Scaling K2. I. Revised Parameters for 222,088 K2 Stars and a K2 Planet Radius Valley at 1.9 R ⊕

Hardegree-Ullman, Kevin K.; Zink, Jon K.; Christiansen, Jessie L.; Dressing, Courtney D.; Ciardi, David R.; Schlieder, Joshua E.

doi:10.3847/1538-4365/ab7230

Cited by 90 publications

(59 citation statements)

References 91 publications

(130 reference statements)

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“…8, we show the distribution of planet-candidate radii from our K2-HERMES sample. Our sample, although smaller than the surveys conducted by Fulton et al (2017) and Hardegree-Ullman et al (2020), also sees a drop off in exoplanetary candidates and confirmed exoplanets centred around 1.8R ⊕ . Hardegree-Ullman et al (2020) in particular showed that K2 planet candidates were depleted within a radius gap centred at 1.9 R ⊕ .…”

Section: P L a N E T C A N D I Dat E Pa R A M E T E R Scontrasting

confidence: 48%

K2-HERMES II. Planet-candidate properties from K2 Campaigns 1-13

Wittenmyer

Clark

Sharma

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Accurate and precise radius estimates of transiting exoplanets are critical for understanding their compositions and formation mechanisms. To know the planet, we must know the host star in as much detail as possible. We present complete results for planet-candidate hosts from the K2-HERMES survey, which uses the HERMES multi-object spectrograph on the Anglo-Australian Telescope to obtain $R\sim 28\, 000$ spectra for more than 30 000 K2 stars. We present complete host-star parameters and planet-candidate radii for 224 K2 candidate planets from C1–C13. Our results cast severe doubt on 30 K2 candidates, as we derive unphysically large radii, larger than 2RJup. This work highlights the importance of obtaining accurate, precise, and self-consistent stellar parameters for ongoing large planet search programs – something that will only become more important in the coming years, as TESS begins to deliver its own harvest of exoplanets.

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Section: P L a N E T C A N D I Dat E Pa R A M E T E R Scontrasting

confidence: 48%

K2-HERMES II. Planet-candidate properties from K2 Campaigns 1-13

Wittenmyer

Clark

Sharma

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…If a significant portion of the sample parameters are inaccurate, we will under-or overestimate the difficulty of detecting planets, and therefore bias the occurrence measurements. To minimize this effect, we use the stellar parameters provided by Hardegree-Ullman et al (2020), as this provides the most uniform and up-to-date stellar parameters for K2. Using Gaia DR2 and LAMOST spectroscopic data, this sample significantly reduces the uncertainty in stellar radius measurements compared to measurements derived primarily by photometry (Huber et al 2016).…”

Section: K2 Stellar Selectionmentioning

confidence: 99%

“…Of these stars, only 865 rely on parameters from Huber et al (2016). The remaining 8392 stars use parameters derived by Hardegree-Ullman et al (2020). Finally, we calculate the two quadratic limb-darkening values for each target, using the ATLAS model coefficients for the Kepler bandpasses tabulated by Claret & Bloemen (2011).…”

Section: K2 Stellar Selectionmentioning

confidence: 99%

Scaling K2. III. Comparable Planet Occurrence in the FGK Samples of Campaign 5 and Kepler

Zink¹,

Hardegree-Ullman²,

Christiansen³

et al. 2020

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Using our K2 Campaign 5 fully automated planet-detection data set (43 planets), which has corresponding measures of completeness and reliability, we infer an underlying planet population model for the FGK dwarf sample (9257 stars). Implementing a broken power law for both the period and radius distributions, we find an overall planet occurrence of-+ 1.00 0.51 1.07 planets per star within a period range of 0.5-38 days. Making similar cuts and running a comparable analysis on the Kepler sample (2318 planets; 94,222 stars), we find an overall occurrence of 1.10±0.05 planets per star. Since the Campaign 5 field is nearly 120 angular degrees away from the Kepler field, this occurrence similarity offers evidence that the Kepler sample may provide a good baseline for Galactic inferences. Furthermore, the Kepler stellar sample is metal-rich compared to the K2 Campaign 5 sample, so a finding of occurrence parity may reduce the role of metallicity in planet formation. However, a weak (1.5σ) difference, in agreement with metal-driven formation, is found when assuming the Kepler model power laws for the K2 Campaign 5 sample and optimizing only the planet occurrence factor. This weak trend indicates that further investigation of metallicity-dependent occurrence is warranted once a larger sample of uniformly vetted K2 planet candidates is made available.

