4,769 research outputs found
Testing convection in stellar models using detached eclipsing binaries
The fundamental properties of detached eclipsing binary stars can be measured
very accurately, which could make them important objects for constraining the
treatment of convection in theoretical stellar models. However, only four or
five pieces of information can be found for the average system, which is not
enough. We discuss studies of more interesting and useful objects: eclipsing
binaries in clusters and eclipsing binaries with pulsating components.Comment: 3 pages, 2 figures, poster proceedings for IAUS 239 (Convection in
Astrophysics). The actual poster, and other resources, can be downloaded from
http://www.astro.keele.ac.uk/~jkt
High-precision photometry of WASP-12 b transits
The transiting extrasolar planet WASP-12 b was found to be one of the most
intensely irradiated exoplanets. It is unexpectedly bloated and is losing mass
that may accrete into the host star. Our aim was to refine the parameters of
this intriguing system and search for signs of transit timing variations. We
gathered high-precision light curves for two transits of WASP-12 b. Assuming
various limb-darkening laws, we generated best-fitting models and redetermined
parameters of the system. Error estimates were derived by the prayer bead
method and Monte Carlo simulations. System parameters obtained by us are found
to agree with previous studies within one sigma. Use of the non-linear
limb-darkening laws results in the best-fitting models. With two new
mid-transit times, the ephemeris was refined to BJD(TDB)=(2454508.97682 +/-
0.00020) + (1.09142245 +/- 0.00000033) E. Interestingly, indications of transit
timing variation are detected at the level of 3.4 sigma. This signal can be
induced by an additional planet in the system. Simplified numerical simulations
shows that a perturber could be a terrestrial-type planet if both planets are
in a low-order orbital resonance. However, we emphasise that further
observations are needed to confirm variation and to constrain properties of the
perturber.Comment: 5 pages, 3 figures, accepted for publication in A&
Observational studies of transiting extrasolar planets (invited review)
The study of transiting extrasolar planets is only 15 years old, but has
matured into a rich area of research. I review the observational aspects of
this work, concentrating on the discovery of transits, the characterisation of
planets from photometry and spectroscopy, the Homogeneous Studies project,
starspots, orbital obliquities, and the atmospheric properties of the known
planets. I begin with historical context and conclude with a glance to a future
of TESS, CHEOPS, Gaia and PLATO.Comment: Invited review paper presented at Living Together: Planets, Host
Stars and Binaries (Litomysl, Czech Republic, September 2014). 15 pages, 9
figures, to be published in ASP Conf. Ser. TEPCat is available at:
http://www.astro.keele.ac.uk/jkt/tepcat
Homogeneous studies of transiting extrasolar planets. III. Additional planets and stellar models
I derive the physical properties of 30 transiting extrasolar planetary
systems using a homogeneous analysis of published data. The light curves are
modelled with the JKTEBOP code, with attention paid to limb darkening and
eccentricity. The light from some systems is contaminated by faint nearby
stars, which if ignored will systematically bias the results. I show that this
must be accounted for using external measurements of the amount of
contaminating light. A contamination of 5% is enough to make the measurement of
a planetary radius 2% too low. The physical properties of the 30 transiting
systems are obtained by interpolating in stellar model predictions to find the
best match to their measured quantities. The error budgets are used to compile
a list of systems which would benefit from additional observations. The
systematic errors arising from the inclusion of stellar models are assessed by
using five different theoretical models. This model dependence sets a lower
limit on the accuracy of measurements of the system properties, and at worst is
1% for the stellar mass. The correlations of planetary surface gravity and mass
with orbital period have significance levels of only 3.1 sigma and 2.3 sigma.
The division of planets into two classes based on Safronov number is
increasingly blurred. Most of the objects studied here would benefit from more
photometry and/or spectroscopy, as well as a better understanding of low-mass
stars.Comment: Accepted for publication in MNRAS. 25 pages, 7 tables, 28 figures.
The physical properties of the 30 transiting planetary systems are tabulated
on pages 19 and 20. An appendix containing extensive results and
bibliographies for each system can be obtained at
http://www.astro.keele.ac.uk/~jkt/pubs/Southworth-TEP3app.pd
Eclipsing Binary Stars: the Royal Road to Stellar Astrophysics
Russell (1948) famously described eclipses as the "royal road" to stellar
astrophysics. From photometric and spectroscopic observations it is possible to
measure the masses and radii (to 1% or better!), and thus surface gravities and
mean densities, of stars in eclipsing binary systems using nothing more than
geometry. Adding an effective temperature subsequently yields luminosity and
then distance (or vice versa) to high precision. This wealth of directly
measurable quantities makes eclipsing binaries the primary source of empirical
information on the properties of stars, and therefore a cornerstone of stellar
astrophysics. In this review paper I summarise the current standing of
eclipsing binary research, present an overview of useful analysis techniques,
and conclude with a glance to the future.Comment: 8 pages, 3 figures. Invited review for the Pas De Deux conference,
Paris, October 201
The DEBCat detached eclipsing binary catalogue
Detached eclipsing binary star systems are our primary source of measured
physical properties of normal stars. I introduce DEBCat: a catalogue of
detached eclipsing binaries with mass and radius measurements to the 2%
precision necessary to put useful constraints on theoretical models of stellar
evolution. The catalogue was begun in 2006, as an update of the compilation by
Andersen (1991). It now contains over 170 systems, and new results are added on
appearance in the refereed literature. DEBCat is available at:
http://www.astro.keele.ac.uk/jkt/debcat/Comment: Poster paper presented at Living Together: Planets, Host Stars and
Binaries (Litomysl, Czech Republic, September 2014). 2 pages, 1 figure, to be
published in ASP Conf. Ser. DEBCat is available at:
http://www.astro.keele.ac.uk/jkt/debcat
School business management: a quiet revolution, part 2
"Revolutions in education tend to occur quietly. The upsurge
in numbers of teaching assistants and higher level classroom
assistants in schools is one such revolution. Another is the
growth of school to school leadership support working beyond
their own school sites to support other leaders and schools in need of help. A third revolution is presently under way; it is the move to the appointment and effective deployment of school business managers (SBMs). - Page 3
Homogeneous studies of transiting planets: an online catalogue
The derived physical properties of the known transiting extrasolar planetary
systems come from a variety of sources, and are calculated using a range of
different methods so are not always directly comparable. I present a catalogue
of the physical properties of 58 transiting extrasolar planet and brown dwarf
systems which have been measured using homogeneous methods, resulting in
quantities which are internally consistent and well-suited to detailed
statistical study. The main results for each object, plus a critical
compilation of literature values for all known systems, have been placed in an
online catalogue. TEPCat can be found at:
http://www.astro.keele.ac.uk/~jkt/tepcat/Comment: Proceedings of IAU Symposium 282. Two pages, one figure. The TEPCat
catalogue can be found at http://www.astro.keele.ac.uk/~jkt/tepcat
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