Evidence for Spin–Orbit Alignment in the TRAPPIST-1 System

Hirano, Teruyuki; Gaidos, Eric; Winn, Joshua N.; Dai, Fei; Fukui, A.; Kuzuhara, Masayuki; Kotani, Takayuki; Tamura, Motohide; Hjorth, María; Albrecht, S.; Huber, Daniel; Bolmont, Émeline; Harakawa, Hiroki; Hodapp, Klaus W.; Ishizuka, Masato; Jacobson, Shane; Konishi, Mihoko; Kudo, Tomoyuki; Kurokawa, Takashi; Nishikawa, Jun; Omiya, Masashi; Serizawa, Takuma; Ueda, Akitoshi; Weiss, Lauren M.

doi:10.3847/2041-8213/ab74dc

Cited by 52 publications

(46 citation statements)

References 48 publications

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“…Hirano et al. ( 2020 ) have very recently made a first potential detection of the Rossiter-McLaughlin effect with the Subaru-IRD spectrograph and derived a projected rotation velocity of TRAPPIST-1 of km s −1 , which corresponds to a maximum stellar rotation period of days, in agreement with the 3.3 days rotation period from the K2 light curves. It is also consistent with the stellar line rotational broadening measurement of TRAPPIST-1 with CARMENES (Reiners et al.…”

Section: Future Prospectsmentioning

confidence: 60%

A Review of Possible Planetary Atmospheres in the TRAPPIST-1 System

et al. 2020

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TRAPPIST-1 is a fantastic nearby (∼39.14 light years) planetary system made of at least seven transiting terrestrial-size, terrestrial-mass planets all receiving a moderate amount of irradiation. To date, this is the most observationally favourable system of potentially habitable planets known to exist. Since the announcement of the discovery of the TRAPPIST-1 planetary system in 2016, a growing number of techniques and approaches have been used and proposed to characterize its true nature. Here we have compiled a state-of-the-art overview of all the observational and theoretical constraints that have been obtained so far using these techniques and approaches. The goal is to get a better understanding of whether or not TRAPPIST-1 planets can have atmospheres, and if so, what they are made of. For this, we surveyed the literature on TRAPPIST-1 about topics as broad as irradiation environment, planet formation and migration, orbital stability, effects of tides and Transit Timing Variations, transit observations, stellar contamination, density measurements, and numerical climate and escape models. Each of these topics adds a brick to our understanding of the likely—or on the contrary unlikely—atmospheres of the seven known planets of the system. We show that (i) Hubble Space Telescope transit observations, (ii) bulk density measurements comparison with H 2 -rich planets mass-radius relationships, (iii) atmospheric escape modelling, and (iv) gas accretion modelling altogether offer solid evidence against the presence of hydrogen-dominated—cloud-free and cloudy—atmospheres around TRAPPIST-1 planets. This means that the planets are likely to have either (i) a high molecular weight atmosphere or (ii) no atmosphere at all. There are several key challenges ahead to characterize the bulk composition(s) of the atmospheres (if present) of TRAPPIST-1 planets. The main one so far is characterizing and correcting for the effects of stellar contamination. Fortunately, a new wave of observations with the James Webb Space Telescope and near-infrared high-resolution ground-based spectrographs on existing very large and forthcoming extremely large telescopes will bring significant advances in the coming decade.

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Section: Future Prospectsmentioning

confidence: 60%

A Review of Possible Planetary Atmospheres in the TRAPPIST-1 System

et al. 2020

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“…With few exceptions (Dalal et al 2019;Huber et al 2013), measurements of the obliquities of stars hosting multiple planets (e.g. Hirano et al 2020;Sanchis-Ojeda et al 2012;Hirano et al 2012;Albrecht et al 2013;Chaplin et al 2013) suggest that the axis of rotation of the host star is likely to be close to parallel to the orbital axis of its planets. Stars with close-in transiting planets, are therefore unlikely to exhibit a quiet light curve since the starspot and the inhomogeneous cloud coverage expected on the stellar surface of late-type M dwarfs and brown dwarfs (Metchev et al 2015;Goldman 2005) will constantly change as seen from Earth due to stellar rotation.…”

