- ID:
- ivo://CDS.VizieR/J/A+A/657/A87
- Title:
- CASCADES I. Sample definition and first results
- Short Name:
- J/A+A/657/A87
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Following the first discovery of a planet orbiting a giant star in 2002, we started the CORALIE radial-velocity search for companions around evolved stars (CASCADES). We present the observations of three stars conducted at the 1.2m Leonard Euler Swiss telescope at La Silla Observatory, Chile, using the CORALIE spectrograph. We aim to detect planetary companions to intermediate-mass G- and K- type evolved stars and perform a statistical analysis of this population. We searched for new planetary systems around the stars HD22532 (TIC200851704), HD64121 (TIC264770836), and HD69123 (TIC146264536). We have followed a volume-limited sample of 641 red giants since 2006 to obtain high-precision radial-velocity measurements. We used the Data & Analysis Center for Exoplanets (DACE) platform to perform a radial-velocity analysis to search for periodic signals in the line profile and activity indices, to distinguish between planetary-induced radial-velocity variations and stellar photospheric jitter, and to search for significant signals in the radial-velocity time series to fit a corresponding Keplerian model. In this paper, we present the survey in detail, and we report on the discovery of the first three planets of the sample around the giant stars HD22532, HD64121, and HD69123.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/159/281
- Title:
- Characteristics of 335 KOI stars
- Short Name:
- J/AJ/159/281
- Date:
- 09 Dec 2021
- Publisher:
- CDS
- Description:
- We propose several descriptive measures to characterize the arrangements of planetary masses, periods, and mutual inclinations within exoplanetary systems. These measures are based on complexity theory and capture the global, system-level trends of each architecture. Our approach considers all planets in a system simultaneously, facilitating both intrasystem and intersystem analysis. We find that based on these measures, Kepler's high-multiplicity (N>=3) systems can be explained if most systems belong to a single intrinsic population, with a subset of high-multiplicity systems (~20%) hosting additional, undetected planets intermediate in period between the known planets. We confirm prior findings that planets within a system tend to be roughly the same size and approximately coplanar. We find that forward modeling has not yet reproduced the high degree of spacing similarity (in log- period) actually seen in the Kepler data. Although our classification scheme was developed using compact Kepler multis as a test sample, our methods can be immediately applied to any other population of exoplanetary systems. We apply this classification scheme to 1- quantify the similarity between systems, 2- resolve observational biases from physical trends, 3- identify which systems to search for additional planets and where to look for these planets.
- 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.
- 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/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/161/265
- Title:
- Compared rotation periods for 1189 CKS host stars
- Short Name:
- J/AJ/161/265
- Date:
- 16 Mar 2022 11:58:11
- Publisher:
- CDS
- Description:
- The radius valley, a bifurcation in the size distribution of small, close-in exoplanets, is hypothesized to be a signature of planetary atmospheric loss. Such an evolutionary phenomenon should depend on the age of the star-planet system. In this work, we study the temporal evolution of the radius valley using two independent determinations of host star ages among the California-Kepler Survey (CKS) sample. We find evidence for a wide and nearly empty void of planets in the period-radius diagram at the youngest system ages (<~2-3Gyr) represented in the CKS sample. We show that the orbital period dependence of the radius valley among the younger CKS planets is consistent with that found among those planets with asteroseismically determined host star radii. Relative to previous studies of preferentially older planets, the radius valley determined among the younger planetary sample is shifted to smaller radii. This result is compatible with an atmospheric loss timescale on the order of gigayears for progenitors of the largest observed super-Earths. In support of this interpretation, we show that the planet sizes that appear to be unrepresented at ages <~2-3Gyr are likely to correspond to planets with rocky compositions. Our results suggest that the size distribution of close-in exoplanets and the precise location of the radius valley evolve over gigayears.
