2,585 research outputs found
Mode identification for Balloon 090100001 using combined multicolour photometry and spectroscopy
In this paper, we show that method of mode identification using combined
multicolour photometry and spectroscopy can be successfully applied to the
pulsating subdwarf B star Balloon 090100001. The method constrains the
spherical degree, l.We confirm that the dominant mode is radial and we show
that for some other modes the method provides values of l consistent with the
observed rotationally split triplet. Moreover, we derive a radius variation of
1.7 per cent for the dominant mode. The identification opens the possibility
for constraining the internal structure of the star by means of seismic
methods.Comment: MNRAS, in press, already at the online-early stag
Time resolved spectroscopy of the multiperiodic pulsating subdwarf B star PG1605+072
We present results for the 2m spectroscopic part of the MultiSite
Spectroscopic Telescope campaign, which took place in May/June 2002. In order
to perform an asteroseismological analysis on the multiperiodic pulsating
subdwarf B star PG 1605+072 we used over 150 hours of time resolved
spectroscopy in order to search for and analyse line profile variations by
using phase binning. We succeeded in finding variations in effective
temperature and gravity for four modes. A pilot analysis using the
\textit{BRUCE} and \textit{KYLIE} programs and assuming strong rotation and low
inclination favours models with or with .Comment: 2 pages, 2 figures, proceedings of the "Vienna Workshop on the Future
of Asteroseismology", to appear in Communications in Asteroseismology v. 14
Evidence for a planetary mass third body orbiting the binary star KIC 5095269
In this paper, we report the evidence for a planetary mass body orbiting the
close binary star KIC 5095269. This detection arose from a search for eclipse
timing variations among the more than 2,000 eclipsing binaries observed by
Kepler. Light curve and periodic eclipse time variations have been analysed
using Systemic and a custom Binary Eclipse Timings code based on the Transit
Analysis Package which indicates a object orbiting every
around a primary and secondary in an
18.6d orbit. A dynamical integration over years suggests a stable
orbital configuration. Radial velocity observations are recommended to confirm
the properties of the binary star components and the planetary mass of the
companion.Comment: 8 pages, 7 figures, Accepted for publication in MNRA
The MultiSite Spectroscopic Telescope campaign: 2m spectroscopy of the V361 Hya variable PG1605+072
We present results and analysis for the 2m spectroscopic part of the
MultiSite Spectroscopic Telescope (MSST) campaign undertaken in May/June 2002.
The goal of the project was to observe the pulsating subdwarf B star PG1605+072
simultaneously in velocity and photometry and to resolve as many of the >50
known modes as possible, which will allow a detailed asteroseismological
analysis. We have obtained over 150 hours of spectroscopy, leading to an
unprecedented noise level of only 207m/s. We report here the detection of 20
frequencies in velocity, with two more likely just below our detection
threshold. In particular, we detect 6 linear combinations, making PG1605+072
only the second star known to show such frequencies in velocity. We investigate
the phases of these combinations and their parent modes and find relationships
between them that cannot be easily understood based on current theory. These
observations, when combined with our simultaneous photometry, should allow
asteroseismology of this most complicated of sdB pulsators.Comment: 9 pages, 5 figures, accepted for publication in A&A; Figure 1 at
lower resolution than accepted versio
Abundance studies of sdB stars using UV echelle HST/STIS spectroscopy
Aims: We test the hypothesis that the pulsations in sdB stars are correlated
with the surface abundances of iron-group elements. Any correlation might
explain why, when given two spectroscopically similar stars, one will pulsate
while the other will not. Methods: We have obtained high-resolution ultraviolet
spectra two pulsating and three non-pulsating sdB stars using the Space
Telescope Imaging Spectrograph onboard the Hubble Space Telescope. We
determined abundances for 25 elements including the iron group and even heavier
elements such as tin and lead using LTE curve-of-growth and spectrum synthesis
techniques. Results: We find no clear correlation between pulsations and metal
abundances, and we comment on the resulting implications, including whether it
is possible to determine the difference between a pulsating and a non-pulsating
sdB spectroscopically. In addition to the main goal of our observations, we
have also investigated the effect of supersolar metallicity on fundamental
parameter determination, possible trends with iron abundance, and the
hypothesis that weak winds may be selectively removing elements from the
stellar envelopes. These effects provide challenges to stellar atmosphere
modelling and diffusion models for sdB stars.Comment: 14 pages, 12 figures, accepted for publication in A&
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