- ID:
- ivo://CDS.VizieR/J/ApJ/799/180
- Title:
- Radii of 430 KOI Earth- to Neptune-sized planets
- Short Name:
- J/ApJ/799/180
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the cumulative catalog of planets detected by the NASA Kepler mission, we reconstruct the intrinsic occurrence of Earth- to Neptune-size (1-4R_{Earth}_) planets and their distributions with radius and orbital period. We analyze 76711 solar-type (0.8<R_*_/R_{sun}_<1.2) stars with 430 planets on 20-200 day orbits, excluding close-in planets that may have been affected by the proximity to the host star. Our analysis considers errors in planet radii and includes an "iterative simulation" technique that does not bin the data. We find a radius distribution that peaks at 2-2.8 Earth radii, with lower numbers of smaller and larger planets. These planets are uniformly distributed with logarithmic period, and the mean number of such planets per star is 0.46+/-0.03. The occurrence is ~0.66 if planets interior to 20 days are included. We estimate the occurrence of Earth-size planets in the "habitable zone" (defined as 1-2 R_{Earth}_, 0.99-1.7AU for solar-twin stars) as 6.4_-1.1_^+3.4^%. Our results largely agree with those of Petigura et al. (2013PNAS..11019273P), although we find a higher occurrence of 2.8-4 Earth-radii planets. The reasons for this excess are the inclusion of errors in planet radius, updated Huber et al. (2014, J/ApJS/211/2) stellar parameters, and also the exclusion of planets that may have been affected by proximity to the host star.
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- ID:
- ivo://CDS.VizieR/J/ApJ/791/10
- Title:
- Radius distribution of planets around cool stars
- Short Name:
- J/ApJ/791/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We calculate an empirical, non-parametric estimate of the shape of the period-marginalized radius distribution of planets with periods less than 150 days using the small yet well-characterized sample of cool (T_eff_< 4000 K) dwarf stars in the Kepler catalog. In particular, we present and validate a new procedure, based on weighted kernel density estimation, to reconstruct the shape of the planet radius function down to radii smaller than the completeness limit of the survey at the longest periods. Under the assumption that the period distribution of planets does not change dramatically with planet radius, we show that the occurrence of planets around these stars continues to increase to below 1 R_{sun}_, and that there is no strong evidence for a turnover in the planet radius function. In fact, we demonstrate using many iterations of simulated data that a spurious turnover may be inferred from data even when the true distribution continues to rise toward smaller radii. Finally, the sharp rise in the radius distribution below ~3 R_{sun}_ implies that a large number of planets await discovery around cool dwarfs as the sensitivities of ground-based transit surveys increase.
- ID:
- ivo://CDS.VizieR/J/AJ/160/238
- Title:
- Reflectivity of 4 Gallilean satellites with ISS
- Short Name:
- J/AJ/160/238
- Date:
- 10 Dec 2021
- Publisher:
- CDS
- Description:
- For terrestrial exoplanets with thin or no atmospheres, the surface contributes light to the reflected light signal of the planet. Measurement of the variety of disk-integrated brightnesses of bodies in the solar system and the variation with illumination and wavelength is essential for both planning imaging observations of directly imaged exoplanets and interpreting the eventual data sets. Here we measure the change in brightness of the Galilean satellites as a function of planetocentric longitude, illumination phase angle, and wavelength. The data span a range of wavelengths from 400 to 950nm and predominantly phase angles from 0{deg} to 25{deg}, with some constraining observations near 60{deg}-140{deg}. Despite the similarity in size and density between the moons, surface inhomogeneities result in significant changes in the disk-integrated reflectivity with planetocentric longitude and phase angle. We find that these changes are sufficient to determine the rotational periods of the moon. We also find that at low phase angles, the surface can produce reflectivity variations of 8%-36%, and the limited high phase angle observations suggest variations will have proportionally larger amplitudes at higher phase angles. Additionally, all of the Galilean satellites are darker than predicted by an idealized Lambertian model at the phases most likely to be observed by direct imaging missions. If Earth-sized exoplanets have surfaces similar to that of the Galilean moons, we find that future direct imaging missions will need to achieve precisions of less than 0.1ppb. Should the necessary precision be achieved, future exoplanet observations could exploit similar observation schemes to deduce surface variations, determine rotation periods, and potentially infer surface composition.
