International Summer Student Internships (ISSI)
Astronomical Observatory (AO) of the Jagiellonian University in Kraków
Projects proposed for the summer 2018
- The geometric properties of the selected inhomogeneous cosmological models
Supervisor: Dr. Szymon W. Sikora
The problem of the impact of the inhomogeneities on the cosmological observables is still a subject of debate. One of the possible approaches to this issue is to study the simplified toy model space-times for which the metric is explicitly given and one can derive all the model properties in a straightforward way. The aim of this project is to analyze the simple geometric properties of the selected model (the expansion scalar, the geodesics, etc.). During the project, the intern will improve the skills in usage of the computer algebra systems (Maxima, Mathematica or Sympy), which are the main tools in these calculations. The basics of the General Relativity and programming is needed.
- Search for minute-like gamma-ray variability in Fermi-LAT light curves of blazars
Supervisor: Dr. Arti Goyal
Blazars are an extreme class of active galactic nuclei (AGN), for which the total radiative output is dominated by a Doppler-boosted, broad-band and non-thermal processes; synchrotron (radio-to-optical) and inverse-Compton (IC; ˜ X-ray-to-gamma-ray) occurring in relativistic jets launched from the centers of supermassive black hole (SMBH)/accretion disk system located at the centers of elliptical galaxies. Various plasma instabilities leading to the formation of shocks and turbulence in the jet flow as well as annihilation of magnetic field lines are believed to heat/accelerate the particles and dissipate energy. Besides showing extreme luminosities up to ˜1047-48 ergs/s, blazars are also extremely variable on timescales ranging from decades to hours and even down to minutes with intensity changes of a factor of few, especially prominent at X-ray and γ-ray energies. The variations on short-timescales provide an additional challenge at higher energies, as large jet bulk Lorentz factors Gamma < 30 are needed to overcome the photon opacity arguments which are rather too extreme to be reconciled with the currently favored models for the jet formation in AGN. Moreover, the notion of fundamental variability timescale in the jet, i.e., "light crossing time" of the SMBH event horizon sets a lower limit on the spatial scales of disturbances propagating down the jet; these correspond to minimum variability timescale of sub-hours for a 108 solar mass black hole (Rg = GM/c2 where Rg is the gravitational radius, G is the gravitational constant and c is the speed of light). On the other hand, the confirmed detection of minute-like timescale variability at gamma-rays could indicate that disturbances in the local plasma conditions are primary candidates for energy dissipation in blazar jets.
Scope of project: We will analyse the publically available gamma-ray data obtained using the Fermi-LAT satellite for the Fermi-bright blazars. The search for minute-like variability will be conducted using the Baysian block analysis. We will re-write the computer code and learn to use archival data and, if time permits, extend the statistical analysis to other frequencies for selected blazars.
- Search for variability timescales in the Swift blazar observations
Supervisor: Dr. Gopal Bhatta
Active galactic nuclei (AGN) are the most luminous sources in the universe. They are widely believed to be powered by accretion on to the supermassive black holes. A sub-class of radio-loud AGNs with their relativistic jets aligned close to the line of sight is known as blazar. The sources are identified by their extreme properties such as high luminosity, rapid flux and polarization variability, and a large output of high energy emission, e.g. X-ray and gamma-ray. Rapid variability on timescales ranging from a few minutes up to a few daysi — widely known intra-day variability — are a commonly observed phenomenon in blazars, and it is considered to originate close to the central engine. The understanding of the physical conditions leading to the observed rapid variability, along with other active galactic nuclei (AGN) processes, might be considered key to the understanding of the process occurring at the interface of super-massive black hole and relativistic jets.
In this project we will perform spectral, timing and cross correlation study of a sample of blazars using the observations from the Space telescope Swift – XRT (X-ray) and UVOT (ultra-violet) instruments). The study will be primarily focused on the following aspects.
1) Search of characteristic timescales
2) Cross correlation between high and low energy emission.
3) Possible relation of variability with flux and spectral states
Note: After the completion of the projects, the participant students will acquire knowledge of high energy emission from active galactic nuclei as well as a number of skills such as X-ray timing and spectral analyses, and use of high energy astronomy related softwares. Also, we will work to publish the results of the study in reputed international journals.
- Is extended radio emission of compact galaxy groups indeed extended?
