318 research outputs found
Measuring the orbit shrinkage rate of hot Jupiters due to tides
A tidal interaction between a star and a close-in exoplanet leads to
shrinkage of the planetary orbit and eventual tidal disruption of the planet.
Measuring the shrinkage of the orbits will allow for the tidal quality
parameter of the star () to be measured, which is an important
parameter to obtain information about stellar interiors. We analyse data from
TESS for two targets known to host close-in hot Jupiters, WASP-18 and WASP-19,
to measure the current limits on orbital period variation and provide new
constrains on . We modelled the transit shape using all the available
TESS observations and fitted the individual transit times of each transit. We
used previously published transit times together with our results to fit two
models, a constant period model, and a quadratic orbital decay model, MCMC
algorithms. We find period change rates of for
WASP-18b and for WASP-19b and we do not find
significant evidence of orbital decay in these targets. We obtain new lower
limits for of in WASP-18 and
in WASP-19, corresponding to upper limits of the
orbital decay rate of and ,
respectively, with a 95% confidence level. We compare our results with other
relevant targets for tidal decay studies. We find that the orbital decay rate
in both WASP-18b and WASP-19b appears to be smaller than the measured orbital
decay of WASP-12b. We show that the minimum value of in WASP-18 is
two orders of magnitude higher than that of WASP-12, while WASP-19 has a
minimum value one order of magnitude higher, which is consistent with other
similar targets. Further observations are required to constrain the orbital
decay of WASP-18 and WASP-19.Comment: 10 pages plus 5-page appendix. To be published in Astronomy and
Astrophysic
Asymmetry in the atmosphere of the ultra-hot Jupiter WASP-76 b
Context. WASP-76 b has been a recurrent subject of study since the detection of a signature in high-resolution transit spectroscopy data indicating an asymmetry between the two limbs of the planet. The existence of this asymmetric signature has been confirmed by multiple studies, but its physical origin is still under debate. In addition, it contrasts with the absence of asymmetry reported in the infrared (IR) phase curve.
Aims. We provide a more comprehensive dataset of WASP-76 b with the goal of drawing a complete view of the physical processes at work in this atmosphere. In particular, we attempt to reconcile visible high-resolution transit spectroscopy data and IR broadband phase curves.
Methods. We gathered 3 phase curves, 20 occultations, and 6 transits for WASP-76 b in the visible with the CHEOPS space telescope. We also report the analysis of three unpublished sectors observed by the TESS space telescope (also in the visible), which represents 34 phase curves.
Results. WASP-76 b displays an occultation of 260 ± 11 and 152 ± 10 ppm in TESS and CHEOPS bandpasses respectively. Depending on the composition assumed for the atmosphere and the data reduction used for the IR data, we derived geometric albedo estimates that range from 0.05 ± 0.023 to 0.146 ± 0.013 and from <0.13 to 0.189 ± 0.017 in the CHEOPS and TESS bandpasses, respectively. As expected from the IR phase curves, a low-order model of the phase curves does not yield any detectable asymmetry in the visible either. However, an empirical model allowing for sharper phase curve variations offers a hint of a flux excess before the occultation, with an amplitude of ~40 ppm, an orbital offset of ~ â30°, and a width of ~20Âș. We also constrained the orbital eccentricity of WASP-76 b to a value lower than 0.0067, with a 99.7% confidence level. This result contradicts earlier proposed scenarios aimed at explaining the asymmetry observed in high-resolution transit spectroscopy.
