SK
SAS
- Distribution of the orbits of sporadic meteoroids
- Analysis and modelling of asteroid activity in terms of rotation, 3D shape and tail morphology changes
- The origin and formation of the inner Oort cloud
- Doubly and multiply eclipsing systems
- Exoplanets transiting early-type stars
- Solar activity cycles – empirical implications for the solar dynamo modelling
- Formation of young stars of T Tauri type and their planetary systems
The Astronomical Institute SAS organizes PhD study in astronomy and astrophysics.
| Application deadline: | May 15th 2023 |
| Address: | Astronomicky ustav SAV, v. v. i. Tatranska Lomnica, 059 60 Vysoke Tatry |
| Interviews: | during June of 2023 |
| PhD study (start): | September 1st 2023 |
Conditions for the interview:
1. Graduation of the University study at the Master level (the 2nd education degree). Applicants from the outside of EU are required to submit “Recognizing certificates on the 1st and 2nd education degree acquired at universities abroad” at the registration of his/her study (around the beginning of September). See: Recognizing certificates on study abroad
2. Filled in application with its attachments sent to the address of the Astronomical Institute SAS within the given deadline.
For the PhD program of Astronomy and Astrophysics, Astronomical Institute SAS advertises the following themes:
- Distribution of the orbits of sporadic meteoroids
Adviser: RNDr. Mária Hajduková Jr., PhD. (Maria.Hajdukova@savba.sk)
Affiliation: Astronomical Institute of the Slovak Academy of Sciences, The Department of Interplanetary Matter, Bratislava
Syllabus
Focus of the thesis: On its orbit around the Sun, the Earth crosses the orbits of a number of meteoroids, and, together with the whole solar system, passes through the interstellar medium. Thus, it collides with nearby particles which can be registered as meteors in the Earth’s atmosphere. Observations of the atmospheric trajectories of meteors lead us to their heliocentric orbits, on which meteoroids moved before their collision with the Earth. These indicate the origin of the meteoroids. We can identify specific parent bodies of meteoroid streams in the Solar system; we can classify sporadic meteoroids (whether they are cometary or asteroidal particles); and we may indicate the origin of meteoroids outside the Solar system. This thesis will focus on the origin of the largest population – sporadic meteoroids, which have lost their identity during their evolution (i.e. no similarity between their orbits and the orbit of their parent body or that of other meteoroids can be found).
Aim of the work: The aim of this work is to map the sporadic background, based on models and the synthesis of observations obtained by different techniques. Observations from Earth of the sporadic background (and its representation in a coordinate system centered at the Earth’s apex) have revealed six apparent sources in which enhanced meteor densities are observed: the so-called helion and antihelion sources, the northern and southern apex sources, and the northern and southern toroidal sources. The distribution of radiants is geometrically determined, but different types of comets or asteroids can be found associated with different regions of enhanced density.
However, the origin of the sporadic background has not been fully explained. Generally, the entire population of comets, as well as various types of asteroids, is considered to be the source. But there are a few specific comets that distribute significantly more particles to the near-Earth region than others. We will investigate these sources on the basis of statistical distributions of the orbital elements and compare them with the results of different models.
Moreover, in the search for a dominant source for given radiant densities, the result turns out to depend on the observation technique. Different techniques are differently sensitive to different particle masses; however, their synthesis will allow a more comprehensive view of the distribution of the sporadic background, including the study of its evolution. In this work, we use meteoroid orbits from various available meteor databases.
Requirements: programming, English
Research field: Dynamical evolution of small solar system bodies
Literature:
[1] Ryabova, Galina O.; Asher, David J.; Campbell-Brown, Margaret J. (Eds.), Meteoroids: Sources of Meteors on Earth and Beyond, ISBN 9781108426718, Cambridge University Press, 2019 (vybrané kapitoly).
[2] Murray, C. D., Dermott, S. F. Solar system dynamics, Cambridge, UK: Cambridge University Press, ISBN 0-521-57295-9 (hc.), ISBN 0-521-57297-4, 1999 (vybrané kapitoly).
[3] Wiegert, Paul, Vaubaillon, Jeremie, Campbell-Brown, Margaret, A dynamical model of the sporadic meteoroid complexc, Icarus, Volume 201, Issue 1, p. 295-310, 2009.
[4] Li, Y., Zhou, Q., Urbina, J., Huang, T.Y., Sporadic micro/meteoroid source radiant distribution inferred from the Arecibo 430 MHz radar obsertvations, MNRAS 515, 2088-2098, 2022. - Analysis and modelling of asteroid activity in terms of rotation, 3D shape and tail morphology changes
Supervisor: Mgr. Marek Husárik, PhD. (mhusarik@astro.sk)
Affiliation: Astronomical Institute of the Slovak Academy of Sciences, Tatranská Lomnica, 059 60 Vysoké Tatry
Syllabus
Focus of the research: The activity of small objects in the Solar System is usually expected (in the case of comets), but in recent decades we have also encountered cases where mostly objects classified orbitally as asteroids show some unexpected activity. The reasons of the activity may be different: an impact of a small body, a rotational splitting, a thermal defragmentation, etc. (the cause is not always clear). Also, the duration of the active phase can vary considerably from a few days to several months. Sometimes the activity is recurrent, but it may not be related to, for example, the arrival of a body in perihelion. Among other things, these bodies leave behind rather unusually shaped tails than those seen in comets.