Supervisor: Dr. Błażej Nikiel-Wroczyński
Compact galaxy groups constitute a phenomena-abundant class of galaxy systems. Violent interactions, and tidal outflows caused by them suggest that there is a possibility that inergalactic magnetised structures can be formed. And it is indeed the case: entities of this type have already been detected, eg. in HCG 15, or HCG 92 - as well as in compact groups that are not referenced in the HCG catalogue. Recently we have completed working on a catalogue of these objects at 1400 MHZ, finding that a non-negligible fraction - around 15% - contains sources of intergalactic radio emission, and an even larger number of additional objects seems also to host similar structures - but due to the beam smearing effects, it is unknown if it is indeed extended, or compact in character, enlarged by the beam size. Therefore, there are two ideas how to overcome this problem:
1) compare the radio flux density of the HCGs form the low-resolution data to that of high-resolution archive data, available for nearly all of these systems in the NRAO archive;
2) do the same, but using the GLEAM (low-res) and TGSS-ADR (hi-res) surveys, at a frequency of 250 MHz, just for the southern, and equatorial systemsa
In case of the second proposal, there is also a chance that even those systems, that do not show any signs of extended features at 1400 MHz will turn out to be the opposite - as there is a chance to discover the older electron population.
The project is intended for one, or - at most - two students. The student will be responsible of making measurements of the radio flux density in both of the surveys, and preparing the information on the radio flux excess. Based on that, a list of the "extended emitters" will be compiled, and extended into a publication that will be sent to one of the leading astronomical journals (ApJ, MNRAS, or A&A).
- Multiwavelength analysis of the structure of relativistic AGN jets
Supervisor: Dr. Volodymyr Marchenko
The aim of this project is to analyze the structure of AGN jets. Since different physical processes can be responsible for radiation in different wavelengths, to study the physics of AGN jets it’s important to use multiwavelength observational data. The main accent will be made on Chandra data analysis, which requires the usage of special dedicated software. This software enables the general data preparation, the simulation of point spread function (PSF), making spacial, temporal and spectral analysis of Chandra data. To analyze the detailed structure of the jet morphology the different techniques for restoring the image will be used: various deconvolution methods and forward-fitting algorithm for modeling the jet structure.
- Analysis of the ELF data
Supervisor: Dr. Volodymyr Marchenko
The project is intended to analyze the data from World ELF Radiolocation Array (WERA), which was developed, installed and maintains by Krakow ELF group. It operates in the Extremely Low Frequency (ELF) range, which enables determining the locations and parameters of atmospheric discharges generating electromagnetic waves in the Earth-ionosphere waveguide. The various physical events that happens in ionosphere can be seen in ELF data in time and frequency domain. Such events are Terrestrial Gamma-ray Flashes (TGF), Solar Proton Events (SPE), Sudden Ionospheric Disturbances (SID) etc. The goal of this project is to analyze the signatures of such events in ELF data.
AO invites applications of students interested in carrying an astronomical research project in our observatory, supervised by the AO staff members. The four weeks' internships will be organized in the summer period (July-September), the time period for each project is provided in the project description. All successful applicants will be granted a small fellowship and a place in a student house will be provided for his/her stay, however no support will be provided for the travel expenses and health insurance. AO will accept up to 4 students for these internships. AO will sign a formal agreements with these students on providing them financial support and accommodation for the internship period.
Applications will be accepted from students of astronomy, physics, and other studies providing a solid knowledge of physics and mathematics. Eligible for application are only students who will finish before the time of the internship their second or higher year of study. Students from all countries of the world can submit application.
Application for any selected project should be submitted in an electronic form
till the April, 30th
both to the ISSI secretary ISSIsecretary [at] oa.uj.edu.pl and to the person supervising the project. The applicant should also provide information if he is interested in performing other projects (which ones) in the case he is not accepted for his favorite one.
Each application should include:
- A letter with a statement of the applicant on his interest in the selected project. This letter can include information which another project from the list could be accepted by the candidate, in the case he is not accepted for his first choice project.
- A certificate from his university about his/her study.
- A list of his/her lectures and exams passed, providing respective obtained grades and including an explanation of the grading rules. The list should be certified by his/her university according to a given university rules.
- CV including eventual candidate's achievements and publications.
- Information (contact details) about a scientist who is ready to provide the candidate a reference letter. Only scientists with publication record in international literature can be suggested.
The candidate evaluation will be done in AO by the evaluation panel and the results will be announced to all candidates via e-mail before May 15th.
All formalities related to the given internship should be arranged with the ISSI secretary ISSIsecretary [at] oa.uj.edu.pl, with cc. the project supervisor. In particular the accepted candidates will obtain scans of the acceptance letters after a qualification process is completed (on request a hard copy of such letter will be send by post). The accepted candidate should provide original forms of the electronic documents 2 and 3 to the ISSI secretary before his/her internship agreement is signed.