The geometries of near-resonant planetary systems offer a relatively pristine window into the initial conditions of exoplanet systems. Given that near-resonant systems have likely experienced minimal dynamical disruptions, the spin-orbit orientations of these systems inform the typical outcomes of quiescent planet formation, as well as the primordial stellar obliquity distribution. However, few measurements have been made to constrain the spin-orbit orientations of near-resonant systems. We present a Rossiter-McLaughlin measurement of the near-resonant warm Jupiter TOI-2202 b, obtained using the Carnegie Planet Finder Spectrograph on the 6.5 m Magellan Clay Telescope. This is the eighth result from the Stellar Obliquities in Long-period Exoplanet Systems survey. We derive a sky-projected 2D spin-orbit angle lambda = 26(-15)(+12 degrees) and a 3D spin-orbit angle Psi = 31(-11)(+13 degrees), finding that TOI-2202 b-the most massive near-resonant exoplanet with a 3D spin-orbit constraint to date-likely deviates from exact alignment with the host star's equator. Incorporating the full census of spin-orbit measurements for near-resonant systems, we demonstrate that the current set of near-resonant systems with period ratios P-2/P-1 less than or similar to 4 is generally consistent with a quiescent formation pathway, with some room for low-level (less than or similar to 20 degrees) protoplanetary disk misalignments or post-disk-dispersal spin-orbit excitation. Our result constitutes the first population-wide analysis of spin-orbit geometries for near-resonant planetary systems.

Analyses of pulsar timing data have provided evidence for a stochastic gravitational wave background in the nanohertz frequency band. The most plausible source of this background is the superposition of signals from millions of supermassive black hole binaries. The standard statistical techniques used to search for this background and assess its significance make several simplifying assumptions, namely (i) Gaussianity, (ii) isotropy, and most often, (iii) a power-law spectrum. However, a stochastic background from a finite collection of binaries does not exactly satisfy any of these assumptions. To understand the effect of these assumptions, we test standard analysis techniques on a large collection of realistic simulated data sets. The data-set length, observing schedule, and noise levels were chosen to emulate the NANOGrav 15 yr data set. Simulated signals from millions of binaries drawn from models based on the Illustris cosmological hydrodynamical simulation were added to the data. We find that the standard statistical methods perform remarkably well on these simulated data sets, even though their fundamental assumptions are not strictly met. They are able to achieve a confident detection of the background. However, even for a fixed set of astrophysical parameters, different realizations of the universe result in a large variance in the significance and recovered parameters of the background. We also find that the presence of loud individual binaries can bias the spectral recovery of the background if we do not account for them.

Stripped-envelope supernovae (SESNe) are a subclass of core-collapse supernovae that are deficient in hydrogen (SN IIb, SN Ib) and possibly helium (SN Ic) in their spectra. Their progenitors are likely stripped of this material through a combination of stellar winds and interactions with a close binary companion, but the exact ejecta mass range covered by each subtype and how it relates to the zero-age main-sequence progenitor mass is still unclear. Using a combination of semianalytic modeling and numerical simulations, we discuss how the properties of SESN progenitors can be constrained through different phases of the bolometric light curve. We find that the light-curve rise time is strongly impacted by the strength of radioactive nickel mixing and treatment of helium recombination. These can vary between events and are often not accounted for in simpler modeling approaches, leading to large uncertainties in ejecta masses inferred from the rise. Motivated by this, we focus on the late-time slope, which is determined by gamma-ray leakage. We calibrate the relationship between ejecta mass, explosion energy, and gamma-ray escape time T 0 using a suite of numerical models. Application of the fitting function we provide to bolometric light curves of SESNe should result in ejecta masses with approximately 20% uncertainty. With large samples of SESNe coming from current and upcoming surveys, our methods can be utilized to better understand the diversity and origin of the progenitor stars.

