Photochemistry versus Escape in the Trappist-1 planets.
(2025)
Abstract:
From Pretransit to Posteclipse: Investigating the Impact of 3D Temperature, Chemistry, and Dynamics on High-resolution Emission Spectra of the Ultrahot Jupiter WASP-76b
Astrophysical Journal 986:1 (2025)
Abstract:
High-resolution spectroscopy has provided a wealth of information about the climate and composition of ultrahot Jupiters (UHJs). However, the 3D structure of their atmospheres makes observations more challenging to interpret, necessitating 3D forward-modeling studies. In this work, we model phase-dependent thermal emission spectra of the archetype UHJ WASP-76b to understand how the line strengths and Doppler shifts of Fe, CO, HJWST NIRISS transmission spectroscopy of the super-Earth GJ 357b, a favourable target for atmospheric retention
Monthly Notices of the Royal Astronomical Society Oxford University Press 540:4 (2025) 3677-3692
Abstract:
We present a JWST Near Infrared Imager and Slitless Spectrograph/Single Object Slitless Spectroscopy transmission spectrum of the super-Earth GJ 357 b: the first atmospheric observation of this exoplanet. Despite missing the first 40 per cent of the transit due to using an out-of-date ephemeris, we still recover a transmission spectrum that does not display any clear signs of atmospheric features. We perform a search for Gaussian-shaped absorption features within the data but find that this analysis yields comparable fits to the observations as a flat line. We compare the transmission spectrum to a grid of atmosphere models and reject, to 3 confidence, atmospheres with metallicities solar (4 g mol−1) with clouds at pressures down to 0.01 bar. We analyse how the retention of a secondary atmosphere on GJ 357 b may be possible due to its higher escape velocity compared to an Earth-sized planet and the exceptional inactivity of its host star relative to other M2.5V stars. The star’s XUV luminosity decays below the threshold for rapid atmospheric escape early enough that the volcanic revival of an atmosphere of several bars of CO is plausible, though subject to considerable uncertainty. Finally, we model the feasibility of detecting an atmosphere on GJ 357 b with MIRI/LRS, MIRI photometry, and NIRSpec/G395H. We find that, with two eclipses, it would be possible to detect features indicative of an atmosphere or surface. Further to this, with three to four transits, it would be possible to detect a 1 bar nitrogen-rich atmosphere with 1000 ppm of CO.Supermassive black hole mass measurement in the spiral galaxy NGC 4736 using JWST/NIRSpec stellar kinematics
Astronomy & Astrophysics EDP Sciences 698 (2025) L9-L9
Abstract:
<jats:p>We present accurate mass measurements of the central supermassive black hole (SMBH) in NGC 4736 (M 94). We used the “gold-standard” stellar absorption features (CO band heads) at ∼2.3 μm, as opposed to gas emission lines, to trace the dynamics in the nuclear region, easily resolving the SMBH’s sphere of influence. The analysis uses observations made with the integral field unit of the Near-Infrared Spectrograph (NIRSpec) on the <jats:italic>James Webb</jats:italic> Space Telescope and a surface brightness profile derived from <jats:italic>Hubble</jats:italic> Space Telescope archival images. We used Jeans anisotropic models within a Bayesian framework, and comprehensive Markov chain Monte Carlo optimization, to determine the best-fit black hole mass, orbital anisotropy, mass-to-light ratio, and nucleus kinematical inclination. We obtained a SMBH mass <jats:italic>M</jats:italic><jats:sub>BH</jats:sub> = (1.60 ± 0.16)×10<jats:sup>7</jats:sup> M<jats:sub>⊙</jats:sub> (1<jats:italic>σ</jats:italic> random error), which is consistent with the <jats:italic>M</jats:italic><jats:sub>BH</jats:sub>–<jats:italic>σ</jats:italic> and <jats:italic>M</jats:italic><jats:sub>BH</jats:sub>–<jats:italic>M</jats:italic><jats:sub>⋆</jats:sub> relations. This is the first dynamical measurement of a <jats:italic>M</jats:italic><jats:sub>BH</jats:sub> in NGC 4736 based on the stellar kinematics observed with NIRSpec. We thus settle a longstanding inconsistency between estimates based on nuclear emission-line tracers and the <jats:italic>M</jats:italic><jats:sub>BH</jats:sub>–<jats:italic>σ</jats:italic> relation. Our analysis shows that NIRSpec can detect SMBHs with <jats:italic>M</jats:italic><jats:sub>BH, min</jats:sub> ≈ 5 × 10<jats:sup>6</jats:sup> M<jats:sub>⊙</jats:sub> in galaxies within 5 Mpc and <jats:italic>σ</jats:italic> ≈ 100 km s<jats:sup>−1</jats:sup>.</jats:p>SiO and a super-stellar C/O ratio in the atmosphere of the giant exoplanet WASP-121 b
Nature Astronomy Nature Research 9:6 (2025) 845-861