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 ($Q'_\star$) 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 $Q'_\star$. 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 $(-0.11\pm0.21)\times10^{-10}$ for WASP-18b and $(-0.35\pm0.22)\times10^{-10}$ for WASP-19b and we do not find significant evidence of orbital decay in these targets. We obtain new lower limits for $Q'_\star$ of $(1.42\pm0.34)\times10^7$ in WASP-18 and $(1.26\pm0.10)\times10^6$ in WASP-19, corresponding to upper limits of the orbital decay rate of $-0.45\times10^{-10}$ and $-0.71\times10^{-10}$, 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 $Q'_\star$ 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

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 ($\sim400$ 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$_e=2.1^{+1.3}_{-1.1}$~M$_{\oplus}$, P$_e\sim4.35$~days) followed by an inflated Neptune-mass planet (M$_b=15.0^{+1.8}_{-1.7}$~M$_{\oplus}$, P$_b\sim8.99$~days) and two external sub-Neptunes (M$_c=8.1\pm2.4$~M$_{\oplus}$, P$_c\sim20.66$~days; M$_d=6.7\pm2.5$~M$_{\oplus}$, P$_d\sim31.72$~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$_b<11.3$ M$_{\oplus}$ (P$_b\sim2.47$~days), M$_c<12.8$ M$_{\oplus}$ (P$_c\sim7.06$~days). The outer planet is a sub-Neptune size planet with an inferred mass of M$_d=8.3^{+5.2}_{-4.7}$ M$_{\oplus}$ (M$_d<21.1$ M$_{\oplus}$, P$_d\sim24.36$~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 ($<7$ 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 M⊕) in comparison with a conventional monotonic cadence strategy. For 20 M⊕ 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 página

The extreme physical properties of the CoRoT-7b super-Earth

International audience► Here, we discuss the extreme physical properties possible for the first characterized rocky super-Earth, CoRoT-7b ( = 1.58 , = 5.7 ). ► We make the working hypothesis that the planet is rocky with no volatiles in its atmosphere, and derive the physical properties that result. ► 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. ► 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

A hot mini-Neptune in the radius valley orbiting solar analogue HD 110113

We report the discovery of HD 110113 b (TESS object of interest-755.01), a transiting mini-Neptune exoplanet on a 2.5-d orbit around the solar-analogue HD 110113 (Teff = 5730 K). Using TESS photometry and High Accuracy Radial velocity Planet Searcher (HARPS) radial velocities gathered by the NCORES program, we find that HD 110113 b has a radius of 2.05 ± 0.12 R⊕ and a mass of 4.55 ± 0.62 M⊕. The resulting density of $2.90^{+0.75}_{-0.59}$ g cm-3 is significantly lower than would be expected from a pure-rock world; therefore HD 110113 b must be a mini-Neptune with a significant volatile atmosphere. The high incident flux places it within the so-called radius valley; however, HD 110113 b was able to hold on to a substantial (0.1-1 per cent) H-He atmosphere over its ∼4 Gyr lifetime. Through a novel simultaneous Gaussian process fit to multiple activity indicators, we were also able to fit for the strong stellar rotation signal with period 20.8 ± 1.2 d from the RVs and confirm an additional non-transiting planet, HD 110113 c, which has a mass of 10.5 ± 1.2 M⊕ and a period of $6.744^{+0.008}_{-0.009}$ d.Fil: Osborn, H. P.. University of Bern; Suiza. Massachusetts Institute of Technology; Estados UnidosFil: Armstrong, D. J.. University of Warwick; Reino UnidoFil: Adibekyan, V.. Universidad de Porto; PortugalFil: Collins, K. A.. Harvard-Smithsonian Center for Astrophysics; Estados UnidosFil: Delgado Mena, E.. Universidad de Porto; PortugalFil: Howell, S. B.. National Aeronautics and Space Administration; Estados UnidosFil: Hellier, C.. Keele University. Faculty Of Humanities And Social Sciences.; Reino UnidoFil: King, G. W.. University of Warwick; Reino UnidoFil: Lillo Box, J.. Consejo Superior de Investigaciones Cientificas. Centro de Astrobiologia.; EspañaFil: Nielsen, Louise D.. Universidad de Ginebra; SuizaFil: Otegi, J. F.. Universidad de Ginebra; SuizaFil: Santos, N. C.. Universidad de Porto; PortugalFil: Ziegler, C.. University of Toronto; CanadáFil: Anderson, D. R.. University of Warwick; Reino UnidoFil: Briceno, C.. Cerro Tololo Inter American Observatory; ChileFil: Burke, C.. Massachusetts Institute of Technology; Estados UnidosFil: Bayliss, D.. University of Warwick; Reino UnidoFil: Barrado, D.. Consejo Superior de Investigaciones Cientificas. Centro de Astrobiologia.; EspañaFil: Bryant, E. M.. University of Warwick; Reino UnidoFil: Brown, D. J. A.. University of Warwick; Reino UnidoFil: Barros, S. C. C.. Universidad de Porto; PortugalFil: Bouchy, F.. Universidad de Ginebra; SuizaFil: Caldwell, D. A.. SETI Institute; Estados UnidosFil: Conti, D. M.. American Association of Variable Star Observers; Estados UnidosFil: Diaz, Rodrigo Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias Físicas. - Universidad Nacional de San Martín. Instituto de Ciencias Físicas; Argentina. International Center for Advanced Studies; Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología. Centro Internacional de Estudios Avanzados; ArgentinaFil: Dragomir, D.. University of New Mexico; Estados UnidosFil: Deleuil, M.. Universidad de Aix-Marsella; Francia. Centre National de la Recherche Scientifique; FranciaFil: Demangeon, O. D. S.. Universidad de Porto; PortugalFil: Dorn, C.. Universitat Zurich; SuizaFil: Daylan, T.. Massachusetts Institute of Technology; Estados Unido