The positions and velocities of stellar streams have been used to constrain the mass and shape of the Milky Way's dark matter halo. Several extragalactic streams have already been detected, though it has remained unclear what can be inferred about the gravitational potential from only 2D photometric data of a stream. We present a fast method to infer halo shapes from the curvature of 2D projected stream tracks. We show that the stream curvature vector must point within 90 degrees of the projected acceleration vector, in the absence of recent time-dependent perturbations. While insensitive to the total magnitude of the acceleration, and therefore the total mass, applying this constraint along a stream can determine halo shape parameters and place limits on disk-to-halo mass ratios. The most informative streams are those with sharp turns or flat segments, since these streams sample a wide range of curvature vectors over a small area (sharp turns) or have a vanishing projected acceleration component (flat segments). We apply our method to low surface brightness imaging of NGC 5907, and find that its dark matter halo is oblate. Our analytic approach is significantly faster than other stream modeling techniques, and indicates which parts of a stream contribute to constraints on the potential. The method enables a measurement of dark matter halo shapes for thousands of systems using stellar stream detections expected from upcoming facilities like Rubin and Roman.

Context. The final stages of molecular cloud evolution involve cloud disruption due to feedback by massive stars, with recent literature suggesting the importance of early (i.e., pre-supernova) feedback mechanisms.

NWA 8785 is a remarkable EL3 chondrite with a high abundance (similar to 34 vol%) of an Fe-rich matrix. This is the highest matrix abundance known among enstatite chondrites (ECs) and more similar to the matrix abundances in some carbonaceous and Rumuruti chondrites. X-ray diffraction and TEM data indicate that the fine-grained portion of the NWA 8785 matrix consists of nanoscale magnetite mixed with a noncrystalline silicate material and submicron-sized enstatite and plagioclase grains. This is the first report of magnetite nanoparticles in an EL3. The Si content of the metal (0.7 wt%), presence of ferroan alabandite, and its O isotopic composition indicate NWA 8785 is EL3-related. Having more abundant matrix than in other ECs, and that the matrix is rich in magnetite nanoparticles, which are not present in any other EC, suggest classification as an EL3 anomalous. Although we cannot completely exclude any of the mechanisms or environments for formation of the magnetite, we find a secondary origin to be the most compelling. We suggest that the magnetite formed due to hydrothermal activity in the meteorite parent body. Although ECs are relatively dry and likely formed within the nebular snow line, ices may have drifted inward from just beyond the snow line to the region where the EL chondrites were accreting, or more likely the snow line migrated inward during the early evolution of the solar system. This may have resulted in the condensation of ices and provided an ice-rich region for accretion of the EL3 parent body. Thus, the EL3 parent body may have had hydrothermal activity and if Earth formed near the EC accretion zone, similar bodies may have contributed to the Earth's water supply. NWA 8785 greatly extends the range of known characteristics of ECs and EC parent body processes.

Volcano geodesy often involves the use of models to explain observed surface deformation. A variety of forward models are used, from analytical point sources to numerical simulations that consider complex magma system geometries, topography, and material properties. Various inversion methods can then be used to relate observed volcano data to models. Ideally, forward models should be verified through intercomparison, to check for implementation errors and quantify the error induced by any approximations used. Additionally, forward models and inversion methods should be validated through tests with synthetic and/or real data, to determine their ability to match data and estimate parameter values within uncertainty. However, to date, there have not been comprehensive verification and validation efforts in volcano geodesy. Here, we report on the first phase of the Drivers of Volcano Deformation (DVD) exercises, which were designed to build community involvement through web-based exercises involving calculations of static elastic displacement around pressurized magma reservoirs. The forward model exercises begin with a spherical reservoir in a homogeneous half space, then introduce topography, heterogeneous elastic properties, and spheroidal geometries. The inversion exercises provide synthetic noisy surface displacement data for a spherical reservoir in a homogeneous half space and assess consistency in estimates of reservoir location and volume/pressure change. There is variability in the results from both forward modeling and inversions, which highlights the strengths and limitations of different forward models, as well as the importance of inversion method choice and uncertainty quantification. This first phase of the DVD exercises serves as a community resource and will facilitate further efforts to develop standards of reproducibility.