We present all available UBV photometry of the symbiotic binary EG And obtained during the last 10 years. The light curves display a double wave through one orbital cycle. It is shown that this behaviour cannot be explained by eclipses of the two detached sources of the continuum radiation. The present models of EG And are not able to simulate satisfactorily variation in both the far ultraviolet and the optical continuum.
This catalog is the result of a program of photographic photometry. Four plates each were taken of M67 in U, B, and V, and were measured and reduced using the standards of Johnson and Sandage (1955) and Eggen and Sandage (1964). The catalog lists identification, V, B-V, U-B, proper motion, and membership probability for 1,053 stars.
The rapidly rotating active stars FK Com and HD 199178 are investigated using extensive long-term photometry. The data set includes previously unpublished photometry, obtained at the Rozhen National Astronomical Observatory. We look for periodicities in the long-term photometric behaviour of both stars, as well as for spots, using light curve modelling. Special attention is paid to the behaviour of the "flip-flop" phenomenon.
We report the discovery of brightness variability in the IR-excess early F supergiant HD 331319, a candidate post-AGB star. Over three years of systematic UBV observations, the star showed low-amplitude (up to 0.17m in V) quasi-periodic brightness variations on a time scale of 45 days. A preliminary analysis of our photometry indicates that HD 331319 and other typical post-AGBF supergiants have a similar pattern of variability. A study of the extinction toward HD 331319 leads us to conclude that the fraction of the circumstellar extinction is small for this star. We present low-resolution spectroscopy for HD 331319 and discuss the spectral classification of post-AGB F supergiants using HD 331319, HD 161796, HD 187885, and HD 56126 as examples.
After a serendipitious discovery that HD 143418 is a light variable, we analyzed numerous UBV observations and Hipparcos H_p_ magnitudes transformed to Johnson V to find out whether the object is a very unusual spectroscopic binary. Initial reductions of new photometry were carried out with the HEC22 program, while the new spectra were reduced in the IRAF and SPEFO programs. Orbital elements were derived with the FOTEL program, the KOREL disentangling was applied, and period searches were carried out using phase dispersion minimalization technique and the program PERIOD04. Final modeling of radial-velocity and light variations was carried out in PHOEBE.
Photometric and spectroscopic monitoring of the B star resulted in the finding that this object is a new bright Be star with a clear positive correlation between the brightness and emission-line strength. The emission-line episodes are relatively short and seem to repeat frequently which makes this star an ideal target for studying the causes of the Be phenomenon.
Photoelectric UBV photometry is presented for over 400 HD stars which lie within about a degree of selected cataclysmic variables. The data will be combined with polarimetry to determine the distances of the CVs.
Our aim is to determine the distance of outer Galaxy star-forming complexes in order to model the kinematic structure of our Galaxy. We searched for exciting star(s) of HII regions, with poor or unknown stellar distance, in the second and third galactic quadrants. We carried out spectroscopic and photometric (when necessary) observations in order to establish their spectral type and their U, B and V magnitudes. From these data, complemented with literature data, we determine the spectro-photometric distance of their associated complexes.
Photoelectric UBV observations of 1782 stars are used to explore properties of the HK objective-prism survey conducted by Beers, Preston, and Shectman with the Curtis-Schmidt telescope of the Cerro Tololo Inter-American Observatory. We construct an intrinsic (U-B)0 versus (B-V)0 relation for blue horizontal branch stars and use it to derive estimates of E(B-V) color excesses in 50 survey fields. Comparison of these with the reddening maps of Burstein and Heiles indicates good agreement except in low-latitude fields toward the Galactic bulge. We describe qualitative features of the stellar content of the HK survey by use of unreddened two-color diagrams and indicate how the photometric data may prove useful in several applications. Finally, we use a halo density model to estimate the variation of completeness with apparent magnitude, B, in our catalog of field horizontal branch star candidates.
We report UBV photoelectric photometry for 273 stars in the fields of the open clusters IC 2395 and BH 47. Our postulate is that, rather than two different clusters in this region of Vela, there is only one, which we call IC 2395 = BH 47. The cluster is centered at about RA = 8h 42min 33s, and DE = -48{deg} 06' 48" (2000), its angular diameter being ~19'. The analysis of the photometric data yields 61 probable cluster members and 16 possible members. Photometric membership probabilities show good agreement with those obtained from a proper motion study for 21 stars in common. The reddening across the cluster appears to be uniform, the mean E(B-V) value being 0.09+/-0.02. The true distance modulus is V_0_-Mv=9.52+/-0.10, corresponding to a distance from the Sun of (800+/-40)pc and 48pc below the Galactic plane. The cluster age, determined by fitting isochrones with core overshooting, turns out to be (6+/-2)Myr. There is a strong likelihood that IC 2395 = BH 47 is physically connected to the Vela OB1C association.
