- ID:
- ivo://CDS.VizieR/J/A+A/615/A117
- Title:
- 55 Cnc geocoronal emission lines template
- Short Name:
- J/A+A/615/A117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The high-energy X-ray to ultraviolet (XUV) irradiation of close-in planets by their host star influences their evolution and might be responsible for the existence of a population of ultra-short period planets eroded to their bare core. In orbit around a bright, nearby G-type star, the super-Earth 55 Cnc e offers the possibility to address these issues through transit observations at UV wavelengths. We used the Hubble Space Telescope to observe the transit in the far-ultraviolet (FUV) over three epochs in April 2016, January 2017, and February 2017. Together, these observations cover nearly half of the orbital trajectory in between the two quadratures, and reveal significant short- and long-term variability in 55 Cnc chromospheric emission lines. In the last two epochs, we detected a larger flux in the CIII, SiIII, and SiIV lines after the planet passed the approaching quadrature, followed by a flux decrease in the SiIV doublet. In the second epoch these variations are contemporaneous with flux decreases in the SiII and CII doublet. All epochs show flux decreases in the NV doublet as well, albeit at different orbital phases. These flux decreases are consistent with absorption from optically thin clouds of gas, are mostly localized at low and redshifted radial velocities in the star rest frame, and occur preferentially before and during the planet transit. These three points make it unlikely that the variations are purely stellar in origin, yet we show that the occulting material is also unlikely to originate from the planet. We thus tentatively propose that the motion of 55 Cnc e at the fringes of the stellar corona leads to the formation of a cool coronal rain. The inhomogeneity and temporal evolution of the stellar corona would be responsible for the differences between the three visits. Additional variations are detected in the CII doublet in the first epoch and in the OI triplet in all epochs with a different behavior that points toward intrinsic stellar variability. Further observations at FUV wavelengths are required to disentangle definitively between star-planet interactions in the 55 Cnc system and the activity of the star.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/619/A1
- Title:
- 55 Cnc radial velocities and photometry
- Short Name:
- J/A+A/619/A1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Orbiting a bright, nearby star the 55 Cnc system offers a rare opportunity to study a multiplanet system that has a wide range of planetary masses and orbital distances. Using two decades of photometry and spectroscopy data, we have measured the rotation of the host star and its solar-like magnetic cycle. Accounting for this cycle in our velocimetric analysis of the system allows us to revise the properties of the outermost giant planet and its four planetary companions. The innermost planet 55 Cnc e is an unusually close-in super-Earth, whose transits have allowed for detailed follow-up studies. Recent observations favor the presence of a substantial atmosphere yet its composition, and the nature of the planet, remain unknown. We combined our derived planet mass (Mp=8.0+/-0.3M_{Earth}_) with refined measurement of its optical radius derived from HST/STIS observations (Rp=1.88+/-0.03R_{Earth}_ over 530-750nm) to revise the density of 55 Cnc e (rho=6.7+/-0.4g/cm^3^). Based on these revised properties we have characterized possible interiors of 55 Cnc e using a generalized Bayesian model. We confirm that the planet is likely surrounded by a heavyweight atmosphere, contributing a few percents of the planet radius. While we cannot exclude the presence of a water layer underneath the atmosphere, this scenario is unlikely given the observations of the planet across the entire spectrum and its strong irradiation. Follow-up observations of the system in photometry and in spectroscopy over different time-scales are needed to further investigate the nature and origin of this iconic super-Earth.
- 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.
- ID:
- ivo://CDS.VizieR/J/AJ/158/87
- Title:
- 86 cool dwarfs observed during K2 Campaigns 1-17
- Short Name:
- J/AJ/158/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present revised stellar properties for 172 K2 target stars that were identified as possible hosts of transiting planets during Campaigns 1-17. Using medium-resolution near-infrared spectra acquired with the NASA Infrared Telescope Facility/SpeX and Palomar/TripleSpec, we found that 86 of our targets were bona fide cool dwarfs, 74 were hotter dwarfs, and 12 were giants. Combining our spectroscopic metallicities with Gaia parallaxes and archival photometry, we derived photometric stellar parameters and compared them to our spectroscopic estimates. Although our spectroscopic and photometric radius and temperature estimates are consistent, our photometric mass estimates are systematically {Delta}M_*_=0.11 M_{sun}_ (34%) higher than our spectroscopic mass estimates for the least massive stars (M_*,phot_<0.4 M_{sun}_). Adopting the photometric parameters and comparing our results to parameters reported in the Ecliptic Plane Input Catalog, our revised stellar radii are {Delta}R_*_=0.15 R_{sun}_ (40%) larger, and our revised stellar effective temperatures are roughly {Delta}T_eff_=65 K cooler. Correctly determining the properties of K2 target stars is essential for characterizing any associated planet candidates, estimating the planet search sensitivity, and calculating planet occurrence rates. Even though Gaia parallaxes have increased the power of photometric surveys, spectroscopic characterization remains essential for determining stellar metallicities and investigating correlations between stellar metallicity and planetary properties.
