We examined light curves of 1138 stars brighter than 18.0mag in the I band and less than a mean magnitude error of 0.1mag in the V band from the Optical Gravitational Lensing Experiment (OGLE)-III eclipsing binary catalogue, and found 90 new binary systems exhibiting apsidal motion. In this study, the samples of apsidal motion stars in the Small Magellanic Cloud (SMC) were increased by a factor of about 3.0 than previously known. In order to determine the period of the apsidal motion for the binaries, we analysed in detail both the light curves and eclipse timings using the MACHO (MAssive Compact Halo Objects) and OGLE photometric data base. For the eclipse timing diagrams of the systems, new times of minimum light were derived from the full light curve combined at intervals of one year from the survey data. The new 90 binaries have apsidal motion periods in the range of 12-897yr. An additional short-term oscillation was detected in four systems (OGLE-SMC-ECL-1634, 1947, 3035, and 4946), which most likely arises from the existence of a third body orbiting each eclipsing binary. Since the systems presented here are based on homogeneous data and have been analysed in the same way, they are suitable for further statistical analysis.
New data on the periods of Ap stars with references are presented (Table 1). 21 further stars are introduced for which a periodic variability has recently been discovered or for which it was known before but it was not reported in previous issues of this catalogue. For many stars also present in previous issues of the catalogue new determinations of the periods are given. Recently attributed variable star names are also quoted. Note: this catalog is included in <III/199>
New data on the periods of Ap stars with references are presented. 161 further stars are introduced for which a periodic variability has recently been discovered or it was known before but it was not reported in previous issues of this catalogue. For many stars also present in previous issues of the catalogue new determinations of the periods are given. Recently attributed variable star names are also quoted.
We obtained the first VRI CCD light curves of the short-period contact eclipsing binary AQ Boo, which was observed on March 22 and April 19 in 2014 at Xinglong station of National Astronomical Observatories, and on January 20, 21 and February 28 in 2015 at Kunming station of Yunnan Observatories of Chinese Academy of Sciences, China. Using our six newly obtained minima and the minima that other authors obtained previously, we revised the ephemeris of AQ Boo. By fitting the O-C (observed minus calculated) values of the minima, the orbital period of AQ Boo shows a decreasing tendency dP/dt=-1.47(0.17)x10^-17^day/year. We interpret the phenomenon by mass transfer from the secondary (more massive) component to the primary (less massive) one. By using the updated Wilson & Devinney (1971ApJ...166..605W) program, we also derived the photometric orbital parameters of AQ Boo for the first time. We conclude that AQ Boo is a near contact binary with a low contact factor of 14.43%, and will become an over-contact system as the mass transfer continues.
We study the distribution of galaxies and galaxy clusters in a 10{deg}x6{deg} field in the Aquarius region. In addition to 63 clusters in the literature, we have found 39 new candidate clusters using a matched-filter technique and a counts-in-cells analysis. From redshift measurements of galaxies in the direction of these cluster candidates, we present new mean redshifts for 31 previously unobserved clusters, while improved mean redshifts are presented for 35 other systems.
We present spectroscopic and photometric data for 920 galaxies selected in 68 fields of the Aquarius Cluster Catalog. Typically, the 15 brightest candidate members with magnitudes in the range 16<b_J_<21 were selected for observations, and ~71% turn out to be cluster members. Using the new redshift determinations, we assign galaxies to groups and clusters, and by including data from the literature we calculate systemic velocities and velocity dispersions for 74 clusters, each with redshifts measured for at least six individual galaxies.
We have imaged the portion of the Shapley Concentration core surrounding the cluster A3556 at wavelengths of 36cm with the Molonglo Observatory Synthesis Telescope (MOST), and at 22 and 13cm with the Australia Telescope Compact Array (ATCA). We have defined a radio sample of 112 radio sources at 22cm. Cross-correlation with optical catalogues allowed the identification of 29 radio sources, nine of which belong to A3556. The radio and optical properties of A3556 have been studied in detail. Two extended radio sources are associated with cluster members, i.e. a narrow-angle-tail source located at a projected distance of 0.06R_A_ from the centre, possibly in the late stages of its existence, and a wide-angle-tail source at the periphery of the cluster. We also performed a statistical analysis of the cluster properties. The optical luminosity function shows that the cluster has an excess of bright optical galaxies. In agreement with well-established results, we found that the probability of radio emission increases for brighter galaxies. Furthermore, our radio luminosity function and those obtained for elliptical galaxies located in different environments (poor groups and rich clusters) are very similar, implying that the peculiar dynamical state of A3556 has no influence on the radio emission properties of the cluster galaxies.
We have performed a search for variable stars in the dwarf irregular galaxy NGC 6822 using wide-field multi-epoch VI photometry down to a limiting magnitude of ~22. A part from the Cepheid variables in this galaxy already reported in an earlier paper by Pietrzynski et al. (2004AJ....128.2815P), we have found 1019 "non-periodic" variable stars, 50 periodically variable stars with periods ranging from 0.12 to 66 days and 146 probably periodic variables. Twelve of these stars are eclipsing binaries and fifteen are likely new, low-amplitude Cepheids.
For the first time, we have detected Cepheid variables in the Sculptor Group spiral galaxy NGC 7793. From wide-field images obtained in the optical V and I bands on 56 nights in 2003-2005, we have discovered 17 long-period (24-62 days) Cepheids whose periods and mean magnitudes define tight period-luminosity relations. We use the (V-I) Wesenheit index to determine a reddening-free true distance modulus to NGC 7793 of 27.68+/-0.05mag (internal error) +/-0.08mag (systematic error).
We present near-infrared J- and K-band photometry of 77 Cepheid variables in the Local Group galaxy NGC 3109. Combining our data with the previously published optical V- and I-band photometry of Cepheids in this galaxy, we derive an accurate distance and interstellar reddening toward NGC 3109.
