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.
Objectives: 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