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1. Stellar Contamination Correction Using Back-to-back Transits of TRAPPIST-1 b and c

Author

Alexander D. Rathcke, Lars A. Buchhave, Julien de Wit, Benjamin V. Rackham, Prune C. August, Hannah Diamond-Lowe, João M. MendonÇa, Aaron Bello-Arufe, Mercedes López-Morales, Daniel Kitzmann, and Kevin Heng

Subjects
Transmission spectroscopy, Stellar atmospheres, Planet hosting stars, Exoplanet atmospheres, Fundamental parameters of stars, Starspots, Astrophysics, QB460-466
Abstract

Stellar surface heterogeneities, such as spots and faculae, often contaminate exoplanet transit spectra, hindering precise atmospheric characterization. We demonstrate a novel, epoch-based, model-independent method to mitigate stellar contamination, applicable to multiplanet systems with at least one airless planet. We apply this method using quasi-simultaneous transits of TRAPPIST-1 b and TRAPPIST-1 c observed on 2024 July 9, with JWST/NIRSpec PRISM. These two planets, with nearly identical radii and impact parameters, are likely to either be bare rocks or possess thin, low-pressure atmospheres, making them ideal candidates for this technique, as variations in their transit spectra would be primarily attributed to stellar activity. Our observations reveal their transit spectra exhibit consistent features, indicating similar levels of stellar contamination. We use TRAPPIST-1 b to correct the transit spectrum of TRAPPIST-1 c, achieving a 2.5 × reduction in stellar contamination at shorter wavelengths. At longer wavelengths, lower signal-to-noise ratio prevents clear detection of contamination or full assessment of mitigation. Still, out-of-transit analysis reveals variations across the spectrum, suggesting contamination extends into the longer wavelengths. Based on the success of the correction at shorter wavelengths, we argue that contamination is also reduced at longer wavelengths to a similar extent. This shifts the challenge of detecting atmospheric features to a predominantly white noise issue, which can be addressed by stacking observations. This method enables epoch-specific stellar contamination corrections, allowing coaddition of planetary spectra for reliable searches of secondary atmospheres with signals of 60–250 ppm. Additionally, we identify small-scale cold (∼2000 K) and warm (∼2600 K) regions almost uniformly distributed on TRAPPIST-1, with overall covering fractions varying by ∼0.1% per hour.

Published
2025
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2. Spectroscopically Resolved Partial Phase Curve of the Rapid Heating and Cooling of the Highly Eccentric Hot Jupiter HAT-P-2b with WFC3

Author

Bob Jacobs, Jean-Michel Désert, Nikole Lewis, Ryan C. Challener, L. C. Mayorga, Zoë L. de Beurs, Vivien Parmentier, Kevin B. Stevenson, Julien de Wit, Saugata Barat, Jonathan Fortney, Tiffany Kataria, and Michael Line

Subjects
Exoplanets, Extrasolar gaseous giant planets, Extrasolar gaseous planets, Exoplanet atmospheres, Exoplanet atmospheric dynamics, Exoplanet atmospheric composition, Astronomy, QB1-991
Abstract

The extreme environments of transiting close-in exoplanets in highly eccentric orbits are ideal for testing exoclimate physics. Spectroscopically resolved phase curves not only allow for the characterization of their thermal response to irradiation changes but also unveil phase-dependent atmospheric chemistry and dynamics. We observed a partial phase curve of the highly eccentric close-in giant planet HAT-P-2b ( e = 0.51, M = 9 M _Jup ) with the Wide Field Camera 3 aboard the Hubble Space Telescope. Using these data, we updated the planet's orbital parameters and radius and retrieved high-frequency pulsations consistent with the planet-induced pulsations reported in Spitzer data. We found that the peak in planetary flux occurred at 6.7 ± 0.6 hr after periastron, with heating and cooling timescales of $9.{0}_{-2.1}^{+3.5}$ hr and $3.{6}_{-0.6}^{+0.7}$ hr, respectively. We compare the light curve to various 1D and 3D forward models, varying the planet's chemical composition. The strong contrast in flux increase and decrease timescales before and after periapse indicates an opacity term that emerges during the planet's heating phase, potentially due to more H ^− than expected from chemical equilibrium models. The phase-resolved spectra are largely featureless, which we interpret as indicative of an inhomogeneous dayside. However, we identified an anomalously high flux in the spectroscopic bin coinciding with the hydrogen Pa β line, and that is likely connected to the planet's orbit. We interpret this as due to shock heating of the upper atmosphere given the short timescale involved, or evidence for other star−planet interactions.

Published
2025
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3. Reliable Transmission Spectrum Extraction with a Three-parameter Limb-darkening Law

Author

Rosa E. Keers, Alexander I. Shapiro, Nadiia M. Kostogryz, Ana Glidden, Prajwal Niraula, Benjamin V. Rackham, Sara Seager, Sami K. Solanki, Yvonne C. Unruh, Valeriy Vasilyev, and Julien de Wit

Subjects
Limb darkening, Exoplanet atmospheres, Transmission spectroscopy, Astrophysics, QB460-466
Abstract

Stellar limb darkening must be properly accounted for to accurately determine the radii of exoplanets at various wavelengths. The standard approach to address limb darkening involves either using laws with coefficients from modeled stellar spectra or determining the coefficients empirically during light-curve fitting of the data. Here, we test how accurately three common laws—quadratic, power, and a three-parameter law—can reproduce stellar limb darkening at different wavelengths and across a broad range of stars. We show that using a quadratic limb-darkening law, which is most frequently employed by the community, leads to wavelength-dependent offsets in retrieved transmission spectra. For planets with high impact parameters ( b larger than about 0.5), the amplitude of these offsets can reach 1% of the transit depth, which in some cases is comparable to and can even exceed the expected signals from the planetary atmosphere. Furthermore, the quadratic law causes an offset in the value of the impact parameter when it is determined by fitting the broadband transit light curves. In contrast, using the Kipping–Sing three-parameter law leads to robust retrievals. We advocate the use of this law in retrievals, especially for transits with large impact parameters.

Published
2024
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4. Empirically Constraining the Spectra of Stellar Surface Features Using Time-resolved Spectroscopy

Author

David Berardo, Julien de Wit, and Benjamin V. Rackham

Subjects
Exoplanets, Stellar surfaces, Transmission spectroscopy, Astronomical techniques, Astrophysics, QB460-466
Abstract

Transmission spectroscopy is currently the technique best suited to study a wide range of planetary atmospheres, leveraging the filtering of a star’s light by a planet’s atmosphere rather than its own emission. However, as both a planet and its star contribute to the information encoded in a transmission spectrum, an accurate accounting of the stellar contribution is pivotal to enabling robust atmospheric studies. As current stellar models lack the required fidelity for such accounting, we investigate here the capability of time-resolved spectroscopy to yield high-fidelity, empirical constraints on the emission spectra of stellar surface heterogeneities (i.e., spots and faculae). Using TRAPPIST-1 as a test case, we simulate time-resolved JWST/NIRISS spectra and demonstrate that with a blind approach incorporating no physical priors, it is possible to constrain the photospheric spectrum to ≤0.5% and the spectra of stellar heterogeneities to within ≲10%, a precision that enables photon-limited (rather than model-limited) science. Now confident that time-resolved spectroscopy can propel the field in an era of robust high-precision transmission spectroscopy, we introduce a list of areas for future exploration to harness its full potential, including wavelength dependency of limb darkening and hybrid priors from stellar models as a means to further break the degeneracy between the position, size, and spectra of heterogeneities.

Published
2024
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5. Updated Spectral Characteristics for the Ultracool Dwarf TRAPPIST-1

Author

Fatemeh Davoudi, Benjamin V. Rackham, Michaël Gillon, Julien de Wit, Adam J. Burgasser, Laetitia Delrez, Aishwarya Iyer, and Elsa Ducrot

Subjects
Exoplanets, M dwarf stars, Exoplanet systems, Astrophysics, QB460-466
Abstract

A comprehensive infrared spectroscopic study of star TRAPPIST-1 is a crucial step toward the detailed examination of its planets. While the presence of Earth’s atmosphere has limited the spectral extent of such a study up to now, the Near Infrared Imager and Slitless Spectrograph (NIRISS) and the Near Infrared Spectrograph instruments aboard the James Webb Space Telescope (JWST) can now yield the 0.6–5 μ m spectral energy distribution (SED) of the star. Here we translate TRAPPIST-1's SED into tight constraints on its luminosity ( L _bol = 0.000566 ± 0.000022 L _⊙ ), effective temperature ( T _eff = 2569 ± 28 K), and metallicity ([Fe/H] = 0.052 ± 0.073) and investigate the behavior of its gravity-sensitive indices. Through band-by-band comparisons of the NIRISS and ground-based spectra, TRAPPIST-1 exhibits a blend of both field source and intermediate-gravity spectral characteristics, suggesting that the star is likely a field-age source with spectral features reminiscent of young objects. We also employ photospheric modeling incorporating theoretical and JWST spectra to constrain stellar surface heterogeneities, finding that the limited fidelity of current stellar spectral models precludes definitive constraints on the physical parameters of the distinct spectral components giving rise to TRAPPIST-1's photospheric heterogeneity and variability. In addition, we find intermodel differences in the inferences of properties (e.g., the effective temperature) over one order of magnitude larger than the instrument-driven uncertainties (∼100 K vs. ∼4 K), pointing toward a model-driven accuracy wall. Our findings call for a new generation of stellar models to support the optimal mining of JWST data and further constraining stellar—and ultimately planetary—properties.

Published
2024
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6. Axisymmetric High Spot Coverage on Exoplanet Host HD 189733 A

Author

Isaac S. Narrett, Benjamin V. Rackham, and Julien de Wit

Subjects
Starspots, Stellar activity, Exoplanet atmospheres, Planet hosting stars, Astronomy, QB1-991
Abstract

Transmission spectroscopy is a powerful tool to study exoplanet atmospheres, which can be affected by the ability of stellar photospheric heterogeneity to mimic or mask exoplanetary spectral signatures. The canonical HD 189733 system provides a textbook example of this spectroscopic discrepancy with features that have been variously interpreted as signatures of scattering by haze in the planetary atmosphere or unocculted spots on the stellar disk. Here, we leverage three archival data sets from the Hubble Space Telescope to directly infer the covering fraction of HD 189733 A and explore the evidence for photospheric heterogeneity in the out-of-transit spectra. We model the stellar spectrum using one to three spectral components in a nested-sampling framework, finding that the two-component model (photosphere and spot) is preferred for all data sets. We find photospheric and spot temperatures of $5295{\pm }_{41}^{43}$ and $3222{\pm }_{116}^{100}$ K, respectively, which are consistent across data sets. The spot covering fraction is large and varies between 38% ± 4% and 47% ± 3%. Combined with time-domain insights from Transiting Exoplanet Survey Satellite data revealing HD 189733 A's 1.4% peak-to-peak variability, our findings imply that the majority of the spots must be distributed axisymmetrically, e.g., in a densely filled latitudinal band or at the poles. More work with complementary data sets is necessary to investigate those possible arrangements.

