arXiv subjects

M. Rozyczka

Publications and source records attributed to M. Rozyczka.

At least 37 records · Page 2Linked to original sources

arXiv2013

The Clusters AgeS Experiment (CASE): The blue straggler Star M55-V60 caught amidst rapid mass exchange

We analyze light and velocity curves of the eclipsing blue straggler V60 in the field of the globular cluster M55. We derive Mp=1.259+-0.025 Msun, Rp=1.102+-0.021 Rsun, Mbol,p=3.03+-0.09 mag for the primary and Ms=0.327+-0.017 Msun, Rs=1.480+-0.011 Rsun, Mbol,s=4.18+-0.12 mag for the secondary. We derive an apparent distance modulus (m-M)V=14.04_-0.09 mag. Based on the systemic velocity, distance, and proper motion of V60 we conclude that the system is a member of the cluster and argue that its present state is a result of rapid but conservative mass exchange which the binary is still undergoing. We report a peculiar blue excess on the ascending branch of the primary eclipse of V60 and discuss its possible origin.

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arXiv2013

The cluster ages experiment (CASE). V. Analysis of three eclipsing binaries in the globular cluster M4

We use photometric and spectroscopic observations of the eclipsing binaries V65, V66 and V69 in the field of the globular cluster M4 to derive masses, radii, and luminosities of their components. The orbital periods of these systems are 2.29, 8.11 and 48.19 d, respectively. The measured masses of the primary and secondary components (Mp and Ms) are 0.8035+-0.0086 and 0.6050+-0.0044 Msun for V65, 0.7842+-0.0045 and 0.7443+-0.0042 Msun for V66, and 0.7665+-0.0053 and 0.7278+-0.0048 Msun for V69. The measured radii (Rp and Rs) are 1.147+_0.010 and 0.6110+-0.0092 Rsun for V66, 0.9347+_0.0048 and 0.8298+-0.0053 Rsun for V66, and 0.8655+-0.0097 and 0.8074+-0.0080 Rsun for V69. The orbits of V65 and V66 are circular, whereas that of V69 has an eccentricity of 0.38. Based on systemic velocities and relative proper motions, we show that all the three systems are members of the cluster. We find that the distance to M4 is 1.82+-0.04 kpc - in good agreement with recent estimates based on entirely different methods. We compare the absolute parameters of V66 and V69 with two sets of theoretical isochrones in mass-radius and mass-luminosity diagrams, and for an assumed [Fe/H] = -1.20, [alpha/Fe] = 0.4, and Y = 0.25 we find the most probable age of M4 to be between 11.2 and 11.3 Gyr. CMD-fitting with the same parameters yields an age close to, or slightly in excess of, 12 Gyr. However, considering the sources of uncertainty involved in CMD fitting, these two methods of age determination are not discrepant. Age and distance determinations can be further improved when infrared eclipse photometry is obtained.

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arXiv2013

A proper motion study of the globular clusters M4, M12, M22, NGC 3201, NGC 6362 and NGC 6752

We derive relative proper motions of stars in the fields of globular clusters M4, M12, M22, NGC 3201, NGC 6362 and NGC 6752 based on a uniform data set collected between 1997 and 2008. We assign a membership class for each star with a measured proper motion, and show that these membership classes can be successfully used to eliminate field stars from color-magnitude diagrams of the clusters. They also allow for the efficient selection of rare objects such as blue/yellow/red stragglers and stars from the asymptotic giant branch. Tables with proper motions and photometry of over 87000 stars are made publicly available via the Internet.

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arXiv2012

Absolute parameters of AE For -- a highly active detached binary of late K type

We present photometric and spectroscopic analysis of AE For -- a detached eclipsing binary composed of two late K dwarfs. The masses of the components are found to be 0.6314 +- 0.0035 and 0.6197 +- 0.0034 Msun and the radii to be 0.67 +- 0.03 and 0.63$ +- 0.03 Rsun for primary and secondary component, respectively. Both components are significantly oversized compared to theoretical models, which we attribute to their high activity. They show Halpha, Hbeta, Hgamma, Ca H and Ca K lines in emission, and are heavily spotted, causing large variations of the light curve.

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arXiv2012

Orbital and physical parameters of eclipsing binaries from the ASAS catalogue - IV. A 0.61 + 0.45 M_sun binary in a multiple system

