SK
SAS
- The early stage of classical nova explosions
- Distribution of the orbits of sporadic meteoroids
- Analysis and modelling of asteroid activity in terms of rotation, 3D shape and tail morphology changes
- Observed characteristics of selected active bodies in the solar system as indicators of their origin and evolution
- The origin and formation of the inner Oort cloud
- Radiation-driven astrochemical processes in ice phases: applications for space environments
- Outburst of the symbiotic star BF Cyg with flares and collimated mass ejections
- 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 2024 |
| Address: | Astronomicky ustav SAV, v. v. i. Tatranska Lomnica, 059 60 Vysoke Tatry |
| Interviews: | during June of 2024 |
| PhD study (start): | September 1st 2024 |
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:
- The early stage of classical nova explosions
Supervisor: Mgr. Ľubomír Hambálek, PhD. (lhambalek@astro.sk)
Consultant: RNDr. Augustin Skopal, DrSc.
Affiliation: Astronomical Institute SAS, Tatranská Lomnica, 059 60 Vysoké Tatry
Syllabus:
Focus of the research: The nova phenomenon is the result of the sudden thermonuclear fusion of hydrogen into helium in the surface layer of a white dwarf (WD). The fuel for this process is hydrogen material that is deposited on the surface of the WD from its companion in the binary. When the pressure at the base of the accumulated layer reaches a critical value, thermonuclear fusion takes place on a time scale of minutes (so-called fast novae) with an energy output of about 1031 W, which ejects the remaining accumulated mass into the surrounding space at a speed of several thousand km/s. High-energy gamma-photons produced by thermonuclear fusion are transmitted through this material and thereby redistribute their energy throughout the electromagnetic spectrum depending on the optical and geometric properties of the ejected matter, which are dependent on the time since the eruption. In the case of fast novae (the case of massive WDs), the maximum brightness in the optical usually occurs within a few days of the explosion and reaches an amplitude of around 9 to 15 magnitudes. For low-mass WDs, the ignition of thermonuclear fusion is not explosive, the optical maximum usually occurs on a scale of weeks to months, and is often accompanied by other less energetic flares before a gradual decrease in brightness (so-called slow novae). The development of classical novae, especially from their first hours to a few days (tens of days) of their life, is still poorly understood. Determining the basic physical parameters and geometric structure of a nova in its early stages will therefore allow us to better understand the nature of nova explosions and their development, and thus also their integration into the evolution of other stars and stellar systems.
bjectives: For selected fast and slow novae, determine the basic physical parameters of the radiation regions of the nova (temperatures, radii, luminosities, emission volume, mass-loss rate) and their geometric structure in the early stages after the explosion. This goal is achieved by modeling the energy distribution in the spectrum of the nova (software available), which will distinguish its individual radiation components. The doctoral student will work with existing observations (UBVRI photometry, spectroscopy). For new objects, it will also be possible to obtain own observations with AI SAS telescopes. He/she will be included in the research team of the VEGA project, which will enable him/her to present the obtained results at international conferences.
Requirements: knowledge of English, basics of programming
Research field: Symbiotic stars and novae - 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. - Observed characteristics of selected active bodies in the solar system as indicators of their origin and evolution
Supervisor: Mgr. Oleksandra Ivanova, PhD. (oivanova@ta3.sk)
Affiliation: Astronomical Institute of the Slovak Academy of Sciences, Tatranská Lomnica, 059 60 Vysoké Tatry
Focus of the research: The investigation of remnant planetesimals in the Solar System is motivated by the endeavor to reveal their connection to the conditions of their formation in the protosolar disk. Recent research on selected active small bodies has highlighted that a significantly larger number of objects undergo phases of activity than previously assumed, often utilizing mechanisms that remain poorly understood. Similarity and dissimilarity in chemical and physical properties of active small bodies can illuminate their origin and/or evolution. The key scientific goal is to understand how activity modifies the characteristics of small bodies and to decipher their current properties in order to elucidate their recent evolution.
Objectives: To identify the physical characteristics and chemical composition of selected active small bodies based on photometry, spectroscopy, and polarimetry. To perform a diagnosis of the physical and optical properties of dust in objects from different populations through numerical modeling. To search for correlations between the physical and dynamical characteristics of small Solar system bodies with the aim of identifying features associated with different regions of their formation or distinct evolutionary paths.