Published
2024
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7. Toward Robust Corrections for Stellar Contamination in JWST Exoplanet Transmission Spectra

Author

Benjamin V. Rackham and Julien de Wit

Subjects
Transmission spectroscopy, Stellar atmospheres, Planet hosting stars, Exoplanet atmospheres, Fundamental parameters of stars, Starspots, Astronomy, QB1-991
Abstract

Transmission spectroscopy is still the preferred characterization technique for exoplanet atmospheres, although it presents unique challenges that translate into characterization bottlenecks when robust mitigation strategies are missing. Stellar contamination is one such challenge that can overpower the planetary signal by up to an order of magnitude, and thus not accounting for it can lead to significant biases in the derived atmospheric properties. Yet this accounting may not be straightforward, as important discrepancies exist between state-of-the-art stellar models and measured spectra and between models themselves. Here we explore the extent to which stellar models can be used to reliably correct for stellar contamination and yield a planet’s uncontaminated transmission spectrum. We find that discrepancies between stellar models can significantly contribute to the noise budget of JWST transmission spectra of planets around stars with heterogeneous photospheres, the true number of unique photospheric spectral components and their properties can only be accurately retrieved when the stellar models have sufficient fidelity, and under such optimistic circumstances the contribution of stellar contamination to the noise budget of a transmission spectrum is considerably below that of the photon noise for the standard transit observation setup. Therefore, we advocate for further development of model spectra of stars and their active regions in a data-driven manner, empirical approaches for deriving spectra of photospheric components using the observatories with which the atmospheric explorations are carried out, and analysis techniques accounting for multimodal posterior distributions for photospheric parameters of interest, which will be increasingly revealed by precise JWST measurements.

Published
2024
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8. Origin and Extent of the Opacity Challenge for Atmospheric Retrievals of WASP-39 b

Author

Prajwal Niraula, Julien de Wit, Iouli E. Gordon, Robert J. Hargreaves, and Clara Sousa-Silva

Subjects
Transmission spectroscopy, Exoplanet atmospheric composition, Exoplanet atmospheres, Astrophysics, QB460-466
Abstract

As the James Webb Space Telescope (JWST) came online last summer, we entered a new era of astronomy. This new era is supported by data products of unprecedented information content that require novel reduction and analysis techniques. Recently, Niraula et al. (N22) highlighted the need for upgraded opacity models to prevent facing a model-driven accuracy wall when interpreting exoplanet transmission spectra. Here, we follow the same approach as N22 to explore the sensitivity of inferences on the atmospheric properties of WASP-39 b to the opacity models used. We find that the retrieval of the main atmospheric properties from this first JWST exoplanet spectrum is mostly unaffected by the current state of the community’s opacity models. Abundances of strong opacity sources like water and carbon dioxide are reliably constrained within ∼0.30 dex, beyond the 0.50 dex accuracy wall reported in N22. Assuming the completeness and accuracy of line lists, N22's accuracy wall is primarily driven by model uncertainties on broadening coefficients and far-wing behaviors, which we find to have marginal consequences for interpreting the transmission spectra of large, hot, high-metallicity atmospheres such as WASP-39 b, in opposition to emission spectra and climate modeling, which depend on deeper parts of a planetary atmosphere. The origin of the opacity challenge in the retrieval of metal-rich hot Jupiters via transmission spectroscopy will thus mostly stem from the incompleteness and inaccuracy of line lists.

Published
2023
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9. Atmospheric Reconnaissance of TRAPPIST-1 b with JWST/NIRISS: Evidence for Strong Stellar Contamination in the Transmission Spectra

Author

Olivia Lim, Björn Benneke, René Doyon, Ryan J. MacDonald, Caroline Piaulet, Étienne Artigau, Louis-Philippe Coulombe, Michael Radica, Alexandrine L’Heureux, Loïc Albert, Benjamin V. Rackham, Julien de Wit, Salma Salhi, Pierre-Alexis Roy, Laura Flagg, Marylou Fournier-Tondreau, Jake Taylor, Neil J. Cook, David Lafrenière, Nicolas B. Cowan, Lisa Kaltenegger, Jason F. Rowe, Néstor Espinoza, Lisa Dang, and Antoine Darveau-Bernier

Subjects
Extrasolar rocky planets, Exoplanets, M dwarf stars, Stellar activity, Starspots, Stellar faculae, Astrophysics, QB460-466
Abstract

TRAPPIST-1 is a nearby system of seven Earth-sized, temperate, rocky exoplanets transiting a Jupiter-sized M8.5V star, ideally suited for in-depth atmospheric studies. Each TRAPPIST-1 planet has been observed in transmission both from space and from the ground, confidently rejecting cloud-free, hydrogen-rich atmospheres. Secondary eclipse observations of TRAPPIST-1 b with JWST/MIRI are consistent with little to no atmosphere given the lack of heat redistribution. Here we present the first transmission spectra of TRAPPIST-1 b obtained with JWST/NIRISS over two visits. The two transmission spectra show moderate to strong evidence of contamination from unocculted stellar heterogeneities, which dominates the signal in both visits. The transmission spectrum of the first visit is consistent with unocculted starspots and the second visit exhibits signatures of unocculted faculae. Fitting the stellar contamination and planetary atmosphere either sequentially or simultaneously, we confirm the absence of cloud-free, hydrogen-rich atmospheres, but cannot assess the presence of secondary atmospheres. We find that the uncertainties associated with the lack of stellar model fidelity are one order of magnitude above the observation precision of 89 ppm (combining the two visits). Without affecting the conclusion regarding the atmosphere of TRAPPIST-1 b, this highlights an important caveat for future explorations, which calls for additional observations to characterize stellar heterogeneities empirically and/or theoretical works to improve model fidelity for such cool stars. This need is all the more justified as stellar contamination can affect the search for atmospheres around the outer, cooler TRAPPIST-1 planets for which transmission spectroscopy is currently the most efficient technique.

Published
2023
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10. Revisiting Orbital Evolution in HAT-P-2 b and Confirmation of HAT-P-2 c

Author

Zoë L. de Beurs, Julien de Wit, Alexander Venner, David Berardo, Jared Bryan, Joshua N. Winn, Benjamin J. Fulton, and Andrew W. Howard

Subjects
Star-planet interactions, Orbital evolution, Astrometry, Radial velocity, Exoplanets, Hot Jupiters, Astronomy, QB1-991
Abstract

One possible formation mechanism for Hot Jupiters is that high-eccentricity gas giants experience tidal interactions with their host star that cause them to lose orbital energy and migrate inwards. We study these types of tidal interactions in an eccentric Hot Jupiter called HAT-P-2 b, which is a system where a long-period companion has been suggested and hints of orbital evolution were detected. Using 5 additional years of radial velocity (RV) measurements, we further investigate these phenomena. We investigated the long-period companion by jointly fitting RVs and Hipparcos-Gaia astrometry and confirmed this long-period companion, significantly narrowed down the range of possible periods ( ${P}_{2}={8500}_{-1500}^{+2600}$ days), and determined that it must be a substellar object ( ${10.7}_{-2.2}^{+5.2}$ M _j ). We also developed a modular pipeline to simultaneously model rapid orbital evolution and the long-period companion. We find that the rate and significance of evolution are highly dependent on the long-period companion modeling choices. In some cases the orbital rates of change reached ${de}/{dt}\,=\,{3.28}_{-1.72}^{+1.75}\times {10}^{-3}$ yr ^−1 , d ω / dt = 1.12° ± 0.22° yr ^−1 , which corresponds to a ∼321 yr apsidal precession period. In other cases, the data is consistent with de / dt = 7.67 ± 18.6 × 10 ^−4 yr ^−1 , d ω / dt = 0.76° ± 0.24° yr ^−1 . The most rapid changes found are significantly larger than the expected relativistic precession rate and could be caused by transient tidal planet–star interactions. To definitively determine the magnitude and significance of potential orbital evolution in HAT-P-2 b, we recommend further monitoring with RVs and precise transit and eclipse timings.

Published
2023
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11. A Massive Hot Jupiter Orbiting a Metal-rich Early M Star Discovered in the TESS Full-frame Images

Author

Tianjun Gan, Charles Cadieux, Farbod Jahandar, Allona Vazan, Sharon X. Wang, Shude Mao, Jaime A. Alvarado-Montes, D. N. C. Lin, Étienne Artigau, Neil J. Cook, René Doyon, Andrew W. Mann, Keivan G. Stassun, Adam J. Burgasser, Benjamin V. Rackham, Steve B. Howell, Karen A. Collins, Khalid Barkaoui, Avi Shporer, Jerome de Leon, Luc Arnold, George R. Ricker, Roland Vanderspek, David W. Latham, Sara Seager, Joshua N. Winn, Jon M. Jenkins, Artem Burdanov, David Charbonneau, Georgina Dransfield, Akihiko Fukui, Elise Furlan, Michaël Gillon, Matthew J. Hooton, Hannah M. Lewis, Colin Littlefield, Ismael Mireles, Norio Narita, Chris W. Ormel, Samuel N. Quinn, Ramotholo Sefako, Mathilde Timmermans, Michael Vezie, and Julien de Wit

Subjects
M dwarf stars, Radial velocity, Photometry, M stars, Extrasolar gaseous planets, Astronomy, QB1-991
Abstract

Observations and statistical studies have shown that giant planets are rare around M dwarfs compared with Sun-like stars. The formation mechanism of these extreme systems has remained under debate for decades. With the help of the TESS mission and ground-based follow-up observations, we report the discovery of TOI-4201b, the most massive and densest hot Jupiter around an M dwarf known so far with a radius of 1.22 ± 0.04 R _J and a mass of 2.48 ± 0.09 M _J , about 5 times heavier than most other giant planets around M dwarfs. It also has the highest planet-to-star mass ratio ( q ∼ 4 × 10 ^−3 ) among such systems. The host star is an early M dwarf with a mass of 0.61 ± 0.02 M _⊙ and a radius of 0.63 ± 0.02 R _⊙ . It has significant supersolar iron abundance ([Fe/H] = 0.52 ± 0.08 dex). However, interior structure modeling suggests that its planet TOI-4201b is metal-poor, which challenges the classical core-accretion correlation of stellar−planet metallicity, unless the planet is inflated by additional energy sources. Building on the detection of this planet, we compare the stellar metallicity distribution of four planetary groups: hot/warm Jupiters around G/M dwarfs. We find that hot/warm Jupiters show a similar metallicity dependence around G-type stars. For M-dwarf host stars, the occurrence of hot Jupiters shows a much stronger correlation with iron abundance, while warm Jupiters display a weaker preference, indicating possible different formation histories.

