Abstract: We present measurements of line core positions in UVES spectra of a sample of K-type stars, using the technique of bisector tracing. In all but two of these stars we detect an excess redshift of Ti I lines with respect to Fe I lines. We explain this invoking

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Abstract: In this research we test the ability of a three Washington filter combination, (C − T1) − (T1− T2), compared with that of the traditional C − T1 color to find multiple populations on two globular clusters: NGC 7099 and NGC 1851, types I and II Globular cluste

Resumen: En este trabajo comparamos la capacidad de una combinación de tres filtros Washington (C − T1) − (T1− T2) con la del color tradicional C − T1 para encontrar poblaciones múltiples en dos cúmulos globulares, NGC 7099 y NGC 1851, de tipo I y II respectivamente.

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Abstract: The large dynamic range in some astrophysical N-body problems led to the use of adaptive multi-time-steps; however, the search for optimal strategies is still challenging. We numerically quantify the performance of the hierarchical Hamiltonian Splitting (HHS)

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Abstract: We present a model for the “Bondi-Hoyle tail” left behind by the hypersonic passage of a compact, massive object through a dense, radiative environment. We derive simple equations for the flow velocity and the mass along the tail, and obtain numerical and app

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Abstract: Radial velocity (RV) and light curve (LC) data for the overcontact binary V563 Lyr have been obtained and analysed with the 2003 version of the Wilson-Devinney (WD) code with results K1 = 147.4 ± 2.1 km/s, K2 = 247.2 ± 1.1 km/s, RVγ = 22.5 ± 1.5 km/s, qsp = 0

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Abstract: The first analysis of the light curves of contact binaries ROTSE J135349.8+305205 (CB1) and 1SWASP J150957.5-115308 (CB2) using the Wilson-Devinney code is presented. Both binary systems are of the A-subtype with a shallow fill-out (20.8% and 15.8% respective

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Abstract: A matter bouncing entropy-corrected cosmological model has been suggested. The model allows only positive curvature with negative pressure and no violation of the null energy condition. The result obtained in this paper is supported by some recent theoretical

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Abstract: We report the mean metallicity and absolute magnitude of RR Lyrae stars in a sample of 37 globular clusters, calculated via the Fourier decomposition of their light curves and ad hoc semi-empirical calibrations, in an unprecedented homogeneous approach. This

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Abstract: We simulate the collapse of a turbulent gas cloud, in which we choose two sub-clouds. A translational velocity vL or vR 7 is added, so that the sub-clouds move towards each other to collide. The radius and pre-collision velocity of the sub-clouds are chosen t

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Abstract: Relativistic, corkscrew jets are produced by some Galactic compact objects (notably, the SS433 outflow) and by some of the central monsters of quasars or AGN. As the result of arrival time-delay effects, the projections of the outflow locus onto the observed

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Abstract: Comet C/1830 F1 (Great March comet) is one of a large number of comets with parabolic orbits. Given that there are sufficient observations of the comet, (428 in right ascension and 424 in declination), it proves possible to calculate a better orbit. The calcu

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Abstract: The mean parallax of the Pleiades open cluster from the Hipparcos catalog is larger than the true value by approximately 1 mas. The origin of this error, as well as a possible algorithm of correcting it, was proposed by Makarov (2002). The problem is reassess

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Abstract: Relativistic isothermal gas spheres are a powerful tool to model many astronomical objects, like compact stars and clusters of galaxies. In the present paper, we introduce an artificial neural network (ANN) algorithm and Taylor series to model the relativisti

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Abstract: We present photometric, astrometric, and kinematic studies of the old open star clusters NGC 1193 and NGC 1798. Both of the clusters are investigated by combining data sets from Gaia Early Data Release 3 (EDR3) and CCD UBV observational data. E(B - V ) color

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Abstract: The aim of this work is to study both light curve and orbital phase spectroscopy of Cen X-3 taking advantage of the MAXI/GSC observation strategy. These studies allow delimiting the stellar wind properties and its interactions with the compact object. From th

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Abstract: The existence of life is one of the most fundamental problems of astrophysics. The intriguing existence of progressively complex and apparently improbable living beings should be a general tendency of life in the Universe. We are looking for general physical

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Abstract: A photometric and astrometric study of the two open star clusters Gulliver18 and Gulliver58 was carried out for the first time using the early third data release of the Gaia space observatory (Gaia-EDR3). By studying the proper motions, parallaxes, and color-

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Abstract: We present a model for the HII region and stellar wind bow shock formed by runaway O stars passing through the Galactic disk. We develop a quasi-analytic approach in which the absorption of stellar ionizing photons by the bow shock is considered. With these m

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Abstract: Analysis of spectral line profile variations observed over 6 decades in the Wolf-Rayet system HD 5980 lead to the conclusion that Star A, the variable member of the system, has always dominated the wind collision zone (WCZ), contrary to suggestions that befor

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