH Virginis

In this paper we parameterize the photoelectric waves in the light curves of BH Vir in B and λ 5125A bands by Hoffmann (1982) by using the Wilson-Devinney program. The principal results are as follows: (1) The mass ratio obtained from the photoelectric light curves is q =m2/m1 = 0.967. (2) The photosphere temperature of the primary is T1 = 5947 K. (3) The distortion waves in the light curves can be fitted satisfactorily with the spot model of two hot spot activities on the primary star.

The spot activity of BH Virginis

In this paper, photoelectric light curves of BH Vir in 4650 and 5500 Å bands observed by Kitamura et al. (1957) [PASJg, 191] were analyzed by using the 1992 version Wilson–Devinney program to investigate spot activity. The results show that: (1) There is a large cool spotted active region on the secondary star in 1953–1954. (2) Around phase 0.65 the distortion waves of two color light curves can be fitted satisfactorily with two different spot models, a cool spot in 5500 Å band, while a hot spot in 4650 Å band. (3) The mass ratio obtained from the photoelectric light curves is q= m 2/ m 1=0.967. It is close to the spectroscopic value of 0.968 obtained by Zhai et al. (1990). [A&A 237, 148]. (4) The photosphere temperature of the primary is T 1=6052±8 K.

A photometric study of the near contact binary star GK Cep

Photoelectric observations of the eclipsing binary GK Cep (BV 382) have been carried out in B and V colors at the Ege University Observatory. Using the (O-C) residuals formed by the photoelectric minima times, an orbital period study of the system was performed. It is confirmed that the sinusoidal (O-C) variation corresponds to a secular period change caused by the light time effect due to an unseen third body in the system. The observed photoelectric light curves of the system were analyzed with the methods of Wilson-Devinney. Simultaneous solutions were made using the radial velocity curves of Bartolini et al. (1965). The system was found to be detached, but not far from the contact phase. The absolute parameters of the system were also deduced. Both compronents are on the Main Sequence.

Star-spots activity on BH Virginis

Virginis is a short-period RS CVn system. From our observations and archival sources we have gained an ephemeris by means of the times of minima. The light curves and the photoelectric observations in B and V obtained by Koch (1967) have been analyzed by using the Wilson-Devinney program. The principal results are as follows: (1) The mass ratio obtained from the photoelectric light curves is q = m(2)/m(1) = 0.967, close to the spectroscopic value 0.968 obtained by Zhai et al. (1990). (2) The photospheric temperature of the primary, T-1, at two epochs (1963-1964 and 1991) was about; 5945 K - 6010 K. (3) Several spotted active regions are revealed on both components in 1963-1964. data sets, while only one small spotted active region appears on the secondary star in 1991.

UBVR photometry of gas-darkened variable systems. EM Cep

Photoelectric UBVR light curves of the gas-darkened variable EM Cep are given. A flare was detected on November 15–16, 1991: while a brightness increase was observed in the R band, a decrease in the star’s U luminosity was observed.