Medium-resolution integral-field spectrographs (IFS) coupled with adaptive-optics such as Keck/OSIRIS, VLT/MUSE, or SINFONI are appearing as a new avenue for enhancing the detection and characterization capabilities of young, gas giant exoplanets at large heliocentric distances (>5 au). We analyzed K-band VLT/SINFONI medium-resolution (R_lambda~5577) observations of the young giant exoplanet HIP 65426 b. Our dedicated IFS data analysis toolkit (TExTRIS) optimized the cube building, star registration, and allowed for the extraction of the planet spectrum. A Bayesian inference with the nested sampling algorithm coupled with the self-consistent forward atmospheric models BT-SETTL15 and Exo-REM using the ForMoSA tool yields Teff=1560 +/- 100K, log(g)<4.40dex, [M/H]=0.05 +/- 0.22dex, and an upper limit on the C/O ratio (<0.55). The object is also re-detected with the so-called "molecular mapping" technique. The technique yields consistent atmospheric parameters, but the loss of the planet pseudo-continuum in the process degrades or modifies the constraints on these parameters. The solar to sub-solar C/O ratio suggests an enrichment by solids at formation if the planet was formed beyond the water snowline (>20 au) by core-accretion. However, a formation by gravitational instability can not be ruled out. The metallicity is compatible with the bulk enrichment of massive Jovian planets from the Bern planet population models. Finally, we measure a radial velocity of 26 +/- 15km/s compatible with our revised measurement on the star. This is the fourth imaged exoplanet for which a radial velocity can be evaluated, illustrating the potential of such observations for assessing the coevolution of imaged systems belonging to star forming regions, such as HIP 65426.
HIP 41378 f is a temperate $9.2\pm0.1 R_{\oplus}$ planet with period of 542.08 days and an extremely low density of $0.09\pm0.02$ g cm$^{-3}$. It transits the bright star HIP 41378 (V=8.93), making it an exciting target for atmospheric characterization including transmission spectroscopy. HIP 41378 was monitored photometrically between the dates of 2019 November 19 and November 28. We detected a transit of HIP 41378 f with NGTS, just the third transit ever detected for this planet, which confirms the orbital period. This is also the first ground-based detection of a transit of HIP 41378 f. Add…
Precision radial velocities from Keck/HIRES reveal a Saturn-mass planet orbiting the nearby M4V star HIP 57050. The planet has a minimum mass of 0.3 Jupiter-mass, an orbital period of 41.4 days, and an orbital eccentricity of 0.31. V-band photometry reveals a clear stellar rotation signature of the host star with a period of 98 days, well separated from the period of the radial velocity variations and reinforcing a Keplerian origin for the observed velocity variations. The orbital period of this planet corresponds to an orbit in the habitable zone of HIP 57050, with an expected planetary tempe…
Wide low-mass substellar companions are known to be very rare among low-mass stars, but appear to become increasingly common with increasing stellar mass. However, B-type stars, which are the most massive stars within ~150 pc of the Sun, have not yet been examined to the same extent as AFGKM-type stars in that regard. In order to address this issue, we launched the ongoing B-star Exoplanet Abundance Study (BEAST) to examine the frequency and properties of planets, brown dwarfs, and disks around B-type stars in the Scorpius-Centaurus (Sco-Cen) association; we also analyzed archival data of B-ty…
The presence of certain elements within a star, and by extension its planet, strongly impacts the formation and evolution of the planetary system. The positive correlation between a host star's iron-content and the presence of an orbiting giant exoplanet has been confirmed; however, the importance of other elements in predicting giant planet occurrence is less certain despite their central role in shaping internal planetary structure. We designed and applied a machine learning algorithm to the Hypatia Catalog (Hinkel et a. 2014) to analyze the stellar abundance patterns of known host stars to …
Observing a 542-day transiting giant with large TTVs: The 2025 transit of HIP 41378 f and new constraints on the outer system
Università degli Studi di Padova（帕多瓦大学）；INAF, Osservatorio Astronomico di Padova（意大利国家天体物理研究所帕多瓦天文台）；Aix Marseille Université（艾克斯-马赛大学）；Université Grenoble Alpes（格勒诺布尔阿尔卑斯大学）；Université de Montréal（蒙特利尔大学）；Trottier Institute for Research on Exoplanets (iREx)（特罗蒂系外行星研究学院）；Center for Astrophysics（天体物理中心）
