Markus Gyergyovits | University of Vienna (original) (raw)

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Papers by Markus Gyergyovits

The Astrophysical Journal, 2012

With more and more extrasolar planets discovered in and around binary star systems, questions con... more With more and more extrasolar planets discovered in and around binary star systems, questions concerning the determination of the classical habitable zone have arisen. Do the radiative and gravitational perturbations of the second star influence the extent of the habitable zone significantly, or is it sufficient to consider the host star only? In this article, we investigate the implications of stellar companions with different spectral types on the insolation a terrestrial planet receives orbiting a Sun-like primary. We present time-independent analytical estimates and compare them to insolation statistics gained via high precision numerical orbit calculations. Results suggest a strong dependence of permanent habitability on the binary's eccentricity, as well as a possible extension of habitable zones toward the secondary in close binary systems.

Even though considerable efforts have been spent on investigating the extent of Habitable Zones (... more Even though considerable efforts have been spent on investigating the extent of Habitable Zones (HZs) in single star systems ([1], [2] and references therein), regions where Earth-analogues could harbor liquid water on the surface in and around binaries have been treated mainly from a dynamical point of view (e.g. [3]). We present analytical estimates for a variable stellar radiation field and the extent of possible HZs in binary star systems as a function of the binaries' orbital elements, as well as numerical predictions on the actual amount of radiation arriving at an orbiting planet.

Proceedings of the International Astronomical Union, 2011

Up to now, more than 500 extra-solar planets have been discovered. Many of these extrasolar syste... more Up to now, more than 500 extra-solar planets have been discovered. Many of these extrasolar systems consist of one star and only one giant planet. However, recently more and more different types of systems have become known, including also extrasolar planets in binaries. In our study, we will concentrate on such systems, since a large percentage of all G-M stars are expected to be part of binary or multiple stellar systems. Therefore, these kinds of systems are worthy of investigation in detail. In particular, we will concentrate on planets in P-Type motion, where the planet orbits around both stars. During the last few years, four such systems (NN Ser, HW Vir, HU Aqr and DP Leo) have been discovered. In our study, we performed dynamical studies for three multi-planetary systems in binaries (NN Ser, HW Vir, HU Aqr), and compared simulated eclipse timing variations (ETV) to current observational data.

Proceedings of the International Astronomical Union, 2012

ABSTRACT The discovery of more and more extra-solar planets in and around binary star systems cau... more ABSTRACT The discovery of more and more extra-solar planets in and around binary star systems cause questions concerning the determination of the classical habitable zone (HZ). We present calculations of the radiative and gravitational perturbations of two stars on a terrestrial planet moving in the HZ in different binary - planet configurations. Two types of planetary motion will be considered, i.e. S-type motion (or circumprimary motion) where the planet orbits one star only and P-type (or circumbinary motion) where the binary revolves inside the planet's orbit. It was found that the HZ in S-type configurations tend to be gravitationally dominated, the radiative input due to the second star is negligible compared to its dynamical influence causing secular changes in the eccentricity of the planets. This alters the amount of incident radiation significantly. In P-type configurations the radiation estimates can be determined on shorter time-scales. The radiation amplitude depends on the eccentricity of the binary in both configurations. Finally we present time independent analytical estimates about the habitability of a terrestrial planet in the HZ of a binary star system as shown by Eggl et al.(2012). This work was financed by the Austrian Science Fonds (FWF) P22603-N16 and AS11608-N16 and S.Eggl was financed by the University of Vienna (Forschungsstipendium 2012). Ref.: Eggl, S., Pilat-Lohinger, E., Gerogakarakos, N., Gyergyovits, M. and Funk, B., "Habitable Zones in S-Type Binary Star Systems", ApJ, submitted.

Context. Today approximately 60 planets have already been discoverd in systems harboring two star... more Context. Today approximately 60 planets have already been discoverd in systems harboring two stars where some of them have binary separations around or smaller than 20 AU. In these systems the gaseous disc together with particles moving in it is exposed to the gravitational forces of the binary and thus strongly influenced by the stars. Aims. In this paper we present first our 2D hydrodynamical code written to work partly on a graphics card and second study the evolution of several thousands of selfgravitating particles embedded in an viscous and radiative circumstellar disc in a binary star system. Methods. We perform hydrodynamical simulations of a binary star system assuming coplanarity of the disc, particles, host star and secondary star. We use a grid based staggered mesh code based on the ideas of ZEUS-2D, where we implemented the FARGO algorithm and an additional energy equation handling radiative cooling according to opacity tables. Results. We show that our program is performing well and additionally that we are able to run simulations with up to 2048 selfgravi-tating particles interacting with a gas disc. Conclusions. We show that 0.01 M gas disc can have significant influence on roughly Moon sized particles when interacting solely gravitationaly.

