The detached eclipsing binary TX Her revisited

This paper presents new CCD Bessell BVRI light curves and photometric analysis of the Algol-type binary star TX Her. The CCD observations were carried out at Çanakkale Onsekiz Mart University Observatory in 2010. New BVRI light curves from this study and radial velocity curves from Popper (1970) were solved simultaneously using modern light and radial velocity curves synthesis methods. The general results show that TX Her is a well-detached eclipsing binary, however, both component stars fill at least half of their Roche lobes. A significant third light contribution to the total light of the system could not be determined. Using O–C residuals formed by the updated minima times, an orbital period study of the system was performed. It was confirmed that the tilted sinusoidal O–C variation corresponds to an apparent period variation caused by the light travel time effect due to an unseen third body. The following absolute parameters of the components were derived: M₁ = 1.62 ± 0.04 M_⊙, M₂ = 1.45 ± 0.03 M_⊙, R₁ = 1.69 ± 0.03 R_⊙, R₂ = 1.43 ± 0.03 R_⊙, L₁ = 8.21 ± 0.90 L_⊙ and L₂ = 3.64 ± 0.60 L_⊙. The distance to TX Her was calculated as 155 ± 10 pc, taking into account interstellar extinction. The position of the components of TX Her in the HR diagram are also discussed. The components are young stars with an age of ～500 Myr.     

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.     

First photometric study of the W UMa system GSC 1042-2191

We present new photometric observations covering eight minima times for the eclipsing binary GSC 1042-2191. The light curves in $\mathit{BVRI}$ colors were analyzed by using WD-code for the system parameters. Eight minima times were obtained from the new observations. The system is found a low mass ratio (q = 0.148), A-type over-contact binary with a fill out parameter of f = 65.01 ± 12.18%. The preliminary absolute dimensions (M₁= 1.26 ± 0.06 M_⊙, M₂ = 0.18 ± 0.06 M_⊙, R₁ = 1.54 ± 0.20 R_⊙, R₂ = 0.69 ± 0.01 R_⊙, ${\mathit{L}}_1$ =3.30 ± 0.30 L_⊙ and ${\mathit{L}}_2$ = 0.59 ± 0.20 L_⊙) indicate the very much oversized and over-luminous secondary component, by assuming the present luminosity of the secondary is its main sequence luminosity, we predict the original mass is about 0.8 M_⊙, this means the present secondary could be transferred and/or lost 77% of its original mass and only its core is left.     

The near-contact binary star RZ Dra revisited

This paper presents the absolute parameters of RZ Dra. New CCD observations were made at the Mt. Suhora Observatory in 2007. Two photometric data sets (1990 BV and 2007 BVRI) were analysed using modern light-curve synthesis methods. Large asymmetries in the light curves may be explained in terms of a dark starspot on the primary component, an A6 type star. Due to this magnetic activity, the primary component would appear to belong to the class of Ap-stars and would show small amplitude with δ Scuti-type pulsations. With this in mind, a time-series analysis of the residual light curves was made. However, we found no evidence of pulsation behaviour in RZ Dra. Combining the solutions of our light curves and Rucinski et al. (2000)’s radial velocity curves, the following absolute parameters of the components were determined: M₁ = 1.63 ± 0.03 M_⊙, M₂ = 0.70 ± 0.02 M_⊙, R₁ = 1.65 ± 0.02R_⊙, R₂ = 1.15 ± 0.02 R_⊙, L₁ = 9.72 ± 0.30 L_⊙ and L₂ = 0.74 ± 0.10 L_⊙. The distance to RZ Dra was calculated as 400 ± 25 pc, taking into account interstellar extinction. The orbital period of the system was studied using updated O–C information. It was found that the orbital period varied in its long-period sinusoidal form, superimposed on a downward parabola. The parabolic term shows a secular period decrease at a slow rate of 0.06 ± 0.02 s per century and is explained by the mass loss via magnetized wind of the Ap-star primary. The tilted sinusoidal form of the period variation may be considered as an apparent change and may be interpreted in terms of the light-time effect due to the presence of a third body.     

Absolute properties of the overcontact binary HH Boo

We obtained multi-colour light curves of the overcontact binary system HH Boo and analysed the orbital period variation of the system. Our analysis tentatively indicates either mass transfer from the secondary to the primary or mass loss from the system at a rate of -5.04 × 10⁻⁷ M_⊙ per year. Through a combined analysis of the published radial velocity curve and light curves, we determined an inclination (i) of 69°.71 ± 0°.16 and a semi-major axis (a) of 2.246 ± 0.064 R_⊙ for HH Boo. The masses of the primary and secondary components were found to be 0.92 ± 0.08 M_⊙ and 0.58 ± 0.06 M_⊙, respectively. The radius determined for the primary was 0.98 ± 0.03 R_⊙, while that determined for the secondary was 0.80 ± 0.02 R_⊙. We demonstrated that HH Boo is most likely a member of the A-type subclass of W UMa binaries.     

