Exoplanets and Stellar Physics

Abstract:

Abstract We present the first spatially resolved kinematic evidence for dust in the outflows of Active Galactic Nuclei (AGN). We utilise observations from JWST with NIRSpec IFU and MIRI MRS data of 10 local Seyferts and use Principal Component Analysis (PCA) tomography to extract the kinematics of Polycyclic Aromatic Hydrocarbon (PAH) features. PAHs comprise the smallest carbonaceous dust molecules in the Interstellar Medium (ISM), and produce emission features in the infrared providing the potential to measure kinematics. This is however challenging due to their broad shapes and variations in their intrinsic profile, prompting the need for techniques such as PCA tomography. We find that the velocity of the PAHs is similar to the molecular gas as traced by the rotational transitions of H2, where for NGC 5728 and NGC 7582, both disk and outflow are present. We detect the outflow in the kinematics of large and neutral PAHs, namely the 11.3 μm and 17 μm PAH features, where after subtracting the disk, the velocity field matches that of high-ionisation potential lines such as [NeVI] (7.65 μm, IP = 158 eV). Finally, we fail to detect kinematics of the 6.2 μm PAH due to an altered intrinsic profile while the the 3.3 μm PAH kinematics purely trace the circumnuclear disk. This suggests the PAHs in the outflow are more neutral and larger than in star-forming regions, consistent with PAH band ratios in previous studies of AGN.

Abstract:

Ultra-hot Jupiters (UHJs) present extreme atmospheric phenomena not found in the solar system. These planets’ daysides experience strong temperature inversions, molecular species (including H2) dissociate, and magnetism effects disrupt atmospheric circulation. On their nightsides, H2 can recombine and clouds may form. Spectroscopic phase curves allow us to measure these spatially inhomogeneous conditions, which can then be interpreted with three-dimensional (3D) models. In this work, we compare the JWST Near Infrared Imager and Slitless Spectrograph (or NIRISS) spectroscopic phase curve of the UHJ WASP-121 b to state-of-the-art 3D models with varying modeling assumptions, including the aforementioned physical phenomena. We demonstrate the importance of accurately accounting for the planet’s radius when comparing data and models, as it changes the implied overall planetary emission. We find that the 3D models predict planetary emission that is ∼12% higher than observed, contributing to the continued tension between measured and predicted hot Jupiter albedos. We identify multiple lines of evidence confirming a strong source of drag operating in this planet’s atmosphere. In addition, the nightside emission spectrum is devoid of strong absorption features, which may be best explained by nightside clouds. One feature of the dataset that is not reproduced by the 3D models is a trend toward increasingly eastward phase offsets at wavelengths shorter than ∼1.4 μm. This result is inconsistent with reflection from dayside clouds, nor can it be explained by removing atmospheric opacity sources. Our analysis highlights the complexities involved in generating 3D models and interpreting observations of UHJs in the JWST era.

Abstract:

Pictoris b is one of the closest known directly imaged gas giant exoplanets with an orbit that is almost edge-on to our line of sight, making it an ideal target for radial velocity monitoring to search for massive exomoons. We measure the radial velocity of Pictoris b over several epochs between October 2024 and March 2025 by using the cross-correlation of a template spectrum with absorption lines in the planet’s atmosphere, giving a mean precision of 160 m s. The resultant set of radial velocities is analysed with a periodogram to search for candidate radial velocity (RV) signals indicating a massive exomoon. Although we do not detect an exomoon signal in our data, our detection limits for a single moon are 80 Earth masses at d and 1 Jupiter at d, comparable to RV exomoon searches around other substellar companions. The RV limit is comparable with the astrometric exomoon limit at a period of 7 d and a mass of 150 , where for longer periods the astrometric searches have lower mass limits. With an additional observing season, the upgraded CRyogenic InfraRed Echelle Spectrograph (CRIRES+) can detect a planet/moon mass ratio of () with a period of up to one day, and can detect a Neptune-mass moon at hundreds of Jupiter radii.