- ID:
- ivo://CDS.VizieR/J/ApJ/795/L14
- Title:
- Refracted light signals to discriminate exoplanets
- Short Name:
- J/ApJ/795/L14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We propose a method to distinguish between cloudy, hazy, and clear sky (free of clouds and hazes) exoplanet atmospheres that could be applicable to upcoming large aperture space- and ground-based telescopes such as the James Webb Space Telescope (JWST) and the European Extremely Large Telescope (E-ELT). These facilities will be powerful tools for characterizing transiting exoplanets, but only after a considerable amount of telescope time is devoted to a single planet. A technique that could provide a relatively rapid means of identifying haze-free targets (which may be more valuable targets for characterization) could potentially increase the science return for these telescopes. Our proposed method utilizes broadband observations of refracted light in the out-of-transit spectrum. Light refracted through an exoplanet atmosphere can lead to an increase of flux prior to ingress and subsequent to egress. Because this light is transmitted at pressures greater than those for typical cloud and haze layers, the detection of refracted light could indicate a cloud- or haze-free atmosphere. A detection of refracted light could be accomplished in <10 hr for Jovian exoplanets with JWST and <5 hr for super-Earths/mini-Neptunes with E-ELT. We find that this technique is most effective for planets with equilibrium temperatures between 200 and 500 K, which may include potentially habitable planets. A detection of refracted light for a potentially habitable planet would strongly suggest the planet was free of a global cloud or haze layer, and therefore a promising candidate for follow-up observations.
- ID:
- ivo://CDS.VizieR/J/ApJ/709/159
- Title:
- Relative Ic photometry of WASP-17
- Short Name:
- J/ApJ/709/159
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of the transiting giant planet WASP-17b, the least-dense planet currently known. It is 1.6 Saturn masses, but 1.5-2 Jupiter radii, giving a density of 6%-14% that of Jupiter. WASP-17b is in a 3.7 day orbit around a sub-solar metallicity, V=11.6, F6 star. Preliminary detection of the Rossiter-McLaughlin effect suggests that WASP-17b is in a retrograde orbit ({lambda}~-150{deg}), indicative of a violent history involving planet-planet or star-planet scattering. WASP-17b's bloated radius could be due to tidal heating resulting from recent or ongoing tidal circularization of an eccentric orbit, such as the highly eccentric orbits that typically result from scattering interactions. It will thus be important to determine more precisely the current orbital eccentricity by further high-precision radial velocity measurements or by timing the secondary eclipse, both to reduce the uncertainty on the planet's radius and to test tidal-heating models. Owing to its low surface gravity, WASP-17b's atmosphere has the largest scale height of any known planet, making it a good target for transmission spectroscopy.
- ID:
- ivo://CDS.VizieR/J/ApJ/692/L100
- Title:
- Relative photometry of WASP-10
- Short Name:
- J/ApJ/692/L100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the photometry of WASP-10 during a transit of its short-period Jovian planet. We employed the novel point-spread function shaping capabilities of the Orthogonal Parallel Transfer Imaging Camera mounted on the UH 2.2m telescope to achieve a photometric precision of 4.7x10^-4^ per 1.3 minute sample. With this new light curve, in conjunction with stellar evolutionary models, we improve on existing measurements of the planetary, stellar, and orbital parameters. We find a stellar radius R_*_=0.698+/-0.012R_{sun}_ and a planetary radius R_P_=1.080+/-0.020R_Jup_. The quoted errors do not include any possible systematic errors in the stellar evolutionary models. Our measurement improves the precision of the planet's radius by a factor of 4, and revises the previous estimate downward by 16% (2.5{sigma}, where {sigma} is the quadrature sum of the respective confidence limits). Our measured radius of WASP-10b is consistent with previously published theoretical radii for irradiated Jovian planets.