Requirements: Programming skills in a commonly used language (IDL or Python) and basic knowledge of LaTeX environment, good knowledge of the English language, experience in observations and the ability to reduce the observed material and obtain the values needed for further analysis are welcome.
Research field: Activity of small bodies in the Solar System
Literature:
[1] Bauer, J. M. (2003). A physical survey of Centaurs. University of Hawai’i at Manoa.
[2] Ivanova, O., Rosenbush, V., Luk’yanyk, I., Markkanen, J., Kleshchonok, V., Kolokolova, L., … & Afanasiev, V. (2023). Quasi-simultaneous photometric, polarimetric, and spectral observations of distant comet C/2014 B1 (Schwartz). Astronomy and Astrophysics, 672, A76.
[3] Ivanova, O., Licandro, J., Moreno, F., Luk’yanyk, I., Markkanen, J., Tomko, D., … & Shubina, O. (2023). Long-lasting activity of asteroid (248370) 2005 QN173. Monthly Notices of the Royal Astronomical Society, 525(1), 402-414.
[4] Jewitt, D., Hsieh, H., & Agarwal, J. (2015). The active asteroids. Asteroids IV, 221-241.
[5] Swamy, K. K. (2010). Physics of comets (Vol. 12). World Scientific.
[6] Thomas, N. (2020). An Introduction to Comets: Post-Rosetta Perspectives. Springer Nature. - 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 - Radiation-driven astrochemical processes in ice phases: applications for space environments
Supervisor: Mgr. Zuzana Kaňuchová, PhD. (zkanuch@ta3.sk)
Affiliation: Astronomical Institute of the Slovak Academy of Sciences, Tatranská Lomnica, 059 60 Vysoké Tatry
Focus of the research: Laboratory investigations of chemical processes occurring in ices relevant to astrophysics have demonstrated the dependence of this chemistry on a number of experimental parameters (e.g., temperature, irradiating particle, dose). Although it has been found that different factors influence this chemistry, one aspect that hasn’t been explored to a great extent is the specific phase of the solid ice being studied. Understanding the solid phases of ices is crucial for studying how their molecular structures influence radiation-driven astrochemical processes (e.g. phase transition, ice compaction, radiolytic decay of molecules, formation of new molecules) occurring in various space environments.
Objectives: The aim of this project will be to systematically and quantitatively characterize the impact of various types of radiation (e.g., electron, ion, photon) on the different phases of various molecular ices relevant to astrochemistry. The candidate will make use of an ultrahigh-vacuum chamber equipped with a substrate that is able to cooled to cryogenic temperatures to prepare astrochemical ice analogues, which will then be irradiated by various radiation sources (e.g., particle accelerators, electron guns, ultraviolet lamps). The candidate will acquire spectroscopic and spectrometric data during these irradiations which will allow him / her to quantify: (i) the rate of destruction of the target ices, (ii) the rate of formation of new product molecules, and, most importantly, (iii) any apparent differences between different phases of the same molecular ice (e.g., between amorphous and crystalline ices). The information gained from these experiments will be of use in further elucidating data obtained by space missions aimed at characterizing the solid-state radiation chemistry of the interstellar medium and the outer Solar System.
Requirements:
– MSc degree (or equivalent) in chemistry, physics, astronomy, engineering, or other relevant quantitative scientific field
– Knowledge of written and spoken English at an advanced level (thesis must be completed in English)
– Knowledge of theoretical and practical aspects of spectroscopy with a particular focus on infrared absorption spectroscopy
– Programming and electrotechnical skills are not required but are certainly very welcome
Research field: astrochemistry of interstellar matter and Solar System objects - Outburst of the symbiotic star BF Cyg with flares and collimated mass ejections
Supervisor: Mgr. Emil Kundra, PhD. (ekundra@astro.sk)
Consultant: RNDr. Augustin Skopal, DrSc.
Affiliation: Astronomical Insititute of Slovak Academy of Sciences, Tatranská Lomnica, 059 60 Vysoké Tatry
Syllabus:
Focus of the research: Symbiotic stars are interacting binaries with very long orbital periods (on the order of years). They consist of a red giant that is losing some of its mass and a white dwarf that is accreting it. Occasionally, on a time scale of tens of years, outbursts occur, during which we observe an increase in the brightness of the system by 2 to 7 magnitudes and significant changes in the spectrum. An outburst is often characterized by a single brightening followed by a decrease to the original brightness. In some cases, the main maximum is accompanied by a secondary flare. In the case of the symbiotic star BF Cyg, the primary outburst occurred in 2006, but the slow decline was interrupted by further flares in 2015 and 2017, after which collimated mass ejections were indicated. The high level of BF Cyg activity continues to the present. The fundamental problem is to clarify the source of energy and the mechanism that maintains such a long-lasting outburst. The essence of symbiotic star outbursts is one of the key problems of their research.