Conclusions. In light of these findings, we hypothesise that WASP-76 b could have night-side clouds that extend predominantly towards its eastern limb. At this limb, the clouds would be associated with spherical droplets or spherically shaped aerosols of an unknown species, which would be responsible for a glory effect in the visible phase curves
Masses for the seven planets in K2-32 and K2-233. Four diverse planets in resonant chain and the first young rocky worlds
High-precision planetary densities are key to derive robust atmospheric
properties for extrasolar planets. Measuring precise masses is the most
challenging part, especially in multi-planetary systems. We measure the masses
and densities of a four-planet near resonant chain system (K2-32), and a young
( Myr old) planetary system consisting of three close-in small planets
(K2-233). We obtained 199 new HARPS observations for K2-32 and 124 for K2-233
covering a more than three year baseline. We find that K2-32 is a compact
scaled-down version of the Solar System's architecture, with a small rocky
inner planet (M~M, P~days)
followed by an inflated Neptune-mass planet
(M~M, P~days) and two external
sub-Neptunes (M~M, P~days;
M~M, P~days). K2-32 becomes one of the
few multi-planetary systems with four or more planets known with measured
masses and radii. Additionally, we constrain the masses of the three planets in
K2-233. For the two inner Earth-size planets we constrain their masses to be
smaller than M M (P~days), M
M (P~days). The outer planet is a sub-Neptune size
planet with an inferred mass of M M
(M M, P~days). Our observations of these two
planetary systems confirm for the first time the rocky nature of two planets
orbiting a young star, with relatively short orbital periods ( days). They
provide key information for planet formation and evolution models of telluric
planets. Additionally, the Neptune-like derived masses of the three planets
K2-32 b, c, d puts them in a relatively unexplored regime of incident flux and
planet mass, key for transmission spectroscopy studies.Comment: Accepted for publication in A&A. 21 pages, 12 figures, 11 Table
The SOPHIE search for northern extrasolar planets. XI. Three new companions and an orbit update: Giant planets in the habitable zone
We report the discovery of three new substellar companions to solar-type
stars, HD191806, HD214823, and HD221585, based on radial velocity measurements
obtained at the Haute-Provence Observatory. Data from the SOPHIE spectrograph
are combined with observations acquired with its predecessor, ELODIE, to detect
and characterise the orbital parameters of three new gaseous giant and brown
dwarf candidates. Additionally, we combine SOPHIE data with velocities obtained
at the Lick Observatory to improve the parameters of an already known giant
planet companion, HD16175 b. Thanks to the use of different instruments, the
data sets of all four targets span more than ten years. Zero-point offsets
between instruments are dealt with using Bayesian priors to incorporate the
information we possess on the SOPHIE/ELODIE offset based on previous studies.
The reported companions have orbital periods between three and five years and
minimum masses between 1.6 Mjup and 19 Mjup. Additionally, we find that the
star HD191806 is experiencing a secular acceleration of over 11 \ms\ per year,
potentially due to an additional stellar or substellar companion. A search for
the astrometric signature of these companions was carried out using Hipparcos
data. No orbit was detected, but a significant upper limit to the companion
mass can be set for HD221585, whose companion must be substellar.
With the exception of HD191806 b, the companions are located within the
habitable zone of their host star. Therefore, satellites orbiting these objects
could be a propitious place for life to develop.Comment: 12 pages + tables, 7 figures. Accepted for publication in Astronomy &
Astrophysic
The SOPHIE search for northern extrasolar planets VIII. A warm Neptune orbiting HD164595
High-precision radial velocity surveys explore the population of low-mass
exoplanets orbiting bright stars. This allows accurately deriving their orbital
parameters such as their occurrence rate and the statistical distribution of
their properties. Based on this, models of planetary formation and evolution
can be constrained. The SOPHIE spectrograph has been continuously improved in
past years, and thanks to an appropriate correction of systematic instrumental
drift, it is now reaching 2 m/s precision in radial velocity measurements on
all timescales. As part of a dedicated radial velocity survey devoted to search
for low-mass planets around a sample of 190 bright solar-type stars in the
northern hemisphere, we report the detection of a warm Neptune with a minimum
mass of 16.1 +- 2.7 Mearth orbiting the solar analog HD164595 in 40 +- 0.24
days . We also revised the parameters of the multiplanetary system around
HD190360. We discuss this new detection in the context of the upcoming space
mission CHEOPS, which is devoted to a transit search of bright stars harboring
known exoplanets.Comment: 11 pages, 9 figure
The SOPHIE search for northern extrasolar planets VIII. Follow-up of ELODIE candidates: long-period brown-dwarf companions
Long-period brown dwarf companions detected in radial velocity surveys are
important targets for direct imaging and astrometry to calibrate the
mass-luminosity relation of substellar objects. Through a 20-year radial
velocity monitoring of solar-type stars that began with ELODIE and was extended
with SOPHIE spectrographs, giant exoplanets and brown dwarfs with orbital
periods longer than ten years are discovered. We report the detection of five
new potential brown dwarfs with minimum masses between 32 and 83 Jupiter mass
