27 September 2017, at 1:00 PM
Binary stars with RR Lyrae component – why so rare?
Marek Skarka
(Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Science)
Large portion of stars of all spectral types is bound in binary systems. However, there is one spectacular exception. Among 100 000 catalogized stars of RR Lyrae type only several tens of binary candidates are known and none of them has been unambiguously confirmed yet. Could this lack of binaries be real? Why it is so difficult to discover RR Lyrae star in binary system? Are there any observational limitations? What methods are suitable for the search for such binaries? I will discuss all these questions, give an overview about the progress in last three years, and will show why many of the candidates could actually be false positives.
23 August, 2017 at 10:30 AM
Instrumentation at Astronomical Institute in the High Tatras-Slovakia
Martin Vanko
(Astronomical Institute of Slovak Academy of Sciences)
Astronomical Institute of the Slovak Academy of Sciences (AI SAS) runes several observatories located at different places in the High Tatras. Our telescopes are equipped with new high-end post-focus instruments producing valuable data in the field of the stellar and exoplanetary astronomy. First results will be presented in my talk. Finally, I will present existing and future projects between our Institutes.
18 May, 2017 at 11:00 AM
Blue atmosphere or stellar activity – is the blue atmosphere of the exoplanet GJ 3470 b real?
Silvia Kunz
(Thueringer Landessternwarte Tautenburg, Germany)
One of the big challenges in the field of exoplanet atmospheres is to distinguish the influence of stellar activity on transit measurements from real effects that can be seen in photometric measurements in different bands. Oshagh et al. (2014) assumed that an increase of planetary radii in the blue part of the spectrum can be explained with the presence of a hot plage region on the stellar surface. In particular they stated that the measured blue atmosphere of the sub-Uranus-mass low-density planet GJ 3470b could be mimicked by a plage region that covers only 2.56% of the star’s surface. We have developed a method to exclude the influence of plage regions on transit measurements. The Ca II H,K lines are tracers of stellar activity – especially of plage regions. If plage regions were occulted those lines should vary during transit. We therefore have observed one transit of GJ 3470 b with the high-resolution UVES spectrograph at the 8.2 m Very Large Telescope. We have found that the difference of the Ca II H,K lines in- and out-of-transit is only 0.67 ± 0.22% and have determined a magnetic filling factor of about 10–15%. In order to confirm the Rayleigh scattering slope we have analyzed the planet‘s lightcurve by observing three transits with the low-resolution OSIRIS spectrograph at the 10.4 m Gran Telescopio Canarias. With those almost simultaneous measurements of GJ3470b‘s transit we were able to confirm its Rayleigh scattering slope towards the blue.”