Assessing the Transiting Exoplanet Survey Satellite’s Yield of Rocky Planets Around Nearby M Dwarfs

Brady, Madison; Bean, Jacob L.

doi:10.3847/1538-3881/ac64a0

Cited by 18 publications

(13 citation statements)

References 46 publications

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“…When compared to the early-to-mid M dwarf sample of Dressing & Charbonneau (2015), we instead find that the cumulative occurrence rate of all planets within our mid-to-late M dwarf sample is consistent with their work within the same period range (0.5-7 days), and lower by a factor of two when considering an equivalent range of insolations (>4 S ⊕ ), as demonstrated in Tables 7 and 8. This is consistent with the findings of Brady & Bean (2022) concluding that the planet occurrence rate likely does not increase and may decrease for the latest M dwarfs. It is also consistent with the recent RV study from Sabotta et al (2021) that did not find evidence in favor of planets orbiting stars with masses below 0.34M being more common than planets orbiting stars with masses above 0.34M , for orbital periods between 1-100 days, although the survey had a low detection sensitivity to most planets below several Earth masses.…”

Section: Notable Trendssupporting

confidence: 92%

The Occurrence Rate of Terrestrial Planets Orbiting Nearby Mid-to-late M Dwarfs from TESS Sectors 1-42

Ment¹,

Charbonneau²

2023

Preprint

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We present an analysis of a volume-complete sample of 363 mid-to-late M dwarfs within 15 pc of the Sun with masses between 0.1 and 0.3 M observed by TESS within Observation Sectors 1 to 42. The median mass of the stars in this sample is 0.17 M . We search the TESS 2-minute cadence light curves for transiting planets with orbital periods below 7 days using a modified Box-Least Squares (BLS) algorithm and recover all 6 known planets within the sample as well as a likely planet candidate orbiting LHS 475 (TESS Object of Interest 910.01). Each of these planets is consistent with a terrestrial composition, with planet radii ranging from 0.91 R ⊕ to 1.31 R ⊕ . In addition, we perform a transit injection and recovery analysis for each of the 363 stars to characterize the transit detection sensitivity as a function of planet radius, insolation, and orbital period. We obtain a cumulative occurrence rate of 0.61 +0.24 −0.19 terrestrial planets per M dwarf with radii above 0.5 R ⊕ and orbital periods between 0.4-7 days. We find that for comparable insolations, planets larger than 1.5 R ⊕ (sub-Neptunes and water worlds) are significantly less abundant around mid-to-late M dwarfs compared to earlier-type stars, while the occurrence rate of terrestrial planets is comparable to that of more massive M dwarfs. We estimate that overall, terrestrials outnumber sub-Neptunes around mid-to-late M dwarfs at a ratio of 14 to 1, in contrast to GK dwarfs where they are roughly equinumerous. We place a 1σ upper limit of 0.07 planets larger than 1.5 R ⊕ per mid-to-late M dwarf, within the orbital period range of 0.5-7 days. We find evidence for a downturn in occurrence rates for planet radii below 0.9R ⊕ , suggesting that Earth-sized and larger terrestrials may be more common around mid-to-late M dwarfs.

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Section: Notable Trendssupporting

confidence: 92%

The Occurrence Rate of Terrestrial Planets Orbiting Nearby Mid-to-late M Dwarfs from TESS Sectors 1-42

Ment¹,

Charbonneau²

2023

Preprint

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“…Their results are supported by occurrence rates measured with RV detections from the CARMENES survey, which found a significant increase in the occurrence rate of low-mass (1 M ⊕ < M i sin p < 10 M ⊕ ) planets with periods less than 10 days around stars with M å < 0.34 M e compared to higher-mass stars (Sabotta et al 2021). However, recent results from the Transiting Exoplanet Survey Satellite (TESS; Ricker et al 2015) suggest that the mission's yield of 0.5-2.0 R ⊕ planet candidates around nearby mid-M dwarfs is best produced by a constant or decreasing planet occurrence rate compared to early-M dwarfs (Brady & Bean 2022;Ment & Charbonneau 2023).…”

Section: Introductionmentioning

confidence: 99%

Predicting the Yield of Small Transiting Exoplanets around Mid-M and Ultracool Dwarfs in the Nancy Grace Roman Space Telescope Galactic Bulge Time Domain Survey

