- ID:
- ivo://CDS.VizieR/J/A+A/655/A99
- Title:
- Chemical abundances of 762 FGK stars
- Short Name:
- J/A+A/655/A99
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- To understand the formation and composition of planetary systems, it is essential to have insights into the chemical composition of their host stars. In particular, C/O elemental ratios are useful for constraining the density and bulk composition of terrestrial planets. We study the carbon abundances with a twofold objective. On the one hand, we want to evaluate the behaviour of carbon in the context of Galactic chemical evolution. On the other hand, we focus on the possible dependence of carbon abundances on the presence of planets and on the impact of various factors (such as different oxygen lines) on the determination of C/O elemental ratios. We derived chemical abundances of carbon from two atomic lines for 757 FGK stars in the HARPS-GTO sample, observed with high-resolution (R~115000) and high-quality spectra. The abundances were derived using a standard Local Thermodinamyc Equilibrium analysis with automatically measured Equivalent Widths injected into the code MOOG and a grid of Kurucz ATLAS9 atmospheres. Oxygen abundances, derived using different lines, were taken from previous papers in this series and updated with the new stellar parameters. We find that thick- and thin-disk stars are chemically disjunct for [C/Fe] across the full metallicity range that they have in common. Moreover, the population of high-{alpha} metal-rich stars also presents higher and clearly separated [C/Fe] ratios than thin-disk stars up to [Fe/H]~0.2dex. The [C/O] ratios present a general flat trend as a function of [O/H] but becomes negative at [O/H]>~0dex. This trend is more clear when considering stars of similar metallicity. We find tentative evidence that stars with low-mass planets at lower metallicities have higher [C/Fe] ratios than stars without planets at the same metallicity, in the same way as has previously been found for {alpha} elements. Finally, the elemental C/O ratios for the vast majority of our stars are below 0.8 when using the oxygen line at 6158{AA} however, the forbidden oxygen line at 6300{AA} provides systematically higher C/O values (going above 1.2 in a few cases) which also show a dependence on Teff. Moreover, by using different atmosphere models the C/O ratios can have a non negligible difference for cool stars. Therefore, C/O ratios should be scaled to a common solar reference in order to correctly evaluate its behaviour. We find no significant differences in the distribution of C/O ratios for the different populations of planet hosts, except when comparing the stars without detected planets with the stars hosting Jupiter-type planets. However, we note that this difference might be caused by the different metallicity distributions of both populations. The derivation of homogeneous abundances from high-resolution spectra in samples that are modest in size is of great utility in constraining models of Galactic chemical evolution. The combination of these high-quality data with the long-term study of planetary presence in our sample is crucial for achieving an accurate understanding of the impact of stellar chemical composition on planetary formation mechanisms.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/647/A49
- Title:
- Chemical analysis of early-type stars with planets
- Short Name:
- J/A+A/647/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We performed a detailed abundance determination in a sample of early-type stars with and without planets via spectral synthesis, searching for a likely relation between lambda Bootis stars and the presence of planets. We found no unique chemical pattern for the group of early-type stars bearing giant planets. However, our results support, in principle, a suggested scenario in which giant planets orbiting pre-main-sequence stars possibly block the dust of the disk and result in a lambda Bootis-like pattern. On the other hand, we do not find a lambda Bootis pattern in different hot-Jupiter planet host stars, which does not support the idea of possible accretion from the winds of hot-Jupiters, recently proposed in the literature. As a result, other mechanisms should account for the presence of the lambda Bootis pattern between main-sequence stars. Finally, we suggest that the formation of planets around lambda Bootis stars, such as HR 8799 and HD 169142, is also possible through the core accretion process and not only gravitational instability.
- ID:
- ivo://CDS.VizieR/J/A+A/653/A173
- Title:
- CHEOPS 55 Cnc light curve
- Short Name:
- J/A+A/653/A173
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- 55 Cnc e is a transiting super-Earth (radius 1.88R_{Earth}_ and mass 8M_{Earth}_) orbiting a G8V host star on a 17-hour orbit. Spitzer observations of the planet's phase curve at 4.5um revealed a time-varying occultation depth, and MOST optical observations are consistent with a time-varying phase curve amplitude and phase offset of maximum light. Both broadband and high-resolution spectroscopic analyses are consistent with either a high mean molecular weight atmosphere or no atmosphere for planet e. A long term photometric monitoring campaign on an independent optical telescope is needed to probe the variability in this system. We seek to measure the phase variations of 55 Cnc e with a broadband optical filter with the 30 cm effective aperture space telescope CHEOPS and explore how the precision photometry narrows down the range of possible scenarios. We observed 55 Cnc for 1.6 orbital phases in March of 2020. We designed a phase curve detrending toolkit for CHEOPS photometry which allows us to study the underlying flux variations of the 55 Cnc system. We detected a phase variation with a full-amplitude of 72+/-7ppm but do not detect a significant secondary eclipse of the planet. The shape of the phase variation resembles that of a piecewise-Lambertian, however the non-detection of the planetary secondary eclipse, and the large amplitude of the variations exclude reflection from the planetary surface as a possible origin of the observed phase variations. They are also likely incompatible with magnetospheric interactions between the star and planet but may imply that circumplanetary or circumstellar material modulate the flux of the system. Further precision photometry of 55 Cnc from CHEOPS will measure variations in the phase curve amplitude and shape over time this year.