Published
2023
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12. TOI 4201 b and TOI 5344 b: Discovery of Two Transiting Giant Planets around M-dwarf Stars and Revised Parameters for Three Others

Author

J. D. Hartman, G. Á. Bakos, Z. Csubry, A. W. Howard, H. Isaacson, S. Giacalone, A. Chontos, N. Narita, A. Fukui, J. P. de Leon, N. Watanabe, M. Mori, T. Kagetani, I. Fukuda, Y. Kawai, M. Ikoma, E. Palle, F. Murgas, E. Esparza-Borges, H. Parviainen, L. G. Bouma, M. Cointepas, X. Bonfils, J. M. Almenara, Karen A. Collins, Kevin I. Collins, Howard M. Relles, Khalid Barkaoui, Richard P. Schwarz, Ghachoui Mourad, Mathilde Timmermans, Georgina Dransfield, Artem Burdanov, Julien de Wit, Emmanuël Jehin, Amaury H. M. J. Triaud, Michaël Gillon, Zouhair Benkhaldoun, Keith Horne, Ramotholo Sefako, A. Jordán, R. Brahm, V. Suc, Steve B. Howell, E. Furlan, J. E. Schlieder, D. Ciardi, T. Barclay, E. J. Gonzales, I. Crossfield, C. D. Dressing, M. Goliguzova, A. Tatarnikov, George R. Ricker, Roland Vanderspek, David W. Latham, S. Seager, Joshua N. Winn, Jon M. Jenkins, Stephanie Striegel, Avi Shporer, Andrew Vanderburg, Alan M. Levine, Veselin B. Kostov, and David Watanabe

Subjects
Exoplanet systems, Astronomy, QB1-991
Abstract

We present the discovery from the TESS mission of two giant planets transiting M-dwarf stars: TOI 4201 b and TOI 5344 b. We also provide precise radial velocity measurements and updated system parameters for three other M dwarfs with transiting giant planets: TOI 519, TOI 3629, and TOI 3714. We measure planetary masses of 0.525 ± 0.064 M _J , 0.243 ± 0.020 M _J , 0.689 ± 0.030 M _J , 2.57 ± 0.15 M _J , and 0.412±0.040 M _J for TOI 519 b, TOI 3629 b, TOI 3714 b, TOI 4201 b, and TOI 5344 b, respectively. The corresponding stellar masses are 0.372 ± 0.018 M _☉ , 0.635 ± 0.032 M _☉ , 0.522 ± 0.028 M _☉ , 0.626 ± 0.033 M _☉ , and 0.612 ± 0.034 M _☉ . All five hosts have supersolar metallicities, providing further support for recent findings that, like for solar-type stars, close-in giant planets are preferentially found around metal-rich M-dwarf host stars. Finally, we describe a procedure for accounting for systematic errors in stellar evolution models when those models are included directly in fitting a transiting planet system.

Published
2023
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13. Refining the Transit-timing and Photometric Analysis of TRAPPIST-1: Masses, Radii, Densities, Dynamics, and Ephemerides

Author

Eric Agol, Caroline Dorn, Simon L. Grimm, Martin Turbet, Elsa Ducrot, Laetitia Delrez, Michaël Gillon, Brice-Olivier Demory, Artem Burdanov, Khalid Barkaoui, Zouhair Benkhaldoun, Emeline Bolmont, Adam Burgasser, Sean Carey, Julien de Wit, Daniel Fabrycky, Daniel Foreman-Mackey, Jonas Haldemann, David M. Hernandez, James Ingalls, Emmanuel Jehin, Zachary Langford, Jérémy Leconte, Susan M. Lederer, Rodrigo Luger, Renu Malhotra, Victoria S. Meadows, Brett M. Morris, Francisco J. Pozuelos, Didier Queloz, Sean N. Raymond, Franck Selsis, Marko Sestovic, Amaury H. M. J. Triaud, and Valerie Van Grootel

Subjects
Extrasolar rocky planets, Exoplanet dynamics, Infrared photometry, Habitable planets, Transit timing variation method, Transit photometry, Astronomy, QB1-991
Abstract

We have collected transit times for the TRAPPIST-1 system with the Spitzer Space Telescope over four years. We add to these ground-based, HST, and K2 transit-time measurements, and revisit an N -body dynamical analysis of the seven-planet system using our complete set of times from which we refine the mass ratios of the planets to the star. We next carry out a photodynamical analysis of the Spitzer light curves to derive the density of the host star and the planet densities. We find that all seven planets’ densities may be described with a single rocky mass–radius relation which is depleted in iron relative to Earth, with Fe 21 wt% versus 32 wt% for Earth, and otherwise Earth-like in composition. Alternatively, the planets may have an Earth-like composition but enhanced in light elements, such as a surface water layer or a core-free structure with oxidized iron in the mantle. We measure planet masses to a precision of 3%–5%, equivalent to a radial-velocity (RV) precision of 2.5 cm s ^−1 , or two orders of magnitude more precise than current RV capabilities. We find the eccentricities of the planets are very small, the orbits are extremely coplanar, and the system is stable on 10 Myr timescales. We find evidence of infrequent timing outliers, which we cannot explain with an eighth planet; we instead account for the outliers using a robust likelihood function. We forecast JWST timing observations and speculate on possible implications of the planet densities for the formation, migration, and evolution of the planet system.

Published
2021
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14. An M dwarf accompanied by a close-in giant orbiter with SPECULOOS

Author

Amaury H M J Triaud, Georgina Dransfield, Taiki Kagetani, Mathilde Timmermans, Norio Narita, Khalid Barkaoui, Teruyuki Hirano, Benjamin V Rackham, Mayuko Mori, Thomas Baycroft, Zouhair Benkhaldoun, Adam J Burgasser, Douglas A Caldwell, Karen A Collins, Yasmin T Davis, Laetitia Delrez, Brice-Oliver Demory, Elsa Ducrot, Akihiko Fukui, Clàudia Jano Muñoz, Emmanuël Jehin, Lionel J García, Mourad Ghachoui, Michaël Gillon, Yilen Gómez Maqueo Chew, Matthew J Hooton, Masahiro Ikoma, Kiyoe Kawauchi, Takayuki Kotani, Alan M Levine, Enric Pallé, Peter P Pedersen, Francisco J Pozuelos, Didier Queloz, Owen J Scutt, Sara Seager, Daniel Sebastian, Motohide Tamura, Samantha Thompson, Noriharu Watanabe, Julien de Wit, Joshua N Winn, and Sebastián Zúñiga-Fernández

Published
2023
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15. A 1.55 R⊕ habitable-zone planet hosted by TOI-715, an M4 star near the ecliptic South Pole

Author

Georgina Dransfield, Mathilde Timmermans, Amaury H M J Triaud, Martín Dévora-Pajares, Christian Aganze, Khalid Barkaoui, Adam J Burgasser, Karen A Collins, Marion Cointepas, Elsa Ducrot, Maximilian N Günther, Steve B Howell, Catriona A Murray, Prajwal Niraula, Benjamin V Rackham, Daniel Sebastian, Keivan G Stassun, Sebastián Zúñiga-Fernández, José Manuel Almenara, Xavier Bonfils, François Bouchy, Christopher J Burke, David Charbonneau, Jessie L Christiansen, Laetitia Delrez, Tianjun Gan, Lionel J García, Michaël Gillon, Yilen Gómez Maqueo Chew, Katharine M Hesse, Matthew J Hooton, Giovanni Isopi, Emmanuël Jehin, Jon M Jenkins, David W Latham, Franco Mallia, Felipe Murgas, Peter P Pedersen, Francisco J Pozuelos, Didier Queloz, David R Rodriguez, Nicole Schanche, Sara Seager, Gregor Srdoc, Chris Stockdale, Joseph D Twicken, Roland Vanderspek, Robert Wells, Joshua N Winn, Julien de Wit, and Aldo Zapparata

Published
2023
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16. Impact of Clouds and Hazes on the Simulated JWST Transmission Spectra of Habitable Zone Planets in the TRAPPIST-1 System

Author

Thomas J. Fauchez, Martin Turbet, Geronimo L Villanueva, Eric T. Wolf, Giada Arney, Ravi K. Kopparapu, Andrew Lincowski, Avram Mandell, Julien de Wit, Daria Pidhorodetska, Shawn D. Domagal-Goldman, and Kevin B. Stevenson

Subjects
Astrophysics
Abstract

The TRAPPIST-1 system, consisting of an ultracool host star having seven known Earth-sized planets, will be a prime target for atmospheric characterization with the James Webb Space Telescope (JWST). However, the detectability of atmospheric molecular species may be severely impacted by the presence of clouds and/or hazes. In this work, we perform 3D general circulation model (GCM) simulations with the LMD-G model supplemented by 1D photochemistry simulations at the terminator with the Atmos model to simulate several possible atmospheres for TRAPPIST-1e, 1f, and 1g: (1) modern Earth, (2) Archean Earth, and (3) CO2-rich atmospheres. The JWST synthetic transit spectra were computed using the GSFC Planetary Spectrum Generator. We find that the TRAPPIST-1e, 1f, and 1g atmospheres, with clouds and/or hazes, could be detected using JWST's NIRSpec Prism from the CO2 absorption line at 4.3 μm in less than 15 transits at 3σ or less than 35 transits at 5σ. However, our analysis suggests that other gases would require hundreds (or thousands) of transits to be detectable. We also find that H2O, mostly confined in the lower atmosphere, is very challenging to detect for these planets or similar systems if the planets' atmospheres are not in a moist greenhouse state. This result demonstrates that the use of GCMs, self-consistently taking into account the effect of clouds and subsaturation, is crucial to evaluate the detectability of atmospheric molecules of interest, as well as for interpreting future detections in a more global (and thus robust and relevant) approach.

Published
2019
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17. Constraining Stellar Photospheres as an Essential Step for Transmission Spectroscopy of Small Exoplanets

Author

Benjamin V. Rackham, Arazi Pinhas, Daniel Apai, Raphaelle Haywood, Heather Cegla, Nestor Espinoza, Johanna Teske, Michael Gully-Santiago, Gioia Rau, Brett M. Morris, Daniel Angerhausen, Thomas Barclay, Ludmila Carone, P. Wilson Cauley, Julien de Wit, Shawn David Domagal-goldman, Chuanfei Dong, Diana Dragomir, Mark S. Giampapa, Yasuhiro Hasegawa, Natalie R. Hinkel, Renyu Hu, Andres Jordan, Irina Nikolaevna Kitiashvili, Laura Kreidberg, Carey Lisse, Joe Llama, Mercedes Lopez-Morales, Bertrand Mennesson, Karan Molaverdikhani, David J. Osip, and Elisa V Quintana

Subjects
Astronomy
Abstract

Transiting exoplanets offer a unique opportunity to study the atmospheres of terrestrial worlds in other systems in the coming decade. By absorbing and scattering starlight, exoplanet atmospheres produce spectroscopic transit depth variations that allow us to probe their physical structures and chemical compositions. These same variations, however, can be introduced by the photospheric heterogeneity of the host star (i.e., the transit light source effect). Recent modeling efforts and increasingly precise observations are revealing that our understanding of transmission spectra of the smallest transiting exoplanets will likely be limited by our knowledge of host star photospheres. Here we outline promising scientific opportunities for the next decade that can provide useful constraints on stellar photospheres and inform interpretations of transmission spectra of the smallest (R < 4R�) exoplanets. We identify and discuss four primary opportunities: (1) refining stellar magnetic active region properties through exoplanet crossing events; (2) spectral decomposition of active exoplanet host stars; (3) joint retrievals of stellar photospheric and planetary atmospheric properties with studies of transmission spectra; and (4) continued visual transmission spectroscopy studies to complement longer-wavelength studies from JWST. In this context, we make four recommendations to the Astro2020 Decadal Survey Committee: (1) identify the transit light source (TLS) effect as a challenge to precise exoplanet transmission spectroscopy and an opportunity ripe for scientific advancement in the coming decade; (2) include characterization of host star photospheric heterogeneity as part of a comprehensive research strategy for studying transiting exoplanets; (3) support the construction of ground-based extremely large telescopes (ELTs); (4) support multi-disciplinary research teams that bring together the heliophysics, stellar physics, and exoplanet communities to further exploit transiting exoplanets as spatial probes of stellar photospheres; and (5) support visual transmission spectroscopy efforts as complements to longer-wavelength observational campaigns with JWST.

