UBVRI Light Curves Research Articles

MY Serpentis: a high-mass triple system in the Ser OB2 association★

We present spectroscopic observations of the massive multiple system HD\,167971, located in the open cluster NGC\,6604. The brighter component of the triple system is the overcontact eclipsing binary MY\,Ser with an orbital period of 3.32\,days. The radial velocities and the previously published UBV data obtained by \citet{may10} and the UBVRI light curves by \citet{dav88} are analysed for the physical properties of the components. We determine the following absolute parameters: for the primary star M$_p$=32.23$\pm$0.54 M$_{\odot}$, R$_p$=14.23$\pm$0.75 R$_{\odot}$; and for the secondary star M$_s$=30.59$\pm$0.53 M$_{\odot}$, R$_s$=13.89$\pm$0.75 R$_{\odot}$. Photoelectric times of minimum light are analyzed under the consideration of the light-time orbit. The center-of-mass of the eclipsing binary is orbiting around the common center-of-gravity of the triple system with a period of 21.2$\pm$0.7\,yr and with a projected semi-major axis of 5.5$\pm$0.7\,AU. The mass function for the third star was calculated as 0.370$\pm$0.036 M$_{\odot}$. The light contributions of the third star to the triple system in the UBV pass-bands were derived and the intrinsic magnitudes and colors were calculated individually for the three stars. The components of the eclipsing pair were classified as O7.5 {\sc iii} and O9.5 {\sc iii}. The intrinsic color indices for the third star yield a spectral type of (O9.5-B0) {\sc iii-i}. {\bf This classification leads to constrain the inclination of the third-body orbit, which should be about 30$^{o}$, and therefore its mass should be about 29 M$_{\odot}$. MY\,Ser is one of the rare massive O-type triple system at a distance of 1.65$\pm$0.13\,kpc, the same as for the NGC\,6604 embedded in the Ser\,OB2 association.}

International observational campaigns of the last two eclipses in EE Cephei: 2003 and 2008/9

Two observational campaigns were carried out during the eclipses of EE Cep in 2003 and 2008/9 to verify whether the eclipsing body in the system is indeed a dark disk and to understand the observed changes in the depth and durations of the eclipses. Multicolour photometric data and spectroscopic observations at both low and high resolution were collected. We numerically modelled the variations in brightness and colour during the eclipses. We tested models with different disk structure. We considered the possibility of disk precession. The complete set of observational data collected during the last three eclipses are made available to the astronomical community. Two blue maxima in the colour indices were detected during these two eclipses, one before and one after the photometric minimum. The first (stronger) blue maximum is simultaneous with a "bump" that is very clear in all the UBVRI light curves. Variations in the spectral line profiles seem to be recurrent during each cycle. NaI lines always show at least three absorption components during the eclipse minimum and strong absorption is superimposed on the H_alpha emission. These observations confirm that the eclipsing object in EE Cep system is indeed a dark, dusty disk around a low luminosity object. The primary appears to be a rapidly rotating Be star that is strongly darkened at the equator and brightened at the poles. Some of the conclusions of this work require verification in future studies: (i) a complex, possibly multi-ring structure of the disk in EE Cep; (ii) our explanation of the "bump" observed during the last two eclipses in terms of the different times of obscuration of the hot polar regions of the Be star by the disk; and (iii) our suggested period of the disk precession (~11-12 P_orb) and predicted depth of about 2 mag the forthcoming eclipse in 2014.

Symbiotic Nova PU Vul - 33 Years of Observations

Abstract We present UBVRI light curves of the symbiotic nova PU Vul after its outburst in 1978. Three observed eclipses of the hot component by the cool one were used to determine the ephemeris of the binary system as JD (Min I) = 2444550(15) + 4897(10) × E days. the 194-day shift of the secondary minimum from its expected positions in 2001 suggests the eccentricity of the binary orbit. Period analysis of the VRI photometry improved the pulsation period of the cool AGB variable in the system to P = 217.7 days. Pulsation of the cool component is detected only in the phases around the primary minimum, when the visible hemisphere of the AGB star is not influenced by the interaction with the hot component.

