58 research outputs found
Modeling the RV and BVS of active stars
We present a method of modeling the radial velocity (RV) measurements which
can be useful in searching for planets hosted by chromospherically active
stars. We assume that the observed RV signal is induced by the reflex motion of
a star as well as by distortions of spectral line profiles, measured by the
Bisector Velocity Span (BVS). The RVs are fitted with a common planetary model
including RV correction term depending linearly on the BVS, which accounts for
the stellar activity. The coefficient of correlation is an additional free
parameter of the RV model. That approach differs from correcting the RVs before
or after fitting the "pure" planetary model. We test the method on simulated
data derived for single-planet systems. The results are compared with the
outcomes of algorithms found in the literature.Comment: 6 pages, 2 figures, proceedings of the conference "Extrasolar planets
in multi-body systems: theory and observations" (August 2008, Torun, Poland
On the habitability of the OGLE-2006-BLG-109L planetary system
We investigate the dynamics of putative Earth-mass planets in the habitable
zone (HZ) of the extrasolar planetary system OGLE-2006-BLG-109L, a close analog
of the Solar system. Our work is inspired by work of Malhotra and Minton
(2008). Using the linear Laplace-Lagrange theory, they identified a strong
secular resonance that may excite large eccentricity of orbits in the HZ.
However, due to uncertain or unconstrained orbital parameters, the sub-system
of Jupiters may be found in dynamically active region of the phase space
spanned by low-order mean-motion resonances. To generalize this secular model,
we construct a semi-analytical averaging method in terms of the restricted
problem. The secular orbits of large planets are approximated by numerically
averaged osculating elements. They are used to calculate the mean orbits of
terrestrial planets by means of a high-order analytic secular theory developed
in our previous works. We found regions in the parameter space of the problem
in which stable, quasi-circular orbits in the HZ are permitted. The excitation
of eccentricity in the HZ strongly depends on the apsidal angle of jovian
orbits. For some combinations of that angle, eccentricities and semi-major axes
consistent with the observations, a terrestrial planet may survive in low
eccentric orbits. We also study the effect of post-Newtonian gravity correction
on the innermost secular resonance.Comment: 9 pages, 9 figures, accepted to Monthly Notices of the Royal
Astronomical Societ
Modeling radial velocities of HD 240210 with the Genetic Algorithm
More than 450 extrasolar planets are known to date. To detect these intriguing objects many photometric and radial velocity surveys are in progress. We developed the Keplerian FITting code, to model published and available radial velocity data. This code is based on a hybrid, quasi-global optimization technique relying on the Genetic Algorithms and simplex algorithm. Here, we re-analyse the radial velocity data of evolved K3III star HD 240210. We found three equally good solutions which might be interpreted as signals of twoplanet systems. Remarkably, one of these best-fits describes long-term stable two-planet system, involved in the 2:1 mean motion resonance. It may be the first instance of this strong mean motion resonance in a multi-planet system hosted by evolved star, as the 2:1 mean motion resonance configurations are already found around a few sun-like dwarfs
Planet-star interactions with precise transit timing: II. The radial-velocity tides and a tighter constraint on the orbital decay rate in the WASP-18 system
From its discovery, the WASP-18 system with its massive transiting planet on a tight orbit was identified as a unique laboratory for studies on tidal planet-star interactions. In an analysis of Doppler data, which include five new measurements obtained with the HIRES/Keck-I instrument between 2012 and 2018, we show that the radial velocity signal of the photosphere following the planetary tidal potential can be distilled for the host star. Its amplitude is in agreement with both theoretical predictions of the equilibriumtide approximation and an ellipsoidalmodulation observed in an orbital phase curve. Assuming a circular orbit, we refine system parameters using photometric time series from TESS. With a new ground-based photometric observation, we extend the span of transit timing observations to 28 yr in order to probe the rate of the orbital period shortening. Since we found no departure from a constant-period model, we conclude that the modified tidal quality parameter of the host star must be greater than 3.9×106with 95% confidence. This result is in line with conclusions drawn from studies of the population of hot Jupiters, predicting that the efficiency of tidal dissipation is 1 or 2 orders of magnitude weaker. As the WASP-18 system is one of the prime candidates for detection of orbital decay, further timing observations are expected to push the boundaries of our knowledge on stellar interiors.Fil: Maciejewski, G.. Nicolaus Copernicus University; PoloniaFil: Knutson, H. A.. California Institute of Technology; Estados UnidosFil: Howard, A. W.. University of Hawaii; Estados UnidosFil: Isaacson, H.. University of California at Berkeley; Estados UnidosFil: Fernandez Lajus, Eduardo Eusebio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Di Sisto, Romina Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Migaszewski, C.. Nicolaus Copernicus University; Poloni
