AU Microscopii (AU Mic) is the second closest pre-main-sequence star, at a distance of 9.79 parsecs and with an age of 22 million years
. AU Mic possesses a relatively rare
and spatially resolved
...edge-on debris disk extending from about 35 to 210 astronomical units from the star
, and with clumps exhibiting non-Keplerian motion
. Detection of newly formed planets around such a star is challenged by the presence of spots, plage, flares and other manifestations of magnetic 'activity' on the star
. Here we report observations of a planet transiting AU Mic. The transiting planet, AU Mic b, has an orbital period of 8.46 days, an orbital distance of 0.07 astronomical units, a radius of 0.4 Jupiter radii, and a mass of less than 0.18 Jupiter masses at 3σ confidence. Our observations of a planet co-existing with a debris disk offer the opportunity to test the predictions of current models of planet formation and evolution.
Abstract
With a mass in the Neptune regime and a radius of Jupiter, WASP-107b presents a challenge to planet formation theories. Meanwhile, the planet’s low surface gravity and the star’s brightness ...also make it one of the most favorable targets for atmospheric characterization. Here, we present the results of an extensive 4 yr Keck/HIRES radial-velocity (RV) follow-up program of the WASP-107 system and provide a detailed study of the physics governing the accretion of the gas envelope of WASP-107b. We reveal that WASP-107b’s mass is only 1.8 Neptune masses (
M
b
= 30.5 ± 1.7
M
⊕
). The resulting extraordinarily low density suggests that WASP-107b has a H/He envelope mass fraction of >85% unless it is substantially inflated. The corresponding core mass of <4.6
M
⊕
at 3
σ
is significantly lower than what is traditionally assumed to be necessary to trigger massive gas envelope accretion. We demonstrate that this large gas-to-core mass ratio most plausibly results from the onset of accretion at ≳1 au onto a low-opacity, dust-free atmosphere and subsequent migration to the present-day
a
b
= 0.0566 ± 0.0017 au. Beyond WASP-107b, we also detect a second, more massive planet (
) on a wide eccentric orbit (
e
c
= 0.28 ± 0.07) that may have influenced the orbital migration and spin–orbit misalignment of WASP-107b. Overall, our new RV observations and envelope accretion modeling provide crucial insights into the intriguing nature of WASP-107b and the system’s formation history. Looking ahead, WASP-107b will be a keystone planet to understand the physics of gas envelope accretion.
Astronomers have discovered thousands of planets outside the Solar System
, most of which orbit stars that will eventually evolve into red giants and then into white dwarfs. During the red giant ...phase, any close-orbiting planets will be engulfed by the star
, but more distant planets can survive this phase and remain in orbit around the white dwarf
. Some white dwarfs show evidence for rocky material floating in their atmospheres
, in warm debris disks
or orbiting very closely
, which has been interpreted as the debris of rocky planets that were scattered inwards and tidally disrupted
. Recently, the discovery of a gaseous debris disk with a composition similar to that of ice giant planets
demonstrated that massive planets might also find their way into tight orbits around white dwarfs, but it is unclear whether these planets can survive the journey. So far, no intact planets have been detected in close orbits around white dwarfs. Here we report the observation of a giant planet candidate transiting the white dwarf WD 1856+534 (TIC 267574918) every 1.4 days. We observed and modelled the periodic dimming of the white dwarf caused by the planet candidate passing in front of the star in its orbit. The planet candidate is roughly the same size as Jupiter and is no more than 14 times as massive (with 95 per cent confidence). Other cases of white dwarfs with close brown dwarf or stellar companions are explained as the consequence of common-envelope evolution, wherein the original orbit is enveloped during the red giant phase and shrinks owing to friction. In this case, however, the long orbital period (compared with other white dwarfs with close brown dwarf or stellar companions) and low mass of the planet candidate make common-envelope evolution less likely. Instead, our findings for the WD 1856+534 system indicate that giant planets can be scattered into tight orbits without being tidally disrupted, motivating the search for smaller transiting planets around white dwarfs.
Abstract
We used high-precision radial velocity measurements of FGKM stars to determine the occurrence of giant planets as a function of orbital separation spanning 0.03–30 au. Giant planets are more ...prevalent at orbital distances of 1–10 au compared to orbits interior or exterior of this range. The increase in planet occurrence at ∼1 au by a factor of ∼4 is highly statistically significant. A fall-off in giant planet occurrence at larger orbital distances is favored over models with flat or increasing occurrence. We measure
14.1
−
1.8
+
2.0
giant planets per 100 stars with semimajor axes of 2–8 au and
8.9
−
2.4
+
3.0
giant planets per 100 stars in the range 8–32 au, a decrease in occurrence with increasing orbital separation that is significant at the ∼2
σ
level. We find that the occurrence rate of sub-Jovian planets (0.1–1 Jupiter masses) is also enhanced for 1–10 au orbits. This suggests that lower-mass planets may share the formation or migration mechanisms that drive the increased prevalence near the water–ice line for their Jovian counterparts. Our measurements of cold gas giant occurrence are consistent with the latest results from direct imaging surveys and gravitational lensing surveys despite different stellar samples. We corroborate previous findings that giant planet occurrence increases with stellar mass and metallicity.
