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10 results on '"Thomas Mikal-Evans"'

1. Tentative Evidence for Water Vapor in the Atmosphere of the Neptune-sized Exoplanet HD106315c

Author

Laura Kreidberg, Paul Mollière, Ian J M Crossfield, Daniel P Thorngren, Yui Kawashima, Caroline V Morley, Björn Benneke, Thomas Mikal-Evans, David Berardo, Molly R Kosiarek, Varoujan Gorjian, David R Ciardi, Jessie L Christiansen, Diana Dragomir, Courtney D Dressing, Jonathan J Fortney, Benjamin J Fulton, Thomas P Greene, Kevin K Hardegree-Ullman, Andrew W Howard, Steve B Howell, Howard Isaacson, Jessica E Krick, John H Livingston, Joshua D Lothringer, Farisa Y Morales, Erik A Petigura, Joseph E Rodriguez, Joshua E Schlieder, and Lauren M Weiss

Subjects
Astronomy
Abstract

We present a transmission spectrum for the Neptune-sized exoplanet HD 106315c from optical to infrared wavelengths based on transit observations from the Hubble Space Telescope/Wide Field Camera 3, K2, and Spitzer. The spectrum shows tentative evidence for a water absorption feature in the 1.1–1.7 μm wavelength range with a small amplitude of 30 ppm (corresponding to just 0.8 ± 0.04 atmospheric scale heights). Based on an atmospheric retrieval analysis, the presence of water vapor is tentatively favored with a Bayes factor of 1.7–2.6 (depending on prior assumptions). The spectrum is most consistent with either an enhanced metallicity or high-altitude condensates, or both. Cloud-free solar composition atmospheres are ruled out at >5σ confidence. We compare the spectrum to grids of cloudy and hazy forward models and find that the spectrum is fit well by models with moderate cloud lofting or haze formation efficiency over a wide range of metallicities (1–100× solar). We combine the constraints on the envelope composition with an interior structure model and estimate that the core mass fraction is ≳0.3. With a bulk composition reminiscent of that of Neptune and an orbital distance of 0.15 au, HD 106315c hints that planets may form out of broadly similar material and arrive at vastly different orbits later in their evolution.

Published
2022
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2. The Hubble PanCET Program: A Featureless Transmission Spectrum for WASP-29b and Evidence of Enhanced Atmospheric Metallicity on WASP-80b

Author

Ian Yu Wong, Yayaati Chachan, Heather Knutson, Gregory W Henry, Danica Adams, Tiffany Kataria, Bjorn Benneke, Peter Gao, Drake Deming, Mercedes Lopez-Morales, David K. Sing, Munazza K Alam, Gilda E Ballester, Joanna K Barstow, Lars Buchhave, Leonardo A. dos Santos, Guangwei Fu, Antonio Garcia Munoz, Ryan J MacDonald, Thomas Mikal-Evans, Jorge Sanz-Forcada, and Hannah R Wakeford

Subjects
Astronomy, Astrophysics
Abstract

We present a uniform analysis of transit observations from the Hubble Space Telescope and Spitzer Space Telescope of two warm gas giants orbiting K-type stars—WASP-29b and WASP-80b. The transmission spectra, which span 0.4–5.0μm, are interpreted using a suite of chemical equilibrium PLATON atmospheric retrievals. Both planets show evidence of significant aerosol opacity along the day–night terminator. The spectrum of WASP-29b is flat throughout the visible and near-infrared, suggesting the presence of condensate clouds extending to low pressures. The lack of spectral features hinders our ability to constrain the atmospheric metallicity and C/O ratio. In contrast, WASP-80b shows a discernible, albeit muted H2O absorption feature at 1.4μm, as well as a steep optical spectral slope that is caused by fine-particle aerosols and/or contamination from unocculted spots on the variable host star. WASP-80b joins the small number of gas-giant exoplanets that show evidence for enhanced atmospheric metallicity: the transmission spectrum is consistent with metallicities ranging from∼30–100 times solar in the case of cloudy limbs to a few hundred times solar in the cloud-free scenario. In addition to the detection of water, we infer the presence of CO2in the atmosphere of WASP-80b based on the enhanced transit depth in the Spitzer 4.5μm bandpass. From a complementary analysis of Spitzer secondary eclipses, we find that the day side emission from WASP-29b and WASP-80b is consistent with brightness temperatures of 937±48 and 851±14 K, respectively, indicating relatively weak day–night heat transport and low Bond albedo.