A resonant chain of four transiting, sub-Neptune planets
Surveys have revealed many multi-planet systems containing super-Earths and Neptunes in orbits of a few days to a few months. There is debate whether in situ assembly or inward migration is the dominant mechanism of the formation of such planetary systems. Simulations suggest that migration creates tightly packed systems with planets whose orbital periods may be expressed as ratios of small integers (resonances), often in a many-planet series (chain). In the hundreds of multi-planet systems of sub-Neptunes, more planet pairs are observed near resonances than would generally be expected, but no individual system has hitherto been identified that must have been formed by migration. Proximity to resonance enables the detection of planets perturbing each other. Here we report transit timing variations of the four planets in the Kepler-223 system, model these variations as resonant-angle librations, and compute the long-term stability of the resonant chain. The architecture of Kepler-223 is too finely tuned to have been formed by scattering, and our numerical simulations demonstrate that its properties are natural outcomes of the migration hypothesis. Similar systems could be destabilized by any of several mechanisms, contributing to the observed orbital-period distribution, where many planets are not in resonances. Planetesimal interactions in particular are thought to be responsible for establishing the current orbits of the four giant planets in the Solar System by disrupting a theoretical initial resonant chain similar to that observed in Kepler-223
The Calan-Hertfordshire Extrasolar Planet Search
The detailed study of the exoplanetary systems HD189733 and HD209458 has
given rise to a wealth of exciting information on the physics of exoplanetary
atmospheres. To further our understanding of the make-up and processes within
these atmospheres we require a larger sample of bright transiting planets. We
have began a project to detect more bright transiting planets in the southern
hemisphere by utilising precision radial-velocity measurements. We have
observed a constrained sample of bright, inactive and metal-rich stars using
the HARPS instrument and here we present the current status of this project,
along with our first discoveries which include a brown dwarf/extreme-Jovian
exoplanet found in the brown dwarf desert region around the star HD191760 and
improved orbits for three other exoplanetary systems HD48265, HD143361 and
HD154672. Finally, we briefly discuss the future of this project and the
current prospects we have for discovering more bright transiting planets.Comment: 4 pages, 2 figures, to appear in the conference proceedings "New
Technologies for Probing the Diversity of Brown Dwarfs and Exoplanets"
Shanghai 200
Populations of planets in multiple star systems
Astronomers have discovered that both planets and binaries are abundant
throughout the Galaxy. In combination, we know of over 100 planets in binary
and higher-order multi-star systems, in both circumbinary and circumstellar
configurations. In this chapter we review these findings and some of their
implications for the formation of both stars and planets. Most of the planets
found have been circumstellar, where there is seemingly a ruinous influence of
the second star if sufficiently close (<50 AU). Hosts of hot Jupiters have been
a particularly popular target for binary star studies, showing an enhanced rate
of stellar multiplicity for moderately wide binaries (>100 AU). This was
thought to be a sign of Kozai-Lidov migration, however recent studies have
shown this mechanism to be too inefficient to account for the majority of hot
Jupiters. A couple of dozen circumbinary planets have been proposed around both
main sequence and evolved binaries. Around main sequence binaries there are
preliminary indications that the frequency of gas giants is as high as those
around single stars. There is however a conspicuous absence of circumbinary
planets around the tightest main sequence binaries with periods of just a few
days, suggesting a unique, more disruptive formation history of such close
stellar pairs.Comment: Invited review chapter, accepted for publication in "Handbook of
Exoplanets", ed. H. Deeg & J. A. Belmont
- …