The Sun as a Star: 13 years of SoHO

The best known Solar oscillation-like star is the Sun. During the last 14 years, the ESA/NASA Solar and Heliospheric Observatory (SoHO) has been continuously observing this star from the Lagrange point L1 with an enormous success. Among the 11 instruments placed onboard, 3 of them are dedicated to helioseismology: GOLF, VIRGO and MDI. The first two observe the Sun as a star by integrating the velocity or intensity signal of the visible solar disk into a single point. They are thus similar to any other observation done in asteroseismology. During this review I will present the most important results obtained during the mission concerning the Sun seen as a star and how this results have evolved our thoughts of the inside of our star.Comment: Proceedings of the Stellar Pulsation Conference. Santa Fe. 6 pages, 4 figure

Changes in Mean Global Physical Parameters of Blazhko RR Lyrae stars -- Derived from Multicolor Photometry

We developed an Inverse Photometric method (IPM) to determine global physical parameters of RR Lyrae stars exclusively from multicolor light curves (S\'odor, Jurcsik & Szeidl, 2009, MNRAS, 394, 261). We showed that for good quality photometric observations of unmodulated RRab stars, the IPM gives similarly good results as direct Baade-Wesselink analyses do, but without the need for spectroscopic measurements. In the course of the development, we payed special attention to the applicability of the IPM for modulated RR Lyrae stars. Since there is no simultaneous spectroscopic radial velocity and photometric observations of any Blazhko star with good phase coverage both in pulsation and modulation, which would allow spectroscopic Baade-Wesselink analysis, the IPM is the only possibility today to study changes in the global physical parameters of Blazhko RR Lyrae stars during the modulation cycle. With the IPM, we have studied the extensive multicolor light curves of 4 Blazhko RRab stars we observed with the 24-inch telescope of the Konkoly Observatory during the past 5 years in the frame of the Konkoly Blazhko Survey. Small but unambiguous changes in the pulsation-averaged mean temperature, mean radius and mean luminosity have been detected in each star. Results on these Blazhko stars (SS Cnc, DM Cyg, RR Gem, and MW Lyr) are shown in this paper.Comment: 5 pages, 1 figure. Appeared in STELLAR PULSATION: CHALLENGES FOR THEORY AND OBSERVATION: Proceedings of the International Conference. AIP Conference Proceedings, Volume 1170, pp. 294-298 (2009

The Cepheid Distance Scale: recent progress in fundamental techniques

This review examines progress on the Pop I, fundamental-mode Cepheid distance scale with emphasis on recent developments in geometric and quasi-geometric techniques for Cepheid distance determination. Specifically I examine the surface brightness method, interferometric pulsation method, and trigonometric measurements. The three techniques are found to be in excellent agreement for distance measures in the Galaxy. The velocity p-factor is of crucial importance in the first two of these methods. A comparison of recent determinations of the p-factor for Cepheids demonstrates that observational measures of p and theoretical predictions agree within their uncertainties for Galactic Cepheids.Comment: An invited review at the Santa Fe, NM, conference -- Stellar Pulsation: Challenges for Theory and Observation; May 31-June 5, 2009 10 pages, 8 figure

New Results of the Konkoly Blazhko Group

During the recent years the Konkoly Blazhko Group (PIs Johanna Jurcsik and B\'ela Szeidl, co-workers \'Ad\'am S\'odor, Zsombor Hurta and several undergraduate, graduate students) published new important results of Blazhko variables in 15 reviewed Journal articles. These results utilize multicolor CCD observations obtained with an automatic 60 cm telescope, and also previously unpublished Konkoly archive photometric data. Our light curves are the most extended multicolor data-sets ever obtained for a Blazhko variable, the observations cover each phase of the pulsation and the modulation as well. We have detected many previously unknown features of the light curve modulation, and based on the different band's observations we also revealed the underlying variations of the mean physical parameters during the Blazhko cycle. In my contribution the main achievements of the Konkoly Blazhko Group are summarised.Comment: in "Stellar Pulsation: Challenges for Theory and Observation", Eds. J. Guzik and P. Bradley. (5 pages, 5 figures

Linear Assignment Maps for Correlated System-Environment States

An assignment map is a mathematical operator that describes initial system-environment states for open quantum systems. We reexamine the notion of assignments, introduced by Pechukas, and show the conditions assignments can account for correlations between the system and the environment, concluding that assignment maps can be made linear at the expense of positivity or consistency is more reasonable. We study the role of other conditions, such as consistency and positivity of the map, and show the effects of relaxing these. Finally, we establish a connection between the violation of positivity of linear assignments and the no-broadcasting theorem.Comment: 6 pages, 1 tabl