Photometric and spectrophotometric observations of Nova Delphini 1967

Photographic, photovisual and photoelectric (V) observations of Nova Delphini 1967 were made from August 8 to October 31 (Table I, Figure 1). Simultaneously spectrophotometric measurements of the continuum were made on objective prism exposures extending to November 26, and spectrophotometric gradients derived (Tables II and III; Figures 3, 4, and 5). The continuum of Nova near its flat maximum is close to that of an early-type star in contrast to late-type absorptionline spectrum.     

An analysis of spectrophotometric observations of comets Austin (1982g) and Bradfield (1980t)

Post-perihelion observed emission fluxes at 388 nm (CN) and 516 nm (C₂) of the coma of comets Austin (1982g) and Bradfield (1980t) are analysed in the framework of the Haser model. Ratios of Haser model CN and C₂ parent production rates with expansion velocity show that each comet behaves normally. For comet Austin (1982g), the Q _CN/v and Q _c2/v values decrease with increase of heliocentric distance of comet. For an assumed %; activity of the total spherical surface area of the nucleus, the water vaporization theory coupled with derived water production rates from the International Ultraviolet Explorer H and OH flux data yields a nuclear diameter of about 6 km for comet Austin (1982g). For comet Bradfield (1980t), the derived nuclear diameter is expected to be of about 1 km. In each comet, the dust mass production rates as well as ratio of dust-to-gas mass production rates decrease with increase of heliocentric distance of comet.     

The photometric observations and analysis of the eclipsing binar V566 Ophiuchi

The system of V566 Oph was observed photometrically in B and V filters in1999 at the Birouni Observatory, Shiraz, Iran. Two light curves were obtained and have been analyzed separately of Wilson-Devinney code. New geometrical and physical elements for the system are given. The absolute dimensions of the binary have been derived by combining the photometric solution with spectroscopic data of the system. Also, the period of the system is calculated.     

B,V, and DDO photometric observations of red variable stars

Light curves of the red variables L₂ Puppis, R Carinae, and S Carinae in the region of the spectrum covered by theB, V, and DDO photometry are presented. The behavior of the DDO color indices and their meaning for this type of star are discussed. S Carinae shows a different behavior from the other two stars that seems to be due to a population effect.     

An analysis of Martian satellite photographic observations of 1967

Photographic observations of the Martian satellites were made at the opposition of 1967 with the Naval Observatory's 61-inch astrometric reflector. A small partially transparent metallic film filter was used to diminish the light from Mars in order that a measurable image for the planetary disk as well as for the satellites could be obtained. The plates were reduced by the method of plate constants using positions for the faint background stars determined from astrographic field plates. The random mean error of these observations was estimated to be not greater than ±0″.10.The main result of the orbital adjustment is a +2° correction to the zero of mean longitude for Phobos. This confirms the findings of Wilkins (1970) and is compatible with the results of the Mariner 9 observations. The scale of the orbits of both satellites gave accordant values for the mass of Mars and the combined value of 30 99 500 ± 2800 (m.e.) is in good agreement with modern determinations.The mean error for Deimos derived from the residuals after solution is ±0″.11, which agrees well with the observational error and indicates no large systematic error in either the theory or the observations. For Phobos, however, the residual error, ±0″.19, is twice the expected observational error. The implications of this discrepancy are discussed.     

The photometric observations of ER vulpeculae: photometric analysis with the W-D code

The photometric observations of ER Vul were obtained in UBV light in 1994, at Birouni Observatory, University of Shiraz, Iran. The three light curves, which are almost complete, have been analyzed separately by means of Wilson and Devinney method (1971). The light curves include proximity effects, wave-like distortions, mutual eclipses, and short term light fluctuations. The appropriate value of the mass ratio of this system was found after extensive searches. ER Vul has a detached configuration where the two components are very nearly fill their Roche lobe. ER Vul has the characteristic of a RS CVn type system. The absolute dimensions for the primary and secondary of this system were calculated from its spectral types and by combining the photometric solution with inferred component radial velocities (Northcott and Bakos, 1967).     

Frequency analysis of photometric observations of HD 101158

Observations of solar radio emission at 3 cm wavelength have been made at Japal-Rangapur Observatory for 1980–1981, the solar maximum year using the 3 m radio telescope. The correlation between microwave solar emissions and the sunspot activity on monthly basis has been found to be high during the maximum phase and in the high cm wavelength band. The basic component has been estimated statistically for successive solar rotations using the data obtained at Japal-Rangapur Observatory. Further, this was compared with the data obtained at other cm wavelengths during 1980–1981 and the solar minimum period 1975–1976 of the 21st cycle. The comparison showed pronounced dips in flux levels at different wavelengths during the summer months of the solar maximum year which may be attributed to the presence of coronal holes in the various levels of the solar atmosphere. The computed basic component values showed pronounced variation at high cm wavelengths for the solar maximum period with dissimilar variations at different wavelengths. During the solar minimum period the variations were negligibly small and showed more or less constant level of activity.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.     