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“…Such extreme environments can radically alter planetary evolution, potentially driving atmospheric mass loss via thermal escape (e.g., Tian 2015; Owen 2019). Mass loss can in turn leave substantial imprints on observed planetary statistics, such as the dearth of planets between 1.5 and 2 Earth radii (the "radius gap" or "evaporation valley") and the so-called "Neptune desert" in the radius-period plane (Lopez & Fortney 2013;Owen & Wu 2013Fulton et al 2017;Fulton & Petigura 2018;van Eylen et al 2018;Cloutier & Menou 2020;Hardegree-Ullman et al 2020). Over the past two decades, most measurements of mass-loss rates for close-in planets have been conducted at ultraviolet wavelengths, with Lyα detections for HD 209458b (Vidal-Madjar et al 2003), HD 189733b (Lecavelier Des Etangs et al 2010;Lecavelier des Etangs et al 2012), GJ 436b (Kulow et al 2014;Ehrenreich et al 2015;Lavie et al 2017), and GJ 3470b (Bourrier et al 2018); tentative/marginal signals for TRAPPIST-1b and c (Bourrier et al 2017a), Kepler-444e and f (Bourrier et al 2017b), and K2-18b (dos Santos et al 2020); and nondetections for 55 Cnc e (Ehrenreich et al 2012), HD 97658b (Bourrier et al 2017c), GJ 1132 b (Waalkes et al 2019), and π Men c (García Muñoz et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Constraints on Metastable Helium in the Atmospheres of WASP-69b and WASP-52b with Ultranarrowband Photometry

Vissapragada

Knutson

Jovanović

et al. 2020

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Infrared observations of metastable 2 3 S helium absorption with ground-and space-based spectroscopy are rapidly maturing, as this species is a unique probe of exoplanet atmospheres. Specifically, the transit depth in the triplet feature (with vacuum wavelengths near 1083.3 nm) can be used to constrain the temperature and mass-loss rate of an exoplanet's upper atmosphere. Here, we present a new photometric technique to measure metastable 2 3 S helium absorption using an ultranarrowband filter (FWHM 0.635 nm) coupled to a beam-shaping diffuser installed in the Wide-field Infrared Camera on the 200 inch Hale Telescope at Palomar Observatory. We use telluric OH lines and a helium arc lamp to characterize refractive effects through the filter and to confirm our understanding of the filter transmission profile. We benchmark our new technique by observing a transit of WASP-69b and detect an excess absorption of 0.498%±0.045% (11.1σ), consistent with previous measurements after considering our bandpass. We then use this method to study the inflated gas giant WASP-52b and place a 95th percentile upper limit on excess absorption in our helium bandpass of 0.47%. Using an atmospheric escape model, we constrain the massloss rate for WASP-69b to be-+-M 5.25 10 Gyr 0.46

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Scaling K2. I. Revised Parameters for 222,088 K2 Stars and a K2 Planet Radius Valley at 1.9 R _⊕

Cited by 90 publications

References 91 publications

K2-HERMES II. Planet-candidate properties from K2 Campaigns 1-13

K2-HERMES II. Planet-candidate properties from K2 Campaigns 1-13

Scaling K2. III. Comparable Planet Occurrence in the FGK Samples of Campaign 5 and Kepler

Constraints on Metastable Helium in the Atmospheres of WASP-69b and WASP-52b with Ultranarrowband Photometry

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