D. R. Faulkner

UBVRc Ic Analysis of the Recently Discovered Totally Eclipsing Extreme Mass Ratio Binary V1853 Orionis, and a Statistical Look at 25 Other Extreme Mass Ratio Solar-type Contact Binaries

We present precision CCD light curves, a period study, photometrically derived standard magnitudes, and a five-color simultaneous Wilson code solution of the totally eclipsing, yet shallow amplitude (Av ~ 0.4 mag) eclipsing, binary V1853 Orionis. It is determined to be an extreme mass ratio, q = 0.20, W-type W UMa overcontact binary. From our standard star observations, we find that the variable is a late-type F spectral-type dwarf, with a secondary component of about 0.24 solar masses (stellar type M5V). Its long eclipse duration (41 minutes) as compared to its period, 0.383 days, attests to the small relative size of the secondary. Furthermore, it has reached a Roche lobe fill-out of ~50% of its outer critical lobe as it approaches its final stages of binary star evolution, that of a fast spinning single star. Finally, a summary of about 25 extreme mass ratio solar-type binaries is given.

BVRcIc Observations and Analyses on V2421 Cygni, a Precontact W UMa Binary

We present the first precision BVRI light curves, synthetic light curve solutions, and a period study for the high amplitude solar type binary, V2421 Cygni. The light curves have the appearance of an Algol (EA) type; however, it is made up of dwarf solar type components in a detached mode with a period of only 0.6331 days with an amplitude of about a full magnitude, i.e., it is a precontact W UMa binary. Flare-like disruptions occur in the light curves following the primary and secondary eclipses possibly due to the line-of-sight track of a gas stream. An associated stream spot and splash spot cause bright equatorial spots on the stellar surface of the primary star. The more massive star is the gainer, making this system a classic, albeit dwarf, Algol.

Comparing the precision 2009 and 2012 light curves of the precontact W UMa binary V1001 Cassiopeia

A 2012 follow up to the analysis of 2009 observations is presented for the very short period (~0.43 days) precontact W UMa binary (PCWB) V1001 Cassiopeia. Its short period, similar to the majority of W UMa binaries, and its distinct EA light curve make it a very rare and interesting system for continuing photometric investigation. Previous photometric VRI standard magnitudes give a K4 spectral type. Our solutions of light curves separated by some three years give approximately the same physical parameters. However, the spots have radically changed in temperature, area, and position. While only one dark spot was used to model the first curves, two hot spots are now needed. This affects the overall shape of the light curve, especially in the secondary eclipses in B and V. Additional eclipse timings now show that the orbital period is changing. We conclude that spots are very active on this solar-type dwarf system and that it may mimic its larger cousins, the RS CVn binaries. The conclusion is that analysis now needs to be directed at the continuous time evolution of PCWBs.

ANALYSIS OF THE SOUTHERN PRE-CONTACT W UMA BINARY ZZ ERIDANI: A 34 YEAR PERIOD STUDY YIELDS A POSSIBLE LOW-MASS COMPANION

Complete Bessel BVRI light curves of ZZ Eridani [2MASS J04130109-1044545, HV 6280, NSVS 14888164 α(2000) = 04{sup h}13{sup m}1{sub ·}{sup s}10, δ(2000) = −10°44′54{sub ·}{sup ″}5 (ICRS), V = 13.9-14.4-15.0] are observed and analyzed. The system is a southern pre-contact W UMa binary. Its light curve has the appearance of an Algol (EA) light curve, however, it is made up of dwarf solar-type components with a period of only 0.4521 days. Our 34 year period study yields a sinusoidal fit or an increasing quadratic fit. The sinusoid may indicate that a third body is orbiting the close binary. The lower-limit mass of the third body is near that of the brown dwarf limit (0.095 M α). Also included is an improved ephemeris, a mass ratio search, and a simultaneous BVRI Wilson–Devinney solution.

BVRI Photometric Analysis and 73 year Period Study of the Totally Eclipsing Binary, DK Andromedae

DK And is a Sonneberg variable, first classified as an RR Lyrae type-C. It was reclassified in 2006 as a totally eclipsing W Ursae Majoris variable with a period of 0.49 d. We present complete BVRI are light curves, a period study, and a simultaneous BVRI light-curve solution. The period study, covering some 73 years, reveals a 4-sigma-level quadratic ephemeris. Our light curves shows a time of constant light in the secondary eclipse of 28 minutes making this a totally eclipsing, A-type W UMa system. The depths of eclipses are only about 0.5 mag in V due to the fairly extreme fill-out. The light curve solution reveals a component temperature difference of ~300 K, fairly high for such variables, and an inclination of 82.5°. Although the variable is near F2V type, it shows definite dark spot activity (31° radius spot). High fill-out binarity evidently induces the convective envelopes responsible for this activity.

