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

Burdanov, Artem; Lederer, Susan M.; Gillon, M.; Delrez, Laetitia; Ducrot, Elsa; Wit, Julien de; Jehin, Emmanuël; Triaud, A. H. M. J.; Lidman, C.; Spitler, Lee R.; Demory, Brice-Olivier; Queloz, D.; Grootel, Valérie Van

doi:10.1093/mnras/stz1375

Cited by 21 publications

(30 citation statements)

References 38 publications

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“…Among these 188 transits, 88 are "new", that is, they were observed in fall 2017 and fall 2019, and were not included in the analysis discussed in D2018 which presented data taken by Spitzer through March 2017. Our aim is to give an overview of the exploration of TRAPPIST-1 system with the Spitzer space telescope, we therefore did not include transits observed with other telescopes, but the results of the analysis of those additional observations can be found in existing papers: Luger et al (2017b) and Grimm et al (2018) for K2 observations, de Wit et al (2016Wit et al ( , 2018; Wakeford et al (2018) for HST observations, Ducrot et al (2018) for SPECULOOS and Liverpool telescope observations, Burdanov et al (2019) for VLT, AAT and UKIRT observations. Nevertheless, we use those results later in the paper to constructed the transit transmission spectra of the planets, in Sect.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

“…In Fig. 11, we show the updated version of the transmission spectra of the seven planets presented by Burdanov et al (2019). This update consists of an additional point at 3.6 µm for planets c-h, updated values at 4.5 µm, and updated weighted mean values for all planets (continuous lines in the plot).…”

Section: Transmission Spectra Of the Planetsmentioning

confidence: 99%

“…Coloured dots stand for the measured transit depth at the effective wavelength of the instrument, ground based measurement are symbolized by circles and space based measurement by hexagons. Each point is associated with a particular observation, in ascending order of wavelength: one point for K2 (value from Ducrot et al 2018), one for SSO (value from Ducrot et al 2018), one for LT (value from Ducrot et al 2018), one in the J-band for UKIRT/WFCAM and/or AAT (value from Burdanov et al 2019), one for the NB-2090 filter band, one point for VLT/HAWK-I only for planet b and c (value from Burdanov et al 2019), in IR 11 points for b and c, 10 for d, e, f and 13 for g taken with HST/WFC3 (values from de Wit et al 2016Wit et al , 2018Wakeford et al 2018) and two points for Spitzer/IRAC channel 1 and 2 (values from this work, Table 6).…”

Section: Transmission Spectra Of the Planetsmentioning

confidence: 99%

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

Ducrot

Gillon

Delrez

et al. 2020

A&A

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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Section: Observations and Data Reductionmentioning

confidence: 99%

Section: Transmission Spectra Of the Planetsmentioning

confidence: 99%

Section: Transmission Spectra Of the Planetsmentioning

confidence: 99%

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

Ducrot

Gillon

Delrez

et al. 2020

A&A

112

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“…Hubble Space Telescope (HST)/Wide Field Camera 3 (WFC3) measurements exhibit no prominent absorption features at near-infrared wavelengths in transmission spectra of six of the TRAPPIST-1 planets (de Wit et al 2016(de Wit et al , 2018Zhang et al 2018;Burdanov et al 2019)…”

Section: Introductionmentioning

confidence: 99%

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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“…Three of these planets E-mail: sebastian.marino.estay@gmail.com lie at a distance from the star where long-lived liquid water could exist on their surfaces (O'Malley-James & Kaltenegger 2017), although constraints on the composition of these planets are still very uncertain despite major efforts (e.g. de Wit et al 2016Wit et al , 2018Moran et al 2018;Wakeford et al 2019;Dorn et al 2018;Grimm et al 2018;Burdanov et al 2019). The composition of these planets is highly dependent on how these planets formed.…”

Section: Introductionmentioning

confidence: 99%

Searching for a dusty cometary belt around TRAPPIST-1 with ALMA

Marino

Wyatt

Kennedy

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Low mass stars might offer today the best opportunities to detect and characterise planetary systems, especially those harbouring close-in low mass temperate planets. Among those stars, Trappist-1 is exceptional since it has seven Earth-sized planets, of which three could sustain liquid water on their surfaces. Here we present new and deep ALMA observations of Trappist-1 to look for an exo-Kuiper belt which can provide clues about the formation and architecture of this system. Our observations at 0.88 mm did not detect dust emission, but can place an upper limit of 23µJy if the belt is unresolved or smaller than 4 au, and 0.15 mJy if resolved and 100 au in radius. These limits correspond to low dust masses of ∼ 10 −5 − 10 −2 M ⊕ , which are expected after 8 Gyr of collisional evolution unless the system was born with a > 20 M ⊕ belt of 100 km-sized planetesimals beyond 40 au. This 20 M ⊕ mass upper limit is comparable to the combined mass in Trappist-1 planets, thus it is possible that most of the available solid mass in these systems was used to form the known planets. A similar analysis of the ALMA data on Proxima Cen leads us to conclude that Proxima Cen cannot have been born with a belt of 100 km-sized planetesimals more massive than 10 M ⊕ between 20-40 au. Future characterisations of debris discs around low mass stars should focus on nearby and young systems which have not suffered significant collisional evolution beyond 10 au.

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

Cited by 21 publications

References 38 publications

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

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

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

Searching for a dusty cometary belt around TRAPPIST-1 with ALMA

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