Published
2022
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5. GJ 1252b: A Hot Terrestrial Super-Earth with No Atmosphere

Author

Ian J. M. Crossfield, Matej Malik, Michelle L. Hill, Stephen R. Kane, Bradford Foley, Alex S. Polanski, David Coria, Jonathan Brande, Yanzhe Zhang, Katherine Wienke, Laura Kreidberg, Nicolas B. Cowan, Diana Dragomir, Varoujan Gorjian, Thomas Mikal-Evans, Björn Benneke, Jessie L. Christiansen, Drake Deming, and Farisa Y. Morales

Published
2022
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6. Tentative Evidence for Water Vapor in the Atmosphere of the Neptune-sized Exoplanet HD 106315c

Author

Laura Kreidberg, Paul Mollière, Ian J. M. Crossfield, Daniel P. Thorngren, Yui Kawashima, Caroline V. Morley, Björn Benneke, Thomas Mikal-Evans, David Berardo, Molly R. Kosiarek, Varoujan Gorjian, David R. Ciardi, Jessie L. Christiansen, Diana Dragomir, Courtney D. Dressing, Jonathan J. Fortney, Benjamin J. Fulton, Thomas P. Greene, Kevin K. Hardegree-Ullman, Andrew W. Howard, Steve B. Howell, Howard Isaacson, Jessica E. Krick, John H. Livingston, Joshua D. Lothringer, Farisa Y. Morales, Erik A. Petigura, Joseph E. Rodriguez, Joshua E. Schlieder, and Lauren M. Weiss

Published
2022
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7. HD 191939: Three Sub-Neptunes Transiting a Sun-like Star Only 54 pc Away

Author

Mariona Badenas-Agusti, Maximilian N. Günther, Tansu Daylan, Thomas Mikal-Evans, Andrew Vanderburg, Chelsea X. Huang, Elisabeth Matthews, Benjamin V. Rackham, Allyson Bieryla, Keivan G. Stassun, Stephen R. Kane, Avi Shporer, Benjamin J. Fulton, Michelle L. Hill, Grzegorz Nowak, Ignasi Ribas, Enric Pallé, Jon M. Jenkins, David W. Latham, Sara Seager, George R. Ricker, Roland K. Vanderspek, Joshua N. Winn, Oriol Abril-Pla, Karen A. Collins, Pere Guerra Serra, Prajwal Niraula, Zafar Rustamkulov, Thomas Barclay, Ian J. M. Crossfield, Steve B. Howell, David R. Ciardi, Erica J. Gonzales, Joshua E. Schlieder, Douglas A. Caldwell, Michael Fausnaugh, Scott McDermott, Martin Paegert, Joshua Pepper, Mark E. Rose, and Joseph D. Twicken

Subjects
Astrophysics, Astronomy
Abstract

We present the discovery of three sub-Neptune-sized planets transiting the nearby and bright Sun-like star HD 191939 (TIC 269701147, TOI 1339), a Ks = 7.18 mag G8 V dwarf at a distance of only 54 pc. We validate the planetary nature of the transit signals by combining 5 months of data from the Transiting Exoplanet Survey Satellite with follow-up ground-based photometry, archival optical images, radial velocities, and high angular resolution observations. The three sub-Neptunes have similar radii (R(b)=3.42(+0.11,-0.11), R(c)=3.23(+0.11,-0.11), and R(d)=3.16(+0.11,-0.11 Rꚛ), and their orbits are consistent with a stable, circular, and coplanar architecture near mean-motion resonances of 1:3 and 3:4 (P(b) = 8.88, P(c) = 28.58, and P(d) = 38.35 days). The HD 191939 system is an excellent candidate for precise mass determinations of the planets with high-resolution spectroscopy due to the host star's brightness and low chromospheric activity. Moreover, the system's compact and near-resonant nature can provide an independent way to measure planetary masses via transit timing variations while also enabling dynamical and evolutionary studies. Finally, as a promising target for multiwavelength transmission spectroscopy of all three planets' atmospheres, HD 191939 can offer valuable insight into multiple sub-Neptunes born from a protoplanetary disk that may have resembled that of the early Sun.

