FQ Cir was an ordinary fast He/N classical nova, peaking at V = 10.9. The pre-eruption and post-eruption counterpart was at V = 14.0, making this the smallest known classical nova amplitude, 3.1 mag. The nova light and the counterpart coincide at 0 .'' 034, and the counterpart is a rare hot/blue emission-line star with flickering, so the identification of the quiescent nova is certain. The counterpart is a weak Be main-sequence star, B1 V(n)(e). A coherent photometric period appears in all four TESS Sectors and in the AAVSO post-eruption light curve, as ellipsoidal modulation with an orbital period of 2.041738 days. The companion must have been spun up to a fast rotation, and like all Be stars, a decretion disk is exuded. With the constraints of the blackbody radius and the main sequence, the companion mass is 13.0( -0.5)(+0.2 )M(circle dot), with radius 6.2 +/- 0.2 R-circle dot. This is the discovery of a cataclysmic variable with a high-mass companion, a new class that we call "high-mass cataclysmic variables." The white dwarf mass is 1.25 +/- 0.10 M(circle dot )and must have an accretion disk that supplies fuel for the nova eruption. FQ Cir represents a new mode of accretion in interacting binaries, with Roche lobe overflow from the decretion disk feeding mass into the usual accretion disk around the white dwarf, for disk-to-disk accretion. From the mass budget of the binary, the primary star must have its initial mass be >7.7 M-circle dot, forming an ONe white dwarf, so FQ Cir can never become a Type Ia supernova.
Flying on board the James Webb Space Telescope (JWST) above Earth's turbulent atmosphere, the Aperture Masking Interferometer (AMI) on the NIRISS instrument is the highest-resolution infrared interferometer ever placed in space. However, its performance was found to be limited by non-linear detector systematics, particularly charge migration - or the Brighter-Fatter Effect. Conventional interferometric Fourier observables are degraded by non-linear transformations in the image plane, with the consequence that the inner working angle and contrast limits of AMI were seriously compromised. Building on the end-to-end differentiable model & calibration code , we here present a regularised maximum-likelihood image reconstruction framework , which can deconvolve AMI images either in the image plane or from calibrated Fourier observables, achieving high angular resolution and contrast over a wider field of view than conventional interferometric limits. This modular code by default includes regularisation by maximum entropy, and total variation defined with $l_1$ or $l_2$ metrics. We present imaging results from dorito for three benchmark imaging datasets: the volcanoes of Jupiter's moon Io, the colliding-wind binary dust nebula WR 137 and the archetypal Seyfert 2 active galactic nucleus NGC 1068. In all three cases, we recover images consistent with the literature at diffraction-limited resolutions. The performance, limitations, and future opportunities enabled by amigo for AMI imaging (and beyond) are discussed.
Studying cold brown dwarfs is key to understanding the diverse characteristics of cold giant exoplanets atmospheres. COCONUTS-2 is a wide binary system composed of a T9 brown dwarf and an M3 star, which presents a unique opportunity to characterize a cold benchmark brown dwarf. As part of a JWST program to study the range of physical and atmospheric properties of the coldest brown dwarfs, we obtained NIRSpec G395H spectra ( R ∼ 2700, 2.87−5.13 μ m) and MIRI F1000W, F1280W, and F1800W photometry for COCONUTS-2 b. In this work, we find a 99% probability of the system belonging to the Corona of Ursa Major moving group (414 ± 23 Myr) using BANYAN Σ and its full kinematics. We also reestimate the astrometry of COCONUTS-2b using the MIRI data. We support this membership with a comparison of the rotation period, metallicity, and C/O ratio of the group with those of the COCONUTS-2 system. We also calculate its bolometric luminosity, which, combined with our age estimation, allows us to derive its mass, effective temperature, surface gravity, and radius with high precision. As a result of our analysis, we support the conclusion that COCONUTS-2 b is a planetary-mass object (7.5 ± 0.4 M _Jup ), which was likely formed via the same mechanism as stars. In addition we compare the JWST spectrum to another object in the sample, J082507.35+280548.5 (0825+2805), a Y0.5 brown dwarf, which is a candidate member of the same moving group, but has a lower mass (3.7 ± 0.2 M _Jup ). We identify absorption feature differences, which could indicate that 0825+2805 has stronger vertical mixing.
The unprecedented accuracy of JWST has led to the detection of silicate clouds in exoplanet atmospheres, allowing astronomers for the first time to probe cloud formation in extreme environments. While parameterized cloud descriptions can fit these observations, the results do not fully agree with microphysical models. To bridge this gap, we developed Nimbus, a fast microphysical cloud model that can constrain cloud formation processes from observations, and utilize Virga, an equilibrium condensation model balancing gravitational settling and diffusion. Using both models, we investigate WASP-107 b, WASP-17 b, VHS-1256 b, and YSES-1 c to determine their cloud structure and constrain cloud formation processes. Our results show that all four planets have cluster-sized silicate particles (r similar to 1 nm) at high altitudes. Within Nimbus and Virga, these particles can only be explained by highly inefficient cloud particle settling (f(sed) < 0.1) or by inefficient growth rates due to low sticking coefficients (s < 10(-4)). Our results also show that the sticking coefficient is directly linked to the vertical extent of clouds and can therefore be constrained using the broad shape of the spectral energy distribution. The sticking coefficients found for VHS-1256 b and YSES-1 c are in agreement with expectations from laboratory experiments under Earth-like conditions (0.01 < s < 0.3). Panchromatic observations were crucial to achieve these constraints. Future cloud studies should therefore aim to combine observational data from 1 mu m to 10 mu m whenever possible.
Living reptiles including turtles, crocodilians, birds and squamates are descended from a common ancestor among the Neodiapsida that lived in the late Permian c . 257 million years ago. Their origin was preceded by key evolutionary changes to cranial architecture that are poorly understood due to the rarity of early neodiapsids in the fossil record. Here, we describe a monospecific aggregation of a new non-saurian neodiapsid from the late Permian of South Africa. Synchrotron microtomography of four complete skulls reveals a mosaic of classic ‘saurian’ features such as a tympanic fossa and cephalic condyle of the quadrate and an open lower temporal bar, alongside surprising plesiomorphies including a rectangular denticle field on the braincase and a comparatively robust stapes. Phylogenetic analysis finds the new taxon within the Younginidae, sister to Akkedops bremneri and Youngina capensis as the earliest-diverging neodiapsid lineage. Our results demonstrate that the mobile (strepostylic) quadrate evolved only shortly after the origin of the tympanic fossa and the loss of the lower temporal bar, among crownward stem reptiles. This suggests a functional evolutionary linkage between these important traits related to hearing and feeding during the rise of crown reptiles.
