The interacting binary V 393 Scorpii: another clue for Double Periodic Variables

We give a brief report on spectroscopic properties of V 393 Scorpii. H alfa emission and shape and radial velocity of He I 5875 are modulated with the long cycle. The long cycle is explained as a relaxation cycle in the circumprimary disc, that cumulates the mass transferred from the donor until certain instability produces disc depletion.Comment: 2 pages, 2 figures in encapsulated postscript format. To be published in Proceedings IAU Symposium No.262, 200

A Study of Twelve Potential Merger Candidate Contact Binary Systems

Photometric observations and analysis of twelve previously poorly studied contact binary systems is presented. All show total eclipses and have extremely low mass ratios ranging from 0.072 to 0.15. Also, all show characteristics of orbital instability with mass ratios within the theoretical orbital instability range. Although none demonstrate a significant O'Connell effect at least nine of the systems have other indicators of increased chromospheric and magnetic activity.Comment: 11 Pages, 2 Figures Accepted Publications of the Astronomical Society of the Pacific (PASP

Photometric and spectroscopic study of two low mass ratio contact binary systems : CRTS J225828.7-121122 and CRTSJ030053.5+230139

The study reports photometric and spectroscopic observations of two recently recognized contact binary systems. Both systems show total eclipses and analysis of the light curves indicates both have very low mass ratios of less than 0.3. We derive absolute parameters from color and distance based calibrations and show that, although both have low mass ratios, they are likely to be in a stable orbit and unlikely to merge. In other respects, both systems have characteristics similar to other contact binaries with the secondary larger and brighter than their main sequence counterparts and we also find that the secondary is considerably denser than the primary in both systems

Simplified method for the identification of low mass ratio contact binary systems that are potential red nova progenitors

This study presents a simplified method to identify potential bright red nova progenitors based on the amplitude of the light curve and infrared (J–H) colour of a contact binary system. We employ published criteria for contact binary orbital instability to show that the amplitude of the light curve for a given contact system with a low mass (<1.4 M⊙) primary must be less than a specified value for it to be potentially unstable. Using this, we search the photometric data of a large survey to identify about 50 potential bright red nova progenitors. We analyse each of the survey photometry to determine the mass ratio and from the estimated mass of the primary, other physical parameters of the systems. We show that each system has physical characteristics indicating potential orbital instability. Using the absolute parameters from our sample, we model the expected instability separation and period for low mass contact binary systems

Photometric analysis of three potential red nova progenitors

We present photometric analysis of three bright red nova progenitor contact binary systems: ASAS J082151-0612.6, TYC 7281-269-1 and TYC 7275-1968-1. The primary components in all three systems are solar-type low mass stars with radii somewhat larger than their zero age main sequence counterparts. The secondaries, as in most contact binary systems, have radii and luminosities well above their main sequence counterparts. All three have extremely low mass ratios ranging from 0.075 to 0.097 and two have high degrees of contact, in excess of 75%. All three have mass ratios and separations below the theoretical values for orbital stability. Chromospheric activity, a hallmark of magnetic activity and magnetic braking, considered important in mediating angular momentum loss, is also explored. All three systems demonstrate the O'Connell effect, and all systems require the introduction of star spots for a better light curve solution. In addition, we show that ASAS J082151-0612.6 and TYC 7281-269-1 have a UV color excess in the range indicating high chromospheric activity. Another measure of potential significant magnetic activity is X-ray luminosity; TYC 7275-1968-1 and probably also TYC 7281-269-1 have X-ray luminosity well above other contact binary systems. We conclude that it is likely that all three are unstable and hence are potential merger candidates

ZZ Piscis Austrinus (ZZ PsA) : a bright red nova progenitor and the instability mass ratio of contact binary stars

ZZ Piscis Austrinus (ZZ PsA) is a neglected bright southern contact binary system with maximum V magnitude of 9.26. We present the first multiband photometric analysis and find the system to be in deep contact (>95 per cent) with an extremely low mass ratio of 0.078. The primary has a mass of 1.213 M in keeping with its reported spectral class of F6. In order to determine if ZZ PsA is a merger candidate, we outline the current status regarding the instability mass ratio and develop new relationship linking the mass of the primary to the instability mass ratio of the system and the degree of contact. We find that ZZ PsA along with two other examples from the literature to be merger candidates while an additional three require further observations to be confirmed as potential merger candidates

A study of six extreme low mass ratio contact binary systems

Multi-band (B, V and R) photometric and spectroscopic observations of six poorly studied contact binaries carried out at the Western Sydney University and Las Cumbres Observatory were analyzed using a recent version of the Wilson–Devenney code. All six were found to be of extreme low mass ratio ranging from 0.073 to 0.149. All are of F spectral class with the mass of the primary component ranging from 1.05M☉ to 1.48M☉. None show light curve features of enhanced choromospheric activity (O’Connel Effect) however five of the six do have significant ultraviolet excess indicating the presence of increased magnetic and chromospheric activity. Period analysis based on available survey data suggests two systems have a slowly increasing period suggesting mass transfer from the secondary to the primary, two have a slow declining period with likely mass transfer from primary to the secondary, while one shows a steady period, and one undergoing transition from a declining to increasing period suggesting possible mass transfer reversal. We also compare light curve solutions against theoretical markers of orbital stability and show that three of the six systems have mass ratios within the theoretical instability limit and may be regarded as potential merger candidates