E. Derman

A period study of V502 Ophiuchus

All available published times of minima of a W-type contact binary V502 Oph have been compiled and critically examined. Ten times of minima were revisted from original observations, and five new times of minima derived from our own observations. A period study covering 53 yr of observations including 84 timings of minima light (63 of them from photoelectric observations) reveals that the orbital period of the system oscillates with a period of about 35 ± 2 yr and amplitude of about 0.020 ± 0.005 day while it undergoes a constant period decrease of about dP/dt ∼ −1.45 10 −7 d/yr

Transit timing analysis in the HAT-P-32 system

We present the results of 45 transit observations obtained for the transiting exoplanet HATP-32b. The transits have been observed using several telescopes mainly throughout the YETI (Young Exoplanet Transit Initiative) network. In 25 cases, complete transit light curves with a timing precision better than 1.4 min have been obtained. These light curves have been used to refine the system properties, namely inclination i, planet-to-star radius ratio R-p/R-s, and the ratio between the semimajor axis and the stellar radius a/R-s. First analyses by Hartman et al. suggests the existence of a second planet in the system, thus we tried to find an additional body using the transit timing variation (TTV) technique. Taking also the literature data points into account, we can explain all mid-transit times by refining the linear ephemeris by 21 ms. Thus, we can exclude TTV amplitudes of more than similar to 1.5min.

Multiband Photometric and Spectroscopic Analysis of HV Cnc

In this paper, radial velocity and VI- and JHKS - (Two Micron All Sky Survey) band photometric data of the detached system HV Cnc have been analyzed. The primary component of HV Cnc, which is a member of the M67 cluster, is suspected to be either a blue straggler or turn-off star. The system is a single-lined spectroscopic binary and its light curve shows a total eclipse. Spectroscopic observations of the system revealed the third component, which shows contribution to the total light of the system. Light curve and radial velocity data have been analyzed using the Wilson-Devinney (W-D) code and JHKS filter definitions computed for the W-D code in this work. Our analysis shows that the mass and radius of the primary and secondary components are 1.31 M ☉, 0.52 M ☉, 1.87 R ☉, and 0.48 R ☉, respectively. All results are compared with previously published literature values and discussed.

UBV photometry of BX andromedae

The UBV observations of a marginal contact system BX And obtained during 1987, 1989 and 1990 seasons at the Ankara University Observatory are presented. Based on all available light curves of the system we studied light curve variations, particularly at the extrema points. Time scale of the variations was found as short as a few cycles of the orbital revolution. Six new estimates of the minima times are given. Some indications are found that the system might be detached or semi-detached.

A period study of GK Cephei

A period study of the times of minima from 1900 to 1988, of a W UMa system GK Cep was performed. The system was found to have no significant secular period change, but the photoelectric observations reveal a short term (∼18 yaer) periodic oscillation of the photometric period with an amplitude of about 0.035 day around the mean value of P = 0.9361653 day. Such oscillation of the photometric period has been discussed in terms of (i) the magnetically induced deformations in the atmosphere, (ii) mass motions in the core of a component star, (iii) cyclic behavior in the mass transfer or mass loss rate, and (iv) the light time effect due to a thrid body in the system

UBV photometry of AW Pegasi

NewUBV observations of the classical Algol system AW Peg were presented. The photometric minima times were collected and used together with the new determinations in a period study. No sign of any period change was found from observations covering more than sixty years. TheB andV light curves are analyzed by means of the Wilson-Devinney approach. It was verified that the system is semi-detached with a Roche lobe filling secondary.

1990 photometry of a small amplitude W UMa system LS Delphini

DifferentialUBV observations, carried out in 1990 observing season, of a small amplitude (0.m15 inV andB) W UMa system LS Del = HD 199497 are presented. Wavelength-dependent light variations from cycle to cycle indicate that the system is in a very active phase, probably due to magnetic flare activity or mass transfer in the system. An analysis of the minima times indicate a probable secular increase of the photometric period which requires a mass transfer from less massive to more massive component. If this is true then the reverse-algol model by Liuet al. (1988) for this system would not be valid.

UBV photometry of HR 1176

We present photoelectricUBV observations of the suspected Caii emission line star HR 1176. A period analysis of the observations by using the method of Shell-Metzner failed to yield any true period which is probably due to (i) the large gaps in the observations, (ii) low-amplitude variation, and (iii) the nonconstancy of the period, or there may be no regular light variation. A visual inspection of the present observations shows no systematic or abrupt variability except some scatter. However, a long period eclipsing nature of HR 1176 cannot be ruled out by this observations.

Photometry of Some Close Binaries at the Ankara University Observatory

Three close binary systems YY Eri, V456 Oph and AW Peg are discussed on the basis of UBV photoelectric observations carried out at the Ankara University Observatory in 1988 and 1989.

On the period of HR 1362

Photoelectric UBV observations, made in 1981 and 1982, of the active star HR 1362, are presented. A period analysis reveals many (all greater than 100 days) probable periods because of the large gaps in the data. If the most probable period around 330 d is true and represents the rotation period, as it does in all other active stars, then HR 1362 would be an extreme case of slow rotation.