We present the orbital and physical parameters of a newly discovered low-mass detached eclipsing binary from the All-Sky Automated Survey (ASAS) database: ASAS J011328-3821.1 A - a member of a visual binary system with the secondary component separated by about 1.4 seconds of arc. The radial velocities were calculated from the high-resolution spectra obtained with the 1.9-m Radcliffe/GIRAFFE, 3.9-m AAT/UCLES and 3.0-m Shane/HamSpec telescopes/spectrographs on the basis of the TODCOR technique and positions of H_alpha emission lines. For the analysis we used V and I band photometry obtained with the 1.0-m Elizabeth and robotic 0.41-m PROMPT telescopes, supplemented with the publicly available ASAS light curve of the system. We found that ASAS J011328-3821.1 A is composed of two late-type dwarfs having masses of M_1 = 0.612 +/- 0.030 M_sun, M_2 = 0.445 +/- 0.019 M_sun and radii of R_1 = 0.596 +/- 0.020 R_sun, R_2 = 0.445 +/- 0.024 R_sun, both show a substantial level of activity, which manifests in strong H_alpha and H_beta emission and the presence of cool spots. The influence of the third light on the eclipsing pair properties was also evaluated and the photometric properties of the component B were derived. Comparison with several popular stellar evolution models shows that the system is on its main sequence evolution stage and probably is more metal rich than the Sun. We also found several clues which suggest that the component B itself is a binary composed of two nearly identical ~0.5 M_sun stars.

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arXiv2012

A second neutron star in M4?

We show that the optical counterpart of the X-ray source CX 1 in M4 is a 20th magnitude star, located in the color-magnitude diagram on (or very close to) the main sequence of the cluster, and exhibiting sinusoidal variations of the flux. We find the X-ray flux to be also periodically variable, with X-ray and optical minima coinciding. Stability of the optical light curve, lack of UV-excess, and unrealistic mean density resulting from period-density relation for semidetached systems, speak against the original identification of CX 1 as a cataclysmic variable. We argue that the X-ray active component of this system is a neutron star (probably a millisecond pulsar).

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arXiv2011

A VIMOS spectroscopy of photometric variables and straggler candidates in omega Centauri

We report a spectroscopic study of 19 photometric variables and 55 blue, yellow and red straggler candidates in the field of omega Centauri. We confirm the cluster membership of 18 variables and 54 straggler candidates. Velocity variations are detected in 22 objects, and another 17 objects are classified as suspected of being velocity-variable. Velocity data of 11 photometric variables phase with their photometric periods, however none of these objects has a mass function indicating the presence of a massive degenerate component. Based on both photometric and spectroscopic data we find that the fraction of binaries among blue stragglers may be as high as 69 per cent.

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arXiv2010

Absolute properties of BG Ind - a bright F3 system just leaving the Main Sequence

We present photometric and spectroscopic analysis of the bright detached eclipsing binary BG Ind. The masses of the components are found to be 1.428 +- 0.008 and 1.293 +- 0.008 Msun and the radii to be 2.290+-0.017 and 1.680+-0.038 Rsun for primary and secondary stars, respectively. Spectra- and isochrone-fitting coupled with color indices calibration yield [Fe/H]=-0.2+-0.1. At an age of 2.65+-0.20 Gyr BG Ind is well advanced in the main-sequence evolutionary phase - in fact, its primary is at TAMS or just beyond it. Together with three similar systems (BK Peg, BW Aqr and GX Gem) it offers an interesting opportunity to test the theoretical description of overshooting in the critical mass range 1.2-1.5 Msun.

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arXiv2010

A search for dormant binaries with degenerate components in omega Centauri and NGC 6397

We report on the first spectroscopic search for quiescent degenerate binaries in globular clusters. Our survey is based on a sample of short-period optical variables which are likely optical counterparts of quiescent X-ray sources in omega Centauri (NGC 5139) and NGC 6397. All of the studied candidates have nearly sinusoidal light curves with amplitudes of 0.1--0.35~mag in $V$ and periods of 0.1--1.3~days. This type of variability, most probably originating from the ellipsoidal effect, has been observed in several X-ray novae when they settled into quiescence after an outburst. We find that two of the surveyed systems harbor dim components with masses in excess of one solar masss, making them attractive targets for future investigations. We also suggest that there are two subpopulations of blue stragglers in omega Centauri, differing in mass-transfer history and/or helium content.

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arXiv2010

A New Lower Main Sequence Eclipsing Binary with Detached Components

We present an analysis of NGC2204-S892 -- a new detached eclipsing binary composed of two late K dwarfs. Based on three photometric campaigns launched in 2008 we obtained 5 light curves (3 in V, 1 in B and 1 in I), and derived an orbital period of 0.451780+-0.000001 d. We also obtained 20 VLT/UVES spectra, enabling accurate radial velocity measurements. The derived masses and radii of the components (m1 = 0.733 +-0.005 Msun and R1 = 0.72 +-0.01 Rsun; m2 = 0.662 +-0.005 Msun and R2 = 0.68 \+-0.02 Rsun) are consistent with the empirical mass-radius relationship established recently for lower main sequence stars in binary systems; in particular we find that both stars are oversized compared to theoretical models. NGC2204-S892 is very active: both components show variable emission in Halpha and Hbeta and are heavily spotted, causing the light curve to show appreciable changes on a timescale of weeks. Our results add to the increasing evidence that the observed inflation of the radii of K and M stars is related to high levels of magnetic activity.

