54 research outputs found
Modeling Kepler Eclipsing Binaries: Homogeneous Inference of Orbital & Stellar Properties
We report on the properties of eclipsing binaries from the Kepler mission
with a newly developed photometric modeling code, which uses the light curve,
spectral energy distribution of each binary, and stellar evolution models to
infer stellar masses without the need for radial velocity measurements. We
present solutions and posteriors to orbital and stellar parameters for 728
systems, forming the largest homogeneous catalogue of full Kepler binary
parameter estimates to date. Using comparisons to published radial velocity
measurements, we demonstrate that the inferred properties (e.g., masses) are
reliable for well-detached main-sequence binaries, which make up the majority
of our sample. The fidelity of our inferred parameters degrades for a subset of
systems not well described by input isochrones, such as short-period binaries
that have undergone interactions, or binaries with post-main sequence
components. Additionally, we identify 35 new systems which show evidence of
eclipse timing variations, perhaps from apsidal motion due to binary tides or
tertiary companions. We plan to subsequently use these models to search for and
constrain the presence of circumbinary planets in Kepler eclipsing binary
systems.Comment: 36 pages, 16 figures; accepted 2019 July 30 to MNRA
On the derivation of radial velocities of SB2 components: a "CCF vs TODCOR" comparison
The radial velocity (RV) of a single star is easily obtained from
cross-correlation of the spectrum with a template, but the treatment of
double-lined spectroscopic binaries (SB2s) is more difficult. Two different
approaches were applied to a set of SB2s: the fit of the cross-correlation
function with two normal distributions, and the cross-correlation with two
templates, derived with the TODCOR code. It appears that the minimum masses
obtained through the two methods are sometimes rather different, although their
estimated uncertainties are roughly equal. Moreover, both methods induce a
shift in the zero point of the secondary RVs, but it is less pronounced for
TODCOR. All-in-all the comparison between the two methods is in favour of
TODCOR.Comment: 5 pages, 4 figures, SF2A Conference 201
Exocomets in the circumstellar gas disk of HD 172555
The source HD172555 is a young A7V star surrounded by a debris disk with a
gaseous component. Here, we present the detection of variable absorption
features detected simultaneously in the Ca II K and H doublet lines (at 3,933
and 3,968 Angstrom). We identified the presence of these absorption signatures
at four different epochs in the 129 HARPS high-resolution spectra gathered
between 2004 and 2011. These transient absorption features are most likely due
to Falling Evaporating Bodies (FEBs, or exocomets) that produce absorbing gas
observed transiting in front of the central star. We also detect a stable Ca II
absorption component at the star's radial velocity. With no corresponding
detection in the Na I line, the resulting very low upper limit for the NaI/CaII
ratio suggests that this absorption is due to circumstellar gas.Comment: Accepted for publication in Astronomy&Astrophysics Letter
CHEOPS's hunt for exocomets: photometric observations of 5 Vul
The presence of minor bodies in exoplanetary systems is in most cases
inferred through infra-red excesses, with the exception of exocomets. Even if
over 35 years have passed since the first detection of exocomets around beta
Pic, only ~ 25 systems are known to show evidence of evaporating bodies, and
most of them have only been observed in spectroscopy. With the appearance of
new high-precision photometric missions designed to search for exoplanets, such
as CHEOPS, a new opportunity to detect exocomets is available. Combining data
from CHEOPS and TESS we investigate the lightcurve of 5 Vul, an A-type star
with detected variability in spectroscopy, to search for non periodic transits
that could indicate the presence of dusty cometary tails in the system. While
we did not find any evidence of minor bodies, the high precision of the data,
along with the combination with previous spectroscopic results and models,
allows for an estimation of the sizes and spatial distribution of the
exocomets.Comment: Accepted for publication in MNRA
Planetary system architectures with low-mass inner planets: Direct imaging exploration of mature systems beyond 1 au
The discovery of planets orbiting at less than 1 au from their host star and
less massive than Saturn in various exoplanetary systems revolutionized our
theories of planetary formation. The fundamental question is whether these
close-in low-mass planets could have formed in the inner disk interior to 1 au,
or whether they formed further out in the planet-forming disk and migrated
inward. Exploring the role of additional giant planets in these systems may
help us to pinpoint their global formation and evolution. We searched for
additional substellar companions by using direct imaging in systems known to
host close-in small planets. The use of direct imaging complemented by radial
velocity and astrometric detection limits enabled us to explore the giant
planet and brown dwarf demographics around these hosts to investigate the
potential connection between both populations. We carried out a direct imaging
survey with VLT/SPHERE to look for outer giant planets and brown dwarf
companions in 27 systems hosting close-in low-mass planets discovered by radial
velocity. Our sample is composed of very nearby (<20pc) planetary systems,
orbiting G-, K-, and M-type mature (0.5-10Gyr) stellar hosts. We performed
homogeneous direct imaging data reduction and analysis to search for and
characterize point sources, and derived robust statistical detection limits. Of
337 point-source detections, we do not find any new bound companions. We
recovered the emblematic very cool T-type brown dwarf GJ229B. Our typical
sensitivities in direct imaging range from 5 to 30 MJup beyond 2 au. The
non-detection of massive companions is consistent with predictions based on
models of planet formation by core accretion. Our pilot study opens the way to
a multi-technique approach for the exploration of very nearby exoplanetary
systems with future ground-based and space observatories.Comment: 49 pages including 31 pages of appendices and references, 31 figures,
A&A, accepte
Exocomets from a Solar System Perspective
Exocomets are small bodies releasing gas and dust which orbit stars other
than the Sun. Their existence was first inferred from the detection of variable
absorption features in stellar spectra in the late 1980s using spectroscopy.
More recently, they have been detected through photometric transits from space,
and through far-IR/mm gas emission within debris disks. As (exo)comets are
considered to contain the most pristine material accessible in stellar systems,
they hold the potential to give us information about early stage formation and
evolution conditions of extra Solar Systems. In the Solar System, comets carry
the physical and chemical memory of the protoplanetary disk environment where
they formed, providing relevant information on processes in the primordial
solar nebula. The aim of this paper is to compare essential compositional
properties between Solar System comets and exocomets. The paper aims to
highlight commonalities and to discuss differences which may aid the
communication between the involved research communities and perhaps also avoid
misconceptions. Exocomets likely vary in their composition depending on their
formation environment like Solar System comets do, and since exocomets are not
resolved spatially, they pose a challenge when comparing them to high fidelity
observations of Solar System comets. Observations of gas around main sequence
stars, spectroscopic observations of "polluted" white dwarf atmospheres and
spectroscopic observations of transiting exocomets suggest that exocomets may
show compositional similarities with Solar System comets. The recent
interstellar visitor 2I/Borisov showed gas, dust and nuclear properties similar
to that of Solar System comets. This raises the tantalising prospect that
observations of interstellar comets may help bridge the fields of exocomet and
Solar System comets.Comment: 25 pages, 3 figures. To be published in PASP. This paper is the
product of a workshop at the Lorentz Centre in Leiden, the Netherland
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