Characterization of a Set of Small Planets with TESS and CHEOPS and an Analysis of Photometric Performance

Dominic, Oddo,; Dragomir, Diana; Brandeker, Alexis; Osborn, H.; Collins, Karen A.; Stassun, Keivan G.; Astudillo-Defru, N.; Bieryla, Allyson; Howell, Steve B.; Ciardi, David R.; Quinn, Samuel N.; Almenara, J. M.; Collins, Kevin I.; Colón, Knicole D.; Conti, Dennis M.; Crouzet, Nicolas; Furlan, Elise; Gan, Tianjun; Gnilka, Crystal L.; Goeke, R.; Gonzales, Erica J.; Harris, M.; Jenkins, Jon M.; Jensen, Eric L. N.; Latham, David W.; Law, Nicholas M.; Lund, Michael B.; Mann, Andrew; Massey, Bob; Murgas, F.; Ricker, G.; Relles, Howard M.; Rowden, Pamela; Schwarz, Richard P.; Schlieder, Joshua E.; Shporer, Avi; Seager, Sara; Srdoč, Gregor; Torres, Guillermo; Twicken, Joseph D.; Vanderspek, R.; Winn, Joshua N.; Ziegler, Carl

doi:10.3847/1538-3881/acb4e3

Cited by 7 publications

(2 citation statements)

References 120 publications

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“…In this work, we confirm and characterize the small (R p = 1.5 R ⊕ ) and close-in (P = 7.4 days) transiting planet TOI-244 b (recently validated in Oddo et al 2023) orbiting the bright (K = 7.97 mag) and nearby (d = 22 pc) M 2.5V star GJ 1018. Based on the transit signal detected from TESS data, we carried out an intensive radial velocity campaign with ESPRESSO in order to confirm its planetary nature, obtain a precise mass measurement, as well as to search for additional planets.…”

Section: Introductionsupporting

confidence: 73%

An unusually low-density super-Earth transiting the bright early-type M-dwarf GJ 1018 (TOI-244)

Castro-González¹,

Lillo-Box²,

Lavie³

et al. 2023

A&A

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Context. Small planets located at the lower mode of the bimodal radius distribution are generally assumed to be composed of iron and silicates in a proportion similar to that of the Earth. However, recent discoveries are revealing a new group of low-density planets that are inconsistent with that description. Aims. We intend to confirm and characterize the TESS planet candidate TOI-244.01, which orbits the bright (K = 7.97 mag), nearby (d = 22 pc), and early-type (M2.5 V) M-dwarf star GJ 1018 with an orbital period of 7.4 days. Methods. We used Markov chain Monte Carlo methods to model 57 precise radial velocity measurements acquired by the ESPRESSO spectrograph together with TESS photometry and complementary HARPS data. Our model includes a planetary component and Gaussian processes aimed at modeling the correlated stellar and instrumental noise. Results. We find TOI-244 b to be a super-Earth with a radius of Rp = 1.52 ± 0.12 R⊕ and a mass of Mp = 2.68 ± 0.30 M⊕. These values correspond to a density of ρ = 4.2 ± 1.1 g cm−3, which is below what would be expected for an Earth-like composition. We find that atmospheric loss processes may have been efficient to remove a potential primordial hydrogen envelope, but high mean molecular weight volatiles such as water could have been retained. Our internal structure modeling suggests that TOI-244 b has a 479−96+128 km thick hydrosphere over a 1.17 ± 0.09 R⊕ solid structure composed of a Fe-rich core and a silicate-dominated mantle compatible with that of the Earth. On a population level, we find two tentative trends in the density-metallicity and density-insolation parameter space for the low-density super-Earths, which may hint at their composition. Conclusions. With a 8% precision in radius and 12% precision in mass, TOI-244 b is among the most precisely characterized super-Earths, which, together with the likely presence of an extended hydrosphere, makes it a key target for atmospheric observations.