- ID:
- ivo://CDS.VizieR/J/ApJ/715/421
- Title:
- Relative photometry of WASP-3
- Short Name:
- J/ApJ/715/421
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new spectroscopic and photometric observations of the transiting exoplanetary system WASP-3. Spectra obtained during two separate transits exhibit the Rossiter-McLaughlin (RM) effect and allow us to estimate the sky-projected angle between the planetary orbital axis and the stellar rotation axis, {lambda}=3.3^+2.5^_-4.4_deg. This alignment between the axes suggests that WASP-3b has a low orbital inclination relative to the equatorial plane of its parent star. During our first night of spectroscopic measurements, we observed an unexpected redshift briefly exceeding the expected sum of the orbital and RM velocities by 140m/s. This anomaly could represent the occultation of material erupting from the stellar photosphere, although it is more likely to be an artifact caused by moonlight scattered into the spectrograph.
- ID:
- ivo://CDS.VizieR/J/ApJ/700/302
- Title:
- Relative photometry of XO-3
- Short Name:
- J/ApJ/700/302
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present photometric and spectroscopic observations of the 2009 February 2 transit of the exoplanet XO-3b. The new data show that the planetary orbital axis and stellar rotation axis are misaligned, as reported earlier by Hebrard and coworkers. We find the angle between the sky projections of the two axes to be 37.3+/-3.7deg, as compared to the previously reported value of 70+/-15deg. The significance of this discrepancy is unclear because there are indications of systematic effects. XO-3b is the first exoplanet known to have a highly inclined orbit relative to the equatorial plane of its parent star, and as such it may fulfill the predictions of some scenarios for the migration of massive planets into close-in orbits. We revisit the statistical analysis of spin-orbit alignment in hot-Jupiter systems. Assuming the stellar obliquities to be drawn from a single Rayleigh distribution, we find the mode of the distribution to be 13^+5^_-2_deg. However, it remains the case that a model representing two different migration channels-in which some planets are drawn from a perfectly aligned distribution and the rest are drawn from an isotropic distribution-is favored over a single Rayleigh distribution.
- ID:
- ivo://CDS.VizieR/J/AJ/141/63
- Title:
- Relative radial velocities of HAT-P-4 and HAT-P-14
- Short Name:
- J/AJ/141/63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present observations of the Rossiter-McLaughlin effect for two exoplanetary systems, revealing the orientations of their orbits relative to the rotation axes of their parent stars. HAT-P-4b is prograde, with a sky-projected spin-orbit angle of {lambda}=-4.9+/-11.9{deg}. In contrast, HAT-P-14b is retrograde, with {lambda}=189.1+/-5.1{deg}. These results conform with a previously noted pattern among the stellar hosts of close-in giant planets: hotter stars have a wide range of obliquities and cooler stars have low obliquities. This, in turn, suggests that three-body dynamics and tidal dissipation are responsible for the short-period orbits of many exoplanets. In addition, our data revealed a third body in the HAT-P-4 system, which could be a second planet or a companion star.
- ID:
- ivo://CDS.VizieR/J/AJ/152/18
- Title:
- Robo-AO Kepler planetary candidate survey. II.
- Short Name:
- J/AJ/152/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We initiated the Robo-AO Kepler Planetary Candidate Survey in 2012 to observe each Kepler exoplanet candidate host star with high angular resolution, visible light, laser adaptive optics (AOs) imaging. Our goal is to find nearby stars lying in Kepler's photometric apertures that are responsible for the relatively high probability of false-positive exoplanet detections and that cause underestimates of the size of transit radii. Our comprehensive survey will also shed light on the effects of stellar multiplicity on exoplanet properties and will identify rare exoplanetary architectures. In this second part of our ongoing survey, we observed an additional 969 Kepler planet candidate hosts and we report blended stellar companions up to {Delta}m{approx}6 that contribute to Kepler's measured light curves. We found 203 companions within ~4'' of 181 of the Kepler stars, of which 141 are new discoveries. We measure the nearby star probability for this sample of Kepler planet candidate host stars to be 10.6%+/-1.1% at angular separations up to 2.5'', significantly higher than the 7.4%+/-1.0% probability discovered in our initial sample of 715 stars; we find the probability increases to 17.6%+/-1.5% out to a separation of 4.0''. The median position of Kepler Objects of Interest (KOIs) observed in this survey are 1.1{deg} closer to the galactic plane, which may account for some of the nearby star probability enhancement. We additionally detail 50 Keck AO images of Robo-AO observed KOIs in order to confirm 37 companions detected at a <5{sigma} significance level and to obtain additional infrared photometry on higher significance detected companions.