- ID:
- ivo://CDS.VizieR/J/AJ/160/131
- Title:
- Compilation of 289 eclipsing binaries parameters
- Short Name:
- J/AJ/160/131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate directly imaging exoplanets around eclipsing binaries using the eclipse as a natural tool for dimming the binary and thus increasing the planet to star brightness contrast. At eclipse, the binary becomes pointlike, making coronagraphy possible. We select binaries where the planet-star contrast would be boosted by >10x during eclipse, making it possible to detect a planet that is >~10x fainter or in a star system that is ~2-3x more massive than otherwise. Our approach will yield insights into planet occurrence rates around binaries versus individual stars. We consider both self-luminous (SL) and reflected light (RL) planets. In the SL case, we select binaries whose age is young enough so that an orbiting SL planet would remain luminous; in U Cep and AC Sct, respectively, our method is sensitive to SL planets of ~4.5 and ~9 M_J_ with current ground- or near-future space-based instruments and ~1.5 and ~6 M_J_ with future ground-based observatories. In the RL case, there are three nearby (<~50 pc) systems-V1412 Aql, RR Cae, and RT Pic-around which a Jupiter-like planet at a planet-star separation of >~20mas might be imaged with future ground- and space-based coronagraphs. A Venus-like planet at the same distance might be detectable around RR Cae and RT Pic. A habitable Earth-like planet represents a challenge; while the planet-star contrast at eclipse and planet flux are accessible with a 6-8m space telescope, the planet-star separation is 1/3-1/4 of the angular separation limit of modern coronagraphy.
- ID:
- ivo://CDS.VizieR/J/ApJ/887/261
- Title:
- Compilation of planets around M dwarfs
- Short Name:
- J/ApJ/887/261
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- M dwarfs host most of the exoplanets in the local Milky Way. Some of these planets, ranging from sub-Earths to super-Jupiters, orbit in their stars' habitable zones (HZs), although many likely possess surface environments that preclude habitability. Moreover, exomoons around these planets could harbor life for long timescales and thus may also be targets for biosignature surveys. Here we investigate the potential habitability, stability, and detectability of exomoons around exoplanets orbiting M dwarfs. We first compile an updated list of known M-dwarf exoplanet hosts, comprising 109 stars and 205 planets. For each M dwarf, we compute and update precise luminosities with the Virtual Observatory spectral energy distribution Analyzer and Gaia DR2 parallaxes to determine inner and outer boundaries of their HZs. For each planet, we retrieve (or, when necessary, homogeneously estimate) their masses and radii, calculate the long-term dynamical stability of hypothetical moons, and identify those planets that can support habitable moons. We find that 33 exoplanet candidates are located in the HZs of their host stars and that four of them could host Moon- to Titan-mass exomoons for timescales longer than the Hubble time.
- ID:
- ivo://CDS.VizieR/J/AJ/158/187
- Title:
- Confirmed members of nearby young moving groups
- Short Name:
- J/AJ/158/187
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first statistical analysis of exoplanet direct imaging surveys combining adaptive optics (AO) imaging at small separations with deep seeing-limited observations at large separations allowing us to study the entire orbital separation domain from 5 to 5000 au simultaneously. Our sample of 344 stars includes only confirmed members of nearby young associations and is based on all AO direct-imaging detection limits readily available online, with addition of our own previous seeing-limited surveys. Assuming that the companion distribution in mass and a semimajor axis follows a power-law distribution and adding a dependence on the mass of the host star, such as d^2^{prop.to}fM^{alpha}^a^{beta}^(M_*_/M_{sun}_)^{gamma}^dMda, we constrain the parameters to obtain {alpha}=-0.18_-0.65_^+0.77^, {beta}=-1.43_-0.24_^+0.23^, and {gamma}=0.62_-0.50_^+0.56^ at a 68% confidence level, and we obtain f=0.11_-0.05_^+0.11^ for the overall planet occurrence rate for companions with masses between 1 and 20 M_Jup_ in the range of 5-5000 au. Thus, we find that occurrence of companions is negatively correlated with a semimajor axis and companion mass (marginally) but is positively correlated with the stellar host mass. Our inferred mass distribution is in good agreement with other distributions found previously from direct imaging surveys for planets and brown dwarfs, but is shallower as a function of mass than the distributions inferred by radial velocity surveys of gas giants in the 1-3 au range. This may suggest that planets at these wide and very wide separations represent the low-mass tail of the brown dwarfs and stellar companion distribution rather than an extension of the distribution of the inner planets.