Published
2019

18. Tidal Distortions as a Bottleneck on Constraining Exoplanet Compositions

Author

David Berardo and Julien de Wit

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), Space and Planetary Science, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

Improvements in the number of confirmed planets and the precision of observations imply a need to better understand subtle effects that may bias interpretations of exoplanet observations. One such effect is the distortion of a short period planet by its host star, affecting its derived density. We extend the work of Burton et al., Correia, and others, using a gravitational potential formulation to a sample of nearly 200 planets with periods less than 3 days. We find five planets exhibiting density variations of >10% and as many as 20 planets with deviations >5%. We derive an analytic approximation for this deviation as a function of the orbital period, transit depth, and mass ratio between the planet and host star, allowing for rapid determination of such tidal effects. We find that current density error bars are typically larger than tidal deviations but that reducing the uncertainty on transit depth and radial velocity (RV) amplitude by a factor of 3 causes tidal effects to dominate density errors (>50%) in >40% of planets in our sample, implying that in the near future upgraded observational precision will cause shape deviations to become a bottleneck with regards to analysis of exoplanet compositions. These two parameters are found to dominate uncertainties compared to errors on stellar mass and radius. We identify a group of eight planets (including WASP-19 b, HAT-P-7 b, and WASP-12 b) for which current density uncertainties are as much as 4x smaller than the potential shift due to tides, implying a possible 4σ bias on their density estimates., 11 pages, 7 figures, 2 tables

Published
2023

19. TESS discovery of a sub-Neptune orbiting a mid-M dwarf TOI-2136

Author

Tianjun Gan, Abderahmane Soubkiou, Sharon X Wang, Zouhair Benkhaldoun, Shude Mao, Étienne Artigau, Pascal Fouqué, Luc Arnold, Steven Giacalone, Christopher A Theissen, Christian Aganze, Adam Burgasser, Karen A Collins, Avi Shporer, Khalid Barkaoui, Mourad Ghachoui, Steve B Howell, Claire Lamman, Olivier D S Demangeon, Artem Burdanov, Charles Cadieux, Jamila Chouqar, Kevin I Collins, Neil J Cook, Laetitia Delrez, Brice-Olivier Demory, René Doyon, Georgina Dransfield, Courtney D Dressing, Elsa Ducrot, Jiahao Fan, Lionel Garcia, Holden Gill, Michaël Gillon, Crystal L Gnilka, Yilen Gómez Maqueo Chew, Maximilian N Günther, Christopher E Henze, Chelsea X Huang, Emmanuel Jehin, Eric L N Jensen, Zitao Lin, Nadine Manset, James McCormac, Catriona A Murray, Prajwal Niraula, Peter P Pedersen, Francisco J Pozuelos, Didier Queloz, Benjamin V Rackham, Arjun B Savel, Nicole Schanche, Richard P Schwarz, Daniel Sebastian, Samantha Thompson, Mathilde Timmermans, Amaury H M J Triaud, Michael Vezie, Robert D Wells, Julien de Wit, George R Ricker, Roland Vanderspek, David W Latham, Sara Seager, Joshua N Winn, Jon M Jenkins, Canada-France-Hawaii Telescope Corporation (CFHT), National Research Council of Canada (NRC)-Centre National de la Recherche Scientifique (CNRS)-University of Hawai'i [Honolulu] (UH), Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), planets and satellites: detection, 530 Physics, 520 Astronomy, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 000 Computer science, knowledge & systems, 500 Science, Astrophysics - Solar and Stellar Astrophysics, [SDU]Sciences of the Universe [physics], Space and Planetary Science, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, stars: individual: TIC 336128819 - TOI-2136, planetary systems, Astrophysics::Galaxy Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics - Earth and Planetary Astrophysics, QB
Abstract

We present the discovery of TOI-2136b, a sub-Neptune planet transiting every 7.85 days a nearby M4.5V-type star, identified through photometric measurements from the TESS mission. The host star is located $33$ pc away with a radius of $R_{\ast} = 0.34\pm0.02\ R_{\odot}$, a mass of $0.34\pm0.02\ M_{\odot}$ and an effective temperature of $\rm 3342\pm100\ K$. We estimate its stellar rotation period to be $75\pm5$ days based on archival long-term photometry. We confirm and characterize the planet based on a series of ground-based multi-wavelength photometry, high-angular-resolution imaging observations, and precise radial velocities from CFHT/SPIRou. Our joint analysis reveals that the planet has a radius of $2.19\pm0.17\ R_{\oplus}$, and a mass measurement of $6.4\pm2.4\ M_{\oplus}$. The mass and radius of TOI2136b is consistent with a broad range of compositions, from water-ice to gas-dominated worlds. TOI-2136b falls close to the radius valley for low-mass stars predicted by the thermally driven atmospheric mass loss models, making it an interesting target for future studies of its interior structure and atmospheric properties., Comment: 19 pages, 15 figures, submitted to MNRAS

Published
2022
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20. (6478) Gault::Physical characterization of an active main-belt asteroid

Author

Simon F. Green, Julien de Wit, Francisco J. Pozuelos, Colin Orion Chandler, Chadwick A. Trujillo, J. P. Rivet, Jean Manfroid, Colin Snodgrass, Davide Farnocchia, Stephen E. Levine, P. Bendjoya, Michaël Gillon, Brian Skiff, Annika Gustafsson, A. Burdanov, Youssef Moulane, Zouhair Benkhaldoun, David Vernet, Galin Borisov, Maxime Devogele, Marco Micheli, L. Abe, Marin Ferrais, Nicholas Moskovitz, Emmanuel Jehin, Université de Liège, Space Sciences, Technologies and Astrophysics Research Institute (STAR), Lowell Observatory [Flagstaff], Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), SUPA School of Physics and Astronomy [Edinburgh], University of Edinburgh, Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, Rotation period, Absolute magnitude, Earth and Planetary Astrophysics (astro-ph.EP), 010504 meteorology & atmospheric sciences, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Albedo, Phase curve, 01 natural sciences, Photographic plate, Amplitude, Space and Planetary Science, Asteroid, 0103 physical sciences, Magnitude (astronomy), astro-ph.EP, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Astrophysics - Earth and Planetary Astrophysics
Abstract

In December 2018, the main-belt asteroid (6478)~Gault was reported to display activity. Gault is an asteroid belonging to the Phocaea dynamical family and was not previously known to be active, nor was any other member of the Phocaea family. In this work we present the results of photometric and spectroscopic observations that commenced soon after the discovery of activity. We obtained observations over two apparitions to monitor its activity, rotation period, composition, and possible non-gravitational orbital evolution. We find that Gault has a rotation period of $P = 2.4929 \pm 0.0003$ hours with a lightcurve amplitude of $0.06$ magnitude. This short rotation period close to the spin barrier limit is consistent with Gault having a density no smaller than $\rho = 1.85$~g/cm$^3$ and its activity being triggered by the YORP spin-up mechanism. Analysis of the Gault phase curve over phase angles ranging from $0.4^{\circ}$ to $23.6^{\circ}$ provides an absolute magnitude of $H = 14.81 \pm 0.04$, $G1=0.25 \pm 0.07$, and $G2= 0.38 \pm 0.04$. Model fits to the phase curve find the surface regolith grain size constrained between 100-500 $\rm{\mu}$m. Using relations between the phase curve and albedo we determine that the geometrical albedo of Gault is $p_{\rm v} = 0.26 \pm 0.05$ corresponding to an equivalent diameter of $D = 2.8^{+0.4}_{-0.2}$ km. Our spectroscopic observations are all consistent with an ordinary chondrite-like composition (S, or Q-type in the Bus-DeMeo taxonomic classification). A search through archival photographic plate surveys found previously unidentified detections of Gault dating back to 1957 and 1958. Only the latter had been digitized, which we measured to nearly double the observation arc of Gault. Finally, we did not find any signal of activity during the 2020 apparition or non-gravitational effects on its orbit., Comment: 15 pages, 11 figures; Accepted in MNRAS

Published
2021
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21. Refining the transit timing and photometric analysis of TRAPPIST-1: Masses, radii, densities, dynamics, and ephemerides

Author

Eric Agol, Khalid Barkaoui, zouhair Benkhaldoun, Emeline Bolmont, Adam Burgasser, Sean Carey, Julien de Wit, Daniel Fabrycky, Daniel Foreman-Mackey, Jonas Haldemann, Hernandez, David M., Caroline Dorn, James Ingalls, Emmanuel Jehin, Zachary Langford, Jeremy Leconte, Lederer, Susan M., Rodrigo Luger, Renu Malhotra, Meadows, Victoria S., Morris, Brett M., Pozuelos, Francisco J., Grimm, Simon L., Didier Queloz, Raymond, Sean M., Franck Selsis, Marko Sestovic, Triaud, Amaury H. M. J., Valerie Van Grootel, Martin Turbet, Elsa Ducrot, Laetitia Delrez, Michael Gillon, Brice-Olivier Demory, Artem Burdanov, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), and Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], FOS: Physical sciences, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

We have collected transit times for the TRAPPIST-1 system with the Spitzer Space Telescope over four years. We add to these ground-based, HST and K2 transit time measurements, and revisit an N-body dynamical analysis of the seven-planet system using our complete set of times from which we refine the mass ratios of the planets to the star. We next carry out a photodynamical analysis of the Spitzer light curves to derive the density of the host star and the planet densities. We find that all seven planets' densities may be described with a single rocky mass-radius relation which is depleted in iron relative to Earth, with Fe 21 wt% versus 32 wt% for Earth, and otherwise Earth-like in composition. Alternatively, the planets may have an Earth-like composition, but enhanced in light elements, such as a surface water layer or a core-free structure with oxidized iron in the mantle. We measure planet masses to a precision of 3-5%, equivalent to a radial-velocity (RV) precision of 2.5 cm/sec, or two orders of magnitude more precise than current RV capabilities. We find the eccentricities of the planets are very small; the orbits are extremely coplanar; and the system is stable on 10 Myr timescales. We find evidence of infrequent timing outliers which we cannot explain with an eighth planet; we instead account for the outliers using a robust likelihood function. We forecast JWST timing observations, and speculate on possible implications of the planet densities for the formation, migration and evolution of the planet system., Final version to be published in the Planetary Sciences Journal. 56 pages, 30 figures. Data from the paper and a complete table of forecast JWST times may be found at https://github.com/ericagol/TRAPPIST1_Spitzer/

Published
2020

22. π Earth: A 3.14 day Earth-sized Planet from K2's Kitchen Served Warm by the SPECULOOS Team

Author

Howard Issacson, Julien de Wit, Roi Alonso, Francisco J. Pozuelos, Sairam Lalitha, Andrew W. Howard, Valérie Van Grootel, Michaël Gillon, Lionel Garcia, Daniel Sebastian, Ian Crossfield, Emmanuel Jehin, Maximilian N. Günther, Didier Queloz, Samantha Thompson, Prajwal Niraula, Corey Beard, Amaury H. M. J. Triaud, Yilen Gómez Maqueo Chew, Laetitia Delrez, A. Burdanov, Benjamin V. Rackham, P. P. Pedersen, Rafael Rebolo-López, Benjamin J. Fulton, Brice-Olivier Demory, C. Murray, Elsa Ducrot, Niraula, P [0000-0002-8052-3893], Wit, JD [0000-0003-2415-2191], Rackham, BV [0000-0002-3627-1676], Ducrot, E [0000-0002-7008-6888], Burdanov, A [0000-0001-9892-2406], Grootel, VV [0000-0003-2144-4316], Alonso, R [0000-0001-8462-8126], Beard, C [0000-0001-7708-2364], Demory, BO [0000-0002-9355-5165], Fulton, BJ [0000-0003-3504-5316], Gillon, M [0000-0003-1462-7739], Günther, MN [0000-0002-3164-9086], Howard, AW [0000-0001-8638-0320], Issacson, H [0000-0002-0531-1073], Jehin, E [0000-0001-8923-488X], Pedersen, PP [0000-0002-5220-609X], Pozuelos, FJ [0000-0003-1572-7707], Queloz, D [0000-0002-3012-0316], Rebolo-López, R [0000-0003-3767-7085], Lalitha, S [0000-0001-8102-3033], Sebastian, D [0000-0002-2214-9258], Thompson, S [0000-0002-8039-194X], Triaud, AHMJ [0000-0002-5510-8751], and Apollo - University of Cambridge Repository

