Light Curve Patterns and Seismology of a White Dwarf with Complex Pulsation

The ZZ Ceti star KUV 02464+3239 was observed over a whole season at the mountain station of Konkoly Observatory. A rigorous frequency analysis revealed 6 certain periods between 619 and 1250 seconds, with no shorter period modes present. We use the observed periods, published effective temperature and surface gravity, along with the model grid code of Bischoff-Kim, Montgomery and Winget (2008) to perform a seismological analysis. We find acceptable model fits with masses between 0.60 and 0.70 M_Sun. The hydrogen layer mass of the acceptable models are almost always between 10^-4 and 10^-6 M_*. In addition to our seismological results, we also show our analysis of individual light curve segments. Considering the non-sinusoidal shape of the light curve and the Fourier spectra of segments showing large amplitude variations, the importance of non-linear effects in the pulsation is clearly seen.Comment: 5 pages, 6 figures, in "Stellar Pulsation: Challenges for Theory and Observation", Eds. J. Guzik and P. A. Bradley, AIP

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

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

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

Fundamental Parameters of Cepheids: Masses and Multiplicity

Masses determined from classical Cepheids in binary systems are a primary test of both pulsation and evolutionary calculations. The first step is to determine the orbit from ground-based radial velocities. Complementary satellite data from Hubble, FUSE, IUE, and Chandra provide full information about the system. A summary of recent results on masses is given. Cepheids have also provided copious information about the multiplicity of massive stars, as well as the distribution of mass ratios and separations. This provides some important constraints for star formation scenarios including differences between high and low mass results and differences between close and wide binaries

Impact Ionization and Hot-Electron Injection Derived Consistently from Boltzmann Transport

We develop a quantitative model of the impact-ionizationand hot-electron–injection processes in MOS devices from first principles. We begin by modeling hot-electron transport in the drain-to-channel depletion region using the spatially varying Boltzmann transport equation, and we analytically find a self consistent distribution function in a two step process. From the electron distribution function, we calculate the probabilities of impact ionization and hot-electron injection as functions of channel current, drain voltage, and floating-gate voltage. We compare our analytical model results to measurements in long-channel devices. The model simultaneously fits both the hot-electron- injection and impact-ionization data. These analytical results yield an energydependent impact-ionization collision rate that is consistent with numerically calculated collision rates reported in the literature

IRSF/SIRIUS JHKs near-infrared variable star survey in the Magellanic Clouds

We carried out a NIR variable star survey toward the Large and Small Magellanic Clouds using the InfraRed Survey Facility (IRSF) at Sutherland, South African Astronomical Observatory. This survey project was initiated in Dember 2000, and since then, we kept monitoring a total area of 3 square degrees along the LMC bar and also an area of 1 square degree around the center of the SMC, sufficiently large to do statistical analysis and to make complete catalog of variable red giants in the Magellanic Clouds. The detection limits (S/N=10) of the survey are 17.0, 16.5 and 15.5 at J, H and Ks, respectively. In this article, we present some results on infrared variables that are not detected by the previous optical surveys. We show that they do not fall on the standard period-Ks magnitude relation for Mira-type variables pulsating in the fundamental mode.Comment: 3 pages, 2 figures. To appear in "Stellar Pulsation: Challenges for Theory and Observation", Eds. J. Guzik and P. Bradle