- ID:
- ivo://CDS.VizieR/J/A+A/659/A74
- Title:
- CHEOPS phase curve of WASP-189 b
- Short Name:
- J/A+A/659/A74
- Date:
- 10 Mar 2022 06:44:26
- Publisher:
- CDS
- Description:
- Gas giants orbiting close to hot and massive early-type stars can reach dayside temperatures that are comparable to those of the coldest stars. These "ultra-hot Jupiters" have atmospheres made of ions and atomic species from molecular dissociation and feature strong day-to-night temperature gradients. Photometric observations at different orbital phases provide insights on the planet atmospheric properties. We analyse the photometric observations of WASP-189 acquired with the instrument CHEOPS to derive constraints on the system architecture and the planetary atmosphere. We implement a light curve model suited for asymmetric transit shape caused by the gravity-darkened photosphere of the fast-rotating host star. We also model the reflective and thermal components of the planetary flux, the effect of stellar oblateness and light-travel time on transit-eclipse timings, the stellar activity and CHEOPS systematics. From the asymmetric transit, we measure the size of the ultra-hot Jupiter WASP-189, R_p_=1.600_-0.016_^+0.017^R_J_, with a precision of 1%, and the true orbital obliquity of the planetary system {Psi}_p_=89.6+/-1.2deg (polar orbit). We detect no significant hotspot offset from the phase curve and obtain an eclipse depth {delta}_ecl_=96.5_-5.0_^+4.5^ppm, from which we derive an upper limit on the geometric albedo: A_g_<0.48. We also find that the eclipse depth can only be explained by thermal emission alone in the case of extremely inefficient energy redistribution. Finally, we attribute the photometric variability to the stellar rotation, either through superficial inhomogeneities or resonance couplings between the convective core and the radiative envelope. Based on the derived system architecture, we predict the eclipse depth in the upcoming TESS observations to be up to ~165ppm. High-precision detection of the eclipse in both CHEOPS and TESS passbands might help disentangle between reflective and thermal contributions. We also expect the right ascension of the ascending node of the orbit to precess due to the perturbations induced by the stellar quadrupole moment J_2_ (oblateness).
- ID:
- ivo://CDS.VizieR/J/A+A/657/A52
- Title:
- CHEOPS transit light curves of WASP-103 b
- Short Name:
- J/A+A/657/A52
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Ultra-short period planets undergo strong tidal interactions with their host star which lead to planet deformation and orbital tidal decay. WASP-103b is the exoplanet with the highest expected deformation signature in its transit light curve and one of the shortest expected spiral-in times. Measuring the tidal deformation of the planet would allow us to estimate the second degree fluid Love number and gain insight into the planet's internal structure. Moreover, measuring the tidal decay timescale would allow us to estimate the stellar tidal quality factor, which is key to constraining stellar physics. We obtained 12 transit light curves of WASP-103b with the CHaracterising ExOplanet Satellite (CHEOPS) to estimate the tidal deformation and tidal decay of this extreme system. We modelled the high-precision CHEOPS transit light curves together with systematic instrumental noise using multi-dimensional Gaussian process regression informed by a set of instrumental parameters. To model the tidal deformation, we used a parametrisation model which allowed us to determine the second degree fluid Love number of the planet. We combined our light curves with previously observed transits of WASP-103b with the Hubble Space Telescope (HST) and Spitzer to increase the signal-to-noise of the light curve and better distinguish the minute signal expected from the planetary deformation. We estimate the radial Love number of WASP-103b to be h_f_=1.59+/-0.53 This is the first time that the tidal deformation is directly detected (at 3 sigma) from the transit light curve of an exoplanet. Combining the transit times derived from CHEOPS, HST, and Spitzer light curves with the other transit times available in the literature, we find no significant orbital period variation for WASP-103b. However, the data show a hint of an orbital period increase instead of a decrease, as is expected for tidal decay. This could be either due to a visual companion star if this star is bound, the Applegate effect, or a statistical artefact. The estimated Love number of WASP-103b is similar to Jupiters. This will allow us to constrain the internal structure and composition of WASP-103b, which could provide clues on the inflation of hot Jupiters. Future observations with James Webb Space Telescope (JWST) can better constrain the radial Love number of WASP-103b due to their high signal-to-noise and the smaller signature of limb darkening in the infrared. A longer time baseline is needed to constrain the tidal decay in this system.
