Exoplanets & Exomoons

The TESS-Keck Survey. XVI. Mass Measurements for 12 Planets in Eight Systems

By Keith Cowing
Status Report
June 29, 2023
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The TESS-Keck Survey. XVI. Mass Measurements for 12 Planets in Eight Systems
The mass-radius diagram for small planets. Data comes from the NASA Exoplanet Archive’s planetary systems table, as accessed on 2022-Nov-17 (NASA Exoplanet Archive 2022). Planets with mass and radius measurements to better than 50% and 15% fractional precision, respectively, are shown as the circles with 1σ error bars. The opacity of the points is proportional to mass measurement precision (i.e., a less precise mass measurement translates to a more transparent marker). Color corresponds to equilibrium temperature assuming zero Bond albedo and full day-night heat redistribution. Underlying contours come from Gaussian kernel density estimation (KDE) of the confirmed planets described above. The 11 transiting planets from this work are overplotted as the stars. Mass upper limits (98% confidence) are plotted for HD 25463 c (yellow star near the radius valley) and HIP 9618 c (labeled). A handful of composition curves are plotted for reference (Lopez & Fortney 2014; Zeng et al. 2016, 2019). The curves of H/He envelopes atop Earth-like cores come from Lopez & Fortney (2014) and are chosen for a planet receiving 10× Earth’s incident flux (i.e., Teq ≈ 500 K) orbiting a 10 Gyr-old, solar-metallicity star. The 50% water plus 50% Earth-like composition curve from Zeng et al. (2019) is calculated for a fixed temperature of 700 K at 100 bar, which determines the planetary model’s specific entropy. Note that familiar features of the planet radius distribution are now visible as two-dimensional features in the mass-radius plane. These include the radius valley (Fulton et al. 2017; Van Eylen et al. 2018), with center near 6 M⊕ and 1.8 R⊕, and the radius cliff (e.g., Kite et al. 2019), as seen by in the steep drop off in the number of planets around 3 R⊕. — astro-ph.EP

With JWST’s successful deployment and unexpectedly high fuel reserves, measuring the masses of sub-Neptunes transiting bright, nearby stars will soon become the bottleneck for characterizing the atmospheres of small exoplanets via transmission spectroscopy.

Using a carefully curated target list and more than two years’ worth of APF-Levy and Keck-HIRES Doppler monitoring, the TESS-Keck Survey is working toward alleviating this pressure. Here we present mass measurements for 11 transiting planets in eight systems that are particularly suited to atmospheric follow-up with JWST. We also report the discovery and confirmation of a temperate super-Jovian-mass planet on a moderately eccentric orbit.

The sample of eight host stars, which includes one subgiant, spans early-K to late-F spectral types (Teff= 5200–6200 K). We homogeneously derive planet parameters using a joint photometry and radial velocity modeling framework, discuss the planets’ possible bulk compositions, and comment on their prospects for atmospheric characterization.

In order of increasing TOI number, the systems presented in this work are:

HIP 8152 (TOI-266): a G dwarf hosting two subNeptunes.

HD 42813 (TOI-469): an early-K dwarf hosting one sub-Neptune.

HD 25463 (TOI-554): a late-F dwarf hosting a sub-Neptune and a super-Earth on opposite sides of the radius valley (Fulton et al. 2017; Van Eylen et al. 2018).

TOI-669: a G dwarf hosting one sub-Neptune.

HD 135694 (TOI-1247): an early-K dwarf hosting one sub-Neptune.

HIP 9618 (TOI-1471): a G dwarf hosting two subNeptunes, each with P > 20 d. The system is also host to a massive, distant companion as seen by a linear trend in the radial velocities. The nature of the companion is uncertain.

HD 6061 (TOI-1473): an early-G dwarf hosting one sub-Neptune. The host star also appears to be gravitationally bound to a mid-M dwarf companion (TIC 600433892). The two stars have a sky-projected separation of about 200 AU.

TOI-1736: a slightly evolved G star hosting one sub-Neptune and one nontransiting, super-Jovianmass planet on a moderately eccentric orbit. The system is also host to a massive, distant companion as seen by a linear trend in the radial velocities. The nature of the companion is uncertain.

Joseph M. Akana Murphy, Natalie M. Batalha, Nicholas Scarsdale, Howard Isaacson, David R. Ciardi, Erica J. Gonzales, Steven Giacalone, Joseph D. Twicken, Anne Dattilo, Tara Fetherolf, Ryan A. Rubenzahl, Ian J. M. Crossfield, Courtney D. Dressing, Benjamin Fulton, Andrew W. Howard, Daniel Huber, Stephen R. Kane, Erik A. Petigura, Paul Robertson, Arpita Roy, Lauren M. Weiss, Corey Beard, Ashley Chontos, Fei Dai, Malena Rice, Judah Van Zandt, Jack Lubin, Sarah Blunt, Alex S. Polanski, Aida Behmard, Paul A. Dalba, Michelle L. Hill, Lee J. Rosenthal, Casey L. Brinkman, Andrew W. Mayo, Emma V. Turtelboom, Isabel Angelo, Teo Močnik, Mason G. MacDougall, Daria Pidhorodetska, Dakotah Tyler, Molly R. Kosiarek, Rae Holcomb, Emma M. Louden, Lea A. Hirsch, Jay Anderson, Jeff A. Valenti

Comments: Accepted for publication in The Astronomical Journal on 2023-Jun-22. 60 pages, 17 Tables, 28 Figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2306.16587 [astro-ph.EP] (or arXiv:2306.16587v1 [astro-ph.EP] for this version)
Submission history
From: Joseph M. Akana Murphy
[v1] Wed, 28 Jun 2023 22:39:32 UTC (30,885 KB)

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) 🖖🏻