Four years of photometry of DK draconis=HR 4665

Differential BV photometry of the K0III+K0III long-period RS CVn-type binary DK Dra=HR 4665 in 1977, 1978, 1979, and 1980 at eight different observatories is presented. A least squares fit to times of maximum and minimum light yields the ephemeris JD=2 443 219.5+63 _. ^d 75E for times of minimum. This photometric period is 1% shorter than the spectroscopically determined orbital period 64 _. ^d 44. The light curve was symmetrical and roughly sinusoidal in 1979 and 1980 but was asymmetrical in 1977 and 1978, with a faster rise to maximum. During these four years DK Dra varied between V=6 _. ^m 07 and 6 _. ^m 35.Of the AAVSO.Amateur Astronomers, Inc.     

Three-colour photometry of GH pegasi

The geometrical elements of the system GH Pegasi and a slightly improved period of 2 _. ^d 556136 have been given.     

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.     

Simultaneous photometry and spectroscopy of the newly discovered γ Doradus variable HR 8330=HD 207223

We present BV photometry and simultaneous high-resolution, high signal-to-noise ratio spectroscopy of the newly-discovered γ Doradus variable HR 8330 taken during the 1997 and 1998 observing seasons. We calculate power spectra for the B - and V -band data sets and for the time series defined throughout the observing season at each point across the Fe  ii λ 4508.289 and the Ti  ii λ 4501.278 line profiles to search for periodic variability. Period analysis reveals a single, 2.6-d period in both the photometric and the spectroscopic data, with a 237° phase lag between them. Based on the location of HR 8330 in the HR diagram and the characteristics of its photometric and spectroscopic variations, we conclude that HR  8330 is a bona fide γ Doradus-type pulsating variable.     

Five years of photometry of λ andromedae

We present photoelectric photometry of this bright long-period RS CVn binary and use it, along with earlier photometry, to derive the photometric period and discuss the changing light curve shape. The best ephemeris for times of minimum light is 2443829.2+53.^d95E. Because times of minimum and maximum extending back to those of Calder in 1933–37 can be phased together properly, the principal dark region must have maintained its identify for almost 50 yr. Over the last five years the brightness range has been 3 ^m .70<V<4 ^m .05. During 1980–81 shallow secondary minima developed at phases where maxima occurred in previous years. λ And remains the only wellestablished case of non synchronous rotation among the known RS CVn binaries.     

Five years of photometry ofσ geminorum

Five years of photoelectric photometry of this bright K1 III RS CVn binary has been obtained at thirteen different observatories. Except for one year, the light curve has shown two minima, separated by roughly a half cycle. At the epoch of discovery (1977.2) one minimum was shallower but as of 1980.2 the two became comparable in depth. During the 1979–80 season the light curve changed shape rapidly, the shallower minimum becoming as deep as the other within about 80 days or perhaps less. Times of both minima can be fit with a photometric period of 19 ^d .423, which is 0.9% shorter than the 19 ^d .603 orbital period. The overall brightness range during the five years has been 4 ^m .13<V<4 ^m .29.Guest Observer, Kitt Peak National Observatory, operated by the Association of Universities for Research in Astronomy, under contract with the National Science Foundation.     

Infrared photometry of the RS CVn binary HR 1099 (V711 Tau)

Infrared observations inJ, H andK of the RS CVn-type binary HR 1099 (V711 Tau) show apparent light variations similar to those in the visible. The phase shift towards increasing phase is confirmed. There is no conspicuous infrared excess attributable to circumstellar emission. The amplitudes of the infrared variation are compatible with the spot model proposed for RS CVn and enable plausible limits on a characteristic spot temperature and effective spot area to the set.     

Infrared photometry of Venus: Variation during 10 years?

The infrared flux of Venus has been observed with a narrowband filter (λ = 3.6 μm, Δλ = 0.08 μm) from 1982 through 1984, covering a range of the phase angle α from 27 to 94°. Normalized values of flux at the Venus-Earth distance of 1 AU were (4.0–5.4) × 10^?17W/cm²/cm^?1 and the α dependence of the data is rather weak. Furthermore, when the evening terminator of Venus was seen, lower values of flux were obtained in contrast with higher values at the morning terminator. The α dependence is quite different from that of J.V. Martonchik and R. Beer (1975, J. Atmos. Sci.32, 1151–1156). Since we cannot find any significant problem in the two observational methods, the difference might suggest an intrinsic time variation of haze particles during these 10 years in the upper haze layer of the Venus cloud.     

UBV photometry of the Ap variable UZ Psc = HD 10783

NewUBV photometry, obtained between late 1965 and early 1969, is presented and combined with existing published photometry to derive an improved ephemeris for times of maximum brightness: 2439758.00+4 _d ^. .1328n. On leave from Dyer Observatory, Vanderbilt University, Nashville, Tennessee, U.S.A.     

BVR photometry of the three RS CVn binary stars: V711 Tau,UX Ari and IM Peg

Differential BVR photometric observations of the three RS CVn binary stars: V711 Tau, UX Ari and IM Peg obtained during the period November 26, 1994–February 24, 1995 using the 0.35 m reflector telescope equipped with photoelectric photometer are presented. Analysis of light curves shows significant changes in shape, amplitude as well as the phases of minimum light of all the three binaries. The amplitude of IM Peg, in particular, is found to have reached a larger value in the present epoch of observation than reported earlier.     