Objectives: The aim of the PhD thesis is to determine the basic physical parameters of the BF Cyg radiation regions (temperatures, radii, luminosities, emission volume, mass-loss rate from the system) during outburst that occurred in 2006, especially during flares in 2015 and 2017. This goal will be achieved by modeling the energy distribution in the BF Cyg spectrum (software available), which will distinguish its individual radiation components. Furthermore, it is the determination of the basic physical parameters of collimated mass ejections and their evolution in different stages of the outburst. Both tasks should contribute to a better understanding of the process of mass accretion onto a white dwarf as well as the mechanism that maintains the high energy output of BF Cyg for a long time (17 years so far). The doctoral student will work with existing observations (UBVRI photometry, spectroscopy) with the possibility of obtaining new observations with the AISAS telescopes.
Requirements: knowledge of English, basics of programming
Research field: Symbiotic stars and novae - Solar activity cycles – empirical implications for the solar dynamo modelling
Supervisor: RNDr. Ján Rybák, CSc. (rybak@astro.sk)
Affiliation: Astronomical Institute of the Slovak Academy of Sciences, Tatranská Lomnica, 059 60 Vysoké Tatry
Syllabus
Focus of the research: An analysis of the long-term observations of the solar activity – sunspots, magnetic fields as well as measurements of prominences and green corona, determined at the AISAS – for determination of behaviour and importance of manifestations of different activity separately on individual hemispheres of the Sun. Searching for empirical implications for modelling of the solar activity by numerical methods describing the solar dynamo.
Objectives: 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 - High-contrast SB2 spectroscopic systems with peculiar early-type component(s)
Supervisor: Dr. Martin Vaňko (vanko@astro.sk)
Affiliation: Astronomical Institute of the Slovak Academy of Sciences, Stellar Department, Tatranská Lomnica
Syllabus
Focus of the research: The easiest proof that a system is a binary star is the presence of eclipses. The second most useful technique is radial-velocity (RV) variations. Such variations are typically detected within spectroscopic surveys, which result in a list of objects catalogued according to their specific stellar attributes. Once such a variation has been detected, targeted and systematic observations must be obtained to characterize the system. In the simplest case, the binary comprises two components of relatively close luminosity which results in two systems of spectral lines in the composed spectrum. When the components differ significantly in luminosity, spectral lines of the fainter secondary component become less evident. The situation gets especially difficult when the secondary is a fast rotator (> 100 km/s). Although the spectral lines of the fast-rotating secondary component are shallow and hard both to identify and model, its light boosts the continuum level, which uniformly reduces the depths of the dominant component’s spectral lines. More rarely, a star might be revealed to be double when discrepancies in the projected rotational velocity, v sin i, determined using spectral lines that have a different sensitivity to the atmospheric effective temperature are detected, e.g., the lines of Mg II at λ 4481 Å and Ca II H and K.
Objectives: Modelling the spectroscopic data of several peculiar, high-contrast, early-type systems on the main sequence with a combination of photometric measurements from the archive of the TESS satellite. The main goal is to determine the RVs and rotational velocities of the studied objects and the possible presence of other components. Our analysis will also be focused on characteristic of possible short-term (tens of minutes) or medium-term (several hours) pulsations of individual components, determination of their atmospheric parameters (surface temperature, metallicity, surface gravity) and absolute parameters (radius, mass, luminosity). Based on the obtained results, the evolutionary status of studied systems will be discussed.
Requirements: good knowledge of English, good knowledge of programming, ability to work independently with literature.
Research field: Binary and multiple stellar systems
For further information, please contact supervisors via email…
In Tatranska Lomnica, February 2nd, 2024
Mgr. Peter Gömöry, PhD.
Director of the AISAS
Requirements
Programme: ASTRONOMY AND ASTROPHYSICS
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- Interview (PDF)
- Dissertation exam: ASTRONOMY (PDF)