The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems I: High Contrast Imaging of the Exoplanet HIP 65426 b from 2-16 $μ$m
In 2015, K2 observations of the bright (V = 8.9, K = 7.7) star HIP 41378 revealed a rich system of at least five transiting exoplanets, ranging in size from super-Earths to gas giants. The 2015 K2 observations only spanned 74.8 days, and the outer three long-period planets in the system were only detected with a single transit, so their orbital periods and transit ephemerides could not be determined at that time. Here, we report on 50.8 days of new K2 observations of HIP 41378 from summer 2018. These data reveal additional transits of the long-period planets HIP 41378 d and HIP 41378 f, yieldi…
Dusty debris disks around pre- and main-sequence stars are potential signposts for the existence of planetesimals and exoplanets. Giant planet formation is therefore expected to play a key role in the evolution of the disk. This is indirectly confirmed by extant sub-millimeter near-infrared images of young protoplanetary and cool dusty debris disks around main sequence stars usually showing substantial spatial structures. A majority of recent discoveries of imaged giant planets have been obtained around young, early-type stars hosting a circumstellar disk. In this context, we have carried out …
We are studying the influence of stellar multiplicity on exoplanet systems, in particular systems that have been detected via radial-velocity searches. We are in particular interested in the closest companions as they would have a strong influence on the evolution of the original planet forming disks. In this study we present new companions detected during our ongoing survey of exoplanet hosts with VLT/SPHERE. We are using the extreme adaptive optics imager SPHERE at the ESO/VLT to search for faint (sub)stellar companions. We utilized the classical coronagraphic imaging mode to perform a snaps…
A Ground-Based Transit Observation of the Long-Period Extremely Low-Density Planet HIP 41378 f
Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology（麻省理工学院卡弗里天体物理与空间研究所）；Center for Astrophysics | Harvard & Smithsonian（哈佛与史密森尼天体物理中心）；Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology（麻省理工学院地球、大气与行星科学系）
The census of known exoplanets exhibits a variety of physical parameters, including densities that are measured to span the range from less dense than styrofoam to more dense than iron. These densities represent a large diversity of interior structures. Despite this staggering diversity, recent analyses have shown that the densities of planets that orbit a common star exhibit remarkable uniformity. A fascinating exception to this is the system HIP 41378 (also known as K2-93), which contains a super-puff planet, HIP 41378 f, as well as several planets with more typical bulk densities. The range…
Detecting exoplanets around giant stars sheds light on the later-stage evolution of planetary systems. We observed the M giant HD 18438 and the K giant HD 158996 as part of a Search for Exoplanets around Northern circumpolar Stars (SENS) and obtained 38 and 24 spectra from 2010 to 2017 using the high-resolution Bohyunsan Observatory Echelle Spectrograph (BOES) at the 1.8m telescope of Bohyunsan Optical Astronomy Observatory in Korea. We obtained precise RV measurements from the spectra and found long-period radial velocity (RV) variations with period 719.0 days for HD 18438 and 820.2 days for …
Transit timing and starspot-induced transit depth variations in the $\sim$17 Myr old HIP 67522 system
University of Geneva（日内瓦大学）；University of Bern（伯尔尼大学）；European Space Agency (ESA)（欧洲空间局）；Queen Mary University of London（伦敦玛丽女王大学）；Leibniz-Institut für Astrophysik Potsdam (AIP)（波茨坦莱布尼茨天体物理研究所）
Doppler observations from Keck Observatory have revealed a triple planet system orbiting the nearby mid-type K dwarf, HIP 57274. The inner planet, HIP 57274b, is a super-Earth with \msini\ = 11.6 \mearth (0.036 \mjup), an orbital period of 8.135 $\pm$ 0.004 d, and slightly eccentric orbit $e=0.19 \pm 0.1$. We calculate a transit probability of 6.5% for the inner planet. The second planet has \msini\ = 0.4 \mjup\ with an orbital period of 32.0 $\pm 0.02$ d in a nearly circular orbit, and $e = 0.05 \pm 0.03$. The third planet has \msini\ = 0.53 \mjup\ with an orbital period of 432 $\pm 8$ d (1.1…
We present first results from a new exoplanet direct imaging survey being carried out with the Subaru Coronagraphic Extreme Adaptive Optics project (SCExAO) coupled to the CHARIS integral field spectrograph and assisted with Keck/NIRC2, targeting stars showing evidence for an astrometric acceleration from the Hipparcos and Gaia satellites. Near-infrared spectra from CHARIS and thermal infrared photometry from NIRC2 constrain newly-discovered companion spectral types, temperatures, and gravities. Relative astrometry of companions from SCExAO/CHARIS and NIRC2 and absolute astrometry of the star …
