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WASP-107b is a warm (approximately 740 K) transiting planet with a Neptune-like mass of roughly 30.5  M ⊕ and Jupiter-like radius of about 0.94  R J (refs.  1 , 2 ), whose extended atmosphere is eroding 3 . Previous observations showed evidence for water vapour and a thick, high-altitude condensate layer in the atmosphere of WASP-107b (refs.  4 , 5 ). Recently, photochemically produced sulfur dioxide (SO 2 ) was detected in the atmosphere of a hot (about 1,200 K) Saturn-mass planet from transmission spectroscopy near 4.05 μm (refs.  6 , 7 ), but for temperatures below about 1,000 K, sulfur is predicted to preferably form sulfur allotropes instead of SO 2 (refs.  8 – 10 ). Here we report the 9 σ detection of two fundamental vibration bands of SO 2 , at 7.35 μm and 8.69 μm, in the transmission spectrum of WASP-107b using the Mid-Infrared Instrument (MIRI) of JWST. This discovery establishes WASP-107b as the second irradiated exoplanet with confirmed photochemistry, extending the temperature range of exoplanets exhibiting detected photochemistry from about 1,200 K down to about 740 K. Furthermore, our spectral analysis reveals the presence of silicate clouds, which are strongly favoured (around 7 σ ) over simpler cloud set-ups. Furthermore, water is detected (around 12 σ ) but methane is not. These findings provide evidence of disequilibrium chemistry and indicate a dynamically active atmosphere with a super-solar metallicity. The JWST MIRI transmission spectrum of WASP-107b, a transiting planet with Neptune-like mass and Jupiter-like radius, shows observations of sulfur dioxide and silicate clouds but no methane in its atmosphere, providing evidence of disequilibrium chemistry and active photochemistry.

The rapid assembly of the first supermassive black holes is an enduring mystery. Until now, it was not known whether quasar ‘feeding’ structures (the ‘hot torus’) could assemble as fast as the smaller-scale quasar structures. We present JWST/MRS (rest-frame infrared) spectroscopic observations of the quasar J1120+0641 at z  = 7.0848 (well within the epoch of reionization). The hot torus dust was clearly detected at λ rest  ≃ 1.3 μm, with a black-body temperature of T dust = 1,413.5 − 7.4 + 5.7  K, slightly elevated compared to similarly luminous quasars at lower redshifts. Importantly, the supermassive black hole mass of J1120+0641 based on the Hα line (accessible only with JWST), M BH  = 1.52 ± 0.17 × 10 9   M ⊙ , is in good agreement with previous ground-based rest-frame ultraviolet Mg ii measurements. Comparing the ratios of the Hα, Paα and Paβ emission lines to predictions from a simple one-phase Cloudy model, we find that they are consistent with originating from a common broad-line region with physical parameters that are consistent with lower-redshift quasars. Together, this implies that J1120+0641’s accretion structures must have assembled very quickly, as they appear fully ‘mature’ less than 760 Myr after the Big Bang. A JWST/MIRI spectrum of an early quasar in the mid-infrared indicates that J1120+0641 had a mature feeding structure 760 Myr after the Big Bang. This finding suggests that supermassive black holes and their torii build up surprisingly quickly.

WASP-107b is a warm (approximately 740 K) transiting planet with a Neptune-like mass of roughly 30.5 M and Jupiter-like radius of about 0.94 R (refs.  ), whose extended atmosphere is eroding . Previous observations showed evidence for water vapour and a thick, high-altitude condensate layer in the atmosphere of WASP-107b (refs.  ). Recently, photochemically produced sulfur dioxide (SO ) was detected in the atmosphere of a hot (about 1,200 K) Saturn-mass planet from transmission spectroscopy near 4.05 μm (refs.  ), but for temperatures below about 1,000 K, sulfur is predicted to preferably form sulfur allotropes instead of SO (refs.  ). Here we report the 9σ detection of two fundamental vibration bands of SO , at 7.35 μm and 8.69 μm, in the transmission spectrum of WASP-107b using the Mid-Infrared Instrument (MIRI) of JWST. This discovery establishes WASP-107b as the second irradiated exoplanet with confirmed photochemistry, extending the temperature range of exoplanets exhibiting detected photochemistry from about 1,200 K down to about 740 K. Furthermore, our spectral analysis reveals the presence of silicate clouds, which are strongly favoured (around 7σ) over simpler cloud set-ups. Furthermore, water is detected (around 12σ) but methane is not. These findings provide evidence of disequilibrium chemistry and indicate a dynamically active atmosphere with a super-solar metallicity.

