Disentangling the Planet from the Star in Late-Type M Dwarfs: A Case Study of TRAPPIST-1g

Wakeford, Hannah R.; Lewis, Nikole K.; Fowler, J.; Bruno, G.; Wilson, Tom J.; Moran, Sarah E.; Valenti, Jeff A.; Batalha, Natasha E.; Filippazzo, Joseph; Bourrier, V.; Hörst, Sarah M.; Lederer, Susan M.; Wit, Julien de

doi:10.3847/1538-3881/aaf04d

Cited by 87 publications

(140 citation statements)

References 54 publications

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“…No prominent absorption features at near-infrared wavelengths in the transmission spectra of the atmospheres of the TRAPPIST-1 planets rule out cloud-free, hydrogen-rich atmospheres (de Wit et al 2016(de Wit et al , 2018Zhang et al 2018;Burdanov et al 2019), whereas a clear hydrogen-rich atmosphere for TRAPPIST-1 f and 1 g is still in dispute (de Wit et al 2018;Moran et al 2018;Wakeford et al 2019). Our results show that all the TRAPPIST-1 planets used to have a hydrogen-rich atmosphere of 10 −2 − 1 wt% just after disk dispersal.…”

Section: Discussionmentioning

confidence: 59%

“…The combined spectrum of the planets rules out cloud-free, hydrogen-dominated atmospheres, except for TRAPPIST-1 f and 1 g (de Wit et al 2018;Moran et al 2018); Wakeford et al (2019) recently suggested that a clear hydrogen-dominated atmosphere may be ruled out for TRAPPIST-1 g. Since high-altitude clouds and haze are not expected to form in hydrogen-dominated atmospheres around temperate planets (e.g. Morley et al 2015), transit spectroscopy of the TRAPPIST-1 planets suggests no atmosphere or a high-metallicity atmosphere referred to as a secondary atmosphere.…”

Section: Introductionmentioning

confidence: 99%

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Do the TRAPPIST-1 Planets Have Hydrogen-rich Atmospheres?

Hori

Ogihara

2020

ApJ

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Recently, transmission spectroscopy in the atmospheres of the TRAPPIST-1 planets revealed flat and featureless absorption spectra, which rule out cloud-free, hydrogen-dominated atmospheres. Earthsized planets orbiting TRAPPIST-1 likely have either a clear or a cloudy/hazy, hydrogen-poor atmosphere. In this paper, we investigate whether a proposed formation scenario is consistent with expected atmospheric compositions of the TRAPPIST-1 planets. We examine the amount of a hydrogen-rich gas that TRAPPIST-1-like planets accreted from the ambient disk until disk dispersal. Since TRAPPIST-1 planets are trapped into a resonant chain, we simulate disk gas accretion onto a migrating TRAPPIST-1-like planet. We find that the amount of an accreted hydrogen-rich gas is as small as 10 −2 wt% and 0.1 wt% for TRAPPIST-1 b and 1 c, 10 −2 wt% for 1 d, 1 wt% for 1 e, a few wt% for 1 f and 1 g and 1 wt% for 1 h, respectively. We also calculate the long-term thermal evolution of TRAPPIST-1-like planets after disk dissipation and estimate the mass loss of their hydrogen-rich atmospheres driven by a stellar X-ray and UV irradiation. We find that all the accreted hydrogen-rich atmospheres can be lost via hydrodynamic escape. Therefore, we conclude that TRAPPIST-1 planets should have no primordial hydrogen-rich gases but secondary atmospheres such as a Venus-like one and water vapor, if they currently retain atmospheres.

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Section: Discussionmentioning

confidence: 59%

Section: Introductionmentioning

confidence: 99%

Do the TRAPPIST-1 Planets Have Hydrogen-rich Atmospheres?

Hori

Ogihara

2020

ApJ

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“…First reconnaissance observations with the Hubble Space Telescope (HST) by de Wit et al (2016Wit et al ( , 2018 showed no hint of clear H/He dominated atmospheres for the six inner planets. Further studies reassessed these findings: Moran et al (2018) supported the presence of secondary volatile-rich atmospheres for planets d, e and f using revised masses (while not entirely ruling out a cloud-free H-rich atmosphere for TRAPPIST-1 e and f) and Wakeford et al (2019) ruled out a clear solar H 2 /He dominated atmosphere for TRAPPIST-1 g.…”