Subjects
Dwarf star, 010504 meteorology & atmospheric sciences, 530 Physics, Exoplanetology, Astrophysics::Cosmology and Extragalactic Astrophysics, EPIC, 01 natural sciences, Planet, 0103 physical sciences, Exoplanet detection methods, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Physics, 520 Astronomy, James Webb Space Telescope, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy, Astronomy and Astrophysics, 500 Science, Exoplanet, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, Transit photometry, Astrophysics - Earth and Planetary Astrophysics
Abstract

We report on the discovery of a transiting Earth-sized (0.95R ⊕) planet around an M3.5 dwarf star at 57 pc, EPIC 249631677. The planet has a period of ∼3.14 days, i.e., ∼π, with an installation of 7.45 S⊕. The detection was made using publicly available data from K2's Campaign 15. We observed three additional transits with SPECULOOS Southern and Northern Observatories, and a stellar spectrum from Keck/HIRES, which allowed us to validate the planetary nature of the signal. The confirmed planet is well suited for comparative terrestrial exoplanetology. While exoplanets transiting ultracool dwarfs present the best opportunity for atmospheric studies of terrestrial exoplanets with the James Webb Space Telescope, those orbiting mid-M dwarfs within 100 pc such as EPIC 249631677b will become increasingly accessible with the next generation of observatories.

Published
2020

23. The TRAPPIST-1 JWST Community Initiative

Author

Benjamin V. Rackham, Adam J. Burgasser, Eric Agol, James E. Owen, Jacob Lustig-Yaeger, Jonathan J. Fortney, Laura Kreidberg, Julien de Wit, Franck Selsis, Victoria S. Meadows, René Doyon, Drake Deming, Michaël Gillon, Selsis, Franck, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), and Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), 010504 meteorology & atmospheric sciences, Computer science, James Webb Space Telescope, Exoplanetology, FOS: Physical sciences, Context (language use), Planetary system, 01 natural sciences, Data science, [SDU] Sciences of the Universe [physics], Planet, [SDU]Sciences of the Universe [physics], 0103 physical sciences, Data analysis, Observational study, Visibility, 010303 astronomy & astrophysics, Astrophysics - Earth and Planetary Astrophysics, 0105 earth and related environmental sciences
Abstract

The upcoming launch of the James Webb Space Telescope (JWST) combined with the unique features of the TRAPPIST-1 planetary system should enable the young field of exoplanetology to enter into the realm of temperate Earth-sized worlds. Indeed, the proximity of the system (12pc) and the small size (0.12 Rsun) and luminosity (0.05 Lsun) of its host star should make the comparative atmospheric characterization of its seven transiting planets within reach of an ambitious JWST program. Given the limited lifetime of JWST, the ecliptic location of the star that limits its visibility to 100d per year, the large number of observational time required by this study, and the numerous observational and theoretical challenges awaiting it, its full success will critically depend on a large level of coordination between the involved teams and on the support of a large community. In this context, we present here a community initiative aiming to develop a well-defined sequential structure for the study of the system with JWST and to coordinate on every aspect of its preparation and implementation, both on the observational (e.g. study of the instrumental limitations, data analysis techniques, complementary space-based and ground-based observations) and theoretical levels (e.g. model developments and comparison, retrieval techniques, inferences). Depending on the outcome of the first phase of JWST observations of the planets, this initiative could become the seed of a major JWST Legacy Program devoted to the study of TRAPPIST-1., Comments and suggestions are welcome and can be addressed to "t1jwstci_board@u.washington.edu". 23 pages, 8 figures

Published
2020

24. An eclipsing substellar binary in a young triple system discovered by SPECULOOS

Author

Adam J. Burgasser, Amaury H. M. J. Triaud, Didier Queloz, Daniella C. Bardalez Gagliuffi, Brice-Olivier Demory, James McCormac, Julien de Wit, P. P. Pedersen, Tim-Oliver Husser, Frederic V. Hessman, Vedad Kunovac Hodžić, C. Murray, Elsa Ducrot, Roi Alonso, Laetitia Delrez, Michaël Gillon, Artem Burdanov, Samantha Thompson, Daniel Sebastian, Emmanuel Jehin, Valérie Van Grootel, Triaud, AHMJ [0000-0002-5510-8751], Burgasser, AJ [0000-0002-6523-9536], Alonso, R [0000-0001-8462-8126], Demory, BO [0000-0002-9355-5165], de Wit, J [0000-0003-2415-2191], and Apollo - University of Cambridge Repository

Subjects
astro-ph.SR, 010504 meteorology & atmospheric sciences, 530 Physics, Brown dwarf, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Luminosity, Planet, Electron degeneracy pressure, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Physics, Earth and Planetary Astrophysics (astro-ph.EP), Solar mass, Planetary habitability, 520 Astronomy, Astronomy and Astrophysics, Exoplanet, Stars, Astrophysics - Solar and Stellar Astrophysics, astro-ph.EP, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

Mass, radius, and age are three of the most fundamental parameters for celestial objects, enabling studies of the evolution and internal physics of stars, brown dwarfs, and planets. Brown dwarfs are hydrogen-rich objects that are unable to sustain core fusion reactions but are supported from collapse by electron degeneracy pressure. As they age, brown dwarfs cool, reducing their radius and luminosity. Young exoplanets follow a similar behaviour. Brown dwarf evolutionary models are relied upon to infer the masses, radii and ages of these objects. Similar models are used to infer the mass and radius of directly imaged exoplanets. Unfortunately, only sparse empirical mass, radius and age measurements are currently available, and the models remain mostly unvalidated. Double-line eclipsing binaries provide the most direct route for the absolute determination of the masses and radii of stars. Here, we report the SPECULOOS discovery of 2M1510A, a nearby, eclipsing, double-line brown dwarf binary, with a widely-separated tertiary brown dwarf companion. We also find that the system is a member of the $45\pm5$ Myr-old moving group, Argus. The system's age matches those of currently known directly-imaged exoplanets. 2M1510A provides an opportunity to benchmark evolutionary models of brown dwarfs and young planets. We find that widely-used evolutionary models do reproduce the mass, radius and age of the binary components remarkably well, but overestimate the luminosity by up to 0.65 magnitudes, which could result in underestimated photometric masses for directly-imaged exoplanets and young field brown dwarfs by 20 to 35%., Comment: preprint to Nature Astronomy, now with correct figures

Published
2020

25. Atmospheric reconnaissance of the habitable-zone Earth-sized planets orbiting TRAPPIST-1

Author

Susan M. Lederer, Laetitia Delrez, Hannah R. Wakeford, Vlada Stamenkovic, Adam J. Burgasser, Frank Selsis, Vincent Bourrier, Amaury H. M. J. Triaud, James E. Owen, Emmanuel Jehin, Simon L. Grimm, Jérémy Leconte, Nikole K. Lewis, Julien de Wit, Brice-Olivier Demory, Michaël Gillon, Emeline Bolmont, Department of Earth, Atmospheric and Planetary Sciences [MIT, Cambridge] (EAPS), Massachusetts Institute of Technology (MIT), University of Exeter, Space Telescope Science Institute (STSci), Cavendish Laboratory, University of Cambridge [UK] (CAM), Space Sciences, Technologies and Astrophysics Research Institute (STAR), Université de Liège, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), ECLIPSE 2018, Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Center for Space and Habitability (CSH), University of Bern, Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève = University of Geneva (UNIGE), Center for Astrophysics and Space Sciences [La Jolla] (CASS), University of California [San Diego] (UC San Diego), University of California (UC)-University of California (UC), NASA Johnson Space Center (JSC), NASA, Astrophysics Group, Blackett Laboratory, Imperial College London-Imperial College London, Division of Geological and Planetary Sciences [Pasadena], California Institute of Technology (CALTECH), School of Physics and Astronomy [Birmingham], University of Birmingham [Birmingham], European Project: 336792,EC:FP7:ERC,ERC-2013-StG,CREATES(2013), European Project: 336480,EC:FP7:ERC,ERC-2013-StG,SPECULOOS(2014), Université de Genève (UNIGE), University of California-University of California, and The Royal Society

Subjects
EXOPLANET, Dwarf star, 010504 meteorology & atmospheric sciences, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], FOS: Physical sciences, Astronomy & Astrophysics, MASS, 01 natural sciences, ULTRACOOL DWARF STAR, Astrobiology, Atmosphere, Planet, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Transit (astronomy), 010303 astronomy & astrophysics, Physics::Atmospheric and Oceanic Physics, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Earth and Planetary Astrophysics (astro-ph.EP), Science & Technology, SPECTROSCOPY, Habitability, Astronomy and Astrophysics, Exoplanet, 13. Climate action, Physical Sciences, Earth (chemistry), Astrophysics::Earth and Planetary Astrophysics, Circumstellar habitable zone, Geology, Astrophysics - Earth and Planetary Astrophysics
Abstract

Seven temperate Earth-sized exoplanets readily amenable for atmospheric studies transit the nearby ultracool dwarf star TRAPPIST-1 (refs 1,2). Their atmospheric regime is unknown and could range from extended primordial hydrogen-dominated to depleted atmospheres (refs 3-6). Hydrogen in particular is a powerful greenhouse gas that may prevent the habitability of inner planets while enabling the habitability of outer ones (refs 6-8). An atmosphere largely dominated by hydrogen, if cloud-free, should yield prominent spectroscopic signatures in the near-infrared detectable during transits. Observations of the innermost planets have ruled out such signatures (ref 9). However, the outermost planets are more likely to have sustained such a Neptune-like atmosphere (refs 10,11). Here, we report observations for the four planets within or near the system's habitable zone, the circumstellar region where liquid water could exist on a planetary surface (refs 12-14). These planets do not exhibit prominent spectroscopic signatures at near-infrared wavelengths either, which rules out cloud-free hydrogen-dominated atmospheres for TRAPPIST-1 d, e and f, with significance of 8, 6 and 4 sigma, respectively. Such an atmosphere is instead not excluded for planet g. As high-altitude clouds and hazes are not expected in hydrogen-dominated atmospheres around planets with such insolation (refs 15,16), these observations further support their terrestrial and potentially habitable nature., Comment: de Wit, Wakeford, Lewis et al. (2018) published in Nature Astronomy on Feb. 05 2018

Published
2018
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26. The Transiting Exoplanet Community Early Release Science Program for JWST