The first JWST/MIRI photometric observations of TRAPPIST-1 b allowed for the detection of the thermal emission of the planet at 15 µm, suggesting that the planet could be a bare rock with a zero albedo and no redistribution of heat. These observations at 15 µm were acquired as part of GTO time that included a twin program at 12.8 µm in order to have a measurement in and outside the CO 2 absorption band. Here we present five new occultations of TRAPPIST-1 b observed with MIRI in an additional photometric band at 12.8 µm. We perform a global fit of the 10 eclipses and derive a planet-to-star flux ratio and 1-σ error of 452 ± 86 ppm and 775 ± 90 ppm at 12.8 µm and 15 µm, respectively. We find that two main scenarios emerge. An airless planet model with an unweathered (fresh) ultramafic surface, that could be indicative of relatively recent geological processes fits well the data. Alternatively, a thick, pure-CO2 atmosphere with photochemical hazes that create a temperature inversion and result in the CO2 feature being seen in emission also works, although with some caveats. Our results highlight the challenges in accurately determining a planet's atmospheric or surface nature solely from broadband filter measurements of its emission, but also point towards two very interesting scenarios that will be further investigated with the forthcoming phase curve of TRAPPIST-1 b.

The role of outflows in the formation of stars and the protostellar disks that generate them is a central question in astrophysics. Outflows are associated with star formation across the entire stellar mass spectrum. In this review, we describe the observational, theoretical, and computational advances on magnetized outflows, and their role in the formation of disks and stars of all masses in turbulent, magnetized clouds. The ability of torques exerted on disks by magnetized winds to efficiently extract and transport disk angular momentum was developed in early theoretical models and confirmed by a variety of numerical simulations. The recent high resolution ALMA observations of disks and outflows now confirm several key aspects of these ideas, e.g. that jets rotate and originate from large regions of their underlying disks. New insights on accretion disk physics show that magneto-rotational instability (MRI) turbulence is strongly damped, leaving magnetized disk winds as the dominant mechanism for transporting disk angular momentum. This has major consequences for star formation, as well as planet formation. Outflows also play an important role in feedback processes particularly in the birth of low mass stars and cluster formation. Despite being almost certainly fundamental to their production and focusing, magnetic fields in outflows in protostellar systems, and even in the disks, are notoriously difficult to measure. Most methods are indirect and lack precision, as for example, when using optical/near-infrared line ratios. Moreover, in those rare cases where direct measurements are possible - where synchrotron radiation is observed, one has to be very careful in interpreting derived values. Here we also explore what is known about magnetic fields from observations, and take a forward look to the time when facilities such as SPIRou and the SKA are in routine operation.

The process of accretion in classical T Tauri stars (CTTSs) has been observed to vary on different timescales. Studying this variability is vital to understanding a star's evolution and provides insight into the complex processes at work within. Understanding the dichotomy between continuum veiling and emission line veiling is integral to accurately measuring the amount of veiling present in stellar spectra. Here, 15 roughly consecutive nights of optical spectroscopic data from the spectropolarimeter ESPaDOnS are utilised to characterise the short-term accretion activity in the CTTS, RU Lup, and investigate its relationship with the veiling in the LiI 6707A absorption line. The accretion-tracing HI Balmer series emission lines were studied and used to obtain the accretion luminosity (Lacc) and mass accretion rate (Macc) for each night, which vary by a factor of ~2 between the brightest and dimmest nights. We also measured the veiling using multiple photospheric absorption lines (NaI 5688A, MnI 6021A, and LiI 6707A) for each night. We find the LiI 6707A line provides measurements of veiling that produce a strong, positive correlation with Lacc in the star. When corrected for Li depletion, the average veiling measured in the LiI 6707A line is r_LiI(avg)~3.25+/-0.20, which is consistent with the other photospheric lines studied (r_avg~3.28+/-0.65). We measured short timescale variability in the Lacc and Macc that are intrinsic and not due to geometric effects. Upon comparing the changes in veiling and Lacc, we find a strong, positive correlation. This study provides an example of how this correlation can be used as a tool to determine whether a measured variability is due to extinction or an intrinsic change in accretion. As the determination of veiling is an independent process from measuring Lacc, their relationship allows further exploration of accretion phenomena in young stars.

We report results of a spectropolarimetric and photometric monitoring of the weak-line T Tauri star LkCa 4 within the SPIRou Legacy Survey large programme, based on data collected with SPIRou at the Canada-France-Hawaii Telescope and the TESS space probe between October 2021 and January 2022. We applied Zeeman-Doppler Imaging to our spectropolarimetric and photometric data to recover a surface brightness distribution compatible with TESS photometry, as well as the large-scale magnetic topology of the star. As expected from the difference in wavelength between near-infrared and optical data, the recovered surface brightness distribution is less contrasted than the previously published one based on ESPaDOnS data, but still features mid-latitude dark and bright spots. The large-scale magnetic field is consistent in shape and strength with the one derived previously, with a poloidal component resembling a 2.2 kG dipole and a toroidal component reaching 1.4 kG and encircling the star at the equator. Our new data confirm that the surface differential rotation of LkCa 4 is about 10 times weaker than that of the Sun, and significantly different from zero. Using our brightness reconstruction and Gaussian Process Regression, we were able to filter the radial velocity activity jitter down to a precision of 0.45 and 0.38 km \\(\\rm s^{-1}\\) (from an amplitude of 6.10 km \\(\\rm s^{-1}\\)), respectively, yielding again no evidence for a close-in massive planet orbiting the star.