Objectives: Analysis of the activity of a normally inactive body with respect to the orientation of the rotation axis in space, with respect to its shape, possible precession or surface albedo variegation. Computational modelling of tail formation and morphology based also on own observations.
Requirements:
(i) knowledge of programming in a commonly used language (Java, C++, preferably Python with astropy, scipy, matplotlib…) and the basics of the LaTeX environment, (ii) good knowledge of the English language, (iii) experience in observations and the ability to reduce the observed material and obtain the values needed for further analysis are welcome.
Research field: Dynamic evolution of small Solar System bodies
Literature:
[1] Binzel, R. P., Gehrels, T., and Matthews, M. S., Asteroids II, 1989
[2] Bottke, W.F. at al., Asteroids III, 2002
[3] Michel P., DeMeo, F., Bottke, W.F., Asteroids IV, 2015
[4] Warner, B.D., A Practical Guide to Lightcurve Photometry and Analysis 2nd ed., 2016
[5] Chandler, C. O., et al., SAFARI: Searching Asteroids for Activity Revealing Indicators, Publications of the Astronomical Society of the Pacific, vol. 130, no. 993, p. 114502, 2018. doi:10.1088/1538-3873/aad03d. - The origin and formation of the inner Oort cloud
Supervisor: Mgr. Marián Jakubík, PhD. (mjakubik@astro.sk)
Affiliation: Astronomical Institute of the Slovak Academy of Sciences, Tatranská Lomnica, 059 60 Vysoké Tatry
Syllabus
Focus of the research: The origin and formation of the Oort cloud, spherically symmetric cloud of comets orbiting the Sun in orbits with semi-major axis from 2000AU to 200000AU, are the focus of our research. The Oort cloud can be divided into 2 parts – inner and outer Oort cloud. There are models, which describe scenarios of the origin and formation of Oort cloud resulting from very recent observations. So far, the most suitable are models from time-period when the Sun was located in its birth star cluster. These models of the formation of Oort cloud (both parts) can realistically describe many details, which we can obtain from observations of comets and trans-neptunian objects.
Objectives: The main aim of this work is detailed description of the origin and formation of inner Oort cloud with main emphasis on models describing the formation of the Oort cloud in its birth star cluster. In more detail, we will solve open questions of this process using numerical simulations with respect of recent observations. Among answers on various open questions, we will find the solution of particular problem related to high number of objects (in the inner Oort cloud) revolving around Sun on retrograde orbits resulting from previous numerical simulations. However, this fact does not result from the analysis of recent available observations of inner Oort cloud objects.
Requirements:
programming skills (python, fortran), English language
Research field:
The dynamical evolution of the small bodies of the Solar system - Doubly and multiply eclipsing systems
Supervisor: Dr. Theodor Pribulla (pribulla@ta3.sk)
Affiliation: Astronomical Institute of the Slovak Academy of Sciences, Stellar Department, Tatranská Lomnica
Syllabus
Focus of the research: Systematic satellite observations aiming at the detection and study of exoplanets (CoRoT, KEPLER, TESS) lead to discovery of triple and quadruple stellar systems showing eclipses both in the inner and outer orbits (multiply eclipsing) or both inner orbits (doubly eclipsing). Because the geometry of the eclipses depends on the size and the mutual inclination of the orbits, it is possible to determine masses of the components without a need for spectroscopic observations. In the case that high-dispersion spectroscopy is available, it is possible to improve the parameters and to derive more parameters. Spectroscopy taken during the eclipses enables us to determine projected spin-axis orbital plane misalignment by using so-called Rossiter-McLaughlin effect. The misalignment strongly affects the apsidal motion rate in systems with eccentric orbits. It also provides us an information on the evolutionary history of the particular multiple system. If the outer-to-inner orbital period ratio is small, it is possible to observe anomalous apsidal motion and sometimes also perturbations of the inner orbits. Modeling of such systems requires inclusion of various effects (for example the finite speed of the light, reflection effect, ellipticity of the components, gravitational darkening). Modeling of high-precision satellite photometry is exacting and requires realistic models and accurate synthesis of observables. Systematic differences of the model and observed light curves point to other yet unknown effects or model inaccuracies (e.g., gravity darkening and reflection effect).
Objectives: Detection and modeling doubly and multiply eclipsing systems. Determination of the orbital and absolute parameters of the components. Including fine light-curve effects in the modeling of eclipses.