Author

Jacob L. Bean, Kevin B. Stevenson, Natalie M. Batalha, Zachory Berta-Thompson, Laura Kreidberg, Nicolas Crouzet, Björn Benneke, Michael R. Line, David K. Sing, Hannah R. Wakeford, Heather A. Knutson, Eliza M.-R. Kempton, Jean-Michel Désert, Ian Crossfield, Natasha E. Batalha, Julien de Wit, Vivien Parmentier, Joseph Harrington, Julianne I. Moses, Mercedes Lopez-Morales, Munazza K. Alam, Jasmina Blecic, Giovanni Bruno, Aarynn L. Carter, John W. Chapman, Leen Decin, Diana Dragomir, Thomas M. Evans, Jonathan J. Fortney, Jonathan D. Fraine, Peter Gao, Antonio García Muñoz, Neale P. Gibson, Jayesh M. Goyal, Kevin Heng, Renyu Hu, Sarah Kendrew, Brian M. Kilpatrick, Jessica Krick, Pierre-Olivier Lagage, Monika Lendl, Tom Louden, Nikku Madhusudhan, Avi M. Mandell, Megan Mansfield, Erin M. May, Giuseppe Morello, Caroline V. Morley, Nikolay Nikolov, Seth Redfield, Jessica E. Roberts, Everett Schlawin, Jessica J. Spake, Kamen O. Todorov, Angelos Tsiaras, Olivia Venot, William C. Waalkes, Peter J. Wheatley, Robert T. Zellem, Daniel Angerhausen, David Barrado, Ludmila Carone, Sarah L. Casewell, Patricio E. Cubillos, Mario Damiano, Miguel de Val-Borro, Benjamin Drummond, Billy Edwards, Michael Endl, Nestor Espinoza, Kevin France, John E. Gizis, Thomas P. Greene, Thomas K. Henning, Yucian Hong, James G. Ingalls, Nicolas Iro, Patrick G. J. Irwin, Tiffany Kataria, Fred Lahuis, Jérémy Leconte, Jorge Lillo-Box, Stefan Lines, Joshua D. Lothringer, Luigi Mancini, Franck Marchis, Nathan Mayne, Enric Palle, Emily Rauscher, Gaël Roudier, Evgenya L. Shkolnik, John Southworth, Mark R. Swain, Jake Taylor, Johanna Teske, Giovanna Tinetti, Pascal Tremblin, Gregory S. Tucker, Roy van Boekel, Ingo P. Waldmann, Ian C. Weaver, Tiziano Zingales, University of Chicago, Space Telescope Science Institute (STSci), NASA Ames Research Center (ARC), Department of Astrophysical and Planetary Sciences [Boulder], University of Colorado [Boulder], Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, Instituto de Astrofisica de Canarias (IAC), Universidad de La Laguna [Tenerife - SP] (ULL), Département de Physique [Montréal], Université de Montréal [Montréal], School of Earth and Space Exploration [Tempe] (SESE), Arizona State University [Tempe] (ASU), University of Exeter, Division of Geological and Planetary Sciences [Pasadena], California Institute of Technology (CALTECH), Grinnell College, Department of Astronomy [College Park], University of Maryland [College Park], University of Maryland System-University of Maryland System, Institut d'Astrophysique de Paris (IAP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), MIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology (MIT), Department of Earth, Atmospheric and Planetary Sciences [MIT, Cambridge] (EAPS), Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), University of Central Florida [Orlando], Space Science Institute [Boulder] (SSI), New York University [Abu Dhabi], NYU System (NYU), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Institute of Astronomy [Leuven], Catholic University of Leuven - Katholieke Universiteit Leuven (KU Leuven), University of California [Santa Cruz] (UCSC), University of California, Lawrence Berkeley National Laboratory [Berkeley] (LBNL), Zentrum für Astronomie und Astrophysik [Berlin] (ZAA), Technische Universität Berlin (TUB), Astrophysics Research Centre [Belfast] (ARC), Queen's University [Belfast] (QUB), Center for Space and Habitability (CSH), University of Bern, Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, Brown University, Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Austrian Academy of Sciences (OeAW), University of Warwick [Coventry], Institute of Astronomy [Cambridge], University of Cambridge [UK] (CAM), GSFC Solar System Exploration Division, NASA Goddard Space Flight Center (GSFC), University of Michigan [Ann Arbor], University of Michigan System, Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, The Foundation for Scientific and Industrial Research (SINTEF), College of Engineering, Mathematics and Physical Sciences [Exeter] (EMPS), Wesleyan University, Amsterdam University of Applied Sciences, Department of Physics and Astronomy [UCL London], University College of London [London] (UCL), Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA (UMR_7583)), Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Blue Marble Space Institute of Science (BMSIS), European Space Astronomy Centre (ESAC), European Space Agency (ESA), Department of Physics and Astronomy [Leicester], University of Leicester, Space Research Institute of Austrian Academy of Sciences (IWF), INAF - Osservatorio Astronomico di Palermo (OAPa), Istituto Nazionale di Astrofisica (INAF), Astrochemistry Laboratory [Greenbelt], Catholic University of America, McDonald Observatory, University of Texas at Austin [Austin], Center for Astrophysics and Space Astronomy [Boulder] (CASA), Department of Physics and Astronomy [Newark], University of Delaware [Newark], Cornell University, Infrared Processing and Analysis Center (IPAC), University of Vienna [Vienna], Department of Atmospheric, Oceanic and Planetary Physics [Oxford] (AOPP), University of Oxford [Oxford], SRON Netherlands Institute for Space Research (SRON), Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), European Southern Observatory [Santiago] (ESO), European Southern Observatory (ESO), Carl Sagan Center, SETI Institute, Department of Physics, University of Rome Tor Vergata, Maison de la Simulation (MDLS), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Recherche en Informatique et en Automatique (Inria)-Université Paris-Sud - Paris 11 (UP11)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Ames Laboratory [Ames, USA], Iowa State University (ISU)-U.S. Department of Energy (DOE), Low Energy Astrophysics (API, FNWI), Laboratoire de Cosmologie, Astrophysique Stellaire & Solaire, de Planétologie et de Mécanique des Fluides ( CASSIOPEE ), Université Nice Sophia Antipolis ( UNS ), Université Côte d'Azur ( UCA ) -Université Côte d'Azur ( UCA ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de la Côte d'Azur, Université Côte d'Azur ( UCA ) -Centre National de la Recherche Scientifique ( CNRS ), Institut d'Astrophysique de Paris ( IAP ), Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), Joseph Louis LAGRANGE ( LAGRANGE ), Université Côte d'Azur ( UCA ) -Université Côte d'Azur ( UCA ) -Observatoire de la Côte d'Azur, Plasmachemistry, CNR-IMIP, Katholieke Universiteit Leuven ( KU Leuven ), University of California [Santa Cruz] ( UCSC ), Eidgenössische Technische Hochschule, Swiss Federal Institute of Technology in Zürich ( ETH Zürich ), Max-Planck-Institut für Astronomie ( MPIA ), Astrophysique Interactions Multi-échelles ( AIM - UMR 7158 - UMR E 9005 ), Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Université Paris Diderot - Paris 7 ( UPD7 ), The Foundation for Scientific and Industrial Research ( SINTEF ), Laboratoire inter-universitaire des systèmes atmosphèriques ( LISA ), Institut national des sciences de l'Univers ( INSU - CNRS ) -Université Paris Diderot - Paris 7 ( UPD7 ) -Université Paris-Est Créteil Val-de-Marne - Paris 12 ( UPEC UP12 ) -Centre National de la Recherche Scientifique ( CNRS ), Department of Astrophysical Sciences [Princeton], Princeton University, Center for Astrophysics and Space Astronomy [Boulder] ( CASA ), University of Colorado Boulder [Boulder], Dept of Physics, University of Florida [Gainesville], Stony Brook University [The State University of New York] ( SBU ), ECLIPSE 2018, Laboratoire d'Astrophysique de Bordeaux [Pessac] ( LAB ), Université de Bordeaux ( UB ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Bordeaux ( UB ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), University College of London [London] ( UCL ), Maison de la Simulation ( MDLS ), Université de Versailles Saint-Quentin-en-Yvelines ( UVSQ ) -Université Paris-Sud - Paris 11 ( UP11 ) -Institut National de Recherche en Informatique et en Automatique ( Inria ) -Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ) -Université Paris-Saclay-Centre National de la Recherche Scientifique ( CNRS ), Iowa State University ( ISU ) -U.S. Department of Energy ( DOE ), Université de Montréal (UdeM), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), University of Central Florida [Orlando] (UCF), University of California [Santa Cruz] (UC Santa Cruz), University of California (UC), Technische Universität Berlin (TU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Stiftelsen for INdustriell og TEknisk Forskning Digital [Trondheim] (SINTEF Digital), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), Cornell University [New York], Università degli Studi di Roma Tor Vergata [Roma], Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut National de Recherche en Informatique et en Automatique (Inria)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Iowa State University (ISU)-U.S. Department of Energy [Washington] (DOE), Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences, Smithsonian Institution-Harvard University [Cambridge], Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Recherche en Informatique et en Automatique (Inria)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Harvard University-Smithsonian Institution, Technical University of Berlin / Technische Universität Berlin (TU), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Agence Spatiale Européenne = European Space Agency (ESA), and University of Oxford

Subjects
MODEL ATMOSPHERES, Exclusive access, 010504 meteorology & atmospheric sciences, Computer science, Science program, observational [methods], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], FOS: Physical sciences, MIDINFRARED INSTRUMENT, Astrophysics::Cosmology and Extragalactic Astrophysics, Astronomy & Astrophysics, Planets and satellites: Individual, 01 natural sciences, EXTRASOLAR GIANT PLANETS, Planets and satellites: Atmospheres, individual (WASP-79b, WASP-43b, WASP-18b) [planets and satellites], Settore FIS/05 - Astronomia e Astrofisica, Methods: Observational, Planet, 0103 physical sciences, Early release, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, LIGHT CURVES, Earth and Planetary Astrophysics (astro-ph.EP), Science & Technology, Community engagement, TIME-SERIES PHOTOMETRY, THERMAL EMISSION, James Webb Space Telescope, Astrophysics::Instrumentation and Methods for Astrophysics, WEBB-SPACE-TELESCOPE, Astronomy and Astrophysics, HOT-JUPITER, atmospheres [planets and satellites], [ SDU.ASTR.EP ] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Data science, Methods observational, Exoplanet, 13. Climate action, Space and Planetary Science, Physical Sciences, HD 189733B, Astrophysics::Earth and Planetary Astrophysics, ATMOSPHERIC CIRCULATION, Astrophysics - Earth and Planetary Astrophysics
Abstract

The James Webb Space Telescope (JWST) presents the opportunity to transform our understanding of planets and the origins of life by revealing the atmospheric compositions, structures, and dynamics of transiting exoplanets in unprecedented detail. However, the high-precision, time-series observations required for such investigations have unique technical challenges, and prior experience with other facilities indicates that there will be a steep learning curve when JWST becomes operational. In this paper we describe the science objectives and detailed plans of the Transiting Exoplanet Community Early Release Science (ERS) Program, which is a recently approved program for JWST observations early in Cycle 1. The goal of this project, for which the obtained data will have no exclusive access period, is to accelerate the acquisition and diffusion of technical expertise for transiting exoplanet observations with JWST, while also providing a compelling set of representative datasets that will enable immediate scientific breakthroughs. The Transiting Exoplanet Community ERS Program will exercise the time-series modes of all four JWST instruments that have been identified as the consensus highest priorities, observe the full suite of transiting planet characterization geometries (transits, eclipses, and phase curves), and target planets with host stars that span an illustrative range of brightnesses. The observations in this program were defined through an inclusive and transparent process that had participation from JWST instrument experts and international leaders in transiting exoplanet studies. Community engagement in the project will be centered on a two-phase Data Challenge that culminates with the delivery of planetary spectra, time-series instrument performance reports, and open-source data analysis toolkits in time to inform the agenda for Cycle 2 of the JWST mission., Comment: PASP in press