- ID:
- ivo://CDS.VizieR/J/A+A/643/A94
- Title:
- CHEOPS WASP-189 b transit light curve
- Short Name:
- J/A+A/643/A94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CHEOPS (CHaracterising ExOPlanets Satellite), launched in December 2019, is a space mission dedicated to exoplanet follow-up with the capacity to perform photometric measurements at the20 ppm level. As CHEOPS observes in a broad optical passband, it can be used provide insights on the reflected light from exoplanets, and constrain the short-wavelength thermal emission for the hottest of planets through the observation of occultations and phase curves. We here report the first observation of an occultation by CHEOPS: that of the hot Jupiter WASP-189b, a M~2M_J_ planet orbiting an A-type star. We detect the occultation of WASP-189b at high significance in individual measurements, and derive an occultation depth of dF=87.9+/-4.3 ppm based on four occultations. We compare this measurement to model predictions and find that, when assuming inefficient heat redistribution, they are consistent with an unreflective atmosphere, heated to a temperature of 3435+/-27K. We furthermore present two transits of WASP-189b observed by CHEOPS. These transits have an asymmetric shape that we attribute to gravity darkening of the host star due to its high rotation rate. We use these measurements to refine the planetary parameters, finding a ~25% deeper transit compared to the discovery paper and updating the radius of WASP-189b to 1.619+/-0.021R_J_. We further measure the projected orbital obliquity to be lambda=86.4(+2.9,-4.4)deg, a value in good agreement with a previous measurement from spectroscopic observations, and derive a true obliquity of Psi=85.4+/-4.3deg. Finally, we provide reference values for the photometric precision attained by the CHEOPS satellite: for the V=6.6 mag star, and using a 1-hour binning, we obtain a residual RMS between 10 and 17ppm on the individual light curves, and 5.7ppm when combining four visits.
- ID:
- ivo://CDS.VizieR/J/A+A/643/A106
- Title:
- 55 close-in (P<100days) small planets list
- Short Name:
- J/A+A/643/A106
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The stars in the Milky Way thin and thick disks can be distinguished by several properties such as metallicity and kinematics. It is not clear whether the two populations also differ in the properties of planets orbiting the stars. In order to study this, a careful analysis of both the chemical composition and mass detection limits is required for a sufficiently large sample. Currently, this information is still limited only to large radial-velocity (RV) programs. Based on the recently published archival database of the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph, we present a first analysis of low-mass (small) planet occurrence rates in a sample of thin- and thick-disk stars. We aim to assess the effects of stellar properties on planet occurrence rates and to obtain first estimates of planet occurrence rates in the thin and thick disks of the Galaxy. As a baseline for comparison, we also aim to provide an updated value for the small close-in planet occurrence rate and compare it with the results of previous RV and transit (Kepler) works. We used archival HARPS RV datasets to calculate detection limits of a sample of stars that were previously analysed for their elemental abundances. For stars with known planets we first subtracted the Keplerian orbit. We then used this information to calculate planet occurrence rates according to a simplified Bayesian model in different regimes of stellar and planet properties. Our results suggest that metal-poor stars and more massive stars host fewer low-mass close-in planets. We find the occurrence rates of these planets in the thin and thick disks to be comparable. In the iron-poor regimes, we find these occurrence rates to be significantly larger at the high-{alpha} region (thick-disk stars) as compared with the low-{alpha} region (thin-disk stars). In general, we find the average number of close-in small planets (2-100 days, 1-20M_{Earth}_) per star (FGK-dwarfs) to be: n^-^_p_=0.36+/-0.05, while the fraction of stars with planets is F_h_=0.23_-0.03_^+0.04^. Qualitatively, our results agree well with previous estimates based on RV and Kepler surveys. This work provides a first estimate of the close-in small planet occurrence rates in the solar neighbourhood of the thin and thick disks of the Galaxy. It is unclear whether there are other stellar properties related to the Galactic context that affect small-planet occurrence rates, or if it is only the combined effects of stellar metal content and mass. A future larger sample of stars and planets is needed to address those questions.
