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B.R.N.O. Contributions #40 Times of minima
Abstract
This paper presents 3394 times of minima for 1096 objects acquired by 82 membersand cooperating observers of the Variable Star and Exoplanet Section of theCzech Astronomical Society (B.R.N.O. Observing project). Observations werecarried out between October 2014 and November 2016. Some newly discoveredstars by the observers of project B.R.N.O. are included in the lis
The Eclipsing Binaries Minima (BIMA) 2.0 Monitoring Project is a continuation of the previous BIMA program that was initiated by the collaboration of Bosscha Observatory - Lembang, Indonesia and The National Astronomical Research Institute of Thailand (NARIT) in 2012. This project aims to build an open database of eclipsing binary minima and establish each system’s orbital period and its variations in a time of minima (ToM) photometric observation using the Thai Robotic Telescope (TRT) network. In this work, we will present the progress of our monitoring program during 3 ∼ months of observations using TRT with proposal ID TRTC11A_009. We have collected ToM data at least once on 18 samples of contact binary stars and carried out O-C diagram analysis on three selected objects: IR Car, V1370 Tau, and GY Pup. We obtained six, three, and four primary minima on IR Car, V1370 Tau, and GY Pup, respectively. These three objects were chosen due to the lack of ToM data in recent years. We also use the TESS space mission ToM data to increase data coverage. Preliminary results show a significant change in O-C values and indicate mass transfer in this system.
In this paper we present the comprehensive analysis of five binary systems: GX Lac, TT Lyr, OGLE LMC-ECL-7641, OGLE LMC-ECL-17660, and OGLE LMC-ECL-17411. With new photometric observations combined with other available data mostly from TESS, MACHO, and OGLE, we calculated new minima timings and study the O−C diagrams. We fitted the light curves and radial velocity curves using PHOEBE software and obtain absolute parameters of these objects. All five binary stars are eccentric. We present the first analysis of TT Lyr, which reveals its nonzero eccentricity. The calculated distance of OGLE LMC-ECL-7641 indicates that this possibly triple system could be located in the Magellanic Stream.
The first photometric solution in the B,V,Rc and Ic filters of the short period GW Psc eclipsing binary is presented based on new ground-based CCD photometric observations. We analysed the BVRI photometric light curves of the system, using Phoebe0.31a, a binary star modelling program, with the Wilson and Devinney (Wilson and Devinney (1971); Wilson (1979) method based on Roche geometry to achieve the best accordance to the photometric observations to estimate their absolute parameters from the light curves. We updated the ephemeris of GW Psc using two new light curve minima derived by our new observational data from those collected in the literature and analysed the change of the system’s orbital period. The O–C plot suggests the presence of a companion. The distance of GW Psc are 318.4±19.4pc. From the solutions, we find that GW Psc is A–subtype W UMa over-contact binaries with q=0.399 mass ratios and f=0.21 fill–out factor. The likely HR diagram positions of the eclipsing binary system’s components are discussed. The system’s estimated absolute dimensions were compared to those of similar binaries in the logTeff−logL, logM−logL, logM−logR and logM−logJ0 diagrams.
GJ 3236 is a low-mass red-dwarf eclipsing binary (EB) with two M4V components. In this paper, new photometric light curves (LCs) of GJ 3236 are presented and analyzed by using the 2013 version of the Wilson-Devinney (W-D) code. Our photometric solutions suggest that GJ 3236 is an active detached EB system with strong magnetic field. Since 2009, we have monitored this target more than 10 years and obtained 22 mid-eclipse times with high precision. By using the O-C method, we revised its period as 0.7712562 days. According to Applegate mechanism, the O-C diagram of GJ 3236 should show a quasi-periodic variation, however, it does not now. Based on these, we thought that it is possible evolved through the accretion of circumstellar matter. Besides, both of components of GJ 3236 present a similar radius inflation, which could be explained by the strong magnetic activity.
We study five W UMa contact binary systems. These binary systems have short periods. We have selected them on the basis that they are less studied. Accordingly, we collected all their times of minima. These times of minima were chosen based on CCD observation and a valid timing method. So we present a new ephemeris for each of them.
We performed the first light curve analysis of GW Leo and a new ephemeris is obtained for QT Boo. In the present photometric study of two contact binary systems, we found that the orbital period of these systems is decreasing at a rate of dP/dt=-0.06087 days/year for GW Leo, and dP/dt=-0.08309 days/year for QT Boo. The light curve investigation also yields that the system GW Leo is a weak-contact W UMa eclipsing binary with a photometric mass ratio of q=0.881+-0.030, a fillout factor of f=3%, and an inclination of 54.060+-0.066 deg. Due to the O'Connell effect which is known as asymmetries in the light curves' maxima, a cold spot is employed along with the solution. We also calculate the distance of GW Leo from the distance modulus formula as 465.58+-23 pc, which is relatively close to the quantity measured by the Gaia DR2 using the binary systems' parallax. Moreover, the positions of their components on the H-R diagram are represented.
The first light curve solutions of the binary systems V1370 Tau and QQ Boo are presented. The periodic changes are calculated, and a new ephemeris presented for each of these two binary systems. O-C analysis is performed using the MCMC method in OCFit code. The changing rate of period was measured as dP/dt= 0.2423 days/year for V1370 Tau and dP/dt= -0.1363 days/year for QQ Boo. The light curve solutions suggest that V1370 Tau is a weak-contact eclipsing binary system with a photometric mass ratio q = 0.829, and that the corresponding fillout factor is 11.06%. Furthermore, it is suggested that the QQ Boo binary system is also a weak-contact W UMa eclipsing binary with a photometric mass ratio q = 0.831, and that its fillout factor equals 10.26%. The light curve solutions require cold spots. Utilizing the Wilson-Devinney code the photometric and geometric parameters of the systems are determined. The distance of both V1370 Tau and QQ Boo are calculated according to the estimated absolute parameters as 159.95 ± 23 pc and 309.03 ± 25 pc, respectively, which are in a good agreement with the distance values derived from the Gaia DR2 parallax within one standard deviation. Moreover, the positions of their components on the H-R diagram are represented.
New observations of the eclipsing binary system V1848 Ori were carried out using the V filter resulting in a determination of new times of minima and new ephemeris were obtained. We presented the first complete analysis of the system’s orbital period behavior and analysis of O-C diagram done by the GA and MCMC approaches in OCFit code. The O-C diagram demonstrates a sinusoidal trend in the data; this trend suggests a cyclic change caused by the LITE effect with a period of 10.57 years and an amplitude of 7.182 minutes. It appears that there is a third body with mass function of f (m3) = 0.0058 M⊙ in this binary system. The light curves were analyzed using the Wilson-Devinney code to determine some geometrical and physical parameters of the system. These results show that V1848 Ori is a contact W UMa binary system with the mass ratio of q = 0.76 and a weak fillout factor of 5.8%. The O’Connell effect was not seen in the light curve and there is no need to add spot.
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