Exoplanets & Exomoons

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

By Keith Cowing

Status Report

astro-ph.EP

March 20, 2023

Filed under astro-ph.EP, exoplanet, Habitable Zone, M Dwarfs, Nancy Grace Roman Space Telescope, Terrestrial Planet, Time Domain Survey, transiting exoplanets

Predicting the Yield of Small Transiting Exoplanets around Mid-M and Ultra-Cool Dwarfs in the Nancy Grace Roman Space Telescope Galactic Bulge Time Domain Survey — An example detection of a planet in our injection and recovery simulation. The host is an M5 dwarf with F146 = 16.5, Rh = 0.133 R, Mh = 0.108 M, Teff = 2895 K, a distance of 193 pc, and an age of 2.68 Gyr. The planet has a radius of 1.24 R⊕, an orbital period of 27.0 days, a/Rh = 136, and i = 89.9◦ . Top: the full simulated light curve which consists of six 72-day campaigns, three near the start of the mission and three near the end. Grey points show the 46.8-s photometry evaluated at a 909.6-s cadence, and black points with error bars show the photometry binned over 1.5-hour timescales. The transit model is shown in blue. Middle: The first of the six campaigns. Bottom: the phase-folded data which we use to assess the transit significance. Black points with error bars show the phased photometry binned over 20 points. The transit was recovered in the phased photometry to an S/N of 40 using Equation 5. — astro-ph.E

We simulate the yield of small (0.5-4.0 R⊕) transiting exoplanets around single mid-M and ultra-cool 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+208−124 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+4−3 habitable, terrestrial planets (Rp<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.

Patrick Tamburo, Philip S. Muirhead, Courtney D. Dressing

Comments: 19 pages, 10 figures, submitted to AJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2303.09959 [astro-ph.EP] (or arXiv:2303.09959v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2303.09959
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Submission history
From: Patrick Tamburo
[v1] Fri, 17 Mar 2023 13:30:32 UTC (29,559 KB)
https://arxiv.org/abs/2303.09959
Astrobiology

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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