Section: Transit Detection Challengesmentioning

confidence: 99%

Global analysis of the TRAPPIST Ultra-Cool Dwarf Transit Survey

Lienhard

Queloz

Gillon

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We conducted a global analysis of the TRAPPIST Ultra-Cool Dwarf Transit Survey – a prototype of the SPECULOOS transit search conducted with the TRAPPIST-South robotic telescope in Chile from 2011 to 2017 – to estimate the occurrence rate of close-in planets such as TRAPPIST-1b orbiting ultra-cool dwarfs. For this purpose, the photometric data of 40 nearby ultra-cool dwarfs were reanalysed in a self-consistent and fully automated manner starting from the raw images. The pipeline developed specifically for this task generates differential light curves, removes non-planetary photometric features and stellar variability, and searches for transits. It identifies the transits of TRAPPIST-1b and TRAPPIST-1c without any human intervention. To test the pipeline and the potential output of similar surveys, we injected planetary transits into the light curves on a star-by-star basis and tested whether the pipeline is able to detect them. The achieved photometric precision enables us to identify Earth-sized planets orbiting ultra-cool dwarfs as validated by the injection tests. Our planet-injection simulation further suggests a lower limit of 10 per cent on the occurrence rate of planets similar to TRAPPIST-1b with a radius between 1 and 1.3 R⊕ and the orbital period between 1.4 and 1.8 days.

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“…In addition, we might we be able to measure the Rossiter-McLaughlin effect for this system, due to its brightness and lack of confounding stellar activity. The obliquity of the system would be a valuable addition to the recent observation by Hirano et al (2020) that the TRAPPIST-1 planets are well-aligned with the host star's spin.…”

Section: Prospects For Radial Velocity Follow-up and Additional Tess mentioning

confidence: 99%

A super-Earth and a sub-Neptune orbiting the bright, quiet M3 dwarf TOI-1266

Demory

Pozuelos

Chew

et al. 2020

A&A

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We report the discovery and characterisation of a super-Earth and a sub-Neptune transiting the bright (K = 8.8), quiet, and nearby (37 pc) M3V dwarf TOI-1266. We validate the planetary nature of TOI-1266 b and c using four sectors of TESS photometry and data from the newly-commissioned 1-m SAINT-EX telescope located in San Pedro Mártir (México). We also include additional ground-based follow-up photometry as well as high-resolution spectroscopy and high-angular imaging observations. The inner, larger planet has a radius of R = 2.37−0.12+0.16 R⊕ and an orbital period of 10.9 days. The outer, smaller planet has a radius of R = 1.56−0.13+0.15 R⊕ on an 18.8-day orbit. The data are found to be consistent with circular, co-planar and stable orbits that are weakly influenced by the 2:1 mean motion resonance. Our TTV analysis of the combined dataset enables model-independent constraints on the masses and eccentricities of the planets. We find planetary masses of Mp = 13.5−9.0+11.0 M⊕ (<36.8 M⊕ at 2-σ) for TOI-1266 b and 2.2−1.5+2.0 M⊕ (<5.7 M⊕ at 2-σ) for TOI-1266 c. We find small but non-zero orbital eccentricities of 0.09−0.05+0.06 (<0.21 at 2-σ) for TOI-1266 b and 0.04 ± 0.03 (< 0.10 at 2-σ) for TOI-1266 c. The equilibrium temperatures of both planets are of 413 ± 20 and 344 ± 16 K, respectively, assuming a null Bond albedo and uniform heat redistribution from the day-side to the night-side hemisphere. The host brightness and negligible activity combined with the planetary system architecture and favourable planet-to-star radii ratios makes TOI-1266 an exquisite system for a detailed characterisation.

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Evidence for Spin–Orbit Alignment in the TRAPPIST-1 System

Cited by 52 publications

References 48 publications

A Review of Possible Planetary Atmospheres in the TRAPPIST-1 System

A Review of Possible Planetary Atmospheres in the TRAPPIST-1 System

Global analysis of the TRAPPIST Ultra-Cool Dwarf Transit Survey

A super-Earth and a sub-Neptune orbiting the bright, quiet M3 dwarf TOI-1266

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