Section: Introductionmentioning

confidence: 86%

Ground-based follow-up observations of TRAPPIST-1 transits in the near-infrared

Burdanov

Lederer

Gillon

et al. 2019

Monthly Notices of the Royal Astronomical Society

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The TRAPPIST-1 planetary system is a favorable target for the atmospheric characterization of temperate earth-sized exoplanets by means of transmission spectroscopy with the forthcoming James Webb Space Telescope (JWST). A possible obstacle to this technique could come from the photospheric heterogeneity of the host star that could affect planetary signatures in the transit transmission spectra. To constrain further this possibility, we gathered an extensive photometric data set of 25 TRAPPIST-1 transits observed in the near-IR J band (1.2 µm) with the UKIRT and the AAT, and in the NB2090 band (2.1 µm) with the VLT during the period 2015-2018. In our analysis of these data, we used a special strategy aiming to ensure uniformity in our measurements and robustness in our conclusions. We reach a photometric precision of ∼ 0.003 (RMS of the residuals), and we detect no significant temporal variations of transit depths of TRAPPIST-1 b, c, e, and g over the period of three years. The few transit depths measured for planets d and f hint towards some level of variability, but more measurements will be required for confirmation. Our depth measurements for planets b and c disagree with the stellar contamination spectra originating from the possible existence of bright spots of temperature 4500 K. We report updated transmission spectra for the six inner planets of the system which are globally flat for planets b and g and some structures are seen for planets c, d, e, and f.

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“…The planets are good potential targets for atmospheric characterization with JWST (Lustig-Yaeger et al 2019;Lincowski et al 2018Lincowski et al , 2019Wunderlich et al 2019;Krissansen-Totton et al 2018; Barstow & Irwin 2016;Fauchez et al 2019b). Preliminary atmospheric prescreening was performed with HST/WFC3 and the resulting low-resolution transmission spectra acquired in the 1.1-1.7 µm spectral range made it possible to exclude clear hydrogen-dominated atmospheres for six of the seven planets (de Wit et al 2016(de Wit et al , 2018Wakeford et al 2018).…”

Section: Introductionmentioning

confidence: 99%

TRAPPIST-1: Global results of theSpitzerExploration Science Program Red Worlds

Ducrot

Gillon

Delrez

et al. 2020

A&A

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112

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Context. With more than 1000 h of observation from Feb. 2016 to Oct. 2019, the Spitzer Exploration Program Red Worlds (ID: 13067, 13175 and 14223) exclusively targeted TRAPPIST-1, a nearby (12 pc) ultracool dwarf star, finding that it is orbited by seven transiting Earth-sized planets. At least three of these planets orbit within the classical habitable zone of the star, and all of them are well-suited for a detailed atmospheric characterization with the upcoming JWST. Aims. The main goals of the Spitzer Red Worlds program were (1) to explore the system for new transiting planets, (2) to intensively monitor the planets’ transits to yield the strongest possible constraints on their masses, sizes, compositions, and dynamics, and (3) to assess the infrared variability of the host star. In this paper, we present the global results of the project. Methods. We analyzed 88 new transits and combined them with 100 previously analyzed transits, for a total of 188 transits observed at 3.6 or 4.5 μm. For a comprehensive study, we analyzed all light curves both individually and globally. We also analyzed 29 occultations (secondary eclipses) of planet b and eight occultations of planet c observed at 4.5 μm to constrain the brightness temperatures of their daysides. Results. We identify several orphan transit-like structures in our Spitzer photometry, but all of them are of low significance. We do not confirm any new transiting planets. We do not detect any significant variation of the transit depths of the planets throughout the different campaigns. Comparing our individual and global analyses of the transits, we estimate for TRAPPIST-1 transit depth measurements mean noise floors of ~35 and 25 ppm in channels 1 and 2 of Spitzer/IRAC, respectively. We estimate that most of this noise floor is of instrumental origins and due to the large inter-pixel inhomogeneity of IRAC InSb arrays, and that the much better interpixel homogeneity of JWST instruments should result in noise floors as low as 10 ppm, which is low enough to enable the atmospheric characterization of the planets by transit transmission spectroscopy. Our analysis reveals a few outlier transits, but we cannot conclude whether or not they correspond to spot or faculae crossing events. We construct updated broadband transmission spectra for all seven planets which show consistent transit depths between the two Spitzer channels. Although we are limited by instrumental precision, the combined transmission spectrum of planet b to g tells us that their atmospheres seem unlikely to be CH4-dominated. We identify and model five distinct high energy flares in the whole dataset, and discuss our results in the context of habitability. Finally, we fail to detect occultation signals of planets b and c at 4.5 μm, and can only set 3-σ upper limits on their dayside brightness temperatures (611 K for b 586 K for c).

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Disentangling the Planet from the Star in Late-Type M Dwarfs: A Case Study of TRAPPIST-1g

Cited by 87 publications

References 54 publications

Do the TRAPPIST-1 Planets Have Hydrogen-rich Atmospheres?

Do the TRAPPIST-1 Planets Have Hydrogen-rich Atmospheres?

Ground-based follow-up observations of TRAPPIST-1 transits in the near-infrared

TRAPPIST-1: Global results of theSpitzerExploration Science Program Red Worlds

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