The Astrophysical Journal, 2012

With more and more extrasolar planets discovered in and around binary star systems, questions con... more With more and more extrasolar planets discovered in and around binary star systems, questions concerning the determination of the classical habitable zone have arisen. Do the radiative and gravitational perturbations of the second star influence the extent of the habitable zone significantly, or is it sufficient to consider the host star only? In this article, we investigate the implications of stellar companions with different spectral types on the insolation a terrestrial planet receives orbiting a Sun-like primary. We present time-independent analytical estimates and compare them to insolation statistics gained via high precision numerical orbit calculations. Results suggest a strong dependence of permanent habitability on the binary's eccentricity, as well as a possible extension of habitable zones toward the secondary in close binary systems.

Even though considerable efforts have been spent on investigating the extent of Habitable Zones (... more Even though considerable efforts have been spent on investigating the extent of Habitable Zones (HZs) in single star systems ([1], [2] and references therein), regions where Earth-analogues could harbor liquid water on the surface in and around binaries have been treated mainly from a dynamical point of view (e.g. [3]). We present analytical estimates for a variable stellar radiation field and the extent of possible HZs in binary star systems as a function of the binaries' orbital elements, as well as numerical predictions on the actual amount of radiation arriving at an orbiting planet.

Proceedings of the International Astronomical Union, 2011

Up to now, more than 500 extra-solar planets have been discovered. Many of these extrasolar syste... more Up to now, more than 500 extra-solar planets have been discovered. Many of these extrasolar systems consist of one star and only one giant planet. However, recently more and more different types of systems have become known, including also extrasolar planets in binaries. In our study, we will concentrate on such systems, since a large percentage of all G-M stars are expected to be part of binary or multiple stellar systems. Therefore, these kinds of systems are worthy of investigation in detail. In particular, we will concentrate on planets in P-Type motion, where the planet orbits around both stars. During the last few years, four such systems (NN Ser, HW Vir, HU Aqr and DP Leo) have been discovered. In our study, we performed dynamical studies for three multi-planetary systems in binaries (NN Ser, HW Vir, HU Aqr), and compared simulated eclipse timing variations (ETV) to current observational data.

Proceedings of the International Astronomical Union, 2012

ABSTRACT The discovery of more and more extra-solar planets in and around binary star systems cau... more ABSTRACT The discovery of more and more extra-solar planets in and around binary star systems cause questions concerning the determination of the classical habitable zone (HZ). We present calculations of the radiative and gravitational perturbations of two stars on a terrestrial planet moving in the HZ in different binary - planet configurations. Two types of planetary motion will be considered, i.e. S-type motion (or circumprimary motion) where the planet orbits one star only and P-type (or circumbinary motion) where the binary revolves inside the planet's orbit. It was found that the HZ in S-type configurations tend to be gravitationally dominated, the radiative input due to the second star is negligible compared to its dynamical influence causing secular changes in the eccentricity of the planets. This alters the amount of incident radiation significantly. In P-type configurations the radiation estimates can be determined on shorter time-scales. The radiation amplitude depends on the eccentricity of the binary in both configurations. Finally we present time independent analytical estimates about the habitability of a terrestrial planet in the HZ of a binary star system as shown by Eggl et al.(2012). This work was financed by the Austrian Science Fonds (FWF) P22603-N16 and AS11608-N16 and S.Eggl was financed by the University of Vienna (Forschungsstipendium 2012). Ref.: Eggl, S., Pilat-Lohinger, E., Gerogakarakos, N., Gyergyovits, M. and Funk, B., "Habitable Zones in S-Type Binary Star Systems", ApJ, submitted.

Context. Today approximately 60 planets have already been discoverd in systems harboring two star... more Context. Today approximately 60 planets have already been discoverd in systems harboring two stars where some of them have binary separations around or smaller than 20 AU. In these systems the gaseous disc together with particles moving in it is exposed to the gravitational forces of the binary and thus strongly influenced by the stars. Aims. In this paper we present first our 2D hydrodynamical code written to work partly on a graphics card and second study the evolution of several thousands of selfgravitating particles embedded in an viscous and radiative circumstellar disc in a binary star system. Methods. We perform hydrodynamical simulations of a binary star system assuming coplanarity of the disc, particles, host star and secondary star. We use a grid based staggered mesh code based on the ideas of ZEUS-2D, where we implemented the FARGO algorithm and an additional energy equation handling radiative cooling according to opacity tables. Results. We show that our program is performing well and additionally that we are able to run simulations with up to 2048 selfgravi-tating particles interacting with a gas disc. Conclusions. We show that 0.01 M gas disc can have significant influence on roughly Moon sized particles when interacting solely gravitationaly.