Pravidelné semináře pořádáme jednou měsíčně (říjen–červen, zpravidla první pondělí v měsíci) od 13 hod v seminární místnosti pracoviště Ondřejov. (archiv seminářů)
16. 05. 2012
Massive star magnetospheres: from X-ray to radio
Abstract: Magnetic massive stars experience confinement of stellar wind plasma by their strong, large-scale magnetic fields. This magnetospheric material can produce observable spectral and photometric effects in wavelengths from X-rays to radio. I will present a summary of the observational and theoretical efforts to study massive star magnetospheres, as well as discuss future possibilities for these stars in the infrared.
Dále pořádáme menší semináře jednotlivých oddělení:
Semináře slunečního oddělení
Každé úterý v 13:00 (září–červen, s výjimkou úterků po celoústavním semináři) v zasedací místnosti slunečního oddělení pracoviště Ondřejov.
24/04/2012, 13:00Prominence mass estimated from multi-spectral dataAbstract: A spectroscopic method for estimation of the total mass of a prominence from multi-spectral observations was developed. Observations in EUV by AIA instrument on board of SDO, in soft X-rays by XRT on Hinode and in H alpha by MFS spectrograph of the Ondrejov observatory are used. The total mass of a prominence is obtained by integration over the whole prominence area, of the column mass derived from the column densities obtained using a semi-automatic code developed according to the method of Heinzel et al. (2008). Non-symmetrical distributions of the coronal X-ray and EUV emissivities in front of and behind the prominence is taken into account as well. We use the so-called alpha factor defining a fraction of the emissivity behind the prominence. The mass determination then depends on the correct specification of this factor. Alpha factor is estimated iteratively by comparing a ratio of the optical thicknesses at 193 A and 211 A derived from observations with the theoretical value calculated according to Anzer and Heinzel (2005). The robustness of the method is tested on several prominences and derived alpha values are compared with approximate value obtained from the intensities measured on the disk and at the limb close to a prominence.
Zářivě-(magneto)hydrodynamické semináře
Zpravidla 1x za 14 dní ve čtvrtek od 11 hod (říjen–červen) v zasedací místnosti slunečního oddělení pracoviště Ondřejov.
01/12/2011, 11:00Konkoly Observatory, Budapest, HungaryThe extreme outburst of the young eruptive star EX Lupi in 2008Abstract: EX Lupi is the prototype of EXors, a spectacular group of low-mass pre-main sequence stars characterized by repetitive optical outbursts of 1-5 mag lasting for a few months-to-few years. The outburst is attributed to enhanced accretion from the inner circumstellar disk (within ^X0.1AU) to the stellar surface, probably triggered by an instability in the disk. The historically largest outburst of EX Lupi in 2008 Jan-Sep offered a unique opportunity to understand deeper the physics of the EXor eruptions. In my talk I will summarize the main results of our coordinated observing campaign, in which we used a large set of telescopes to observe and characterize the path of accretion from the disk onto the stellar surface, with the aim of comparing the different models of outburst physics. Our measurements also demonstrated that the brief episodes of highly increased accretion, apart from contributing to the build-up of the final stellar mass, have substantial effect on the structure and composition of the circumstellar material: We discovered episodic crystallization of silicate grains in the disk surface due to the increased luminosity during the 2008 outburst, resulting in material that forms the building blocks of comets and planets.
Semináře oddělení GPS
Zpravidla v knihovně pracoviště Praha–Spořilov v různé dny.
28. 05. 2012, 14:00Ludwig-Maximilians-Universitaet, MunichCosmology and cluster astrophysics with the South Pole TelescopeAbstract: The South Pole Telescope (SPT) is 10-meter telescope operating at millimeter wavelengths whose primary goal is to search for clusters of galaxies via the Sunyaev-Zel'dovich (SZ) effect - the distortion of the cosmic microwave background imprinted by the hot intercluster plasma.
The mass and redshift distribution of the cluster population is sensitive to the geometry of the Universe and to the rate of structure growth. Galaxy clusters thus provide important insights into cosmological questions such as the nature of cosmic acceleration and the Gaussian character of underlying density perturbations. They can also serve as a consistency test of the general theory of relativity on cosmological scales.
I will explain the principles of cluster cosmology and give an overview of the SPT survey. I will discuss the current cosmological constraints from the SPT cluster data, highlighting the constraints on the dark energy equation of state, and the sum of the neutrino masses. I will also demonstrate the use of SPT clusters to answer astrophysical questions such as the cosmic evolution of gas cooling in the cluster cores and give examples of interesting individual systems discovered by SPT, raging from spectacular merging clusters to the most massive relaxed objects in the Universe.(Takes place at: Sporilov library)