FIRST PRECISION LIGHT CURVE ANALYSIS OF THE NEGLECTED EXTREME MASS RATIO SOLAR-TYPE BINARY HR BOOTIS

HR Bootis is a neglected binary that is found to be a solar-type (G2V) extreme mass ratio binary (EMRB). It was discovered by Hanley & Shapley in 1940. Surprisingly, little has been published in the intervening years. In 1999 it was characterized by a 0.31587 day orbital period. Since that time it has been observed by various observers who have determined ?20 timings of minimum light over the past ?15,000 orbits. Our observations in 2012 represent the first precision curves in the BVRcIc Johnson?Cousins wavelength bands. The light curves have rather low amplitudes, averaging some 0.5 magnitudes, yet they exhibit total eclipses, which is typical of the rare group of solar-type EMRBs. An improved linear ephemeris was computed along with a quadratic ephemeris showing a decaying orbit, which indicates magnetic breaking may be occurring. The light curve solution reveals that HR Boo is a contact system with a somewhat low 21% Roche-lobe fill-out but a mass ratio of q = 4.09 (0.2444), which defines it as an EMRB. Two spots, both hot, were allowed to iterate to fit the light curve asymmetries. Their radii are 32? and 16?. Both are high-latitude polar spots indicative of strong magnetic activity. The shallow contact yet nearly equal component temperatures makes it an unusual addition to this group.

UBVRI Analysis of the Totally Eclipsing Extreme Mass Ratio W UMa Binary, GSC 3208 1986

GSC 3208 1986 is an NSVS and TYCHO binary, first observed from 1999 to 2000. It is a W UMa binary with a period of 0.405 days. The present observations were taken in 2012 September and are of high precision, averaging a standard deviation of better than 5 mmag. The amplitude of the light curve is very nearly 0.5 mag yet it undergoes total eclipses. Dominion Astrophysical Observatory spectra give an F3V type ( K) for the system, the earliest of the extreme mass ratio W UMa binaries. The linear period determination of 0.4045672 days was calculated with the two sets of epochs available. An early NSVS light curve reveals that the period has been smoothly decreasing over its past 12,000 orbits. The binary may be undergoing sinusoidal oscillations due to the presence of a third body, possibly with a period of years. The high inclination of 85° results in a long duration secondary total eclipse, lasting some 49.5 minutes. Findings indicate that GSC 3208 1986 is an immaculate extreme mass ratio, q(m2/m1) = 0.24, A-type W UMa binary.

Photometric Analysis and 60-Year Period Study of the Detached but Near-Contact System VV Virginis

VV Vir is a near-contact but detached mid-G-type eclipsing binary with an asymmetrical light curve due to a weak but regular mass exchange. The binary is apparently approaching contact and has a stream impact spot on the secondary component that is responsible for a quadratically decreasing period. Our period study included more than 140 minima observed over the past 60 years. We explore other possible near-contact configurations for this binary.

AC Piscium, A Short-Period Cool Dwarf Algol Binary

AC Piscium was found to be a near-contact, cool dwarf (K7-M4 type), short-period (P = 0.335 day) binary system. The binary is in a semidetached, Algol-type configuration. The binary could also be classified as a precontact W UMa binary. This system bears future study to further determine its absolute configuration and orbital evolution.

PHOTOMETRIC STUDY OF THE NEAR CRITICAL CONTACT SYSTEM, GSC 3355 0394

GSC 3355 0394 has an EB-type light curve, which is dominated by hot and cool spot activities. It displays night-to-night variations in light-curve shapes. The period study yields six new times of minimum light and the first precision ephemeris, HJD T{sub min}I = 2, 454, 408.9547 {+-} 0.0017 + 0.4621603 {+-} 0.0000008d*E. VR{sub c}I{sub c} standard magnitudes are presented. BVRI Wilson synthetic light-curve solutions are calculated for both a Mode 4 (V1010 Oph-type, semidetached, more massive component filling its Roche lobe) configuration and a Mode 3, contact configuration (fill-out 100% or critical contact). The critical contact is the lowest residual solution. Four major spot regions are needed to model this binary, at least one is evidently a stream spot.