- ID:
- ivo://CDS.VizieR/J/AJ/157/101
- Title:
- Cloud Atlas: HST/WFC3 NIR spectral library
- Short Name:
- J/AJ/157/101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Bayesian atmospheric retrieval tools can place constraints on the properties of brown dwarfs' and hot Jupiters' atmospheres. To fully exploit these methods, high signal-to-noise spectral libraries with well-understood uncertainties are essential. We present a high signal-to-noise spectral library (1.10-1.69 {mu}m) of the thermal emission of 76 brown dwarfs and hot Jupiters. All our spectra have been acquired with the Hubble Space Telescope's Wide Field Camera 3 instrument and its G141 grism. The near-infrared spectral types of these objects range from L4 to Y1. Eight of our targets have estimated masses below the deuterium-burning limit. We analyze the database to identify peculiar objects and/or multiple systems, concluding that this sample includes two very-low-surface-gravity objects and five intermediate-surface-gravity objects. In addition, spectral indices designed to search for composite-atmosphere brown dwarfs indicate that eight objects in our sample are strong candidates to have such atmospheres. None of these objects are overluminous, so their composite atmospheres are unlikely to be companion-induced artifacts. Five of the eight confirmed candidates have been reported as photometrically variable, suggesting that composite atmospheric indices are useful in identifying brown dwarfs with strongly heterogeneous cloud covers. We compare hot Jupiters and brown dwarfs in a near-infrared color-magnitude diagram. We confirm that the coldest hot Jupiters in our sample have spectra similar to mid-L dwarfs, and the hottest hot Jupiters have spectra similar to those of M-dwarfs. Our sample provides a uniform data set of a broad range of ultracool atmospheres, allowing large-scale comparative studies and providing an HST legacy spectral library.
- ID:
- ivo://CDS.VizieR/J/AJ/160/239
- Title:
- Cluster difference imaging photometric survey. II.
- Short Name:
- J/AJ/160/239
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of TOI837b and its validation as a transiting planet. We characterize the system using data from the NASA Transiting Exoplanet Survey Satellite mission, the ESA Gaia mission, ground-based photometry from El Sauce and ASTEP400, and spectroscopy from CHIRON, FEROS, and Veloce. We find that TOI837 is a T=9.9mag G0/F9 dwarf in the southern open cluster IC2602. The star and planet are therefore 35_-5_^+11^ million years old. Combining the transit photometry with a prior on the stellar parameters derived from the cluster color-magnitude diagram, we find that the planet has an orbital period of 8.3days and is slightly smaller than Jupiter (R_p_=0.77_-0.07_^+0.09^R_Jup_). From radial velocity monitoring, we limit M_p_sin(i) to less than 1.20M_Jup_(3{sigma}). The transits either graze or nearly graze the stellar limb. Grazing transits are a cause for concern, as they are often indicative of astrophysical false-positive scenarios. Our follow-up data show that such scenarios are unlikely. Our combined multicolor photometry, high-resolution imaging, and radial velocities rule out hierarchical eclipsing binary scenarios. Background eclipsing binary scenarios, though limited by speckle imaging, remain a 0.2% possibility. TOI837b is therefore a validated adolescent exoplanet. The planetary nature of the system can be confirmed or refuted through observations of the stellar obliquity and the planetary mass. Such observations may also improve our understanding of how the physical and orbital properties of exoplanets change in time.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A136
- Title:
- 7 CMa system velocity curves
- Short Name:
- J/A+A/631/A136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of a second planet orbiting the K giant star 7 CMa based on 166 high-precision radial velocities obtained with Lick, HARPS, UCLES and SONG. The periodogram analysis reveals two periodic signals of approximately 745 and 980d, associated to planetary companions. A double-Keplerian orbital fit of the data reveals two Jupiter-like planets with minimum masses M_b_sini~1.9Mj and M_c_sini~0.9Mj, orbiting at semi-major axes of a_b_~1.75au and a_c_~2.15au, respectively. Given the small orbital separation and the large minimum masses of the planets close encounters may occur within the time baseline of the observations, thus, a more accurate N-body dynamical modeling of the available data is performed. The dynamical best-fit solution leads to collision of the planets and we explore the long-term stable configuration of the system in a Bayesian framework, confirming that 13% of the posterior samples are stable for at least 10Myr. The result from the stability analysis indicates that the two-planets are trapped in a low-eccentricity 4:3 mean-motion resonance. This is only the third discovered system to be inside a 4:3 resonance, making it very valuable for planet formation and orbital evolution models.