Absolute and geometric parameters of W UMa type contact binary TYC 1174-344-1

We present the results of our investigation on the geometrical and physical parameters of W UMa-type binary TYC1174-344-1 from analyzed CCD (BVRI) light curves and radial velocity data. The photometric data were obtained in 2009 at Ankara University Observatory (AUO) and the spectroscopic observations were made in 2008 at Astrophysical Observatory of Asiago (Italy). Light and radial velocity observations were analyzed simultaneously by using the well-known Wilson–Devinney (2007 revision) code to obtain absolute and geometrical parameters. According to our solutions, the system is found to be a low mass-ratio A-type W UMa system. Combining our photometric solution with the spectroscopic data, we derived mass and radii of the eclipsing system as M₁ = 1.381 M_⊙, M₂ = 0.258 M_⊙, R₁ = 1.449 R_⊙ and R₂ = 0.714 R_⊙. We finally discussed the evolutionary condition of the system.     

CCD Photometry of the W UMa type star QX Andromeda

We present new B- and V-band photometry of the W UMa-type binary system QX And, which is a member of the open cluster NGC 752. Revised orbital period and new ephemerides were given for the binary system based on the data of times of light minima. The result of a period analysis reveals that the system is undergoing a continuous orbital period increase during the past decades. The rate of period increasing turns out to be about 2.7 × 10^?7 d yr^?1. With the Wilson–Devinney code, a photometric solution is computed. It yields a contact configuration for the system with a filling factor of 0.361. Combining the results from the photometric solution along with that from the radial-velocity observations, we have determined the absolute parameters for the two components of the system. The masses, radii and luminosity of the primary and secondary stars are calculated as 1.43 ± 0.04 M_⊙, 1.45 ± 0.09 R_⊙, 2.87 ± 0.40 L_⊙ and 0.44 ± 0.02 M_⊙, 0.87 ± 0.05 R_⊙, 0.99 ± 0.13 L_⊙, respectively. The evolutionary status and physical nature of the contact binary system were discussed compared with the theoretical models.     

BV photometry of quadrupole system ET Bootis

In this study, we present the first Johnson BV photometry of the eclipsing binary star ET Bootis, which is member of a physically connected visual pair. Analysis of times of light minima enables us to calculate accurate ephemeris of the system via O–C analysis and observed an increase in period which we believe is a result of the light-time effect in the outer visual orbit. Secondly, we determined the total brightness and color of the system in light maxima and minima. Photometric solution of the system indicates that the contribution of the visual pair to the total light is about 40% in Johnson V band. Furthermore, photometric analysis shows that the primary star in the eclipsing binary has F8 spectral type while it confirms the G5 spectral type for the visual pair. Masses of the components in eclipsing binary are M₁ = 1.109 ± 0.014 M_⊙ and M₂ = 1.153 ± 0.011 M_⊙. Absolute radii of the components are R₁ = 1.444 ± 0.007 R_⊙ and R₂ = 1.153 ± 0.007 R_⊙. Physical properties of the components leads 176 ± 7 pc distance for the system and suggests an age of 6.5 billion years.     

Spectroscopic and photometric study of the contact binary BO CVn

We present the results of the study of the contact binary system BO CVn. We have obtained physical parameters of the components based on combined analysis of new, multi-color light curves and spectroscopic mass ratio. This is the first time the latter has been determined for this object. We derived the contact configuration for the system with a very high filling factor of about 88%. We were able to reproduce the observed light curve, namely the flat bottom of the secondary minimum, only if a third light has been added into the list of free parameters. The resulting third light contribution is significant, about 20–24%, while the absolute parameters of components are: M₁ = 1.16, M₂ = 0.39, R₁ = 1.62 and R₂ = 1.00 (in solar units).The O-C diagram shows an upward parabola which, under the conservative mass transfer assumption, would correspond to a mass transfer rate of dM/dt = 6.3 × 10^?8M_⊙/yr, matter being transferred from the less massive component to the more massive one. No cyclic, short-period variations have been found in the O-C diagram (but longer-term variations remain a possibility).     