Transiting extrasolar planets are key objects in the study of the formation, migration, and evolution of planetary systems. In particular, the exploration of the atmospheres of giant planets, through transmission spectroscopy or direct imaging, has revealed a large diversity in their chemical composition and physical properties. Studying these giant planets allows one to test the global climate models that are used for the Earth and other solar system planets. However, these studies are mostly limited either to highly-irradiated transiting giant planets or directly-imaged giant planets at larg…
A Search for exoplanets around northern circumpolar stars VIII. filter out a planet cycle from the multi-period radial velocity variations in M giant HD 3638
Gaia Exoplanet Orbits, Demographics, and Evolution Survey (GEODES): Characteristics of Three Long-Period Companions Accelerating their Host Stars
University of California, Santa Barbara（加州大学圣塔芭芭拉分校）；University of California Los Angeles（加州大学洛杉矶分校）；University of California, Santa Cruz（加州大学圣克鲁兹分校）；Princeton University（普林斯顿大学）
We use the stellar evolution code MESA-binary and follow the evolution of three exoplanets and two brown dwarfs (BDs) to determine their potential role in the future evolution of their parent star on the red giant branch (RGB) and on the asymptotic giant branch (AGB). We limit this study to exoplanets and BDs with orbits that have semi-major axis of 1AU<a0<20AU, a high eccentricity, e0>0.25, and having a parent star of mass M>1Mo. We find that the star HIP 75458 will engulf its planet HIP 75458 b during its RGB phase. The planet will remove the envelope and terminate the RGB evolution, leaving…
Accurate stellar properties are crucial for determining exoplanet characteristics. Gaia DR2 presents revised distances, luminosities, and radii for 1.6 billion stars. Here, we report the calculation of revised radii and densities for 320 exoplanets using this data and present updated calculations of the incident flux received by 690 known exoplanets. This allows the likelihood that those planets orbit in the habitable zone of their host stars to be reassessed. As a result of this analysis, three planets can be added to the catalogue of potentially habitable worlds: HIP~67537~b, HD~148156~b, an…
In this paper we consider the magnetosphere-ionosphere (M-I) coupling at Jupiter-like exoplanets with internal plasma sources such as volcanic moons, and we have determined the best candidates for detection of these radio emissions by estimating the maximum spectral flux density expected from planets orbiting stars within 25 pc using data listed in the NASA/IPAC/NExScI Star and Exoplanet Database (NStED). In total we identify 91 potential targets, of which 40 already host planets and 51 have stellar X-ray luminosity 100 times the solar value. In general, we find that stronger planetary field s…
We present the discovery of a transiting hot Jupiter orbiting HIP 67522 ($T_{eff}\sim5650$ K; $M_* \sim 1.2 M_{\odot}$) in the 10-20 Myr old Sco-Cen OB association. We identified the transits in the TESS data using our custom notch-filter planet search pipeline, and characterize the system with additional photometry from Spitzer, spectroscopy from SOAR/Goodman, SALT/HRS, LCOGT/NRES, and SMARTS/CHIRON, and speckle imaging from SOAR/HRCam. We model the photometry as a periodic Gaussian process with transits to account for stellar variability, and find an orbital period of 6.9596$^{+0.000016}_{-0…
The majority of stars have one or more stellar companions. As exoplanets continue to be discovered, it is crucial to examine planetary systems to identify their stellar companions. By observing a change in proper motion, companions can be detected by the acceleration they induce on their host stars. We selected 701 stars from the Hipparcos-Gaia Catalog of Accelerations (HGCA) that have existing adaptive optics imaging data gathered with Gemini/NIRI. Of these, we examined 21 stars known to host planet candidates and reduced their archival NIRI data with Gemini's DRAGONS software. We assessed th…
Netherlands Institute for Radio Astronomy, ASTRON（荷兰射电天文研究所，ASTRON）；Leibniz-Institut für Astrophysik Potsdam, AIP（波茨坦莱布尼兹天体物理研究所，AIP）；Kapteyn Astronomical Institute, University of Groningen（格罗宁根大学卡普坦天文研究所）；Institut für Physik und Astronomie, Universität Potsdam（波茨坦大学物理与天文研究所）；Anton Pannenkoek Institute for Astronomy, University of Amsterdam（阿姆斯特丹大学安东·潘农科克天文研究所）；Department of Astronomy, Stockholm University（斯德哥尔摩大学天文学系）；Geneva Observatory, Universit（日内瓦观测台，大学）
