LABORATORY FOR TRANSIENT PHENOMENA IN STARS

The head of the Laboratory for Transient Phenomena in Stars is Ph.D. B. Yu. Zhilyaev.

Investigations of the Laboratory are concerned with study of rapid small-scale variability of stars from observations with a single telescope and simultaneous observations with several telescopes.

THE STAFF OF THE LABORATORY:

MAIN RESEARCH AREAS OF THE LABORATORY:

• Investigation of high-frequency small-scale activity of variable stars with the Synchronous Network of Optical Telescopes.

• Development of techniques and algorithms for analysis of data based on photon counting statistics.

The Laboratory equipment:

two high-speed two channel UBVR photometers mounted respectively on the 2m Ritchey-Chretien telescope (Peak Terskol, North Caucasus, 3100 m a.s.l.) and 50 inch reflector (Crimean Astrophysical Observatory), and a single-channel high-speed photometer mounted on the 2m telescope at the Rozhen Observatory in Bulgaria.

SIGNIFICANT RESULTS OBTAINED BY THE LABORATORY RESEARCHERS:

• A new approach had been developed to search for microvariability and high-speed phenomena in variable stars. Statistical photometry stands on three pillars: the digital filtering technique, the Mandel equation based on photon counting statistics and integral transforms of the light curves. These techniques, entering the practically unexplored territories permit to investigate extreme low-amplitude and rapid variability in stars.

• Many-site multichannel simultaneous observations of the flare star EV Lac have revealed high-frequency brightness oscillations (HFO) superperimposed on the mean flare light curve. HFO occur suddenly at the earliest stage of a flare and are visible during high state. Coherent oscillations around 26 and 13 sec were seen during three flare events. The pulsed fractions are some 2.5% in the B band and 10-15% in the U one. This oscillatory phenomenon is capable to improve our understanding of the flare process.

• The flares fine structure lies often below the detection limit for raw photometric data. UBVRI high-speed observations combined with synchronous monitoring at two telescopes, situated far each other allowed us to detect new small amplitude features in flare activity of EV Lac. The digital filtering of the light curves was used. We found that some flare events are composed of a flare and an attendant intensity drop having crater-shaped structure centered at the flare peak. Fading amplitudes extend from 0.1 to 0.01 mag.

• Short-term coherent brightness oscillations of Jupiter, Saturn and their satellites Io, Europa and Rhea resulting from many-site multichannel high-speed monitoring had been detected in the ultraviolet. Their frequencies are in the range from roughly 0.02 to 1 Hz and amplitudes of a few parts per thousand. We show phase coherence between planetary and satellite oscillations and time delay between them. In all instances the time delay observed is equal to a distance difference between the Sun, the target objects and the observer expressed in light seconds. All this evidence points clearly that the Sun is mainly responsible for rapid variability of planets and their satellites.

• If primordial low-mass black holes (BH) exist in the Universe, then many of stars and planetary bodies appear to be "infected" by them. This is also true in regard to the Sun and most likely to Jupiter and Saturn. The availability of even the very low-mass inner BH reactor may lead to essential changes in evolution scenario of a celestial body on cosmological time scale.