Published
2018
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27. A seven-planet resonant chain in TRAPPIST-1

Author

Emmanuel Jehin, Simon L. Grimm, Y. Almleaky, Thomas Barclay, Michaël Gillon, Julien de Wit, Geert Barentsen, Pierre Magain, Susan M. Lederer, Adam J. Burgasser, Emeline Bolmont, Kevin Heng, Zouhair Benkhaldoun, Brett M. Morris, Didier Queloz, Laetitia Delrez, Jérémy Leconte, James G. Ingalls, Catarina Silva Fernandes, Sean N. Raymond, Valérie Van Grootel, Marko Sestovic, Daniel Luke Holdsworth, Ethan Kruse, Rodrigo Luger, Amaury H. M. J. Triaud, Eric Agol, Martin Turbet, Daniel Foreman-Mackey, Franck Selsis, Daniel C. Fabrycky, Steve B. Howell, Brice-Olivier Demory, University of Washington [Seattle], NASA Astrobiology Institute (NAI), University of Bern, Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), University of Chicago, Université de Liège, Center for Astrophysics and Space Sciences [La Jolla] (CASS), University of California [San Diego] (UC San Diego), University of California-University of California, Infrared Processing and Analysis Center, California Institute of Technology (IPAC), California Institute of Technology (CALTECH), Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), ECLIPSE 2017, Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institute of Astronomy [Cambridge], University of Cambridge [UK] (CAM), NASA Ames Research Center Cooperative for Research in Earth Science in Technology (ARC-CREST), NASA Ames Research Center (ARC), Bay Area Environmental Research Institute (BAER), Cavendish Laboratory, Department of Earth, Atmospheric and Planetary Sciences [MIT, Cambridge] (EAPS), Massachusetts Institute of Technology (MIT), Jeremiah Horrocks Institute for Mathematics, Physics and Astronomy [Preston], University of Central Lancashire [Preston] (UCLAN), NASA Johnson Space Center (JSC), NASA, Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), King Abdulaziz University, Université Cadi Ayyad [Marrakech] (UCA), Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève (UNIGE), ANR-13-BS05-0003,MOJO,Modélisation du processus de croissance des planètes Joviennes/(2013), European Project: 647383,H2020,ERC-2014-CoG,SPIRE(2015), European Project: 336480,EC:FP7:ERC,ERC-2013-StG,SPECULOOS(2014), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), University of California (UC)-University of California (UC), Infrared Processing and Analysis Center (IPAC), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université de Genève = University of Geneva (UNIGE), and École normale supérieure - Paris (ENS Paris)-École normale supérieure - Paris (ENS Paris)

Subjects
Rotation period, Dwarf star, 010504 meteorology & atmospheric sciences, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], FOS: Physical sciences, F500, Astrophysics, Star (graph theory), 01 natural sciences, Earth radius, Planet, 0103 physical sciences, Transit (astronomy), 10. No inequality, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Physics, Earth and Planetary Astrophysics (astro-ph.EP), Astronomy and Astrophysics, Radius, Planetary system, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

The TRAPPIST-1 system is the first transiting planet system found orbiting an ultra-cool dwarf star. At least seven planets similar to Earth in radius and in mass were previously found to transit this host star. Subsequently, TRAPPIST-1 was observed as part of the K2 mission and, with these new data, we report the measurement of an 18.77 d orbital period for the outermost planet, TRAPPIST-1h, which was unconstrained until now. This value matches our theoretical expectations based on Laplace relations and places TRAPPIST-1h as the seventh member of a complex chain, with three-body resonances linking every member. We find that TRAPPIST-1h has a radius of 0.727 Earth radii and an equilibrium temperature of 173 K. We have also measured the rotational period of the star at 3.3 d and detected a number of flares consistent with a low-activity, middle-aged, late M dwarf., 42 pages, 8 figures, 2 tables

Published
2017
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28. A map of the large day–night temperature gradient of a super-Earth exoplanet

Author

Vlada Stamenkovic, Emeline Bolmont, Nikole K. Lewis, Kevin Heng, Stephen R. Kane, Björn Benneke, Julien de Wit, Nikku Madhusudhan, Jessica Krick, Didier Queloz, Tiffany Kataria, Michaël Gillon, Brice-Olivier Demory, Renyu Hu, Demory, Brice-Oliver [0000-0002-9355-5165], Nikku, Madhusudhan [0000-0002-4869-000X], Queloz, Didier [0000-0002-3012-0316], and Apollo - University of Cambridge Repository

Subjects
Brightness, 010504 meteorology & atmospheric sciences, 530 Physics, FOS: Physical sciences, 01 natural sciences, Atmosphere, Planet, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Physics, Earth and Planetary Astrophysics (astro-ph.EP), Multidisciplinary, Super-Earth, 520 Astronomy, Astronomy, Exoplanet, Tidal locking, Temperature gradient, Brightness temperature, astro-ph.EP, Physics::Space Physics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

Over the past decade, observations of giant exoplanets (Jupiter-size) have provided key insights into their atmospheres, but the properties of lower-mass exoplanets (sub-Neptune) remain largely unconstrained because of the challenges of observing small planets. Numerous efforts to observe the spectra of super-Earths (exoplanets with masses of one to ten times that of Earth) have so far revealed only featureless spectra. Here we report a longitudinal thermal brightness map of the nearby transiting super-Earth 55 Cancri e revealing highly asymmetric dayside thermal emission and a strong day-night temperature contrast. Dedicated space-based monitoring of the planet in the infrared revealed a modulation of the thermal flux as 55 Cancri e revolves around its star in a tidally locked configuration. These observations reveal a hot spot that is located 41 +- 12 degrees east of the substellar point (the point at which incident light from the star is perpendicular to the surface of the planet). From the orbital phase curve, we also constrain the nightside brightness temperature of the planet to 1380 +- 400 kelvin and the temperature of the warmest hemisphere (centred on the hot spot) to be about 1300 kelvin hotter (2700 +- 270 kelvin) at a wavelength of 4.5 microns, which indicates inefficient heat redistribution from the dayside to the nightside. Our observations are consistent with either an optically thick atmosphere with heat recirculation confined to the planetary dayside, or a planet devoid of atmosphere with low-viscosity magma flows at the surface., Comment: Published in Nature on 14 April 2016. Preprint version includes 32 pages, 11 figures and 2 tables

Published
2016

29. Unveiling the atmospheres of giant exoplanets with an EChO-class mission

Author

Julien de Wit, Vivien Parmentier, and Adam P. Showman

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), Physics, Cosmic Vision, Gas giant, Echo (computing), Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astronomy, Astronomy and Astrophysics, Exoplanet, Atmosphere, Space and Planetary Science, Observatory, Astrophysics::Solar and Stellar Astrophysics, Transit (astronomy), Astrophysics::Earth and Planetary Astrophysics, Spectral resolution, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics - Earth and Planetary Astrophysics
Abstract

More than a thousand exoplanets have been discovered over the last decade. Perhaps more excitingly, probing their atmospheres has become possible. With current data we have glimpsed the diversity of exoplanet atmospheres that will be revealed over the coming decade. However, numerous questions concerning their chemical composition, thermal structure, and atmospheric dynamics remain to be answered. More observations of higher quality are needed. In the next years, the selection of a space-based mission dedicated to the spectroscopic characterization of exoplanets would revolutionize our understanding of the physics of planetary atmospheres. Such a mission was proposed to the ESA cosmic vision program in 2014. Our paper is therefore based on the planned capabilities of the Exoplanet Characterization Observatory (EChO), but it should equally apply to any future mission with similar characteristics. With its large spectral coverage ($4-16\, \rm{\mu m}$), high spectral resolution ($\Delta\lambda/\lambda>300$ below $5\,\rm{\mu m}$ and $\Delta\lambda/\lambda>30$ above $5\,\rm{\mu m}$) and $1.5\rm{m}$ mirror, a future mission such as EChO will provide spectrally resolved transit lightcurves, secondary eclipses lightcurves, and full phase curves of numerous exoplanets with an unprecedented signal-to-noise ratio. In this paper, we review some of today's main scientific questions about gas giant exoplanets atmospheres, for which a future mission such as EChO will bring a decisive contribution., Comment: Accepted to the Experimental Journal of Astronomy

Published
2014

30. INFERENCE OF INHOMOGENEOUS CLOUDS IN AN EXOPLANET ATMOSPHERE

Author

Nicolas B. Cowan, Jean-Michel Desert, Nikku Madhusudhan, Thomas Barclay, Michaël Gillon, Jonathan J. Fortney, Heather A. Knutson, Brice-Olivier Demory, Kevin Heng, Andras Zsom, Julien de Wit, Sara Seager, Vivien Parmentier, Nikole K. Lewis, Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences, Demory, Brice-Olivier, de Wit, Julien, Lewis, Nikole, Zsom, Andras, and Seager, Sara

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), Physics, Planetary equilibrium temperature, Infrared, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Surface gravity, Exoplanet, Atmosphere, symbols.namesake, Space and Planetary Science, Geometric albedo, Hot Jupiter, symbols, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Rayleigh scattering, Physics::Atmospheric and Oceanic Physics, Astrophysics::Galaxy Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

We present new visible and infrared observations of the hot Jupiter Kepler-7b to determine its atmospheric properties. Our analysis allows us to 1) refine Kepler-7b's relatively large geometric albedo of Ag=0.35+-0.02, 2) place upper limits on Kepler-7b thermal emission that remains undetected in both Spitzer bandpasses and 3) report a westward shift in the Kepler optical phase curve. We argue that Kepler-7b's visible flux cannot be due to thermal emission or Rayleigh scattering from H2 molecules. We therefore conclude that high altitude, optically reflective clouds located west from the substellar point are present in its atmosphere. We find that a silicate-based cloud composition is a possible candidate. Kepler-7b exhibits several properties that may make it particularly amenable to cloud formation in its upper atmosphere. These include a hot deep atmosphere that avoids a cloud cold trap, very low surface gravity to suppress cloud sedimentation, and a planetary equilibrium temperature in a range that allows for silicate clouds to potentially form in the visible atmosphere probed by Kepler. Our analysis does not only present evidence of optically thick clouds on Kepler-7b but also yields the first map of clouds in an exoplanet atmosphere., 7 pages, 5 figures. In press. Accepted to ApJL on 2013 August 20

Published
2013

31. Towards consistent mapping of distant worlds: secondary-eclipse scanning of the exoplanet HD189733b

Author

Sara Seager, Brice-Olivier Demory, Michaël Gillon, and Julien de Wit

Subjects
Physics, Earth and Planetary Astrophysics (astro-ph.EP), 520 Astronomy, FOS: Physical sciences, Astronomy and Astrophysics, Orbital eccentricity, Astrophysics, Light curve, Exoplanet, Radial velocity, Photometry (optics), Space and Planetary Science, Hot Jupiter, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Stellar density, Eclipse, Astrophysics - Earth and Planetary Astrophysics
Abstract