We present a uniform transiting exoplanet candidate list for Campaign 5 of the K2 mission. This catalog contains 75 planets with seven multi-planet systems (five double, one triple, and one quadruple ...planet system). Within the range of our search, we find eight previously undetected candidates, with the remaining 67 candidates overlapping 51% of the study of Kruse et al. that manually vets candidates from Campaign 5. In order to vet our potential transit signals, we introduce the Exoplanet Detection Identification Vetter (EDI-Vetter), which is a fully automated program able to determine whether a transit signal should be labeled as a false positive or a planet candidate. This automation allows us to create a statistically uniform catalog, ideal for measurements of planet occurrence rate. When tested, the vetting software is able to ensure that our sample is 94.2% reliable against systematic false positives. Additionally, we inject artificial transits at the light-curve level of the raw K2 data and find that the maximum completeness of our pipeline is 70% before vetting and 60% after vetting. For convenience of future studies of occurrence rate, we include measurements of stellar noise (CDPP) and the three-transit window function for each target. This study is part of a larger survey of the K2 data set and the methodology that will be applied to the entirety of that set.
We report on the discovery and characterization of three planets orbiting the F8 star HD 28109, which sits comfortably in TESS ’s continuous viewing zone. The two outer planets have periods of 56 . ...0067 ±0 . 0003 d and 84 . 2597 + 0 . 0010 −0 . 0008 d, which implies a period ratio very close to that of the first-order 3:2 mean motion resonance, exciting transit timing variations (TTVs) of up to 60 min. These two planets were first identified by TESS , and we identified a third planet in the TESS photometry with a period of 22 . 8911 ±0 . 0004 d. We confirm the planetary nature of all three planetary candidates using ground-based photometry from Hazelwood , ASTEP , and LCO , including a full detection of the ∼9 h transit of HD 28109 c from Antarctica. The radii of the three planets are R b = 2 . 199 + 0 . 098 −0 . 10 R ⊕, R c = 4 . 23 ±0 . 11 R ⊕, and R d = 3 . 25 ±0 . 11 R ⊕; we characterize their masses using TTVs and precise radial velocities from ESPRESSO and HARPS, and find them to be M b = 18 . 5 + 9 . 1 −7 . 6 M ⊕, M c = 7 . 9 + 4 . 2 −3 . 0 M ⊕, and M d = 5 . 7 + 2 . 7 −2 . 1 M ⊕, making planet b a dense, massive planet while c and d are both underdense. We also demonstrate that the two outer planets are ripe for atmospheric characterization using transmission spectroscopy, especially given their position in the CVZ of James Webb Space Telescope . The data obtained to date are consistent with resonant (librating) and non-resonant (circulating) solutions; additional observations will show whether the pair is actually locked in resonance or just near-resonant.
NASA's Transiting Exoplanet Survey Satellite (TESS) presents us with an unprecedented volume of space-based photometric observations that must be analyzed in an efficient and unbiased manner. With at ...least ∼1,000,000 new light curves generated every month from full-frame images alone, automated planet candidate identification has become an attractive alternative to human vetting. Here we present a deep learning model capable of performing triage and vetting on TESS candidates. Our model is modified from an existing neural network designed to automatically classify Kepler candidates, and is the first neural network to be trained and tested on real TESS data. In triage mode, our model can distinguish transit-like signals (planet candidates and eclipsing binaries) from stellar variability and instrumental noise with an average precision (the weighted mean of precisions over all classification thresholds) of 97.0% and an accuracy of 97.4%. In vetting mode, the model is trained to identify only planet candidates with the help of newly added scientific domain knowledge, and achieves an average precision of 69.3% and an accuracy of 97.8%. We apply our model on new data from Sector 6, and present 288 new signals that received the highest scores in triage and vetting and were also identified as planet candidates by human vetters. We also provide a homogeneously classified set of TESS candidates suitable for future training.
Abstract
We present a high-precision radial velocity (RV) survey of 719 FGKM stars, which host 164 known exoplanets and 14 newly discovered or revised exoplanets and substellar companions. This ...catalog updated the orbital parameters of known exoplanets and long-period candidates, some of which have decades-longer observational baselines than they did upon initial detection. The newly discovered exoplanets range from warm sub-Neptunes and super-Earths to cold gas giants. We present the catalog sample selection criteria, as well as over 100,000 RV measurements, which come from the Keck-HIRES, APF-Levy, and Lick-Hamilton spectrographs. We introduce the new RV search pipeline
RVSearch
(
https://california-planet-search.github.io/rvsearch/
) that we used to generate our planet catalog, and we make it available to the public as an open-source Python package. This paper is the first study in a planned series that will measure exoplanet occurrence rates and compare exoplanet populations, including studies of giant planet occurrence beyond the water ice line, and eccentricity distributions to explore giant planet formation pathways. We have made public all radial velocities and associated data that we use in this catalog.
Abstract
We provide the first full K2 transiting exoplanet sample, using photometry from Campaigns 1–8 and 10–18, derived through an entirely automated procedure. This homogeneous planet candidate ...catalog is crucial to perform a robust demographic analysis of transiting exoplanets with K2. We identify 747 unique planet candidates and 57 multiplanet systems. Of these candidates, 366 have not been previously identified, including one resonant multiplanet system and one system with two short-period gas giants. By automating the construction of this list, measurements of sample biases (completeness and reliability) can be quantified. We carried out a light-curve-level injection/recovery test of artificial transit signals and found a maximum completeness of 61%, a consequence of the significant detrending required for K2 data analysis. Through this operation we attained measurements of the detection efficiency as a function of signal strength, enabling future population analysis using this sample. We assessed the reliability of our planet sample by testing our vetting software
EDI-Vetter
against inverted transit-free light curves. We estimate that 91% of our planet candidates are real astrophysical signals, increasing up to 94% when limited to the FGKM dwarf stellar population. We also constrain the contamination rate from background eclipsing binaries to less than 5%. The presented catalog, along with the completeness and reliability measurements, enable robust exoplanet demographic studies to be carried out across the fields observed by the K2 mission for the first time.
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