New orbital solutions and absolute elements of the eclipsing binary TV Cet

Abstract We present new differential, four-color photoelectric photometry for the eclipsing binary TV Cet. UBVR light curves and radial velocities published previously are solved simultaneously using the Wilson–Devinney computer program. Our solutions indicate that TV Cet includes a third light contribution with 2.3% in U, 1.9% in B, 1.3% in V and 1.6% in R. The masses of the component stars are 1.34 ± 0.05 and 1.23 ± 0.05 M ⊙ , while the radii are 1.47 ± 0.02 and 1.21 ± 0.01 R ⊙ for the primary and secondary components, respectively. Using new absolute properties and our previous results from period analysis, we calculated the observational and theoretical internal structure constants to be k ¯ 2 , obs = - 1.66 and k ¯ 2 , theo = - 2.25 , respectively. Taking into account the third light contribution from the Wilson–Devinney solution and properties of the third body orbit from period analysis, the mass of the third body is obtained as 0.56 M ⊙ , corresponding to the inclination value i 3 = 20 ° . Evolutionary status of the component stars is also studied. We present the position of the stars in an H–R diagram for solar compositions.

BM Cas – a long-period eclipsing young supergiant binary system in common envelope stage

Abstract We report main results of the analysis of UBVR light curves of the long-period eclipsing binary BM Cas obtained between 1967 and 1996 in Tallinn observatory. The orbital period variations, evolutionary stage, peculiarities of the light curves and colour variations are discussed.

Modeling the Eclipsing Binary System VW Cygni

Five color UBVRI photometric and polarimetric measurements of the eclipsing binary VW Cyg are reported. It is shown that in the primary minimum the luminosity is attenuated (at short wavelengths) even after passage of the second contact. This fact is interpreted as evidence of gaseous structures in the system. The exchange of matter among the system components is also confirmed by the O-C curve constructed from data covering nearly a hundred years. Polarimetric analysis makes it possible to isolate the intrinsic (P=0.030±0.02) and interstellar components of the polarization. The UBVRI light curves of VW Cyg have been resolved. This was done using an algorithm for synthesizing theoretical light curves in the Roche model. Good agreement was obtained between the theoretical curves and observations in the V, R, and I bands, but the observed minimum depths in the U and B bands exceed the theoretical values. This appears to be caused by gas flows in the system.

New light curve analysis and period changes of the overcontact binary XY Leonis

Light curves and photometric solutions of the contact binary XY Leo are presented. The UB VRlight curves appear to be almost symmetric. The B and V light curves were analysed with the Wilson-Devinney code and the orbital parameters of the system were obtained and compared with those obtained in previous studies. All the times of minimum light were collected and combined with the new ones obtained in this study. The orbital period of the system oscillates with a period of 19:6 years and a semi-amplitude of 0:023 day. This regular change was analysed under the assumption of the third body hypothesis. The time delay and advance due to the orbit of the eclipsing pair around the third component were computed and subtracted from the original residuals obtained with the linear light elements. The remaining residuals also show a parabolic change. Therefore, we assumed that the orbital period of the system changes with time due to at least two dierent causes. The parabolic change of the period may be attributed to either mass transfer from less massive component to the more massive one, or an additional component bounded to the double binary system with a longer period.

UBVR photometry of gas-darkened variable systems. EM Cep

Photoelectric UBVR light curves of the gas-darkened variable EM Cep are given. A flare was detected on November 15–16, 1991: while a brightness increase was observed in the R band, a decrease in the star’s U luminosity was observed.

Multicolor photoelectric and photographic observations of the long-period variable Y Ori

Results of observations of the long-period variable Y Ori are presented. The photoelectric observations in UBVR were made at the 60-cm telescope of the high-altitude Maydanak station of the Tashkent Astronomical Institute during the autumn of 1989. The UBVR lightcurves as well as the variations in the color indices U-B, B-V, and V-R are presented. The photographic observations were made at the 40″ Schmidt telescope of the Byurakan Observatory and at the 70-cm Maksutov telescope of the Abastumani Observatory. A nebulosity was discovered around Y Ori in red light near the brightness maximum. Such a formation is observed for the first time, not only for Y Ori but also for long-period variables in general. The obtained results are discussed in this work.