Tamburo

Muirhead

Dressing

2023

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We simulate the yield of small (0.5–4.0 R ⊕) transiting exoplanets around single mid-M and ultracool dwarfs (UCDs) in the Nancy Grace Roman Space Telescope Galactic Bulge Time Domain Survey. We consider multiple approaches for simulating M3–T9 sources within the survey fields, including scaling local space densities and using Galactic stellar population synthesis models. These approaches independently predict ∼100,000 single mid-M dwarfs and UCDs brighter than a Roman F146 magnitude of 21 that are within the survey fields. Assuming planet occurrence statistics previously measured for early-to-mid-M dwarfs, we predict that the survey will discover 1347 − 124 + 208 small transiting planets around these sources, each to a significance of 7.1σ or greater. Significant departures from this prediction would test whether the occurrence rates of small planets increase or decrease around mid-M dwarfs and UCDs compared to early-M dwarfs. We predict the detection of 13 − 3 + 4 habitable, terrestrial planets (R p < 1.23 R ⊕) in the survey. However, atmospheric characterization of these planets will be challenging with current or near-future space telescope facilities due to the faintness of the host stars. Nevertheless, accurate statistics for the occurrence of small planets around mid-M dwarfs and UCDs will enable direct tests of predictions from planet formation theories and will determine our understanding of planet demographics around the objects at the bottom of the main sequence. This understanding is critical given the prevalence of such objects in our galaxy, whose planets may therefore comprise the bulk of the galactic census of exoplanets.

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“…Statistical analyses of large samples of surveyed stars show that planets are ubiquitous, with occurrence rates greater than 0.5 planets per FGK-type star for orbital periods between one day and a few hundred days, based on estimates using radial velocity (RV) data (Howard et al 2010;Mayor et al 2011) and transits (Fressin et al 2013;Petigura et al 2013;Kunimoto & Matthews 2020). Occurrence rates for planets with low-mass M-dwarf hosts are even higher, with values exceeding one planet per star (Cassan et al 2012;Bonfils et al 2013;Dressing & Charbonneau 2015;Gaidos et al 2016;Sabotta et al 2021;Mulders et al 2021) and possibly further increasing from early-to-mid M-type dwarfs (Hardegree-Ullman et al 2019, but see Brady & Bean 2022 for the opposite).…”

Section: Introductionmentioning

confidence: 99%

A detailed analysis of the Gl 486 planetary system

Caballero

González-Álvarez

Brady

et al. 2022

A&A

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Context. The Gl 486 system consists of a very nearby, relatively bright, weakly active M3.5 V star at just 8 pc with a warm transiting rocky planet of about 1.3 R ⊕ and 3.0 M ⊕ that is ideal for both transmission and emission spectroscopy and for testing interior models of telluric planets. Aims. To prepare for future studies, we thoroughly characterise the planetary system with new accurate and precise data collected with state-ofthe-art photometers from space and spectrometers and interferometers from the ground. Methods. We collected light curves of seven new transits observed with the CHEOPS space mission and new radial velocities obtained with MAROON-X at the 8.1 m Gemini North and CARMENES at the 3.5 m Calar Alto telescopes, together with previously published spectroscopic and photometric data from the two spectrographs and TESS. We also performed near-infrared interferometric observations with the CHARA Array and new photometric monitoring with a suite of smaller telescopes (AstroLAB, LCOGT, OSN, TJO). This extraordinary and rich data set was the input for our comprehensive analysis. Results. From interferometry, we measure a limb-darkened disc angular size of the star Gl 486 at θ LDD = 0.390 ± 0.018 mas. Together with a corrected Gaia EDR3 parallax, we obtain a stellar radius R = 0.339 ± 0.015 R . We also measure a stellar rotation period at P rot = 49.9 ± 5.5 d, an upper limit to its XUV (5-920 Å) flux with new Hubble/STIS data, and, for the first time, a variety of element abundances (Fe, Mg, Si, V, Sr, Zr, Rb) and C/O ratio. Besides, we impose restrictive constraints on the presence of additional components, either stellar or substellar, in the system. With the input stellar parameters and the radial-velocity and transit data, we determine the radius and mass of the planet Gl 486 b at R p = 1.343 +0.063 −0.062 R ⊕ and M p = 3.00 +0.13 −0.13 M ⊕ , with relative uncertainties in planet radius and mass of 4.7 % and 4.2 %, respectively. From the planet parameters and the stellar element abundances, we infer the most probable models of planet internal structure and composition, which are consistent with a relatively small metallic core with respect to the Earth, a deep silicate mantle, and a thin volatile upper layer. With all these ingredients, we outline prospects for Gl 486 b atmospheric studies, especially with forthcoming James Webb Space Telescope observations.

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Assessing the Transiting Exoplanet Survey Satellite’s Yield of Rocky Planets Around Nearby M Dwarfs

Cited by 18 publications

References 46 publications

The Occurrence Rate of Terrestrial Planets Orbiting Nearby Mid-to-late M Dwarfs from TESS Sectors 1-42

The Occurrence Rate of Terrestrial Planets Orbiting Nearby Mid-to-late M Dwarfs from TESS Sectors 1-42

Predicting the Yield of Small Transiting Exoplanets around Mid-M and Ultracool Dwarfs in the Nancy Grace Roman Space Telescope Galactic Bulge Time Domain Survey

A detailed analysis of the Gl 486 planetary system

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