The understanding of planet formation has changed recently, embracing the new idea of pebble accretion. This means that the influx of pebbles from the outer regions of planet-forming disks to their inner zones could determine the composition of planets and their atmospheres. The solid and molecular components delivered to the planet-forming region can be best characterized by mid-infrared spectroscopy. With Spitzer low-resolution (R=100, 600) spectroscopy, this approach was limited to the detection of abundant molecules such as H2O, C2H2, HCN and CO2. This contribution will present first results of the MINDS (MIRI mid-IR Disk Survey, PI: Th. Henning) project. Due do the sensitivity and spectral resolution (R~1500-3500) provided by JWST we now have a unique tool to obtain the full inventory of chemistry in the inner disks of solar-types stars and brown dwarfs, including also less abundant hydrocarbons and isotopologues. The Integral Field Unit (IFU) capabilities enable at the same time spatial studies of the continuum and line emission in extended sources such as debris disks, the flying saucer and also the search for mid-IR signatures of forming planets in systems such as PDS70. These JWST observations are complementary to ALMA and NOEMA observations of the outer disk chemistry; together these datasets provide an integral view of the processes occurring during the planet formation phase.

Very low-mass Class I protostars have been investigated very little thus far. Variability of these young stellar objects (YSOs) and whether or not they are capable of strong episodic accretion is also left relatively unstudied. We investigate accretion variability in IRS54, a Class I very low-mass protostar with a mass of M\\(_{\\star}\\) ~ 0.1 - 0.2 M\\(_{\\odot}\\). We obtained spectroscopic and photometric data with VLT/ISAAC and VLT/SINFONI in the near-infrared (\\(J\\), \\(H\\), and \\(K\\) bands) across four epochs (2005, 2010, 2013, and 2014). We used accretion-tracing lines (Pa\\(\\beta\\) and Br\\(\\gamma\\)) and outflow-tracing lines (H\\(_2\\) and [FeII] to examine physical properties and kinematics of the object. A large increase in luminosity was found between the 2005 and 2013 epochs of more than 1 magnitude in the \\(K\\) band, followed in 2014 by a steep decrease. Consistently, the mass accretion rate (\\(\\dot{M}_{acc}\\)) rose by an order of magnitude from ~ 10\\(^{-8}\\) M\\(_{\\odot}\\) yr\\(^{-1}\\) to ~ \\(10^{-7}\\) M\\(_{\\odot}\\) yr\\(^{-1}\\) between the two early epochs. The visual extinction (\\(A_V\\)) has also increased from ~ 15 mag in 2005 to ~ 24 mag in 2013. This rise in \\(A_V\\) in tandem with the increase in \\(\\dot{M}_{acc}\\) is explained by the lifting up of a large amount of dust from the disc of IRS54, following the augmented accretion and ejection activity in the YSO, which intersects our line of sight due to the almost edge-on geometry of the disc. Because of the strength and timescales involved in this dramatic increase, this event is believed to have been an accretion burst possibly similar to bursts of EXor-type objects. IRS54 is the lowest mass Class I source observed to have an accretion burst of this type, and therefore potentially one of the lowest mass EXor-type objects known so far.

The redistribution of angular momentum is a long standing problem in our understanding of protoplanetary disk (PPD) evolution. The magnetorotational instability (MRI) is considered a likely mechanism. We present the results of a study involving multifluid global simulations including Ohmic dissipation, ambipolar diffusion and the Hall effect in a dynamic, self-consistent way. We focus on the turbulence resulting from the non-linear development of the MRI in radially stratified PPDs and compare with ideal MHD simulations. In the multifluid simulations the disk is initially set up to transition from a weak Hall dominated regime, where the Hall effect is the dominant non-ideal effect but approximately the same as or weaker than the inductive term, to a strong Hall dominated regime, where the Hall effect dominates the inductive term. As the simulations progress a substantial portion of the disk develops into a weak Hall dominated disk. We find a transition from turbulent to laminar flow in the inner regions of the disk, but without any corresponding overall density feature. We introduce a dimensionless parameter, \\(\\alpha_\\mathrm{RM}\\), to characterise accretion with \\(\\alpha_\\mathrm{RM} \\gtrsim 0.1\\) corresponding to turbulent transport. We calculate the eddy turnover time, \\(t_\\mathrm{eddy}\\), and compared this with an effective recombination timescale, \\(t_\\mathrm{rcb}\\), to determine whether the presence of turbulence necessitates non-equilibrium ionisation calculations. We find that \\(t_\\mathrm{rcb}\\) is typically around three orders of magnitude smaller than \\(t_\\mathrm{eddy}\\). Also, the ionisation fraction does not vary appreciably. These two results suggest that these multifluid simulations should be comparable to single fluid non-ideal simulations.