Some results of the cooperative photometric observations of the UV Cet-type flare stars in the years 1967–71

The list of the cooperative photometric observations of the UV Cet-type flare stars that have been organized during the years 1967 to 1971 by the Working Group on Flare Stars of the IAU Commission 27 is given. The completeness and reliability of the data obtained are evaluated by comparing simultaneous observations at different observatories. the statistical analysis of the UV Cet, YZ CMi, EV Lac and AD Leo flares observed in the B-band is carried out. The flare energy spectrum in the energy range where observational selection effects are small is found to be d lnv/d lnE _B=–1.4 to –1.9,v is an occurrence of flares with radiation energy ofE _B. The total flares' radiation is equal to 1.7%, 1.2%, 0.3% and 0.4% of the quiet radiation in the B-band of the stars listed, and the main part of this total radiation is due to the strongest flares. Distributions of flare rise times (t _r) and of rates of flare absolute luminosity increase (d² E _B/dt _r ²Ë _r) are considered; these parameters of flare are independent statistically for all stars studied. Correlation coefficientsr (E _B,t _r) andr (E _B,r(E _B,Ë _r)) are rather small except r (E _B,t _r)=0.86 for the AD Leo flares. Contradictory conclusions on temporal distribution of flares infered by different investigators are noted.     

An analysis of close binaries (CB) based on photometric measurements (VI)

The paper is devoted to the actual problematics in the determination of orbital and physical parameters of active CB on the basis of the interpretation of photometric observations. One solves the problem in two stages: by obtaining a synthetic light curve in the case when the parameters of the corresponding CB model (Djuraevi, 1992a) are given a priori (direct problem) and by determining the parameters of the given model for which the best fit between the synthetic light curve and the observations is achieved (inverse problem) (Djuraevi, 1992b). In this paper, the above procedure is applied to a particular case of an interpretation of CB light curves WZ Cep and FT Lupi.     

New findings based on long-term photometric observations of the eclipsing binary V471 Tauri

The post-common envelope and pre-cataclysmic binary V471 Tau has been observed by the authors since 1973. At least a complete light curve in B and V bands and more than two eclipse timings were obtained in each year. All the available data published so far (including the authors') have been collected and analysed for the brightness and orbital period changes. The system brightened about 0.22 mag in both B and V bands more or less regularly up to 1997 and started to decrease afterwards. A search for periodicity of this variation yields a period longer than 85 yr. In addition to this long-period variation, a small amplitude of about 0.08 mag and short time-interval fluctuations on the mean brightness have been detected. The variations of the mean brightness have been discussed and plausible causes suggested. The changes of the apparent period have been attributed to a third body. Analysis of all the 'observed−calculated' (O−C) data yields a period of 32.4 yr, with a semi-amplitude of 151 s and an eccentricity of 0.30 for the third-body orbit. For orbital inclinations greater than 34° the mass of the third body would possibly match to a brown dwarf. One of the most interesting features in the light curve of V471 Tau is the decrement of the eclipse depth with time. The depth of the eclipse in the B band has been decreased from 0.082 to 0.057 mag over 34 yr. Subtracting the variation of the depth due to the brightening of the red dwarf star, the actual variation in depth, originated from from the white dwarf, was found to be about 0.012 mag. This change in the brightness of the compact object has been attributed to the mass accretion from its primary component via thermally driven wind and/or flare-like events.     

BVRI photometric observations,light curve solutions and orbital period analysis of BF Pav

A new ephemeris,period change analysis and light curve modeling of the W UMa-type eclipsing binary BF Pav are presented in this study.Light curves of the system taken in BVRI filters from two observatories,in Australia and Argentina,were modeled using the Wilson-Devinney code.The results of this analysis demonstrate that BF Pav is a contact binary system with a photometric mass ratio q=1.460 ± 0.014,a fillout factor f=12.5%,an inclination of 87.97 ± 0.45 deg and a cold spot on the secondary component.By applying the distance modulus formula,the distance of BF Pav was calculated to be d=268 ± 18 pc which is in good agreement with the Gaia EDR3 distance.We obtain an orbital period increase at a rate of 0.142 s century-1 due to a quadratic trend in the O-C diagram.Also,an alternative sudden period jump probably occurred which could be interpreted as a rapid mass transfer from the lower mass star to its companion of about ΔM=2.45 × 10~(-6) M_⊙.Furthermore,there is an oscillatory behavior with a period of 18.3±0.3 yr.Since BF Pav does not seem to have significant magnetic activity,this behavior could be interpreted as the light-time effect caused by an undetected third body in this system.In this case,the probability for the third body to be a low mass star with M≥ 0.075 M_⊙or a brown dwarf is 5.4% and 94.6% respectively.If we assume i'=90°,a_3=8.04±0.33 AU.The mass of the secondary component was also determined following two different methods which result close to each other.     