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arXiv2009

An Unusual Eclipsing Blue Straggler V8-NGC 6752

We report the analysis of a binary blue straggler in NGC 6752 with a short orbital period of 0.315 d and a W UMA-type light curve. We use photometric data spanning 13 years to place limits on the mass ratio (0.15<q<0.35), luminosity ratio (L1/L2 about 4.0) and the ratio of the radii of the components (r1/r2 about 2.0). The effective temperatures of the components are nearly identical, and the system is detached or semi-detached (in the latter case the component filling its Roche lobe is the secondary). Such a configuration is unusual given the shortness of the orbital period, and it must have resulted from substantial mass exchange. We suggest that some secondaries of W UMa-type stars, normally regarded as main sequence objects which fill their Roche lobes to different degrees, in fact may be shell-burning cores of originally more massive components.

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arXiv2008

Variable Stars in the Field of the Open Cluster NGC2204

We present the results of a variable stars search in the field of the old open cluster NGC 2204. Five new variables were found, four of them being eclipsing binaries. The sample includes a detached binary located at the turnoff, a W UMa - type system, and an interesting detached low-mass binary with a period of 0.45d which, however, is a foreground object. We provide V-light curves and finder charts for all variables together with color-magnitude diagrams of the cluster. For four variables incomplete I-light curves are also provided.

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arXiv2005

Two-dimensional models of layered protoplanetary discs - II. The effect of a residual viscosity in the dead zone

We study axisymmetric models of layered protoplanetary discs taking radiative transfer effects into account, and allowing for a residual viscosity in the dead zone. We also explore the effect of different viscosity prescriptions. In addition to the ring instability reported in the first paper of the series we find an oscillatory instability of the dead zone, accompanied by variations of the accretion rate onto the central star. We provide a simplified analytical description explaining the mechanism of the oscillations. Finally, we find that the residual viscosity enables stationary accretion in large regions of layered discs. Based on results obtained with the help of a simple 1-D hydrocode we identify these regions, and discuss conditions in which layered discs can give rise to FU~Orionis phenomena.

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arXiv2005

2-D models of layered protoplanetary discs: I. The ring instability

In this work we use the radiation hydrodynamic code TRAMP to perform a two-dimensional axially symmetric model of the layered disc. Using this model we follow the accumulation of mass in the dead zone due to the radially varying accretion rate. We found a new type of instability which causes the dead zone to split into rings. This "ring instability" works due to the positive feedback between the thickness of the dead zone and the mass accumulation rate. We give an analytical description of this instability, taking into account non-zero thickness of the dead zone and deviations from the Keplerian rotational velocity. The analytical model agrees reasonably well with results of numerical simulations. Finally, we speculate about the possible role of the ring instability in protoplanetary discs and in the formation of planets.

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arXiv2003

Doppler Tomograms from Hydrodynamical Models of Dwarf Nova Disks

We present three-dimensional models of accretion disks in U Gem - like systems and calculate their Doppler tomograms. The tomograms are based on two different assumptions concerning the origin of line emission from the disk. The assumption of lines originating due to irradiation of the surface layer of the disk by the central source leads to a better agreement with observations. We argue that fully three-dimensional modelling is necessary to properly interpret the observed tomograms.

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arXiv2002

HII regions in symbiotic binaries and their radio emission

The slow and dense wind from a symbiotic red giant can be significantly deflected toward the orbital plane by the gravitational pull of the companion star. In such an environment, the ionizing radiation from the companion creates a highly asymmetric HII region. We present three-dimensional models of HII regions in symbiotic S-type systems, for which we calculate radio maps and radio spectra. We show that the standard assumption of spherically symmetric RG wind results in wrong shapes, sizes and spectra of ionized regions, which in turn affects the observational estimates of orbital separation and mass loss rate. A sample of radio maps and radio spectra of our models is presented and the results are discussed in relation to observational data.

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arXiv2000

Hydrodynamical Models of Accretion Disks in SU UMa Systems

We numerically test the mode-coupling model (Lubow 1991a) of tidal instability in SU UMa systems. So far, all numercial models confirming it have been based on SPH codes and isothermal equation of state. In our paper we present Eulerian models, using both isothermal approximation and the full energy equation. We also investigate influence of different ways of mass transfer. While isothermal models behave similarly to SPH simulations, the behaviour of models with full energy equation is quite different, and the mode-coupling model is not confirmed in this case.

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arXiv2000

High-resolution simulations and visualization of protoplanetary disks

A problem of mass flow in the immediate vicinity of a planet embedded in a protoplanetary disk is studied numerically in two dimensions. Large differences in temporal and spatial scales involved suggest that a specialized discretization method for solution of hydrodynamical equations may offer great savings in computational resources, and can make extensive parameter studies feasible. Preliminary results obtained with help of Adaptive Mesh Refinement technique and high-order explicit Eulerian solver are presented. This combination of numerical techniques appears to be an excellent tool which allows for direct simulations of mass flow in vicinity of the accretor at moderate computational cost. In particular, it is possible to resolve the surface of the planet and to model the process of planet growth with minimal set of assumptions. Some issues related to visualization of the results and future prospects are discussed briefly.

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