Published
2020
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8. A Super-Earth and Sub-Neptune Transiting the Late-type M Dwarf LP 791-18

Author

Ian J. M. Crossfield, William Waalkes, Elisabeth R. Newton, Norio Narita, Philip Muirhead, Kristo Ment, Elisabeth Matthews, Adam Kraus, Veselin Kostov, Molly R. Kosiarek, Stephen R. Kane, Howard Isaacson, Sam Halverson, Erica Gonzales, Mark Everett, Diana Dragomir, Karen A. Collins, Ashley Chontos, David Berardo, Jennifer G. Winters, Joshua N. Winn, Nicholas J. Scott, Barbara Rojas-Ayala, Aaron C. Rizzuto, Erik A. Petigura, Merrin Peterson, Teo Mocnik, Thomas Mikal-Evans, Nicholas Mehrle, Rachel Matson, Masayuki Kuzuhara, Jonathan Irwin, Daniel Huber, Chelsea Huang, Steve Howell, Andrew W. Howard, Teruyuki Hirano, Benjamin J. Fulton, Trent Dupuy, Courtney Dressing, Paul A. Dalba, David Charbonneau, Jennifer Burt, Zachory Berta-Thompson, Björn Benneke, Noriharu Watanabe, Joseph D. Twicken, Motohide Tamura, Joshua Schlieder, S. Seager, Mark E. Rose, George Ricker, Elisa Quintana, Sébastien Lépine, David W. Latham, Takayuki Kotani, Jon M. Jenkins, Yasunori Hori, Knicole Colon, and Douglas A. Caldwell

Subjects
Astronomy, Astrophysics
Abstract

Planets occur most frequently around cool dwarfs, but only a handful of specific examples are known to orbit the latest-type M stars. Using TESS photometry, we report the discovery of two planets transiting the low-mass star called LP 791-18 (identified by TESS as TOI 736). This star has spectral type M6V, effective temperature 2960 K, and radius 0.17 Rꙩ, making it the third-coolest star known to host planets. The two planets straddle the radius gap seen for smaller exoplanets; they include a 1.1Rꚛ planet on a 0.95 day orbit and a 2.3Rꚛ planet on a 5 day orbit. Because the host star is small the decrease in light during these planets' transits is fairly large (0.4% and 1.7%). This has allowed us to detect both planets' transits from ground-based photometry, refining their radii and orbital ephemerides. In the future, radial velocity observations and transmission spectroscopy can both probe these planets' bulk interior and atmospheric compositions, and additional photometric monitoring would be sensitive to even smaller transiting planets.

Published
2019
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9. Phase Curves of Hot Neptune LTT 9779b Suggest a High-metallicity Atmosphere

Author

Ian J. M. Crossfield, Diana Dragomir, Nicolas B. Cowan, Tansu Daylan, Ian Wong, Tiffany Kataria, Drake Deming, Laura Kreidberg, Thomas Mikal-Evans, Varoujan Gorjian, James S. Jenkins, Björn Benneke, Karen A. Collins, Christopher J. Burke, Christopher E. Henze, Scott McDermott, Ismael Mireles, David Watanabe, Bill Wohler, George Ricker, Roland Vanderspek, Sara Seager, and Jon M. Jenkins

Published
2020
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10. A Super-Earth and Sub-Neptune Transiting the Late-type M Dwarf LP 791-18

Author

Ian J. M. Crossfield, William Waalkes, Elisabeth R. Newton, Norio Narita, Philip Muirhead, Kristo Ment, Elisabeth Matthews, Adam Kraus, Veselin Kostov, Molly R. Kosiarek, Stephen R. Kane, Howard Isaacson, Sam Halverson, Erica Gonzales, Mark Everett, Diana Dragomir, Karen A. Collins, Ashley Chontos, David Berardo, Jennifer G. Winters, Joshua N. Winn, Nicholas J. Scott, Barbara Rojas-Ayala, Aaron C. Rizzuto, Erik A. Petigura, Merrin Peterson, Teo Mocnik, Thomas Mikal-Evans, Nicholas Mehrle, Rachel Matson, Masayuki Kuzuhara, Jonathan Irwin, Daniel Huber, Chelsea Huang, Steve Howell, Andrew W. Howard, Teruyuki Hirano, Benjamin J. Fulton, Trent Dupuy, Courtney D. Dressing, Paul A. Dalba, David Charbonneau, Jennifer Burt, Zachory Berta-Thompson, Björn Benneke, Noriharu Watanabe, Joseph D. Twicken, Motohide Tamura, Joshua Schlieder, S. Seager, Mark E. Rose, George Ricker, Elisa Quintana, Sébastien Lépine, David W. Latham, Takayuki Kotani, Jon M. Jenkins, Yasunori Hori, Knicole Colon, and Douglas A. Caldwell

Published
2019
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