The substructure in the heads of comets with type I and type II tails

On a number of Comet Halley 1910 photographs of short exposures (Helwan material) a substructure in dust emission in the inner coma becomes detectable. Narrow and diffuse dust streamers leave the nucleus area within a smaller or larger cone opened in the direction to the Sun. On plates with longer exposures these structures merge together in a parabolic envelope. Structures of the type I tail are not visible for lower heliocentric distances (r<1) in the inner coma; however, occasionally CN, C₂ eject circular emission areas.The present note represents a preliminary account of a larger publication which will contain a great number of details and also many photographic reproductions. The preparation of the latter will, however, take some time.     

CCD photometric analysis of the W UMa-type binary V376 Andromeda

This study presents the absolute parameters of the contact binary system V376 And. CCD photometric observations were made at the Çanakkale Onsekiz Mart University Observatory in 2004. The instrumental magnitudes of all observed stars were converted into standard magnitudes. New BV light curves of the system were analysed using the Wilson–Devinney method supplemented with a Monte Carlo type algorithm. Since there are large asymmetries between maxima (i.e., O’Connell effect) in these light curves, two different models (one with a cool spot and one with a hot spot) were applied to the photometric data. The best fit, which was obtained with a large hot spot on the secondary component, gives V376 And as an A sub-type contact binary in poor thermal contact and a small value of the filling factor (f ≈ 0.07). Combining the solutions of our light curves and Rucinski et al. (2001)’s radial velocity curves, the following absolute parameters of the components were determined: M₁ = 2.44 ± 0.04 M_⊙, M₂ = 0.74 ± 0.03 M_⊙, R₁ = 2.60 ± 0.03 R_⊙, R₂ = 1.51 ± 0.02 R_⊙, L₁ = 40 ± 4 L_⊙ and L₂ = 5 ± 1 L_⊙. We also discuss the evolution of the system, which appears to have an age of 1.6 Gyr. The distance to V376 And was calculated as 230 ± 20 pc from this analysis, taking into account interstellar extinction.     

An analysis of close binaries (CB) based on photometric measurements (V)

The author considers the current problematics in the determination of the orbital and physical parameters for active close binaries (CB) of W Ser type based on the interpretation of photometric observations. In the particular case one analyses the light curves of CB RX Cas in the framework of the accretion-disc model explained in the second paper of this series (Djuraevi, 1992a). The change of the light curves with that of the system's physical-activity phase is analysed and the orbital and physical parameters of the system are determined for the maximum, minimum and the transition regime of the physical activity by applying the inverse-problem method described in the third paper of the series (Djuraevi, 1992b). In the paper a graphical illustration of the solutions obtained is also given.     

Polarimetric and photometric observations of long-period variables

Observations of 35 long-period variables have been done mainly at the Byurakan Astrophysical Observatory during the last years. A polarimetric monitoring of 34 stars has been carried out with simultaneous photometric measurements for some of them. Photometric data in the UBVR bands have been obtained for the star Y Ori, which is the faintest one. The results show that the degree of light polarization is correlated with the period and brightness of these stars. This indicates that the degree of light polarization is connected with the mass loss as well. Finally the photoelectric observations of the stars Y Ori, T Cep, R Gem, and R Boo show a short-term increase of their brightness in the decreasing branch of their light curves. The measured (U-B) or (B-V) colors of detected rapid variations are bluer than the colors of the star measured before these events. It is supposed that the change of polarization with time, the relatively blue colors of miras near their minimum brightness, and the colors of detected rapid variations may be explained by the influence of a invisible blue companion, as in the case of the star R Aqr. Published in Astrofizika, Vol. 42, No. 3, pp. 341–350, July–September, 1999.     

Spectral and photometric observations of the star Y Ori

Data are presented from a spectral and photometric study of the long-period variable star Y Ori, which we have classified as a type M7IIIe near its brightness minimum. In the blue part of the spectrum, features from a star of an earlier spectral class are superimposed on the spectrum of a cool giant, so that a variable excess emission is observed at wavelengths of 4000–4200 Å. As opposed to the monotonically decreasing intensity of the Balmer lines (EWHα > EWHβ > EWHγ > EWHδ) in normal stars belonging to the earlier spectral classes, a reverse relationship, with EWHγ < EWHδ is detected in Y Ori. Translated from Astrofizika, Vol. 51, No. 4, pp. 567–575 (November 2008).     

Polarimetric and photometric observations of the star m cephei

The results of photometric and polarimetric observations of the star Μ Cep at Byurakan Observatory are presented. Some interesting correlations between the parameters of the star’s brightness variation and the degree of polarization of the light are obtained. It is suggested that the recorded rapid changes in the degree of polarization may result from Μ Cep being a double star. Translated from Astrofizika, Vol. 43, No. 2, pp. 219-228, April–June, 2000.     

The first photometric analysis of the near-contact binary star V370 Cygni

The first complete CCD light curves of the eclipsing binary system V370 Cygni have been obtained in the B, V, R and I filters during 5 consecutive nights in 2005 at Kryoneri Observatory, Greece. These curves were analyzed with the Wilson–Devinney program in order to determine the geometrical and physical parameters of the system. The analysis indicates a semi-detached configuration and a mildly evolved state of the system.