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PhD study at the Astronomical Institute

PhD research topics:

  1. Interstellar particles in the Solar system's interplanetary medium
  2. Short-term color changes in comets at large heliocentric distances
  3. Doubly and multiply eclipsing systems
  4. Exoplanets transiting early-type stars
  5. Solar activity cycles - empirical implications for the solar dynamo modelling
  6. Formation of young stars of T Tauri type and their planetary systems

The Astronomical Institute organizes PhD study in astronomy and astrophysics.

Application deadline: May 15th 2021
Address: Astronomicky ustav SAV
059 60 Tatranska Lomnica
Interviews: end of June 2021
PhD study (start): September 1st 2021

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:

  1. Interstellar particles in the Solar system's interplanetary medium
    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 research: The interaction of our Solar system with the interstellar medium, due to the motion of the Sun relative to the local interstellar cloud, should lead to the presence of interstellar particles, or, at least, interstellar dust grains. Viewed from within the Solar system, a flow of interstellar matter should be observed. Since identifying particles of interstellar origin is a challenge, the true abundance of interstellar particles in the Solar system has not yet been unambiguously determined.
        Objectives: The aim of this work is to map the influx of the interstellar particles and follow their trajectories through the Solar system. These are influenced by their interaction with the interplanetary medium and controlled by a number of size-dependent forces. The emphasis of this work lies on large particles approaching the Earth's orbit on hyperbolic orbits with respect to the Sun, which can be observed as meteors.
    Computer simulations of interstellar particles' trajectories will be compared with observational data from the avaliable meteor databases. The substantial question is the ratio of the interstellar particles to those belonging to the interplanetary medium, which we should register in a particular region. This depends on the distance from both the Sun and the ecliptic. Therefore, the results of Earth-based and space-born observations will be synthesized to achieve a broader view.
    Requirements:
    programming, the English language
    Research field:
    The dynamical evolution of the small bodies of the Solar system
  2. Short-term color changes in comets at large heliocentric distances
    Supervisor: Mgr. Oleksandra Ivanova, PhD. (oivanova@astro.sk)
    Affiliation: Astronomical Institute of the Slovak Academy of Sciences, The Department of Interplanetary Matter, Tatranska Lomnica
    Syllabus
        Focus of the research: Microphysical properties of dust particles in the vast majority of comets can be deduced only using remote-sensing techniques based on the interaction of dust with solar radiation. Such interaction is manifested in three sets of phenomena: the elastic scattering of the sunlight in visible and near-IR bands, thermal emission of the absorbed solar radiation in mid-IR, and the radiation pressure that affects the motion of dust particles and, their spatial distribution in the coma and tail.
    Photometric colour of dust particles is defined as the ratio of scattered-radiation fluxes measured at two different wavelengths. Its strength lies in the relative nature as it depends directly on the microphysical properties of the dust particles, and it is independent of their number within the field of view. This is important because it is known that the number of dust particles forming a cometary coma is a subject to rapid and significant variations.
    Main goal of the work is using long-lasting observations of selected distant comets searching for variations of its colour. Detecting of fast changes in colour of distant comets provides important clues for better understanding of the microphysical properties of its dust.
        Methods: Photometry with broadband filters of selected distant comets. Studying fast variations of the color index in selected distant comets, searching for the frequency of occurrence of this phenomenon in various comets, its interrelation with other features of comets. Building the color maps of the comets. The use of the spectrum will provide exhaustive information on the presence of gaseous emissions in comets, which makes it very possible to derive the colour of cometary dust.
    Requirements:
    knowledge of English language, good background in physics, basic knowledge in programing (IDL), ability to work independently with literature.
    Research field:
    Structure of meteoroid streams and complexes of small bodies of the Solar System, evolution and physical characteristics of the parent bodies of meteoroids.
  3. 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
  4. 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, knowledge of programming, ability to work independently with literature
    Research field:
    Extrasolar planets, brown dwarfs and low-mass stars
  5. 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, The Department of Solar Physics, Tatranska Lomnica
    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
  6. 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, The Department of Solar Physics, Tatranska Lomnica
    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 eShel (R=11000, Shelyak Instruments) mounted at 60-cm Cassegrain telescope in the pavilion G1 at the Stará Lesná observatory, and with 1.3-m Nasmyth-Cassegrain telescope at Skalnaté Pleso observatory (https://www.ta3.sk/l3.php?p3=sto).
    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 11th, 2021

Mgr. Peter Gömöry, PhD.
Director of the AISAS

Requirements

Programme: ASTRONOMY AND ASTROPHYSICS

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