A photometric study of the detached binary WY Hydrae with twin components

We present a multicolor photometry for the eclipsing binary WY Hydrae, observed on four nights of 2008 December. From our new observations and Carr’s data, the photometric solutions were deduced by using the updated W–D program. The results show that WY Hya is a detached binary with a mass ratio of q = 0.970(±0.005).By analyzing the O–C curve, it is found that there exists either a continuous period increase or a cyclic variation. From Eq. (2), the orbital period of WY Hya secularly increases at a rate of dP/dt = +3.56(±0.37) × 10^?7 days/yr, which may be interpreted by some mass transfer for the near-contact configuration or tidal dissipation. From Eq. (3), the period and semi-amplitude of the periodic oscillation are P₃ = 95.4(±4.2) yr and A = 0^d.0087(±0^d.0003), respectively. This may be likely attributed by light-time effect via the presence of the assumed third body. Assumed in the coplanar orbit with the binary, the mass of the third body should be M₃ = 0.18 M_⊙. If the unseen additional companion exists, it will extract angular momentum from the binary system. Finally, WY Hya with high fill-out factors (i.e., f_1,2 > 80%), may evolve into a semi-detached configuration.     

Spectral behavior of the symbiotic nova AG Pegasi observed with IUE and HST

Ultraviolet spectra from the International Ultraviolet Explorer (IUE) and from the Hubble Space Telescope (HST) of the symbiotic novae AG Peg during the period 1978–1996 are analyzed. Some spectra showing the modulations of spectral lines at different times are presented. We determined the reddening from the 2200 Å feature, finding that E(B−V) = 0.10 ± 0.02. We studied N IV] at 1486 Å, C IV 1550 Å, and O III] at 1660 Å, produced in the fast wind from the hot white dwarf. The mean wind velocity of the three emission lines is 1300 km s⁻¹ (FWHM). The mean wind mass loss rate is ∼6 × 10⁻⁷ M_⊙ yr⁻¹. The mean temperature is ∼6.5 × 10⁵ K. The mean ultraviolet luminosity is ∼5 × 10³³ erg s⁻¹. The modulations of line fluxes in the emitting region at different times are attributed to the variations of density and temperature of the ejected matter as a result of variations in the rate of mass loss.     

The outcome of the protoplanetary disk of very massive stars

We suggest that planets, brown dwarfs, and even low mass stars can be formed by fragmentation of protoplanetary disks around very massive stars (M ? 100 M_⊙). We discuss how fragmentation conditions make the formation of very massive planetary systems around very massive stars favorable. Such planetary systems are likely to be composed of brown dwarfs and low mass stars of ～0.1–0.3 M_⊙, at orbital separations of ～ few × 100–10⁴ AU. In particular, scaling from solar-like stars suggests that hundreds of Mercury-like planets might orbit very massive stars at ～10³ AU where conditions might favor liquid water. Such fragmentation objects can be excellent targets for the James Webb Space Telescope and other large telescopes working in the IR bands. We predict that deep observations of very massive stars would reveal these fragmentation objects, orbiting in the same orbital plane in cases where there are more than one object.     

A Kinematical Study of the Galaxy Based on the Revised Hipparcos Astrometric Data

On the basis of the revised Hipparcos data recently released, the zero-point of the period-luminosity relation for classical cepheids is reexamined. Fitting the proper motion and radial velocity data via an axisymmetric model, the Oort constants and circular rotation velocity of the LSR are calculated to obtain the Galactocentric distance of the Sun, R₀ = 8.0 ± 0.8 kpc. From the rotation curve in solar neighborhood, the existence of weak ellipticity of the Galactic potential is found. Adopting a simple asymmetric model, we have obtained the ellipticity ∈(R₀) = 0.067 ± 0.036 at the Sun, while the minor axis points to φ_b = 32° ± 15°.     

Photometric study of neglected eclipsing binary GSC 3576-0170

The new multi-color BVRI photometric light curves of the short-period eclipsing binary GSC 3576-0170 were obtained on two consecutive nights (October 5 and 6, 2009). With the 2003 version of Wilson–Devinney program, the precise photometric solutions are derived for the first time. The result shows that GSC 3576-0170 is a semi-detached binary system with a large temperature difference of approximately 1490 K. The light-curve distortions are further explained by a hot spot on the secondary component through mass transfer via a stream hitting the facing surface of the secondary component. By analyzing all available light minimum times, we also derived an update ephemeris and found for the first time a possible periodic oscillation with an amplitude of 0.0038 days and a period of 4.3 years. The periodic oscillation could be explained either by the light-time effect due to a presumed third component or by magnetic activity cycle of the system.     