- ID:
- ivo://CDS.VizieR/J/AJ/160/96
- Title:
- CORALIE and PFS radial velocities of HD 86226
- Short Name:
- J/AJ/160/96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Transiting Exoplanet Survey Satellite (TESS) mission was designed to find transiting planets around bright, nearby stars. Here, we present the detection and mass measurement of a small, short-period (~4days) transiting planet around the bright (V=7.9), solar-type star HD86226 (TOI-652, TIC22221375), previously known to host a long-period (~1600days) giant planet. HD86226c (TOI-652.01) has a radius of 2.16{+/-}0.08R_{Earth}_ and a mass of 7.25_-1.12_^+1.19^M_{Earth}_, based on archival and new radial velocity data. We also update the parameters of the longer-period, not-known-to-transit planet, and find it to be less eccentric and less massive than previously reported. The density of the transiting planet is 3.97g/cm^3^, which is low enough to suggest that the planet has at least a small volatile envelope, but the mass fractions of rock, iron, and water are not well- constrained. Given the host star brightness, planet period, and location of the planet near both the "radius gap" and the "hot Neptune desert," HD86226c is an interesting candidate for transmission spectroscopy to further refine its composition.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A122
- Title:
- CoRoT-30b and CoRoT-31b radial velocity curves
- Short Name:
- J/A+A/635/A122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery as well as the orbital and physical characterizations of two new transiting giant exoplanets, CoRoT-30 b and CoRoT-31 b, with the CoRoT space telescope. We analyzed two complementary data sets: photometric transit light curves measured by CoRoT, and radial velocity curves measured by the HARPS spectrometer. To derive the absolute masses and radii of the planets, we modeled the stars from available magnitudes and spectra. We find that CoRoT-30 b is a warm Jupiter on a close-to-circular 9.06-day orbit around a G3V star with a semi-major axis of about 0.08AU. It has a radius of 1.01+/-0.08R_Jup_, a mass of 2.90+/-0.22M_Jup_, and therefore a mean density of 3.45+/-0.65g/cm^3^. The hot Jupiter CoRoT-31 b is on a close to circular 4.63-day orbit around a G2 IV star with a semi-major axis of about 0.05AU. It has a radius of 1.46+/-0.30R_Jup_, a mass of 0.84+/-0.34M_Jup_, and therefore a mean density of 0.33+/-0.18g/cm^3^. Neither system seems to support the claim that stars hosting planets are more depleted in lithium. The radii of both planets are close to that of Jupiter, but they differ in mass; CoRoT-30 b is ten times denser than CoRoT-31 b. The core of CoRoT-30 b would weigh between 15 and 75 Earth masses, whereas relatively weak constraints favor no core for CoRoT-31 b. In terms of evolution, the characteristics of CoRoT-31 b appear to be compatible with the high-eccentricity migration scenario, which is not the case for CoRoT-30 b. The angular momentum of CoRoT-31 b is currently too low for the planet to evolve toward synchronization of its orbital revolution with stellar rotation, and the planet will slowly spiral-in while its host star becomes a red giant. CoRoT-30 b is not synchronized either: it looses angular momentum owing to stellar winds and is expected reach steady state in about 2Gyr. CoRoT-30 and 31, as a pair, are a truly remarkable example of diversity in systems with hot Jupiters.
- ID:
- ivo://CDS.VizieR/J/A+A/619/A97
- Title:
- CoRoT transit catalogue
- Short Name:
- J/A+A/619/A97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The CoRoT space mission observed 163665 stars over 26 stellar fields in the faint star channel. The exoplanet teams detected a total of 4123 transit-like features in the 177454 light curves. We present the complete re-analysis of all these detections carried out with the same softwares so that to ensure their homogeneous analysis. Although the vetting process involves some human evaluation, it also involves a simple binary flag system over basic tests: detection significance, presence of a secondary, difference between odd and even depths, colour dependence, V-shape transit, and duration of the transit. We also gathered the information from the large accompanying ground-based programme carried out on the planet candidates and checked how useful the flag system could have been at the vetting stage of the candidates. From the initial list of transit-like features, we identified and separated 824 false alarms of various kind, 2269 eclipsing binaries among which 616 are contact binaries and 1653 are detached ones, 37 planets and brown dwarfs, and 557 planet candidates. We provide the catalogue of all these transit-like features, including false alarms. For the planet candidates, the catalogue gives not only their transit parameters but also the products of their light curve modelling: reduced radius, reduced semi-major axis, and impact parameter, together with a summary of the outcome of follow-up observations when carried out and their current status. For the detached eclipsing binaries, the catalogue provides, in addition to their transit parameters, a simple visual classification. Among the planet candidates whose nature remains unresolved, we estimate that eight (within an error of three) planets are still to be identified. After correcting for geometric and sensitivity biases, we derived planet and brown dwarf occurrences and confirm disagreements with Kepler estimates, as previously reported by other authors from the analysis of the first runs: small-size planets with orbital period less than ten days are underabundant by a factor of three in the CoRoT fields whereas giant planets are overabundant by a factor of two. These preliminary results would however deserve further investigations using the recently released CoRoT light curves that are corrected of the various instrumental effects and a homogeneous analysis of the stellar populations observed by the two missions.
