1,889 research outputs found
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unpublished Konkoly archive photometric data.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
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
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
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