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Section: Introductionsupporting

confidence: 73%

An unusually low-density super-Earth transiting the bright early-type M-dwarf GJ 1018 (TOI-244)

Castro-González¹,

Lillo-Box²,

Lavie³

et al. 2023

A&A

Self Cite

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“…These considerations show that it is necessary to work on a case-by-case basis (i.e. for each R p − P − T 0 scenario) if we want to compare the performances of both instruments (see Oddo et al 2023 for a detailed discussion on this subject). This is not our goal here, which is rather to get a global picture of the overall detection potential of both datasets in the R p − P parameter space.…”

Section: Detection Limitsmentioning

confidence: 99%

Exploring the Nu2 Lupi system with CHEOPS

Delrez

2024

Preprint

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***Results under embargo. Paper accepted for publication at Nature Astronomy, to be published in June.*** Multi-transiting planetary systems around bright stars offer unique windows to comparative exoplanetology. Nu2 Lupi (HD 136352) is a naked-eye (V=5.8) Sun-like star that was discovered to host three low-mass planets with orbital periods of 11.6, 27.6, and 107.6 days via radial velocity monitoring with the HARPS spectrograph. The two inner planets (b and c) were recently found to transit by the TESS mission, prompting us to follow up the system with ESA's brand-new CHaracterizing ExOPlanets Satellite (CHEOPS). This led to the exciting discovery that the outer planet d is also transiting. With its bright Sun-like star, long period, and mild irradiation (&#8764;5.7 times the irradiation of Earth), Nu2 Lupi d unlocks a completely new region in the parameter space of exoplanets amenable to detailed characterization. By combining all available space and ground-based data, we measured its radius and mass to be 2.56&#177;0.09 REarth and 8.82&#177;0.94 MEarth, respectively, and refined the properties of all three planets: planet b likely has a rocky mostly dry composition, while planets c and d seem to have retained small hydrogen-helium envelopes and a possibly large water fraction. This diversity of planetary compositions makes the Nu2 Lupi system an excellent laboratory for testing formation and evolution models of low-mass planets.

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Refining the properties of the TOI-178 system with CHEOPS and TESS

Delrez,

Leleu,

Brandeker

et al. 2023

A&A

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Context. The TOI-178 system consists of a nearby late K-dwarf transited by six planets in the super-Earth to mini-Neptune regime, with radii ranging from ~1.1 to 2.9 R⊕ and orbital periods between 1.9 and 20.7 days. All planets but the innermost one form a chain of Laplace resonances. Mass estimates derived from a preliminary radial velocity (RV) dataset suggest that the planetary densities do not decrease in a monotonic way with the orbital distance to the star, contrary to what one would expect based on simple formation and evolution models. Aims. To improve the characterisation of this key system and prepare for future studies (in particular with JWST), we performed a detailed photometric study based on 40 new CHEOPS visits, one new TESS sector, and previously published CHEOPS, TESS, and NGTS data. Methods. First we updated the parameters of the host star using the new parallax from Gaia EDR3. We then performed a global analysis of the 100 transits contained in our data to refine the physical and orbital parameters of the six planets and study their transit timing variations (TTVs). We also used our extensive dataset to place constraints on the radii and orbital periods of potential additional transiting planets in the system. Results. Our analysis significantly refines the transit parameters of the six planets, most notably their radii, for which we now obtain relative precisions of ≲3%, with the exception of the smallest planet, b, for which the precision is 5.1%. Combined with the RV mass estimates, the measured TTVs allow us to constrain the eccentricities of planets c to g, which are found to be all below 0.02, as expected from stability requirements. Taken alone, the TTVs also suggest a higher mass for planet d than that estimated from the RVs, which had been found to yield a surprisingly low density for this planet. However, the masses derived from the current TTV dataset are very prior-dependent, and further observations, over a longer temporal baseline, are needed to deepen our understanding of this iconic planetary system.

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Characterization of a Set of Small Planets with TESS and CHEOPS and an Analysis of Photometric Performance

Cited by 7 publications

References 120 publications

An unusually low-density super-Earth transiting the bright early-type M-dwarf GJ 1018 (TOI-244)

An unusually low-density super-Earth transiting the bright early-type M-dwarf GJ 1018 (TOI-244)

Exploring the Nu2 Lupi system with CHEOPS

Refining the properties of the TOI-178 system with CHEOPS and TESS

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