Results 1 to 10 of about 3,353,500 (213)

Constraining Atmospheric Composition from the Outflow: Helium Observations Reveal the Fundamental Properties of Two Planets Straddling the Radius Gap

The Astronomical Journal
TOI-836 is a ∼2–3 Gyr K dwarf with an inner super Earth ( R  = 1.7 R _⊕ , P = 3.8 days) and an outer mini-Neptune ( R  = 2.6 R _⊕ , P = 8.6 days). JWST/NIRSpec 2.8–5.2 μ m transmission spectra are flat for both planets.
Michael Zhang, Jacob L. Bean, David Wilson, Girish Duvvuri, Christian Schneider, Heather A. Knutson, Fei Dai, Karen A. Collins, Cristilyn N. Watkins, Richard P. Schwarz, Khalid Barkaoui, Avi Shporer, Keith Horne, Ramotholo Sefako, Felipe Murgas, Enric Palle   +15 more
doaj   +1 more source

Nonthermal Atmospheric Escape on the Kepler-11 “Super-Earths” Driven by Stellar Wind Sputtering

The Astrophysical Journal, 2023
Jeans escape or hydrodynamic escape is believed to dominate atmospheric loss for hot Jupiters. However, nonthermal mechanisms likely contribute substantially on hydrogen-rich “super-Earths” with relatively cold and extended atmospheres.
Hao Gu, Xiaoshu Wu, Xu Huang, Jianheng Guo, Jun Cui   +4 more
doaj   +1 more source

Helium Depletion in Escaping Atmospheres of Sub-Neptunes: A Signature of Primary-to-secondary Transition

The Astrophysical Journal
Short-period sub-Neptunes are common in extrasolar systems. These sub-Neptunes are generally thought to have primary atmospheres of protoplanetary-disk gas origin.
Issei Kobayashi, Hiroyuki Kurokawa, Laura Schaefer, Satoshi Okuzumi   +3 more
doaj   +1 more source

Transmission Spectroscopy of the Lowest-density Gas Giant: Metals and a Potential Extended Outflow in HAT-P-67b

The Astronomical Journal, 2023
Extremely low-density exoplanets are tantalizing targets for atmospheric characterization because of their promisingly large signals in transmission spectroscopy.
Aaron Bello-Arufe, Heather A. Knutson, João M. Mendonça, Michael M. Zhang, Samuel H. C. Cabot, Alexander D. Rathcke, Ana Ulla, Shreyas Vissapragada, Lars A. Buchhave   +8 more
doaj   +1 more source

A Metal-poor Atmosphere with a Hot Interior for a Young Sub-Neptune Progenitor: JWST/NIRSpec Transmission Spectrum of V1298 Tau b

The Astronomical Journal
We present the JWST/NIRSpec G395H transmission spectrum of the young (10–30 Myr) transiting planet V1298 Tau b (9.85 ± 0.35 R _⊕ , T _eq  = 670 K). Combined Hubble Space Telescope and JWST observations reveal a haze-free, H/He-dominated atmosphere with a
Saugata Barat, Jean-Michel Désert, Sagnick Mukherjee, Jayesh M. Goyal, Qiao Xue, Yui Kawashima, Allona Vazan, William Misener, Hilke E. Schlichting, Jonathan J. Fortney, Jacob L. Bean, Swaroop Avarsekar, Gregory W. Henry, Robin Baeyens, Michael R. Line, John H. Livingston, Trevor David, Erik A. Petigura, James T. Sikora, Hinna Shivkumar, Adina D. Feinstein, Antonija Oklopčić   +21 more
doaj   +1 more source

Sub-Neptune Memories. I. Implications of Inefficient Mantle Cooling and Silicate Rain

The Astrophysical Journal
We explore the evolution of sub-Neptune (radii between ∼1.5 and 4 R _⊕ ) exoplanet interior structures using our upgraded evolution code, APPLE , which self-consistently couples the thermal and compositional evolution of the whole structure.
Roberto Tejada Arevalo, Akash Gupta, Adam Burrows, Donghao Zheng, Yao Tang, Jie Deng   +5 more
doaj   +1 more source

Strong Fractionation of Deuterium and Helium in Sub-Neptune Atmospheres along the Radius Valley

The Astrophysical Journal
We simulate atmospheric fractionation in escaping planetary atmospheres using IsoFATE , a new open-source numerical model. We expand the parameter space studied previously to planets with tenuous atmospheres that exhibit the greatest helium and deuterium
Collin Cherubim, Robin Wordsworth, Renyu Hu, Evgenya Shkolnik   +3 more
doaj   +1 more source

Outflowing Helium from a Mature Mini-Neptune

The Astrophysical Journal Letters, 2023
We announce the detection of escaping helium from TOI 2134b, a mini-Neptune a few gigayears old. The average in-transit absorption spectrum shows a peak of 0.37% ± 0.05% and an equivalent width of W _avg = 3.3 ± 0.3 mÅ.
Michael Zhang, Fei Dai, Jacob L. Bean, Heather A. Knutson, Federica Rescigno   +4 more
doaj   +1 more source

Helium Escape in Context: Comparative Signatures of Four Close-in Exoplanets

The Astrophysical Journal
Observations of escaping atmospheres on close-in exoplanets show a wide range in the strength and morphology of He I 10830 Å and H I absorption. Scaling relations attempt to link the He I signal to X-ray and UV irradiation, mass loss, and bulk planetary ...
Anna Ruth Taylor, Tommi T. Koskinen, Chenliang Huang, Anthony Arfaux, Panayotis Lavvas   +4 more
doaj   +1 more source

Far-ultraviolet Flares and Variability of the Young M Dwarf AU Mic: A Nondetection of Planet C in Transit at Lyα

The Astronomical Journal
Atmospheric escape’s potential to shape the exoplanet population motivates detailed observations of systems actively undergoing escape. AU Mic is a young and active M dwarf hosting two close-in transiting sub- to Neptune-sized planets. Atmospheric escape
Keighley E. Rockcliffe, Elisabeth R. Newton, Allison Youngblood, Girish M. Duvvuri, Emily A. Gilbert, Peter Plavchan, Peter Gao, Hans-R. Müller, Adina D. Feinstein, Thomas Barclay, Eric D. Lopez   +10 more
doaj   +1 more source