Young eccentric binary KL CMa revisited in the light of spectroscopy

The absolute dimensions of the components of the eccentric eclipsing binary KL CMa have been determined. The solution of light and radial velocity curves of high ($\mathrm{\Delta }\lambda =0.14$ Å) and intermediate ($\mathrm{\Delta }\lambda =1.1$ Å) resolution spectra yielded masses M₁ = 3.55 ± 0.27 M_⊙, M₂ = 2.95 ± 0.24 M_⊙ and radii R₁ = 2.37 ± 0.09 R_⊙, R₂ = 1.70 ± 0.1 R_⊙ for primary and secondary components, respectively. The system consists of two late B-type components at a distance of 220 ± 20 pc for an estimated reddening of $E(B-V)=0.127$.The present study provides an illustration of spectroscopy’s crucial role in the analysis of binary systems in eccentric orbits. The eccentricity of the orbit ($e=0.20$) of KL CMa is found to be bigger than the value given in the literature ($e=0.14$). The apsidal motion rate of the system has been updated to a new value of $\dot{w}=0°.0199\pm 0.0002{\text{cycle}}^{-1}$, which indicates an apsidal motion period of $U=87\pm 1$ yrs, two times slower than given in the literature. Using the absolute dimensions of the components yielded a relatively weak relativistic contribution of ${\dot{w}}_{\mathit{rel}}=0°.0013{\text{cycle}}^{-1}$. The observed internal-structure component ($\log k_{2\text{,}\mathit{obs}}=-2.22\pm 0.01$) is found to be in agreement with its theoretical value ($\log k_{2\text{,}\mathit{theo}}=-2.23$).Both components of the system are found very close to the zero-age main-sequence and theoretical isochrones indicate a young age ($\tau =50$ Myr) for the system. Analysis of the spectral lines yields a faster rotation ($V_{\mathit{rot}1\text{,}2}=100$ km s⁻¹) for the components than their synchronization velocities ($V_{\mathit{rot}\text{,}\mathit{syn}1}=68$ km s⁻¹, $V_{\mathit{rot}\text{,}\mathit{syn}1}=49$ km s⁻¹).     

Massive and refined: A sample of large galaxy clusters simulated at high resolution. I: Thermal gas and properties of shock waves

We present a sample of 20 massive galaxy clusters with total virial masses in the range of 6 × 10¹⁴ M_⊙ ? M_vir ? 2 × 10¹⁵ M_⊙, re-simulated with a customized version of the 1.5. ENZO code employing adaptive mesh refinement. This technique allowed us to obtain unprecedented high spatial resolution (≈25 kpc/h) up to the distance of ～3 virial radii from the clusters center, and makes it possible to focus with the same level of detail on the physical properties of the innermost and of the outermost cluster regions, providing new clues on the role of shock waves and turbulent motions in the ICM, across a wide range of scales.In this paper, a first exploratory study of this data set is presented. We report on the thermal properties of galaxy clusters at z = 0. Integrated and morphological properties of gas density, gas temperature, gas entropy and baryon fraction distributions are discussed, and compared with existing outcomes both from the observational and from the numerical literature. Our cluster sample shows an overall good consistency with the results obtained adopting other numerical techniques (e.g. Smoothed Particles Hydrodynamics), yet it provides a more accurate representation of the accretion patterns far outside the cluster cores. We also reconstruct the properties of shock waves within the sample by means of a velocity-based approach, and we study Mach numbers and energy distributions for the various dynamical states in clusters, giving estimates for the injection of Cosmic Rays particles at shocks. The present sample is rather unique in the panorama of cosmological simulations of massive galaxy clusters, due to its dynamical range, statistics of objects and number of time outputs. For this reason, we deploy a public repository of the available data, accessible via web portal at http://data.cineca.it.     

The formation heritage of Jupiter Family Comet 10P/Tempel 2 as revealed by infrared spectroscopy

We present spectral and spatial information for major volatile species in Comet 10P/Tempel 2, based on high-dispersion infrared spectra acquired on UT 2010 July 26 (heliocentric distance R_h = 1.44 AU) and September 18 (R_h = 1.62 AU), following the comet’s perihelion passage on UT 2010 July 04. The total production rate for water on July 26 was (1.90 ± 0.12) × 10²⁸ molecules s^?1, and abundances of six trace gases (relative to water) were: CH₃OH (1.58% ± 0.23%), C₂H₆ (0.39% ± 0.04%), NH₃ (0.83% ± 0.20%), and HCN (0.13% ± 0.02%). A detailed analysis of intensities for water emission lines provided a rotational temperature of 35 ± 3 K. The mean OPR is consistent with nuclear spin populations in statistical equilibrium (OPR = 3.01 ± 0.18), and the (1σ) lower bound corresponds to a spin temperature >38 K. Our measurements were contemporaneous with a jet-like feature observed at optical wavelengths. The spatial profiles of four primary volatiles display strong enhancements in the jet direction, which favors release from a localized vent on the nucleus. The measured IR continuum is much more sharply peaked and is consistent with a dominant contribution from the nucleus itself. The peak intensities for H₂O, CH₃OH, and C₂H₆ are offset by ～200 km in the jet direction, suggesting the possible existence of a distributed source, such as the release of icy grains that subsequently sublimed in the coma. On UT September 18, no obvious emission lines were present in our spectra, nevertheless we obtained a 3σ upper limit Q(H₂O) < 2.86 × 10²⁷ molecules s^?1.