UBV photometry of Vesta

A lightcurve of Vesta, obtained on four nights between June 23 and 30 June 1978 during the coordinated campaign for the determination of the rotation period, is presented. The observations were performed at the 91-cm telescope of the Catania Observatory employing UBV filters and a photon counting photometer. The V lightcurve apparently shows a single maximum, suggesting that the 5^h20^m29^s.2 period is the correct one. Features are evident near the maximum and the minimum closely resembling those of Johnson's lightcurve of 22 December 1950 and Taylor's of January 21, 1973. The amplitude in V light is 0^m.105 and small variations are also found in the color indices. The largest color variation is for the U-V with Δm = 0.^m.05, which is slightly larger than the value 0^m.02 found by T. Gehrels [Astron. J.72, 929 (1967)]. The maximum and minimum values occur at the same phase with respect to the maximum V light as found by Gehrels, i.e., Vesta appears bluer near 0^p.25 and redder near 0^p.7. Corrections with the solar phase angle were made using the coefficients given by Gehrels for the B-V and U-V while a new value of 0.036 mag/deg was assumed for the V observations. The available amplitudes of Vesta's lightcurve were analyzed with respect to the longitude position and the solar phase angle.     

UBV photometry of Triton

UBV measurements of Triton relative to Neptune were obtained with an area-scanning photometer on 11 nights during the 1977 apparition. Observed orbital brightness variation shows that Triton is locked in synchronous rotation around Neptune. Its leading side, seen at greatest western elongation, is found to be 0.06 mag brighter than its trailing hemisphere.     

UBV photometry of DX Aquarii

U, B, V photometry of the eclipsing binary DX Aqr has been presented for the first time. The period of the system comes out to be nearly half the period given by Strohmeier (1966) and a value of O^d.472502 has been determined. The colour of the system has been discussed. The primary eclipse is a total occulation. The orbit seems to be eccentric. The system belongs to Algol type. DX Aqr may be a very complicated system. The present results are considerably different from those of earlier investigations.     

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.     

UBV photometry of FK Comae

UBV photometry of the peculiar star FK Comae, obtained during the period January–June 1983, is presented. The amplitude of the photometric variation has raised with respect to the previous observations performed in 1981 and 1982, attaining about 0.18 mag in theV filter. Colour curves indicate that the star is redder at minimum light; this fact is consistent with both the models presented to explain the properties of FK Comae. A Fourier analysis of the light curves available in the literature has been performed; the phases of minimum and maximum light turn out to be noticeably stable in time. This fact is difficult to be reconciled with the hypothesis of dark spots that are observed to migrate in other active stars. Rather, it could be explained by the model of Walter and Basri (1982a, b), implying an extremely evolved Algol-type system accreting mass on its primary component.     

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.     

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.     

UBV photometry of ER Vulpeculae

UBV photometry of RS CVn-type eclipsing binary system ER Vulpeculae has been presented. The period comes out to be 0 _. ^d 698093. The average depths of primary and secondary minima are, respectively, 0 _. ^m 21 and 0 _. ^m 12. The colours at various phases have been given. A dip is seen around phase 0 _. ^p 73 as was seen in the observations of Arevaloet al. (1988). Large scatter is present in the observations as noticed earlier, and may be due to activity of the components.     

Light-time effect in RT Persei

The minimum time residuals (O–C) of RT Persei, obtained by using all the times of minima is interpreted in terms of light-time effect, caused by the presence of two more distant components. This system possesses a third body of a mass of about 0.74M with 41.86 yr orbital period moving in an orbit of eccentricity equal to 0.3, while the hypothetical fourth body of an approximate mass of 0.59M moving with an orbital period of 100 years has an eccentricity equal to 0.6. The need to study this system astrometrically should be emphasized.     

UBV photometry of asteroid 433 Eros

UBV observations of asteroid 433 Eros were conducted on 17 nights during the winter of 1974/75. The peak-to-peak amplitude of the lightcurve varied from about 0.3 mag to nearly 1.4mmag. The absolute V mag at maximum light, extrapolated to zero phase, is 10.85. Phase coefficients of 0.0233 mag/degree, 0.0009 mag/degree and 0.0004 mag/degree were derived for V, B-V, and U-B, respectively. The zero-phase color of Eros (B?V = 0.88, U?B = 0.50) is representative of an S (silicaceous) compositional type asteroid. The color does not vary with rotation. The photometric behavior of Eros can be modeled by a cylinder with rounded ends having an axial ratio of about 2.3:1. The asteroid is rotating about a short axis with the north pole at λ₀ = 15° and β₀ = 9°.     

UBV photometry of the Galilean satellites

UBV observations of the Galilean satellites made at Lowell Observatory and Cerro Tololo Inter-American Observatory during 1973 and 1974 are reported. The dependence of brightness on solar phase angle for various faces of each satellite is determined. Significant differences in this dependence are found between different faces of the same satellite, between satellites, and between the present results and those of previous investigators. Rotational light and color-index curves are presented for the satellites and compared with earlier work. An apparent secular brightening of all four satellites between 1973 and 1974 is discussed.     

