799 research outputs found
SOAP-T: A tool to study the light-curve and radial velocity of a system with a transiting planet and a rotating spotted star
We present an improved version of SOAP (Boisse et al. 2012) named "SOAP-T",
which can generate the radial velocity variations and light-curves for systems
consisting of a rotating spotted star with a transiting planet. This tool can
be used to study the anomalies inside transit light-curves and the
Rossiter-McLaughlin effect, to better constrain the orbital configuration and
properties of planetary systems and active zones of their host stars. Tests of
the code are presented to illustrate its performance and to validate its
capability when compared with analytical models and real data. Finally, we
apply SOAP-T to the active star, HAT-P-11, observed by the NASA Kepler space
telescope and use this system to discuss the capability of this tool in
analyzing light-curves for the cases where the transiting planet overlaps with
the star's spots.Comment: 9 pages, 7 figures, accepted for publication in Astronomy and
Astrophysic
A Physically-Motivated Photometric Calibration of M Dwarf Metallicity
The location of M dwarfs in the V-K_s--M_Ks color-magnitude diagram (CMD) has
been shown to correlate with metallicity. We demonstrate that previous
empirical photometric calibrations of M dwarf metallicity exploiting this
correlation systematically underestimate or overestimate metallicity at the
extremes of their range. We improve upon previous calibrations in three ways.
We use both a volume-limited and kinematically-matched sample of F and G dwarfs
from the Geneva-Copehnagen Survey (GCS) to infer the mean metallicity of M
dwarfs in the Solar Neighborhood, we use theoretical models of M dwarf
interiors and atmospheres to determine the effect of metallicity on M dwarfs in
the V-K_s--M_Ks CMD, and we base our final calibration purely on
high-resolution spectroscopy of FGK primaries with M dwarf companions. As a
result, we explain an order of magnitude more of the variance in the
calibration sample than previous photometric calibrations. We
non-parametrically quantify the significance of the observation that M dwarfs
that host exoplanets are preferentially in a region of the V-K_s--M_Ks plane
populated by metal-rich M dwarfs. We find that the probability p that
planet-hosting M dwarfs are distributed across the V-K_s--M_Ks CMD in the same
way as field M dwarfs is p = 0.06 +/- 0.008. Interestingly, the subsample of M
dwarfs that host Neptune and sub-Neptune mass planets may also be
preferentially located in the region of the V-K_s--M_Ks plane populated by
high-metallicity M dwarfs. The probability of this occurrence by chance is p =
0.40 +/- 0.02, and this observation hints that low-mass planets may be more
likely to be found around metal-rich M dwarfs. An increased rate of low-mass
planet occurrence around metal-rich M dwarfs would be a natural consequence of
the core-accretion model of planet formation. (abridged)Comment: 10 pages, 4 figures, and 1 table in A&A format; accepted for
publication in A&
Life-stage specific environments in a cichlid fish: Implications for inducible maternal effects
Through environmentally induced maternal effects females may fine-tune their offspring's phenotype to the conditions offspring will encounter after birth. If juvenile and adult ecologies differ, the conditions that mothers experienced as juveniles may better predict their offspring's environment than the adult females' ambient conditions. Maternal effects induced by the environment experienced by females during their early ontogeny should evolve when three ecological conditions are met: (i) Adult ecology does not predict the postnatal environmental conditions of offspring; (ii) Environmental conditions for juveniles are correlated across successive generations; and (iii) Juveniles occasionally settle in conditions that differ from the juvenile habitat of their mothers. By combining size-structured population counts, ecological surveys and a genetic analysis of population structure we provide evidence that all three conditions hold for Simochromis pleurospilus, a cichlid fish in which mothers adjust offspring quality to their own juvenile ecology. Adults of many species cannot predict offspring's environment from ambient cues. Hence we predict that life-stage specific maternal effects are common in animals. Therefore, it is important to incorporate parental ontogeny in the study of parental effects when juveniles and adults inhabit different environments
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
SWEET-Cat: A catalogue of parameters for Stars With ExoplanETs I. New atmospheric parameters and masses for 48 stars with planets
Due to the importance that the star-planet relation has to our understanding
of the planet formation process, the precise determination of stellar
parameters for the ever increasing number of discovered extra-solar planets is
of great relevance. Furthermore, precise stellar parameters are needed to fully
characterize the planet properties. It is thus important to continue the
efforts to determine, in the most uniform way possible, the parameters for
stars with planets as new discoveries are announced. In this paper we present
new precise atmospheric parameters for a sample of 48 stars with planets. We
then take the opportunity to present a new catalogue of stellar parameters for
FGK and M stars with planets detected by radial velocity, transit, and
astrometry programs. Stellar atmospheric parameters and masses for the 48 stars
were derived assuming LTE and using high resolution and high signal-to-noise
spectra. The methodology used is based on the measurement of equivalent widths
for a list of iron lines and making use of iron ionization and excitation
equilibrium principles. For the catalog, and whenever possible, we used
parameters derived in previous works published by our team, using well defined
methodologies for the derivation of stellar atmospheric parameters. This set of
parameters amounts to over 65% of all planet host stars known, including more
than 90% of all stars with planets discovered through radial velocity surveys.
