Doktorské studium

Studijní obor Teoretická fyzika a astrofyzika

Název práce: Limity vysoce přesného měření radiálních rychlostí hvězd

Školitel: RNDr. Petr Škoda, CSc.

Předběžné zadání:

The first computing code for precise estimation of radial velocities using Iodine cell in front of the spectrograph, developed a quarter century ago by R.P. Butler finally confirmed the existence of first exoplanet orbiting Sun-like star (discovered by Mayer and Queloz) and led to the discovery of a number of other exoplanets in the framework of the Lick observatory planet search program.

Despite the manufacturing of expensive super-precise spectrographs like HARPS or SOPHIE, the I2 cell remains a good alternative for boosting the RV precision of common high resolution echelle spectrographs allowing the smaller observatories with medium-sized telescopes to participate in a top-science research of stellar variability requiring measurements of small velocity changes, like stellar photospheric and chromospheric activity, convection, pulsations or even wind clumping.

These phenomena, however, strongly limit the detectability of exoplanet signals, introducing noise of the similar scale as well-known instrumental effects. The goal of the thesis is to make a complex study of limits of detectability of various star-related physical activity as well as estimates of limits for spectroscopic follow-ups of exoplanet candidates delivered by numerous photometry transient surveys - current ( e.g. Gaia, Kepler, PANSTARRS, Catalina, PTS) or future (namely space missions CHEOPS, TESS, LSST, PLATO, EUCLID).

The applicant is expected to:
  1. Make a survey of instrumental effects influencing the RV measurements and analyze the methods for their elimination
  2. Create the open-source code allowing the routine pipeline processing of echelle spectra containing I2 Cell absorption, namely focusing on instrument profile variability reconstruction. The code may benefit from massively parallelized computing on multi-core processors and GPGPUs as well as from availability of advanced high-level processing, visualization and statistics Python libraries in AstroPy, Scikit-learn, AstroML and similar.
  3. Perform a long-time observation and collect existing spectra of a number of stellar objects with known features mentioned above (e.g. bright late type F,G, K giants, as well as a set of well-suited exoplanet-hosting stars) and analyze the results using 2)
  4. Discuss the statistical relevance of measurements and make recommendation for the objects well suited for the analysis using your code.

During the PhD. studies an active collaboration with world experts in the field is foreseen as well as participation on various scientific projects.

Requirements of the applicant's skills:
  • Good knowledge of programming in Python and its libraries
  • Expertise in echelle spectra reduction (at least in IRAF)
  • Basic knowledge of Bayesian statistics

The thesis is expected to be written in English

Recommended Literature:

Marcy, G. W., Butler, R.P.: 1992, Publications of the Astronomical Society of the Pacific, 104, 270

Valenti, J.A., Butler, R.P., Marcy, G.W.: 1995, Publications of the Astronomical Society of the Pacific, 107, 966

Butler, R.P., et al.: 1996, Publications of the Astronomical Society of the Pacific, 108, 500

Endl, M., Kürster, M., Els, S.: 2000, Astronomy and Astrophysics, 362, 585

Sato, B., et al.: 2002, Publications of the Astronomical Society of Japan, 54, 873

Kambe, E., et al.: 2008, Publications of the Astronomical Society of Japan, 60, 45

Abouav, D.A., Improving Radial Velocity Analysis at Lick Observatory, master thesis, San Francisco State University, 2007, available at

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