orbiting solar-type stars with periods longer than ten years. An upper mass
limit of these companions is provided using astrometric Hipparcos data,
high-angular resolution imaging made with PUEO, and a deep analysis of the
cross-correlation function of the main stellar spectra to search for blend
effects or faint secondary components. These objects double the number of known
brown dwarf companions with orbital periods longer than ten years and reinforce
the conclusion that the occurrence of such objects increases with orbital
separation. With a projected separation larger than 100 mas, all these brown
dwarf candidates are appropriate targets for high-contrast and high angular
resolution imaging.Comment: 17 pages, 9 figures, accepted in A&
Composition of super-Earths, super-Mercuries, and their host stars
Because of their common origin, it was assumed that the composition of planet building blocks should, to a first order, correlate with stellar atmospheric composition, especially for refractory elements. In fact, information on the relative abundance of refractory and major rock-forming elements such as Fe, Mg, Si has been commonly used to improve interior estimates for terrestrial planets. Recently Adibekyan et al. (2021) presented evidence of a tight chemical link between rocky planets and their host stars. In this study we add six recently discovered exoplanets to the sample of Adibekyan et al. and re-evaluate their findings in light of these new data. We confirm that i) iron-mass fraction of rocky exoplanets correlates (but not a 1:1 relationship) with the composition of their host stars, ii) on average the iron-mass fraction of planets is higher than that of the primordial f star iron , iii) super-Mercuries are formed in disks with high iron content. Based on these results we conclude that disk-chemistry and planet formation processes play an important role in the composition, formation, and evolution of super-Earths and super-Mercuries
KOBEsim: A Bayesian observing strategy algorithm for planet detection in radial velocity blind-search surveys
Context. Ground-based observing time is precious in the era of exoplanet follow-up and characterization, especially in high-precision radial velocity instruments. Blind-search radial velocity surveys thus require a dedicated observational strategy in order to optimize the observing time, which is particularly crucial for the detection of small rocky worlds at large orbital periods. Aims. We developed an algorithm with the purpose of improving the efficiency of radial velocity observations in the context of exoplanet searches, and we applied it to the K-dwarfs Orbited By habitable Exoplanets experiment. Our aim is to accelerate exoplanet confirmations or, alternatively, reject false signals as early as possible in order to save telescope time and increase the efficiency of both blind-search surveys and follow-up of transiting candidates. Methods. Once a minimum initial number of radial velocity datapoints is reached in such a way that a periodicity starts to emerge according to generalized Lomb-Scargle periodograms, that period is targeted with the proposed algorithm, named KOBEsim. The algorithm selects the next observing date that maximizes the Bayesian evidence for this periodicity in comparison with a model with no Keplerian orbits. Results. By means of simulated data, we proved that the algorithm accelerates the exoplanet detection, needing 29-33% fewer observations and a 41-47% smaller time span of the full dataset for low-mass planets (mp < 10 Mâ) in comparison with a conventional monotonic cadence strategy. For 20 Mâ planets we found a 16% enhancement in the number of datapoints. We also tested KOBEsim with real data for a particular KOBE target and for the confirmed planet HD 102365 b. These two tests demonstrate that the strategy is capable of speeding up the detection by up to a factor of 2 (i.e., reducing both the time span and number of observations by half).14 pĂĄgina
The extreme physical properties of the CoRoT-7b super-Earth
International audienceâș Here, we discuss the extreme physical properties possible for the first characterized rocky super-Earth, CoRoT-7b ( = 1.58 , = 5.7 ). âș We make the working hypothesis that the planet is rocky with no volatiles in its atmosphere, and derive the physical properties that result. âș The dayside is very hot (2500 K at the sub-stellar point) while the nightside is very cold (⌠50 K). The sub-stellar point is as hot as the tungsten filament of an incandescent bulb, resulting in the melting and distillation of silicate rocks and the formation of a lava ocean. âș These possible features of CoRoT-7b should be common to many small and hot planets, including Kepler-10b. They define a new class of objects that we propose to name ''Lava-ocean planets''
WASP-186 and WASP-187: two hot Jupiters discovered by SuperWASP and SOPHIE with additional observations by <i>TESS</i>
We present the discovery of two new hot Jupiters identified from the WASP survey, WASP-186b and WASP-187b (TOI-1494.01 and TOI-1493.01). Their planetary nature was established from SOPHIE spectroscopic observations, and additional photometry was obtained from TESS. Stellar parameters for the host stars are derived from spectral line, IRFM, and isochrone placement analyses. These parameters are combined with the photometric and radial velocity data in an MCMC method to determine the planetary properties. WASP-186b is a massive Jupiter (4.22±0.18 MJ, 1.11 ±0.03 RJ) orbiting a mid-F star on a 5.03 day eccentric (e=0.327±0.008) orbit. WASP-187b is a low density (0.80 ±0.09 MJ, 1.64 ±0.05RJ) planet in a 5.15 day circular orbit around a slightly evolved early F-type star
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