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Early 2017 observations of TRAPPIST-1 with Spitzer

Delrez, L. and Gillon, M. and Triaud, A. H. M. J. and Demory, B.-O. and de Wit, J. and Ingalls, J. G. and Agol, E. and Bolmont, E. and Burdanov, A. and Burgasser, A. J. and Carey, S. J. and Jehin, E. and Leconte, J. and Lederer, S. and Queloz, D. and Selsis, F. and Van Grootel, V. (2018) Early 2017 observations of TRAPPIST-1 with Spitzer. Monthly Notices of the Royal Astronomical Society, 475 (3). pp. 3577-3597. ISSN 0035-8711. doi:10.1093/mnras/sty051.

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The recently detected TRAPPIST-1 planetary system, with its seven planets transiting a nearby ultracool dwarf star, offers the first opportunity to perform comparative exoplanetology of temperate Earth-sized worlds. To further advance our understanding of these planets’ compositions, energy budgets, and dynamics, we are carrying out an intensive photometric monitoring campaign of their transits with the Spitzer Space Telescope. In this context, we present 60 new transits of the TRAPPIST-1 planets observed with Spitzer/Infrared Array Camera (IRAC) in 2017 February and March. We combine these observations with previously published Spitzer transit photometry and perform a global analysis of the resulting extensive data set. This analysis refines the transit parameters and provides revised values for the planets’ physical parameters, notably their radii, using updated properties for the star. As part of our study, we also measure precise transit timings that will be used in a companion paper to refine the planets’ masses and compositions using the transit timing variations method. TRAPPIST-1 shows a very low level of low-frequency variability in the IRAC 4.5-μm band, with a photometric RMS of only 0.11 per cent at a 123-s cadence. We do not detect any evidence of a (quasi-)periodic signal related to stellar rotation. We also analyse the transit light curves individually, to search for possible variations in the transit parameters of each planet due to stellar variability, and find that the Spitzer transits of the planets are mostly immune to the effects of stellar variations. These results are encouraging for forthcoming transmission spectroscopy observations of the TRAPPIST-1 planets with the James Webb Space Telescope.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Delrez, L.0000-0001-6108-4808
Gillon, M.0000-0003-1462-7739
Triaud, A. H. M. J.0000-0002-5510-8751
Demory, B.-O.0000-0002-9355-5165
de Wit, J.0000-0003-2415-2191
Ingalls, J. G.0000-0003-4714-1364
Agol, E.0000-0002-0802-9145
Bolmont, E.0000-0001-5657-4503
Burgasser, A. J.0000-0002-6523-9536
Carey, S. J.0000-0002-0221-6871
Queloz, D.0000-0002-3012-0316
Selsis, F.0000-0001-9619-5356
Additional Information:© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2017 December 31. Received 2017 December 21; in original form 2017 October 12. We thank E. Gillen for interesting discussions and valuable suggestions. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. This work was partially supported by a grant from the Simons Foundation (PI Queloz, grant number 327127). The research leading to these results also received funding from the European Research Council (ERC) under the FP/2007-2013 ERC grant agreement no. 336480, and under the H2020 ERC grant agreement no. 679030; and from an Action de Recherche Concertée (ARC) grant, financed by the Wallonia-Brussels Federation. LD acknowledges support from the Gruber Foundation Fellowship. VVG and MG are F.R.S.-FNRS Research Associates. EJ is F.R.S.-FNRS Senior Research Associate. B-OD acknowledges support from the Swiss National Science Foundation in the form of a SNSF Professorship (PP00P2_163967). EB acknowledges funding by the European Research Council through ERC grant SPIRE 647383. AJB acknowledges funding support from the US–UK Fulbright Scholarship programme.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Simons Foundation327127
European Research Council (ERC)336480
European Research Council (ERC)679030
Communauté française de Belgique - Actions de recherche concertée - Académie universitaire Wallonie-Brussels FederationUNSPECIFIED
Gruber FoundationUNSPECIFIED
Fonds de la Recherche Scientifique (FNRS)UNSPECIFIED
Swiss National Science Foundation (SNSF)PP00P2_163967
European Research Council (ERC)647383
Fulbright FoundationUNSPECIFIED
Subject Keywords:techniques: photometric – stars: individual: TRAPPIST-1 – planetary systems
Issue or Number:3
Record Number:CaltechAUTHORS:20180411-114459507
Persistent URL:
Official Citation:L Delrez, M Gillon, A H M J Triaud, B-O Demory, J de Wit, J G Ingalls, E Agol, E Bolmont, A Burdanov, A J Burgasser, S J Carey, E Jehin, J Leconte, S Lederer, D Queloz, F Selsis, V Van Grootel; Early 2017 observations of TRAPPIST-1 with Spitzer, Monthly Notices of the Royal Astronomical Society, Volume 475, Issue 3, 11 April 2018, Pages 3577–3597,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:85754
Deposited By: George Porter
Deposited On:11 Apr 2018 20:17
Last Modified:15 Nov 2021 20:31

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