New Photometric Investigations of G-type Contact Binary TU Boo

Two sets of CCD photometric observations for contact binary TU Boo were obtained in 2020 and 2021.Different from its asymmetric light curves published from the literature,our BVRcIc-band curves show that the heights of maximum are almost equal.These distortions of light curves possibly indicate that the components were active in past 25 yr,but they were stable in the last two years.For total-eclipse binary TU Boo,due to some star-spots on the surface of the components,the physical structure obtained by many investigators are different.Therefore,the symmetric multi-color light curves in 2020,2021 are important for understanding configuration and evolution of this system.By using the Wilson–Devinney program,it is confirmed that TU Boo is an A-type shallow-contact binary with the temperature difference ofΔT=152 K and fill-out of f=14.67%.In the O−C diagram of orbital period analysis,a cyclic oscillation superimposed on a continuous decrease was determined.The long-term decreasing is often explained by the mass transfer from the more massive star to less massive one,this system will evolve into a deeper contact binary with time.The cyclic oscillations computed from much more CCD times of light minimum maybe result from the light-travel time effect via the presence of a third body.These characters of structure,evolution and ternary belong to typical A-type W UMa binaries with spectral G.

On properties of mass transfer in an Algol-type binary system:an example of VV Vir

Some properties of mass transfer within a semi-detached binary system are discussed based on an example of VV Vir. The observations and analysis of VV Vir show that it is a semi-detached binary system with the less massive cooler component filling its Roche lobe, which is also called an Algol-type binary system. Based on the parameters of this semi-detached binary, a theoretical study on the mass flow is carded out, including the trajectory of the mass flow, the position, radius and temperature of the impact spot caused by the mass flow, the inconsistent form of the mass flow and the possibly huge rate of energy transfer carried by the mass flow. Humps and distortions in light curves of VV Vir are deemed to be weak evidence for the theoretical results.

Multi-color light curves and orbital period research of eclipsing binary V1073 Cyg

New multi-color BVRcIc photometric observations are presented for the W UMa type eclips- ing binary V1073 Cyg. The multi-color light curve analysis with the Wilson-Devinney procedure yielded the absolute parameters of this system, showing that V 1073 Cyg is a shallow contact binary system with a fill-out factor f = 0.124（±0.011）. We collected all available times of light minima spanning 119yr, including CCD data to construct the O - C curve, and performed detailed O - C analysis. The O - C diagram shows that the period change is complex. A long-term continuous decrease and a cyclic vari- ation exist. The period is decreasing at a rate ofP = -1.04（±0.18） × 10-10 d cycle-land, with the period decrease, V1073 Cyg will evolve to the deep contact stage. The cyclic variation with a period of P3 = 82.7（±3.6） yr and an amplitude of A = 0.028（±0.002） d may be explained by magnetic activ- ity of one or both components or the light travel time effect caused by a distant third companion with M3（i1 = 90°） = 0.511 M⊙.

The first photometric investigation of the contact binary OQ Cam

The first charge-coupled device photometric light curves in B,V,Rc,and Ic bands of the short-period contact binary star OQ Cam are presented.Through analyzing the light curves with the WilsonDevinney code,it is found that OQ Cam is a W-type shallow contact binary star with a contact degree of f=20.2%.Based on the O-C analyzing,the orbit period displays a long term increasing with a rate of d P/dt=4.40×10^-7 d yr-1.The increasing in orbit period can be interpreted by mass transfer from the less massive component to the more massive one.As the orbit period increases,OQ Cam would evolve from the present shallow contact configuration to a non-contact stage.So it may be a potential candidate to confirm the thermal relaxation oscillation theory.

A photometric-spectroscopic study of the infrared-excess eclipsing binary V2364 Cyg

The eclipsing binary V2364 Cyg is an A7 V-type contact binary with a period of 0.5921 d.We present six spectra from LAMOST and BVRc light curves(LCs),which are simultaneously analyzed to obtain the absolute physical parameters.The first light maxima are brighter than the second ones by up to 0.m038,0.m036 and 0.m024 for BVRc bands,respectively.These distorted LCs are modeled by a cool spot on the less massive component.Its mass ratio and over-contact degree are q=0.319(±0.004) and f=28.4%(±1.0) % respectively.From the mass-luminosity diagram,the primary component is a normal main-sequence star,while the secondary one is a subgiant star.From the(O-C) curve,the orbital period secularly decreases at a rate dP/dt=-1.62(±0.03) × 10^-7 dyr^-1,which is mainly attributed to mass loss via stellar wind from the binary system.This may result in the observed infrared excess in the W4 band.

Studies on the Equatorial Spot of G-type Contact Binary UV Lyn

New CCD photometric observations of G-type contact binary UV Lyn were obtained in 2006 and 2020,when the light curves(LCs)showed positive O'Connell effect and negative O'Connell effect,respectively.From the previous studies,the LCs by other ground-based telescope are variable from 1973 to 2020,particularly the magnitude difference between the two maxima.These phenomena indicate that the component has been active in the past 47 yr.In addition,during monitoring by the space telescope Transiting Exoplanet Survey Satellite(TESS)from January to March 2020,we fortunately found continuous variations from the O'Connell effect in every cycle for the first time.The analysis also shows that in a short time,the positive O'Connell effect has been transformed into the negative one,which demonstrates that there are stronger magnetic activities on the surface of the component.By using the Wilson-Devinney code with a spot model,these photometric solutions confirm UV Lyn is a shallow W-subtype contact binary with a cool equatorial spot on the less massive component.The successive variability of the O'Connell effect possibly results from one equatorial cool spot shifting gradually along with time.We also investigated its O-C curve from these continuous LCs,and there is no apparent variation in such a short time.However,regarding the O'Connell effect as the indicator of magnetic activity indicates the system is possibly undergoing a periodic trend with a period of nearly 38 days.Comparing with the trend of the O-C curve,we could not find any relation between the period variation and magnetic activity.

SDSS J012119.10 001949.9:a very short period M dwarf contact binary from SDSS stripe 82

We present the first multicolor photometric observations of the short period low-mass eclipsing binary SDSS J012119.10-4301949.9. By using the 2013 version of the Wilson-Devinney code, the photometric solutions are derived. It is found that the system is in a contact configuration （f = 18.9± 6.0%） with a moderate mass ratio of 0.5 ± 0.01. A third light contributing about 6.1± 1.3% of the total luminosity in the V band was found, which may come from a cool tertiary component. The derived high orbital inclination （i - 83.9°± 0.5°） and the almost symmetric three light curves suggest that the determined parameters are reliable. Both the color class and spectral class of the system correspond to a spectral type of M0, which may indicate that SDSS J012119.10-001949.9 belongs to a very rare class of M dwarf contact binaries that are below the theoretical short period limit.