Mapping distant worlds is the next frontier for exoplanet infrared photometry studies. Ultimately, constraining spatial and temporal properties of an exoplanet atmosphere will provide further insight into its physics. For tidally-locked hot Jupiters that transit and are eclipsed by their host star, the first steps are now possible. Our aim is to constrain an exoplanet's shape, brightness distribution (BD) and system parameters from its light curve. Notably, we rely on the eclipse scanning. We use archived Spitzer 8-{\mu}m data of HD189733 (6 transits, 8 secondary eclipses, and a phase curve) in a global MCMC procedure for mitigating systematics. We also include HD189733's out-of-transit radial velocity measurements. We find a 6-{\sigma} deviation from the expected occultation of a uniformly-bright disk. This deviation emerges mainly from HD189733b's thermal pattern, not from its shape. We indicate that the correlation of the orbital eccentricity, e, and BD (uniform time offset) does also depend on the stellar density, \rho*, and the impact parameter, b (e-b-\rho*-BD correlation). For HD189733b, we find that relaxing the e-constraint and using more complex BDs lead to lower stellar/planetary densities and a more localized and latitudinally-shifted hot spot. We obtain an improved constraint on the upper limit of HD189733b's orbital eccentricity, e, Comment: Accepted for publication in A&A. Final version will be available soon at http://www.aanda.org by Free Open Access

Published
2012

33. Stellar Parameters for Trappist-1.

Author

Valérie Van Grootel, Catarina S. Fernandes, Michael Gillon, Emmanuel Jehin, Jean Manfroid, Richard Scuflaire, Adam J. Burgasser, Khalid Barkaoui, Zouhair Benkhaldoun, Artem Burdanov, Laetitia Delrez, Brice-Olivier Demory, Julien de Wit, Didier Queloz, and Amaury H. M. J. Triaud

Subjects
STELLAR mass, TELESCOPES, STELLAR populations, ATOMIC mass, STELLAR luminosity function
Abstract

TRAPPIST-1 is an ultracool dwarf star transited by seven Earth-sized planets, for which thorough characterization of atmospheric properties, surface conditions encompassing habitability, and internal compositions is possible with current and next-generation telescopes. Accurate modeling of the star is essential to achieve this goal. We aim to obtain updated stellar parameters for TRAPPIST-1 based on new measurements and evolutionary models, compared to those used in discovery studies. We present a new measurement for the parallax of TRAPPIST-1, 82.4 ± 0.8 mas, based on 188 epochs of observations with the TRAPPIST and Liverpool Telescopes from 2013 to 2016. This revised parallax yields an updated luminosity of , which is very close to the previous estimate but almost two times more precise. We next present an updated estimate for TRAPPIST-1 stellar mass, based on two approaches: mass from stellar evolution modeling, and empirical mass derived from dynamical masses of equivalently classified ultracool dwarfs in astrometric binaries. We combine them using a Monte-Carlo approach to derive a semi-empirical estimate for the mass of TRAPPIST-1. We also derive estimate for the radius by combining this mass with stellar density inferred from transits, as well as an estimate for the effective temperature from our revised luminosity and radius. Our final results are , , and 2516 ± 41 K. Considering the degree to which the TRAPPIST-1 system will be scrutinized in coming years, these revised and more precise stellar parameters should be considered when assessing the properties of TRAPPIST-1 planets. [ABSTRACT FROM AUTHOR]

Published
2018
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34. The nature of the TRAPPIST-1 exoplanets

Author

Daniel C. Fabrycky, Emeline Bolmont, David M. Hernandez, Brice-Olivier Demory, Emmanuel Jehin, Marko Sestovic, Michaël Gillon, Martin Turbet, Amaury H. M. J. Triaud, Julien de Wit, Sean N. Raymond, Jérémy Leconte, Eric Agol, Adam J. Burgasser, James G. Ingalls, Sean Carey, Franck Selsis, Laetitia Delrez, Kevin Heng, Caroline Dorn, Artem Burdanov, Susan M. Lederer, Anthony Caldas, Simon L. Grimm, Didier Queloz, Valérie Van Grootel, University of Zurich, Bern University of Arts, Cavendish Laboratory, University of Cambridge [UK] (CAM), Institut d'Astrophysique et de Géophysique [Liège], Université de Liège, Institute of Geophysics, Université de Lausanne (UNIL), Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève (UNIGE), Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), ECLIPSE 2018, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Center for Space and Habitability (CSH), University of Bern, and Deutsches Elektronen-Synchrotron [Hamburg] (DESY)

Subjects
Dwarf star, 010504 meteorology & atmospheric sciences, 530 Physics, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], FOS: Physical sciences, Astrophysics, Parameter space, Protoplanetary disk, 01 natural sciences, 1912 Space and Planetary Science, Planet, 0103 physical sciences, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, Earth and Planetary Astrophysics (astro-ph.EP), 520 Astronomy, Astronomy and Astrophysics, Exoplanet, Space and Planetary Science, 10231 Institute for Computational Science, Terrestrial planet, 3103 Astronomy and Astrophysics, TRAPPIST, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

Context. The TRAPPIST-1 system hosts seven Earth-sized, temperate exoplanets orbiting an ultra-cool dwarf star. As such, it represents a remarkable setting to study the formation and evolution of terrestrial planets that formed in the same protoplanetary disk. While the sizes of the TRAPPIST-1 planets are all known to better than 5% precision, their densities have significant uncertainties (between 28% and 95%) because of poor constraints on the planet's masses. Aims.The goal of this paper is to improve our knowledge of the TRAPPIST-1 planetary masses and densities using transit-timing variations (TTV). The complexity of the TTV inversion problem is known to be particularly acute in multi-planetary systems (convergence issues, degeneracies and size of the parameter space), especially for resonant chain systems such as TRAPPIST-1. Methods. To overcome these challenges, we have used a novel method that employs a genetic algorithm coupled to a full N-body integrator that we applied to a set of 284 individual transit timings. This approach enables us to efficiently explore the parameter space and to derive reliable masses and densities from TTVs for all seven planets. Results. Our new masses result in a five- to eight-fold improvement on the planetary density uncertainties, with precisions ranging from 5% to 12%. These updated values provide new insights into the bulk structure of the TRAPPIST-1 planets. We find that TRAPPIST-1\,c and e likely have largely rocky interiors, while planets b, d, f, g, and h require envelopes of volatiles in the form of thick atmospheres, oceans, or ice, in most cases with water mass fractions less than 5%., Comment: in press in Astronomy & Astrophysics, 24 pages, 13 figures

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35. SPECULOOS Northern Observatory: Searching for Red Worlds in the Northern Skies

Author

Artem Y. Burdanov, Julien de Wit, Michaël Gillon, Rafael Rebolo, Daniel Sebastian, Roi Alonso, Sandrine Sohy, Prajwal Niraula, Lionel Garcia, Khalid Barkaoui, Patricia Chinchilla, Elsa Ducrot, Catriona A. Murray, Peter P. Pedersen, Emmanuël Jehin, James McCormac, and Sebastián Zúñiga-Fernández

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), Space and Planetary Science, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics - Earth and Planetary Astrophysics
Abstract

SPECULOOS is a ground-based transit survey consisting of six identical 1-m robotic telescopes. The immediate goal of the project is to detect temperate terrestrial planets transiting nearby ultracool dwarfs (late M-dwarf stars and brown dwarfs), which could be amenable for atmospheric research with the next generation of telescopes. Here, we report the developments of the northern counterpart of the project - SPECULOOS Northern Observatory, and present its performance during the first three years of operations from mid-2019 to mid-2022. Currently, the observatory consists of one telescope, which is named Artemis. The Artemis telescope demonstrates remarkable photometric precision, allowing it to be ready to detect new transiting terrestrial exoplanets around ultracool dwarfs. Over the period of the first three years after the installation, we observed 96 objects from the SPECULOOS target list for 6000 hours with a typical photometric precision of $0.5\%$, and reaching a precision of $0.2\%$ for relatively bright non-variable targets with a typical exposure time of 25 sec. Our weather downtime (clouds, high wind speed, high humidity, precipitation and/or high concentration of dust particles in the air) over the period of three years was 30% of overall night time. Our actual downtime is 40% because of additional time loss associated with technical problems., Accepted for publication in PASP (Publications of the Astronomical Society of the Pacific), 13 pages, 9 figures

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36. Transiting Exoplanet Studies and Community Targets for JWST 's Early Release Science Program

Author

Jonathan J. Fortney, Jonathan Fraine, Tiffany Kataria, Kevin Heng, Heather A. Knutson, Nicolas Crouzet, Caroline V. Morley, Joanna K. Barstow, Brian M. Kilpatrick, Gregory S. Tucker, Charles A. Beichman, Eric Agol, David K. Sing, Nicolas B. Cowan, David Ehrenreich, Thomas P. Greene, David Charbonneau, Michael R. Line, Drake Deming, Shannon Curry, Nikku Madhusudhan, Kamen O. Todorov, Jessica Krick, Hannah R. Wakeford, Adam Burrows, Marco Rocchetto, David Lafrenière, Everett Schlawin, Joseph Harrington, John E. Gizis, Avi Shporer, Patricio E. Cubillos, Stephan M. Birkmann, Nikole K. Lewis, Diana Dragomir, Paul A. Dalba, Jeff A. Valenti, Laura Kreidberg, Evgenya L. Shkolnik, Avi Mandell, Neale P. Gibson, Kevin B. Stevenson, Antonio García Muñoz, Jean-Michel Desert, Mercedes Lopez-Morales, Julien de Wit, Jacob L. Bean, Daniel Angerhausen, Joshua D. Lothringer, Eliza M.-R. Kempton, René Doyon, Pierre Olivier Lagage, and Low Energy Astrophysics (API, FNWI)

Subjects
Brightness, 010504 meteorology & atmospheric sciences, Computer science, Science program, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astronomy & Astrophysics, 01 natural sciences, 0103 physical sciences, Spectral resolution, Early release, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), 0105 earth and related environmental sciences, Earth and Planetary Astrophysics (astro-ph.EP), James Webb Space Telescope, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy, Astronomy and Astrophysics, telescopes, atmospheres [planets and satellites], Exoplanet, 3. Good health, Space and Planetary Science, individual [planets and satellites], astro-ph.EP, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, Astronomical and Space Sciences, Astrophysics - Earth and Planetary Astrophysics, astro-ph.IM
Abstract

The James Webb Space Telescope will revolutionize transiting exoplanet atmospheric science due to its capability for continuous, long-duration observations and its larger collecting area, spectral coverage, and spectral resolution compared to existing space-based facilities. However, it is unclear precisely how well JWST will perform and which of its myriad instruments and observing modes will be best suited for transiting exoplanet studies. In this article, we describe a prefatory JWST Early Release Science (ERS) program that focuses on testing specific observing modes to quickly give the community the data and experience it needs to plan more efficient and successful future transiting exoplanet characterization programs. We propose a multi-pronged approach wherein one aspect of the program focuses on observing transits of a single target with all of the recommended observing modes to identify and understand potential systematics, compare transmission spectra at overlapping and neighboring wavelength regions, confirm throughputs, and determine overall performances. In our search for transiting exoplanets that are well suited to achieving these goals, we identify 12 objects (dubbed "community targets") that meet our defined criteria. Currently, the most favorable target is WASP-62b because of its large predicted signal size, relatively bright host star, and location in JWST's continuous viewing zone. Since most of the community targets do not have well-characterized atmospheres, we recommend initiating preparatory observing programs to determine the presence of obscuring clouds/hazes within their atmospheres. Measurable spectroscopic features are needed to establish the optimal resolution and wavelength regions for exoplanet characterization. Other initiatives from our proposed ERS program include testing the instrument brightness limits and performing phase-curve observations.(Abridged), This is a white paper that originated from an open discussion at the Enabling Transiting Exoplanet Science with JWST workshop held November 16 - 18, 2015 at STScI (http://www.stsci.edu/jwst/science/exoplanets). Accepted for publication in PASP

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