93 research outputs found
Asteroseismology of the {\it Kepler} target KIC\,9204718
The high precision data obtained by the {\it Kepler} satellite allows us to
detect hybrid type pulsator candidates more accurately than the data obtained
by ground-based observations. In this study, we present preliminary results on
the new analysis of the {\it Kepler} light curve and high resolution
spectroscopic observations of pulsating Am star KIC\,9204718. Our tentative
analysis therefore show that the star has hybrid pulsational characteristics.Comment: 'Proceedings of Wide Field variability surveys : a 21 st Century 22nd
Los Alamos Stellar Pulsation Conference San Pedro De Atacama ,Chile Nov
28-Dec 2, 2016' to be published by the EPJ Web of Conference
Photometric and spectroscopic variability of 53 Per
A new investigation of the variability of the SPB-type star 53 Per is
presented. The analysis of the BRITE photometry allowed us to determine eight
independent frequencies and the combination one. Five of these frequencies and
the combination one were not known before. In addition, we gathered more than
1800 new moderate and high-resolution spectra of 53 Per spread over
approximately six months. Their frequency analysis revealed four independent
frequencies and the combination one, all consistent with the BRITE results.Comment: 2 pages, accepted for publication in the Proceedings of the PAS
(Proc. of the 2nd BRITE Science conference, Innsbruck
Mode identification in the high-amplitude {\delta} Scuti star V2367 Cyg
We report on a multi-site photometric campaign on the high-amplitude
Scuti star V2367 Cyg in order to determine the pulsation modes. We also used
high-dispersion spectroscopy to estimate the stellar parameters and projected
rotational velocity. Time series multicolour photometry was obtained during a
98-d interval from five different sites. These data were used together with
model atmospheres and non-adiabatic pulsation models to identify the spherical
harmonic degree of the three independent frequencies of highest amplitude as
well as the first two harmonics of the dominant mode. This was accomplished by
matching the observed relative light amplitudes and phases in different
wavebands with those computed by the models. In general, our results support
the assumed mode identifications in a previous analysis of Kepler data.Comment: 9 pages, 5 figures, 4 tables. Accepted for publication in MNRA
Rotational velocities of the giants in symbiotic stars: III. Evidence of fast rotation in S-type symbiotics
We have measured the projected rotational velocities (vsini) in a number of
symbiotic stars and M giants using high resolution spectroscopic observations.
On the basis of our measurements and data from the literature, we compare the
rotation of mass-donors in symbiotics with vsini of field giants and find that:
(1) the K giants in S-type symbiotics rotate at vsini>4.5 km/s, which is 2-4
times faster than the field K giants;
(2) the M giants in S-type symbiotics rotate on average 1.5 times faster than
the field M giants. Statistical tests show that these differences are highly
significant: p-value < 0.001 in the spectral type bins K2III-K5III,
M0III-M6III, and M2III-M5III;
(3) our new observations of D'-type symbiotics also confirm that they are
fast rotators.
As a result of the rapid rotation, the cool giants in symbiotics should have
3-30 times larger mass loss rates. Our results suggest also that bipolar
ejections in symbiotics seem to happen in objects where the mass donors rotate
faster than the orbital period.
All spectra used in our series of papers can be obtained upon request from
the authors.Comment: MNRAS (accepted), 7 pages, 5 figure
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