Time‐series photometric spot modelling – VI. A new computer code and its application to 23 years of photometry of the active giant IM Pegasi

We present and apply a new computer program named SpotModeL to analyze single and multiple bandpass photometric data of spotted stars. It is based on the standard analytical formulae from Budding and Dorren. The program determines the position, size, and temperature of up to three spots by minimizing the fit residuals with the help of the Marquardt‐Levenberg non‐linear least‐squares algorithm. We also expand this procedure to full time‐series analysis of differential data, just as real observations would deliver. If multi‐bandpass data are available, all bandpasses can be treated simultaneously and thus the spot temperature is solved for implicitly. The program may be downloaded and used by anyone. In this paper, we apply our code to an ≈23 year long photometric dataset of the spotted RS CVn giant IM Peg. We extracted and modelled 33 individual light curves, additionally, we fitted the entire V dataset in one run. The resulting spot parameters reflect the long term light variability and reveal two active longitudes on the substellar point and on the antipode. The radius and longitude of the dominant spot show variations with 29.8 and 10.4 years period, respectively. Our multicolour data suggests that the spot temperature is increasing with the brightening of the star. The average spot temperature from V, I_C is 3550 ± 150 K or approximately 900 K below the effective temperature of the star.     

Photometric elements of the eclipsing binary DN UMa=HR 4560

A total of 704 previously published photoelectricB colour observations of the multiple system HR 4560 are analyzed by means of the light curve models NDE (Popper and Etzel, 1981) and WINK (Wood, 1972) in an iterative procedure. As a result, we have found that componentC of the multiplpe system ADS 8347 is the most probable origin of the observed eclipses. Some relevant astrophysical parameters of the component stars which indicate a normal Main-Sequence binary star have also been estimated.     

Photoelectric photometry of the RS CVn binary EI Eridani = HD 26337

DifferentialUBV(RI) _KC andUBVRI photometry of the RS CVn binary EI Eridani obtained during December 1987 and January 1988 at fourteen different observatories is presented. A combined visual bandpass light curve, corrected for systematic errors of different observatories, utilizes the photometric period of 1.945 days to produce useful results. Analysis shows the visual light curve to have twin maxima, separated by about 0.4 phase, and a full amplitude of approximately 0.06 mag for the period of observation, a smaller amplitude than reported in the past. The decrease in amplitude may be due to a decrease or homogenization of spot coverage. To fit the asymmetrical light curve, a starspot model would have to employ at least two spotted regions separated in longitude.     

Analysis of observations of the dwarf nova pegasi 2010

Analysis of photometric and spectroscopic observations of GSC 02197-00886 at the outburst maximum (on May 8, 2010) and at the stage of relaxation towards the quiescent (on August 4, 2010) was performed. Radiation of an optically thick accretion disc with a hot boundary layer dominates the spectra, which are consistent with the spectra of a WZ Sge-type dwarf novae. In the relaxation phase, an optically thin accretion disc with radiation in the HI and HeI emission lines is observed against the background of the absorption spectrum of a white dwarf. The parameters of GSC 02197-00886, which were determined by combining the radial velocities of the components with the assumption that the secondary component is close to mainsequence stars, differ significantly from the parameters that characterize other WZ Sge-type systems. We hypothesize that the secondary component was excited in the course of the outburst and experienced long-lasting relaxation towards the main-sequence state.     

Seven years photometry of the W UMa‐type eclipsing binary V2612 Oph

We present the first long‐term Johnson UBVR observations and comprehensive photometric analysis of the W UMa‐type eclipsing binary V2612 Oph. Observations in the time interval between 2003 and 2009 enabled us to reveal the seasonal and long‐term variations of the light curve. Hence, we found that the mean brightness level of the light curve shows a variation with a period of 6.7 years. Maximum and minimum brightness levels of the light curve exhibit a variation from year to year which we attribute to a solar‐like activity. The O – C variation of eclipse timings of the system shows a decreasing parabolic trend and reveals a period decrease at a rate of P = 6.27×10^‐7 day yr^‐1 with an additional low‐amplitude sinusoidal variation that has a similar period as the long‐term brightness variations. Our light curve analysis shows that the system is a W‐subtype W UMa eclipsing binary. We calculated masses and radii of the primary and secondary components as M₁ = 1.28 M_⊙, M₂ = 0.37 M_⊙ and R₁ = 1.31 R_⊙, R₂ = 0.75 R_⊙, respectively. The derived absolute photometric parameters allow us to calculate a distance of 140 pc, which confirms that the system is a foreground star in the sky field of the Galactic open cluster NGC 6633. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

1988–1991 photometry of the chromospherically active double-lined binary system HD 163621 = V835 Herculis

Photometry inV andB with a 16inch automatic telescope from 1988 to 1991 confirms the synchronous rotation suspected earlier and reveals variability up to 0^M.10 in theB bandpass at one epoch. Five spots formed with lifetimes ranging from 0.15 to 0.77 years. As with other rapid rotators, the differential rotation coefficient (k = 0.03) is significantly smaller than that of the Sun (k = 0.19).     

Photoelectric photometry of JV

UBV photometry of JV near greatest western elongation shows this satellite to be about one magnitude fainter than previously believed. It is observed to be very red, having a B-V color index near +1.5 mag. Unlike the Galilean satellites, JV appears to bea low-albedo object.     

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.