Atmospheric characterization of HIP 67522 b with VLT/CRIRES+. VLT/CRIRES+ suggests a heavier planet and hints at deuterium fractionation
Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse, CNRS UMR 5277（天体物理学与行星学研究所，图卢兹大学）；Department of Physics, University of Oxford（牛津大学物理系）；LIRA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université Paris Cité（巴黎天文台，巴黎文理研究大学）；Laboratoire Lagrange, Observatoire de la Côte d’Azur, CNRS, Université Côte d’Azur（蔚蓝海岸大学拉格朗日实验室）；Centro de Astrobiología (CAB), CSIC-INTA（西班牙国家航空航天技术研究所/西班牙国家科学研究委员会天体生物学中心）；Center for Astrophysics | Harvard & Smithsonian（哈佛史密森尼天体物理中心）
We report the detection of a planetary companion around HIP 13044, a metal-poor star on the red Horizontal Branch. The detection is based on radial velocity observations with FEROS, a high-resolution spectrograph at the 2.2-m MPG/ESO telescope, located at ESO La Silla observatory in Chile. The periodic radial velocity variation of P = 16.2 days can be distinguished from the periods of the stellar activity indicators. We computed a minimum planetary mass of 1.25 MJup and an orbital semi-major axis of 0.116 AU for the planet. This discovery is unique in three aspects: First, it is the first plan…
An intriguing, growing class of planets are the "super-puffs," objects with exceptionally large radii for their masses and thus correspondingly low densities ($\lesssim0.3\rm\,g\,cm^{-3}$). Here we consider whether they could have large inferred radii because they are in fact ringed. This would naturally explain why super-puffs have thus far only shown featureless transit spectra. We find that this hypothesis can work in some cases but not all. The close proximity of the super-puffs to their parent stars necessitates rings with a rocky rather than icy composition. This limits the radius of the…
The Medium Resolution Spectrometer on board JWST/MIRI will give access to mid-IR spectra while retaining spatial information. With the unparalleled sensitivity of JWST and the MIRI detectors, the MRS has the potential to revolutionise our understanding of giant exoplanet atmospheres. Molecular mapping is a promising detection and characterisation technique used to study the spectra of directly imaged exoplanets. We aim to examine the feasibility and application of this technique to MRS observations. We used the instrument simulator MIRISIM to create mock observations of resolved star and exopl…
ADI and SDI are well-established high-contrast imaging techniques, but their application is challenging for companions at small angular separations. The aim of this paper is to investigate to what extent adaptive-optics assisted, medium-resolution (R$\sim$5000) integral field spectrographs (IFS) can be used to directly detect the absorption of molecular species in the spectra of planets and substellar companions when these are not present in the spectrum of the star. We analyzed archival data of $β$ Pictoris taken with the SINFONI integral field spectrograph (VLT), originally taken to image $β…
Through our HARPS radial velocity survey for planets around solar twin stars, we have identified a promising Jupiter twin candidate around the star HIP11915. We characterize this Keplerian signal and investigate its potential origins in stellar activity. Our analysis indicates that HIP11915 hosts a Jupiter-mass planet with a 3800-day orbital period and low eccentricity. Although we cannot definitively rule out an activity cycle interpretation, we find that a planet interpretation is more likely based on a joint analysis of RV and activity index data. The challenges of long-period radial veloci…
The third Gaia data release includes a catalog of exoplanets and exoplanet candidates identified via the star's astrometric motion. This paper reports on tests for consistency between the Gaia two-body orbital solutions and precise Doppler velocities, for the stars currently amenable to such a comparison. For BD 17-0063, HD 81040, and HD 132406, the Gaia orbital solution and the Doppler data were found to be consistent, and were fitted jointly to obtain the best possible constraints on the planets' orbits and masses. Inconsistencies were found for 4 stars: HD 111232, probably due to additional…
