172 research outputs found
Radial velocity measurements of a sample of K-giants with the Hobby-Eberly telescope
We present motivation and initial results of a large RV survey of K giants aimed at a detection of low-mass companions. The survey, performed with the Hobby-Eberly Telescope, utilizes high resolution (60,000) spectra for high precision radial velocity measurements. The primary goal of the survey is the selection of astrometrically stable reference stars for the Extrasolar Planet Interferometric Survey key project to be carried out with the Space Interferometry Mission
Tidal interactions of close-in extrasolar planets: the OGLE cases
Close-in extrasolar planets experience extreme tidal interactions with their
host stars. This may lead to a reduction of the planetary orbit and a spin-up
of stellar rotation. Tidal interactions have been computed for a number of
extrasolar planets in circular orbits within 0.06 AU, namely for OGLE-TR-56 b.
We compare our range of the tidal dissipation value with two dissipation models
from Sasselov (2003) and conclude that our choices are equivalent to these
models. However, applied to the planet OGLE-TR-56 b, we find in contrast to
Sasselov (2003) that this planet will spiral-in toward the host star in a few
billion years. We show that the average and maximum value of our range of
dissipation are equivalent to the linear and quadratic dissipation models of
Sasselov (2003). Due to limitations in the observational techniques, we do not
see a possibility to distinguish between the two dissipation models as outlined
by Sasselov (2003). OGLE-TR-56 b may therefore not serve as a test case for
dissipation models. The probable existence of OGLE-TR-3 b at 0.02 AU and the
discovery of OGLE-TR-113 b at 0.023 AU and OGLE-TR-132 b at 0.03 AU may also
counter Sasselovs (2003) assumption of a pile-up stopping boundary at 0.04 AU.Comment: 7 pages, 4 figure
Constraining the relative inclinations of the planets B and C of the millisecond pulsar PSR B1257+12
We investigate on the relative inclination of the planets B and C orbiting
the pulsar PSR B1257+12 in connection with potential violations of the
equivalence principle (Abridged).Comment: LaTex2e, 10 pages, 1 table, 3 figures, 17 references. Small stylistic
changes. Version to appear in Journal of Astrophysics and Astronomy (JAA
Orbital and physical parameters of eclipsing binaries from the All-Sky Automated Survey catalogue - VI. AK Fornacis - a rare, bright K-type eclipsing binary
We present the results of the combined photometric and spectroscopic analysis
of a bright (V=9.14), nearby (d=31 pc), late-type detached eclipsing binary AK
Fornacis. This P=3.981 d system has not been previously recognised as a
double-lined spectroscopic binary, and this is the first full physical model of
this unique target. With the FEROS, CORALIE and HARPS spectrographs we
collected a number of high-resolution spectra in order to calculate radial
velocities of both components of the binary. Measurements were done with our
own disentangling procedure and the TODCOR technique, and were later combined
with the photometry from the ASAS and SuperWASP archives. We also performed an
atmospheric analysis of the component spectra with the Spectroscopy Made Easy
(SME) package. Our analysis shows that AK For consists of two active, cool
dwarfs having masses of and
M and radii of and
R, slightly less metal abundant than the Sun. Parameters of both
components are well reproduced by the models.
AK For is the brightest system among the known eclipsing binaries with K or M
type stars. Its orbital period is one of the longest and rotational velocities
one of the lowest, which allows us to obtain very precise radial velocity
measurements. The precision in physical parameters we obtained places AK For
among the binaries with the best mass measurements in the literature. It also
fills the gap in our knowledge of stars in the range of 0.5-0.8 M, and
between short and long-period systems. All this makes AK For a unique benchmark
for understanding the properties of low-mass stars.Comment: 9 pages, 11 figures, 3 tables, accpeted for publication in A&
Orbital and physical parameters of eclipsing binaries from the ASAS catalogue -- I. A sample of systems with components' masses between 1 and 2 M
We derive the absolute physical and orbital parameters for a sample of 18
detached eclipsing binaries from the \emph{All Sky Automated Survey} (ASAS)
database based on the available photometry and our own radial velocity
measurements. The radial velocities (RVs) are computed using spectra we
collected with the 3.9-m Anglo-Australian Telescope and its \emph{University
College London Echelle Spectrograph} and the 1.9-m SAAO Radcliffe telescope and
its \emph{Grating Instrument for Radiation Analysis with a Fibre Fed Echelle}.
In order to obtain as precise RVs as possible, most of the systems were
observed with an iodine cell available at the AAT/UCLES and/or analyzed using
the two-dimensional cross-correlation technique (TODCOR). The RVs were measured
with TODCOR using synthetic template spectra as references. However, for two
objects we used our own approach to the tomographic disentangling of the binary
spectra to provide observed template spectra for the RV measurements and to
improve the RV precision even more. For one of these binaries, AI Phe, we were
able to the obtain an orbital solution with an RV of 62 and 24 m s
for the primary and secondary respectively. For this system, the precision in
is 0.08%. For the analysis, we used the photometry available in
the ASAS database. We combined the RV and light curves using PHOEBE and JKTEBOP
codes to obtain the absolute physical parameters of the systems. Having precise
RVs we were able to reach 0.2 % precision (or better) in masses in
several cases but in radii, due to the limited precision of the ASAS
photometry, we were able to reach a precision of only 1% in one case and 3-5 %
in a few more cases. For the majority of our objects, the orbital and physical
analysis is presented for the first time.Comment: 16 pages, 2 figures, 6 tables in the main text, 1 table in appendix,
to appear in MNRA
- …