For the remaining targets, stellar parameters were collected from the
literature.Comment: Astronomy & Astrophysics, accepted for publicatio
The HARPS search for southern extrasolar planets XXV. Results from the metal-poor sample
Searching for extrasolar planets around stars of different metallicity may
provide strong constraints to the models of planet formation and evolution. In
this paper we present the overall results of a HARPS (a high-precision
spectrograph mostly dedicated to deriving precise radial velocities) program to
search for planets orbiting a sample of 104 metal-poor stars (selected [Fe/H]
below -0.5). Radial velocity time series of each star are presented and
searched for signals using several statistical diagnostics. Stars with detected
signals are presented, including 3 attributed to the presence of previously
announced giant planets orbiting the stars HD171028, HD181720, and HD190984.
Several binary stars and at least one case of a coherent signal caused by
activity-related phenomena are presented. One very promising new, possible
giant planet orbiting the star HD107094 is discussed, and the results are
analyzed in light of the metallicity-giant planet correlation. We conclude that
the frequency of giant planets orbiting metal-poor stars may be higher than
previously thought, probably reflecting the higher precision of the HARPS
survey. In the metallicity domain of our sample, we also find evidence that the
frequency of planets is a steeply rising function of the stellar metal content,
as found for higher metallicity stars.Comment: Accepted for publication in A&
The HARPS search for southern extra-solar planets I. HD330075 b: a new 'hot Jupiter'
We report on the first extra-solar planet discovered with the brand new HARPS
instrument. The planet is a typical 'hot Jupiter' with m2sini = 0.62 MJup and
an orbital period of 3.39 days, but from the photometric follow-up of its
parent star HD330075 we can exclude the presence of a transit. The induced
radial-velocity variations exceed 100 m/s in semi-amplitude and are easily
detected by state-of-the-art spectro-velocimeters. Nevertheless, the faint
magnitude of the parent star (V = 9.36) benefits from the efficient instrument:
With HARPS less than 10 observing nights and 3 hours of total integration time
were needed to discover the planet and characterize its orbit. The orbital
parameters determined from the observations made during the first HARPS run in
July 2003 have been confirmed by 7 additional observations carried out in
February 2004. The bisector analysis and a photometric follow-up give no hint
for activity-induced radial-velocity variations, indicating that the velocity
curve is best explained by the presence of a low-mass companion to the star. In
this paper we present a set of 21 measurements of excellent quality with
weighted rms as low as 2.0 m/s. These measurements lead to a well defined orbit
and consequently to the precise orbital parameters determination of the
extra-solar planet HD330075b.Comment: 5 pages, 2 figures, accepted for publication by Astronomy and
Astrophysics, see also http://obswww.unige.ch/~udry/planet/planet.htm
Stellar Variabilities: Challenges for the Detection and Characterization of Exoplanets
The photometric and RV techniques, although extremely efficient to detect and characterize planets, are, however, indirect techniques (as well as astrometry). Phenomena such as stellar pulsation, inhomogeneous convection, spots or magnetic cycles can prevent us from finding planets or they might degrade the parameters estimation. We will consider the challenges related to the knowledge of stellar activity for the next decade: detect telluric planets in the habitable zone of their stars (from G to M dwarfs), understand the activity in the low-mass end of M dwarf (on which will focus future near-infrared high-resolution spectrograph like SPIRou or CARMENES), limitation to the process of summing several transit observations (in order to characterize the atmospheric components) due to the variability of stellar activity (from the ground or with Spitzer or JWST), as well as the methods proposed and used to overcome this issu
How the planetary research helps to the stellar dynamo understanding
Most of the exoplanet science is dependent on the stellar knowledge. One of them that has to be understood is the magnetic activity when we search for planets with radial velocity or photometry measurements. The main shape of stellar activity and spots properties have to be understood, for example, to choose the best targets to search for low-mass planets in the habitable zone or to derive the accurate parameters of a planetary system. With that aim, we show in this presentation how these studies lead to give clues on spots latitudes and on the long term variation of stellar activity. The properties of magnetic activity on the low rotators solar-type stars are not easily reachable by other techniques (spectropolarimetry or Doppler imaging) and these studies should be used to constrain theories of stellar dynam
Extrasolar planets and brown dwarfs around A--F type stars. VIII. A giant planet orbiting the young star HD113337
In the frame of the search for extrasolar planets and brown dwarfs around
early-type main-sequence stars, we present the detection of a giant planet
around the young F-type star HD113337. We estimated the age of the system to be
150 +100/-50 Myr. Interestingly, an IR excess attributed to a cold debris disk
was previously detected on this star. The SOPHIE spectrograph on the 1.93m
telescope at Observatoire de Haute-Provence was used to obtain ~300 spectra
over 6 years. We used our SAFIR tool, dedicated to the spectra analysis of A
and F stars, to derive the radial velocity variations. The data reveal a 324.0
+1.7/-3.3 days period that we attribute to a giant planet with a minimum mass
of 2.83 +- 0.24 Mjup in an eccentric orbit with e=0.46 +- 0.04. A long-term
quadratic drift, that we assign to be probably of stellar origin, is
superimposed to the Keplerian solution.Comment: 7 pages, 4 figure
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