We have been conducting a exoplanet search survey using Bohyunsan Observatory Echelle Spectrograph (BOES) for the last 18 years. We present the detection of exoplanet candidate in orbit around HD 18438 from high-precision radial velocity (RV) mesurements. The target was already reported in 2018 (Bang et al. 2018). They conclude that the RV variations with a period of 719 days are likely to be caused by the pulsations because the Lomb-Scargle periodogram of HIPPARCOS photometric and Ha EW variations for HD 18438 show peaks with periods close to that of RV variations and there were no correlatio…
The great majority of exoplanets discovered so far are orbiting cool, low-mass stars whose properties are relatively similar to the Sun. However, the stellar magnetism of these stars can be significantly different from the solar one, both in topology and intensity. In addition, due to the present-day technology used in exoplanetary searches, most of the currently known exoplanets are found orbiting at extremely close distances to their host stars ($< 0.1$ au). The dramatic differences in stellar magnetism and orbital radius can make the interplanetary medium of exoplanetary systems remarkably …
The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems III: Aperture Masking Interferometric Observations of the star HIP 65426 at 3.8 um
Young giant planets are the best targets for characterization with direct imaging. The Medium Resolution Spectrometer (MRS) of the Mid-Infrared Instrument (MIRI) of the recently launched James Webb Space Telescope (JWST) will give access to the first spectroscopic data for direct imaging above 5 $μ$m with unprecedented sensitivity at a spectral resolution up to 3700. This will provide a valuable complement to near-infrared data from ground-based instruments for characterizing these objects. We aim to evaluate the performance of MIRI/MRS to detect molecules in the atmosphere of exoplanets and t…
Clouds are expected to form in a wide range of conditions in the atmosphere of exoplanets given the large range of possible condensible species. However this diversity might lead to very different small-scale dynamics depending on radiative transfer in various thermal conditions: we aim at providing some insights into these dynamical regimes. We perform an analytical linear stability analysis of a compositional discontinuity with a heating source term that depends on composition. We also perform idealized two-dimensional (2D) simulations of an opacity discontinuity in a stratified medium with …
We present high-precision radial-velocity measurements of three solar-type stars: HD 13908, HD 159243, and HIP 91258. The observations were made with the SOPHIE spectrograph at the 1.93-m telescope of Observatoire de Haute-Provence (France). They show that these three bright stars host exoplanetary systems composed of at least two companions. HD 13908 b is a planet with a minimum mass of 0.865+-0.035 Mjup, on a circular orbit with a period of 19.382+-0.006 days. There is an outer massive companion in the system with a period of 931+-17 days, e = 0.12+-0.02, and a minimum mass of 5.13+-0.25 Mju…
CONTEXT. Exoplanet searches have demonstrated that giant planets are preferentially found around metal-rich stars and that their fraction increases with the stellar mass. AIMS. During the past six years, we have conducted a radial velocity follow-up program of 166 giant stars, to detect substellar companions, and characterizing their orbital properties. Using this information, we aim to study the role of the stellar evolution in the orbital parameters of the companions, and to unveil possible correlations between the stellar properties and the occurrence rate of giant planets. METHODS. Using F…
We report the discovery of a candidate brown dwarf or a very low mass stellar companion (MARVELS-5b) to the star HIP 67526 from the Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS). The radial velocity curve for this object contains 31 epochs spread over 2.5 years. Our Keplerian fit using a Markov Chain Monte Carlo approach, reveals that the companion has an orbital period of $90.2695^{+0.0188}_{-0.0187}$ days, an eccentricity of $0.4375 \pm 0.0040$ and a semi-amplitude of $2948.14^{+16.65}_{-16.55}$ m s$^{-1}$. Using additional high-resolution spectroscopy, we find the h…
(Abridged) The existence of an extended neutral hydrogen exosphere around small planets can be used as an evidence for the presence of water in their lower atmosphere but, to date, such feature has not been securely detected in rocky exoplanets. Planetary exospheres can be observed using transit spectroscopy of the Lyman-$α$ line, which is limited mainly by interstellar medium absorption in the core of the line, and airglow contamination from the geocorona when using low-orbit space telescopes. Our objective is to assess the detectability of the neutral hydrogen exosphere of an Earth-like plan…