Requirements: good knowledge of English, knowledge of programming, ability to work independently with literature
Research field: Classical binaries and multiple stellar systems - Exoplanets transiting early-type stars
Supervisor: Dr. Theodor Pribulla (pribulla@ta3.sk)
Affiliation: Astronomical Institute of the Slovak Academy of Sciences, Stellar Department, Tatranská Lomnica
Syllabus
Focus of the research:
Majority of the known exoplanets was found orbiting solar-type stars of late spectral types. Detection of exoplanets around early-type stars is complicated mainly by the large ratio of the parent star’s and planet’s radii which results in a small transit depth. The spectroscopic detection is complicated by the high rotational velocity of the parent star and small number of available spectral lines, which significantly decreases the precision of the radial-velocity measurements. Another complication are sometimes pulsations of the parent star. Hence, it is often necessary to prove the existence of the planet by the Doppler tomography of its transits. The transit progress across the spectral line profiles, however, enables us to determine the projected misalignment of the stellar rotation axis with respect to the exoplanet orbital plane normal. If we have high-precision satellite photometry of the transit, we can determine the true (not projected) misalignment. This is holds clues to the evolutionary history of the object. Some objects (e.g. Kepler-13Ab) were found to show precession of the exoplanet orbit caused by the tides due to the rotationally-deformed parent star. These cause changes of the transit duration (TDV) due to the shift of the the transit cord across the stellar surface. Exoplanet orbit precession and the connected precession of the parent’s star rotational axis brings us information on the internal structure of the star.
Objectives: Detection of transiting exoplanets showing transit duration changes (TDV). Realistic modeling of exoplanet transits in rapidly rotating stars including fine light-curve effects (exact stellar and planetary shapes, Doppler beaming, gravity darkening). Finding the wavelength effects on the transit light curves relevant for the upcoming mission ARIEL.
Requirements: good knowledge of English, good knowledge of programming, ability to work independently with literature.
Research field: Extrasolar planets, brown dwarfs and low-mass stars. - Solar activity cycles – empirical implications for the solar dynamo modelling
Adviser: RNDr. Ján Rybák, CSc. (choc@astro.sk)
Affiliation: Astronomical Institute of the Slovak Academy of Sciences, Tatranská Lomnica, 059 60 Vysoké Tatry
Syllabus
An analysis of the long-term observations of the solar activity – sunspots, magnetic fields as well as measurements of prominences and green corona – for determination of behaviour and importance of manifestations of different activity separately on individual hemispheres of the Sun with searching for empirical implications for modelling of the solar activity by numerical methods describing the solar dynamo. An expected output of the research is determination of the temporal evolution of the time-latitude asymmetry of the solar activity for time period of several solar activity cycles and an analysis of its importance for different periods together with searching for probable periodicities of the activity.
Requirements: English language, programming skills, physical background
Research field: Research of physical properties and processes in the atmosphere of the Sun - Formation of young stars of T Tauri type and their planetary systems
Adviser: Mgr. Martin Vaňko, PhD. (vanko@astro.sk)
Affiliation: Astronomical Institute of the Slovak Academy of Sciences, Tatranská Lomnica, 059 60 Vysoké Tatry
Syllabus
Context: T Tauri are young (up to 100 Myr), low mass (less than 3 solar masses) highly variable late-type (later than F-type) stars with peculiar emission line spectra, associated with nearby molecular clouds the Star-Forming Regions (SFR, e.g. Rho Ophiuchi cloud complex, Orion Nebula, Taurus-Auriga, Cepheus-Cassiopeia). Their spectra also show high abundance of lithium with respect to that of the Sun and other main-sequence stars. T Tau stars are divided into two subgroups:(i) classical” TTS always embedded in a circumstellar envelope (CTTS), and (ii) the “weak-line” TTS with no longer indicated circumstellar envelope (WTTS). It has been found that TTS, in particular of the WTTS type, can be associated with strong X-ray emission and high rotation velocities (tens of km/s). High-resolution near-IR surveys indicate that a majority of the young stars are binaries or multiple systems with a typical separation of 0.3 – 0.5 arcsec. A study of TTS, in particular within binaries and multiple systems, allows us to better understand their origin and evolution until the stage when they will start to shine in the optical and become normal stars, as well as possible formation of their planetary systems.
Aims: Follow-up observations for candidate T Tauri stars and modelling of binary components containing a few Myr young stars to determine their physical parameters, rotational periods, character and nature of the observed photometric variability. Acquiring of multicolour photometry (including much desired U-band) of selected T Tauri stars.
Methods: Photometric monitoring of selected objects in the Cepheus-Cassiopeia region using telescopes of AI SAS. Spectroscopic observations will be used to obtain radial velocity curves and to detect the Li 670.8 nm line, as an indicator of the age. The selected targets are suitable for observations with échelle spectrograph MISICOS (R=35000) mounted at 1.3-m Nasmyth-Cassegrain telescope at Skalnaté Pleso Observatory.
Requirements:
English language, programming skills, physical basis
Research area:
Classical binaries and multiple stellar systems
For further information, please contact supervisors via email…
In Tatranska Lomnica, February 10th, 2023
Mgr. Peter Gömöry, PhD.
Director of the AISAS
Requirements
Programme: ASTRONOMY AND ASTROPHYSICS
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- Interview (PDF)
- Dissertation exam: ASTRONOMY (PDF)