UBV photometry of 262 southern galaxies

Multi-aperture photometry of 262 bright southern galaxies in the JohnsonUBV system is given. Most of these are south of =–30°, although some northward to =–10° are included. A total of 169 objects have published radial velocity determinations. These provide distances, and enable construction of colour-magnitude diagrams for this subset of bbjects through a physical diameter of 2.0 kpc (withH _o=100). The two-colour diagrams for the inner regions of the galaxies differ from those of integrated galaxies due to the colour changes towards their centres. Comparison with theoretical models of Larson and Tinsley (1978) suggest that the colours of the inner portions of most ellipticals and lenticulars are consistent with their having all stars formed at nearly one epoch with little subsequent star formation, while for spirals larger amounts of star formation, either in bursts or continuously, are suggested. This simple picture is complicated by the presence of certain objects having peculiar colours indicative of large amounts of recent star formation.     

V758 Centauri:UBV photometry

The W UMa system V758 Centauri has been observed photoelectrically in theUBV system at Bosque Alegre Station, and the comparison and check stars at Cerro Tololo Observatory. Full light curves were constructed from 1043 differentialUBV observations. A study of 11 photoelectric times of minimum light and of earlier photographic data shows that the period remained constant in the last century, V758 Cen shows a total occultation at secondary minimum, thus being an A-type W UMa system. Asymmetries are observed at primary minima whereas maxima are of different heights. Thermal decoupling of the components is suggested by the depth ratio of the minima; V758 Cen may be at the broken phase (or marginal contact) of a thermal relaxation oscillation.     

UBV photometry and light-curve analysis of Algol

Photoelectric observations of the eclipsing variable β Per, were obtained inUBV standard system, and new elements for the primary minimum were determined as $$J.D. = 2445641.5135,O - C = 0_.^d 0.009.$$ The light curves of the system were analysed using Fourier techniques in the frequency-domain. The fractional radii of both components are $$r_1 = 0.217 \pm 0.002,r_2 = 0.233 \pm 0.002andi = 85.5 \pm 0.5.$$ Absolute elements were derived and the effective temperatures are $$T_1 = 11800K,T_2 = 5140K.$$      

On the period variations of RT Persei

The observed minima of RT Persei up to 1971 are collected and treated by the method of least squares to establish periodic terms with a fundamental period of 40^y0 and, furthermore, a quadratic term. It is shown that the periodic terms might be explained by the presence of a third body, but this hypothesis seems unlikely, and could be definitively ruled out by new spectroscopic observations. A dynamical instability of the system may constitute a more likely explanation of the observed period changes.     

UBV photometry of small and distant asteroids

Photoelectric magnitudes and colors on the UBV system are presented for 65 minor planets, including four Mars crossers, six Trojans, and main-belt objects down to 6 km in diameter. The Trojans all have very similar colors not characteristics of the main-belt population. A paucity of S-type asteroids at the smallest diameters, predicted from trends seen at larger sizes, is not observed. The newly available color data for small objects ranging from 1.0 to 5.2 AU in heliocentric distance show the main belt to be a transition zone between predominantly silicate and carbonaceous compositions.     

UBV photometry of clusters in M31

A critical review is given of all published photoelectricUBV photometry of star clusters in the Andromeda Nebula. Observations by Sharovet al. are shown to exhibit rather large random errors, but no systematic deviations from theUBV system.     

Photoelectric photometry and photometric elements of LX Persei

In this paper we present the observations of the eclipsing binary LX Per, which were obtained in 1983. There is a wave-like distortion at outside eclipses with an amplitude ranging from 0.03 to 0.08 mag. The wave-like distortion was removed with a new approach. Then, the light curves were analyzed by the methods of Wood and Nelson, Davis, and Etzel. The absolute parameters of the components were also calculated. The physical parameters of the components indicate that the cooler star has seperated or has been departing from the Main Sequence.     

Analysis of UBV photometry in selected area 133

We interpret the de‐reddened UBV data for the field SA 133 to deduce the stellar density and metallicity distribution functions. The logarithmic local space density for giants, D*(0) = 6.40, and the agreement of the luminosity function for dwarfs and sub‐giants with the one of Hipparcos confirms the empirical method used for their separation. The metallicity distribution for dwarfs gives a narrow peak at [Fe/H] = +0.13 dex, due to apparently bright limiting magnitude, V_o = 16.5, whereas late‐type giants extending up to z ∼ 4.5 kpc from the galactic plane have a multimodal distribution. The metallicity distribution for giants gives a steep gradient d[Fe/H]/dz = –0.75 dex kpc^–1 for thin disk and thick disk whereas a smaller value for the halo, i.e. d[Fe/H]/dz = –0.45 dex kpc^–1. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

UBV photometry of the WR binary CQ Cephei

Photoelectric observations of the WR binary CQ Cephei (WN6+O9) are presented. the depths of the eclipses in the light curves are best represented by an inclination of the orbit i = (68°.8±0.6) and the width of the very asymmetric eclipse curves can be represented by only an overcontact configuration (Ω₁ = Ω₂ = 3.65 ± 0.05, and f = 27%). Simultaneous solution of the light and radial velocity curves strongly supports CQ Cep's membership of the Cep OB1 association. By considering this membership we obtained absolute dimensions of the system, which lead to a consistent physical model for CQ Cephei. The more luminous WR primary turns out to be the hotter but slightly less massive component: M_WR = 20.8 M⊙, R_WR = 8.2R⊙, T_eff(WR) = 43600 K, and M_o = 21.4 M⊙, R_o = 8.3 R⊙, T_eff(O) = 37000 K.