Search Publications
Detection of Ongoing Mass Loss from HD 63433c, a Young Mini-Neptune
Henry, Gregory W.; Knutson, Heather A.; Dai, Fei +9 more
We detect Lyα absorption from the escaping atmosphere of HD 63433c, a R = 2.67R ⊕, P = 20.5 day mini-Neptune orbiting a young (440 Myr) solar analog in the Ursa Major Moving Group. Using Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph, we measure a transit depth of 11.1 ± 1.5% in the blue wing and 8 ± 3% in the red. Th…
Escaping Helium from TOI 560.01, a Young Mini-Neptune
Knutson, Heather A.; Dai, Fei; Zhang, Michael +2 more
We report helium absorption from the escaping atmosphere of TOI 560.01 (HD 73583b), an R = 2.8R ⊕, P = 6.4 day mini-Neptune orbiting a young (~600 Myr) K dwarf. Using Keck/NIRSPEC, we detect a signal with an average depth of 0.68% ± 0.08% in the line core. The absorption signal repeats during a partial transit obtained a month later, bu…
The K2-3 System Revisited: Testing Photoevaporation and Core-powered Mass Loss with Three Small Planets Spanning the Radius Valley
Youngblood, Allison; Crossfield, Ian J. M.; Kreidberg, Laura +11 more
Multiplanet systems orbiting M dwarfs provide valuable tests of theories of small-planet formation and evolution. K2-3 is an early M dwarf hosting three small exoplanets (1.5-2.0 R ⊕) at distances of 0.07-0.20 au. We measure the high-energy spectrum of K2-3 with HST/COS and XMM-Newton and use empirically driven estimates of Lyα and extr…
AU Microscopii in the Far-UV: Observations in Quiescence, during Flares, and Implications for AU Mic b and c
France, Kevin; Youngblood, Allison; Gaidos, Eric +13 more
High-energy X-ray and ultraviolet (UV) radiation from young stars impacts planetary atmospheric chemistry and mass loss. The active ~22 Myr M dwarf AU Mic hosts two exoplanets orbiting interior to its debris disk. Therefore, this system provides a unique opportunity to quantify the effects of stellar X-ray and UV irradiation on planetary atmospher…
More Evidence for Variable Helium Absorption from HD 189733b
Redfield, Seth; Knutson, Heather A.; France, Kevin +5 more
We present a new Keck/NIRSPEC observation of metastable helium absorption from the upper atmosphere of HD 189733b, a hot Jupiter orbiting a nearby moderately active star. We measure an average helium transit depth of 0.420% ± 0.013% integrated over the [-20, 20] km s-1 velocity range. Comparing this measurement to eight previously publi…
The Hubble PanCET Program: A Featureless Transmission Spectrum for WASP-29b and Evidence of Enhanced Atmospheric Metallicity on WASP-80b
Deming, Drake; Mikal-Evans, Thomas; Sing, David K. +19 more
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 0.4-5.0 µm, are interpreted using a suite of chemical equilibrium PLATON atmospheric retrievals. Both planets show evidence …
Multiwavelength Modeling the SED of Luminous Supersoft X-Ray Sources in Large Magellanic Cloud and Small Magellanic Cloud
Skopal, Augustin
Classical supersoft X-ray sources (SSSs) are understood as close binary systems in which a massive white dwarf accretes from its companion at rates sustaining steady hydrogen burning on its surface generating bolometric luminosities of 1036-2 × 1038 erg s-1. Here, we perform for the first time the global supersoft …
The Shellless Supernova Remnant B0532-67.5 in the Large Magellanic Cloud
Chu, You-Hua; Li, Chuan-Jui; Chuang, Chen-Yu +1 more
The supernova remnant (SNR) B0532-67.5 in the Large Magellanic Cloud (LMC) was first diagnosed by its nonthermal radio emission, and its SNR nature was confirmed by the observation of diffuse X-ray emission; however, no optical SNR shell is detected. The OB association LH75, or NGC 2011, is projected within the boundary of this SNR. We have analyz…