The First Multiband Photometric Light Curve Solutions of the V Gru Binary System from the Southern Hemisphere

The first multiband photometric solutions of the short-period V Gru eclipsing binary from the southern hemisphere are presented in this study.Light curves of the system were observed through BVI filters at the Congarinni Observatory in Australia for 15 nights.In addition to the new ground-based data,we also used the TESS observations in two sectors.We analyzed the light curves of the system using the PHysics Of Eclipsing BinariEs(PHOEBE)2.4.7 version code to achieve the best accordance with the photometric observations.The solutions suggest that V Gru is a near-contact binary system with q=1.302(81)mass ratio,f_(1)=0.010(23),f_(2)=-0.0.009(21),and i=73.45(38).We considered the two hot spots on the hotter and cooler components for the light curve analysis.We extracted the minima times from the light curves based on the Markov Chain Monte Carlo(MCMC)approach.Using our new light curves,TESS,and additional literature minima,we computed the ephemeris of V Gru.The system’s eclipse timing variation trend was determined using the MCMC method.This system is a good and challenging case for future studies.

BVRI photometric observations,light curve solutions and orbital period analysis of BF Pav

A new ephemeris,period change analysis and light curve modeling of the W UMa-type eclipsing binary BF Pav are presented in this study.Light curves of the system taken in BVRI filters from two observatories,in Australia and Argentina,were modeled using the Wilson-Devinney code.The results of this analysis demonstrate that BF Pav is a contact binary system with a photometric mass ratio q=1.460 ± 0.014,a fillout factor f=12.5%,an inclination of 87.97 ± 0.45 deg and a cold spot on the secondary component.By applying the distance modulus formula,the distance of BF Pav was calculated to be d=268 ± 18 pc which is in good agreement with the Gaia EDR3 distance.We obtain an orbital period increase at a rate of 0.142 s century-1 due to a quadratic trend in the O-C diagram.Also,an alternative sudden period jump probably occurred which could be interpreted as a rapid mass transfer from the lower mass star to its companion of about ΔM=2.45 × 10-6 M⊙.Furthermore,there is an oscillatory behavior with a period of 18.3±0.3 yr.Since BF Pav does not seem to have significant magnetic activity,this behavior could be interpreted as the light-time effect caused by an undetected third body in this system.In this case,the probability for the third body to be a low mass star with M≥ 0.075 M⊙or a brown dwarf is 5.4% and 94.6% respectively.If we assume i’=90°,a3=8.04±0.33 AU.The mass of the secondary component was also determined following two different methods which result close to each other.

The First Photometric Study of AH Mic Contact Binary System

The first multi-color light curve analysis of the AH Mic binary system is presented.This system has very few past observations from the southern hemisphere.We extracted the minima times from the light curves based on the Markov Chain Monte Carlo(MCMC)approach and obtained a new ephemeris.To provide modern photometric light curve solutions,we used the Physics of Eclipsing Binaries(PHOEBE)software package and the MCMC approach.Light curve solutions yielded a system temperature ratio of 0.950,and we assumed a cold starspot for the hotter star based on the O’Connell effect.This analysis reveals that AH Mic is a W-subtype W UMa contact system with a fill-out factor of 21.3%and a mass ratio of 2.32.The absolute physical parameters of the components are estimated by using the Gaia Early Data Release 3(EDR3)parallax method to be M_(h)(M_(⊙))=0.702(26),M_(c)(M_(⊙))=1.629(104),R_(h)(R_(⊙))=0.852(21),R_(c)(R_(⊙))=1.240(28),L_(h)(L_(⊙))=0.618(3)and L_(c)(L_(⊙))=1.067(7).The orbital angular momentum of the AH Mic binary system was found to be 51.866(35).The components’positions of this system are plotted in the Hertzsprung-Russell diagram.