The parameters of circumbinary gas in the interacting binary system SZ camelopardalis

Abstract UBVR light curves of the interacting early-type binary system SZ Camelopardalis have been analyzed and compared with model light curves which take into account the influence of anisotropic stellar wind from one of the components. It is indicated that the best fit can be achieved assuming mass transfer from the secondary component with the mass loss rate of 1÷ 5 × 10−TM⊙ /yr.

HW Virginis: a short-period eclipsing binary containing an sdB star

Simultaneous photometry of the binary star HW Vir, a detached system with an orbital period of 2 h 48 min is described. The new UBVR light curves obtained using the Wilson-Devinney code are found to constrain the orbital inclination of the system within the narrow range of 80.6 +/-0.2 deg. The temperature of the primary star is between 29,000 and 36,000 K, and the temperature of the secondary star is near 3,700 K. The possible masses and radii of the two stars are calculated using the published amplitude of the radial velocity curve of the primary star, 87.9 +/-4.8 km/s. It is found that, for the primary star log g1 is greater than 4.8 and less than or equal to 5.8. From the temperature and gravity of the primary star, its distance is found to be in the range between 42 and 151 pc. It is suggested that the system will begin mass transfer when the orbital period has decreased enough to bring the secondary star into contact with its Roche lobe.

Eclipse studies of the dwarf nova HT Cassiopeiae. II - White dwarf and accretion disk

The simultaneous UBVR light curves presented by Horne, Wood, & Stiening (1991, ApJ, 378) are used to investigate the white dwarf and accretion disk in the dwarf nova HT Cas. For the white dwarf, log g = 8 and pure hydrogen model atmospheres are used to fit the UBVR fluxes, subject to the constraint that the models are consistent with the observed UV flux. A temperature T W = 14000 ± 1000 K and a distance D = 125 ± 8 pc for E(B-V) = 0.0 are found

Photoelectric photometry of the nova-like eclipsing variable PG1030+590

PG1030+590 is a recently discovered nova-like eclipsing variable. Here we present our results of high-speed photoelectric photometry and its UBVR light curves. Using the model of cataclysmic variables, we found its geometrical and physical parameters to be as follows: mass of the white dwarf component, M 1 = 0.83±0.22 M⊙, radius of the late-type component, M 2 = 0.35±0.06 M⊙, and orbital inclination, i = 81°±2°. Also, using two different methods, we found the radius of the accretion disk around the white dwarf to be R d ≈0.32 R⊙. This result was compared with the various theoretical models of accretion disks in close binaries.

2.3 metre multi-colour photometry of a new AM Herculis variable

AbstractWe present UBVRI photometry of the faint and highly erratic cataclysmic variable discovered by Hawkins (1983) from a sequence of U.K. Schmidt plates. Observations using the ANU 2.3 m telescope over two nights in September 1986 show pronounced and repeatable modulation at a binary period of 108.6 min. Dramatic colour differences are evident in the folded UBVRI light curves: in the U band, a single sinusoidal peak is present, while at longer wavelengths, a second red peak dominates at a phase separation of Δϕ = 0.5. This behaviour is strongly suggestive of cyclotron emission from two magnetic accretion funnels in an AM Herculis binary system. Furthermore, the binary period lies in the narrow range of 100-115 minutes that characterizes most of the AM Herculis variables lying on the short side of the 2-3 hour period gap. We conclude therefore that the object is almost certainly a new AM Herculis system, and develop a model in which the blue and red components originate from two non-diametrically opposed cyclotron regions that are characterized by differing electron temperatures and opacities. Predictions are made regarding the linear and circular polarization properties of this important new magnetic variable.

Ubvr light curves of 44i Bootis during 1978

In this paper theU, B, V, R light curves of the eclipsing variable 44i Boo, obtained during 1978, are represented and discussed.