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Abstract We introduce the OATMEAL survey, an effort to measure the obliquities of stars with transiting brown dwarf companions. We observed a transit of the close-in (P_orb= 1.74 days) brown dwarf GPX-1 b using the Keck Planet Finder spectrograph to measure the sky-projected angle between its orbital axis and the spin axis of its early F-type host star (λ). We measuredλ= 6.°9 ± 10.°0, suggesting an orbit that is prograde and well aligned with the stellar equator. Hot Jupiters around early F stars are frequently found to have highly misaligned orbits, with polar and retrograde orbits being commonplace. It has been theorized that these misalignments stem from dynamical interactions, such as von Zeipel–Kozai–Lidov cycles, and are retained over long timescales due to weak tidal dissipation in stars with radiative envelopes. By comparing GPX-1 to similar systems under the frameworks of different tidal evolution theories, we argued that the rate of tidal dissipation is too slow to have re-aligned the system. This suggests that GPX-1 may have arrived at its close-in orbit via coplanar high-eccentricity migration or migration through an aligned protoplanetary disk. Our result for GPX-1 is one of few measurements of the obliquity of a star with a transiting brown dwarf. By enlarging the number of such measurements and comparing them with hot-Jupiter systems, we will more clearly discern the differences between the mechanisms that dictate the formation and evolution of both classes of objects. 

We present the current design of WFOS, a wide-field UV/optical (0.31-1.0 µm) imaging spectrograph planned for first-light on the TMT International Observatory 30 m telescope. WFOS is optimized for high sensitivity across the entire optical waveband for low-to-moderate resolution (R ∼ 1500-5000) long-slit and multi-slit spectroscopy of very faint targets over a contiguous field of view of 8′ .3×3 ′ .0 at the f/15 Nasmyth focus of TMT. A key design goal for WFOS is stability and repeatability in all observing modes, made possible by its gravity-invariant opto-mechanical structure, with a vertical rotation axis and all reconfigurable components moving only in planes defined by tiered optical benches parallel to the Nasmyth platform. WFOS’s optics include a linear ADC correcting a 9′ diameter field, including both the science FoV and 4 patrolling acquisition, guiding, and wavefront sensing camera systems; a novel 2-mirror reflective collimator allowing the science FoV to be centered on the telescope optical axis; a dichroic beamsplitter dividing the collimated beam into 2 wavelength-optimized spectrometer channels (blue: 0.31-0.56 µm; red: 0.54-1.04 µm); selectable transmissive dispersers (VPH and/or VBG) with remotely configurable grating tilt (angle of incidence) and camera articulation that enable optimization of diffraction efficiency and wavelength coverage in each channel; all-refractive, wavelength-optimized f/2 spectrograph cameras, and UV/blue and red-optimized detector systems. The predicted instrumental through put of WFOS for spectroscopy averages > 56% over the full 0.31-1 µm range, from the ADC to the detector. When combined with the 30 m TMT aperture, WFOS will realize a factor of ∼20 gain in sensitivity compared to the current state of the art on 8-10 m-class telescopes. 

The Keck Planet Finder (KPF) is a fiber-fed, high-resolution, echelle spectrometer that specializes in the discovery and characterization of exoplanets using Doppler spectroscopy. In designing KPF, the guiding principles were high throughput to promote survey speed and access to faint targets, and high stability to keep uncalibrated systematic Doppler measurement errors below 30 cm s−1. KPF achieves optical illumination stability with a tip-tilt injection system, octagonal cross-section optical fibers, a double scrambler, and active fiber agitation. The optical bench and optics with integral mounts are made of Zerodur to provide thermo-mechanical stability. The spectrometer includes a slicer to reformat the optical input, green and red channels (445-600 nm and 600-870 nm), and achieves a resolving power of ∼97,000. Additional subsystems include a separate, medium-resolution UV spectrometer (383-402 nm) to record the Ca II H & K lines, an exposure meter for real-time flux monitoring, a solar feed for sunlight injection, and a calibration system with a laser frequency comb and etalon for wavelength calibration. KPF was installed and commissioned at the W. M. Keck Observatory in late 2022 and early 2023 and is now in regular use for scientific observations. This paper presents an overview of the as-built KPF instrument and its subsystems, design considerations, and initial on-sky performance. 

Abstract We presentnimbus: a hierarchical Bayesian framework to infer the intrinsic luminosity parameters of kilonovae (KNe) associated with gravitational-wave (GW) events, based purely on nondetections. This framework makes use of GW 3D distance information and electromagnetic upper limits from multiple surveys for multiple events and self-consistently accounts for the finite sky coverage and probability of astrophysical origin. The framework is agnostic to the brightness evolution assumed and can account for multiple electromagnetic passbands simultaneously. Our analyses highlight the importance of accounting for model selection effects, especially in the context of nondetections. We show our methodology using a simple, two-parameter linear brightness model, taking the follow-up of GW190425 with the Zwicky Transient Facility as a single-event test case for two different prior choices of model parameters: (i) uniform/uninformative priors and (ii) astrophysical priors based on surrogate models of Monte Carlo radiative-transfer simulations of KNe. We present results under the assumption that the KN is within the searched region to demonstrate functionality and the importance of prior choice. Our results show consistency withsimsurvey—an astronomical survey simulation tool used previously in the literature to constrain the population of KNe. While our results based on uniform priors strongly constrain the parameter space, those based on astrophysical priors are largely uninformative, highlighting the need for deeper constraints. Future studies with multiple events having electromagnetic follow-up from multiple surveys should make it possible to constrain the KN population further. 

The Keck Planet Finder (KPF) is a fiber-fed, high-resolution, high-stability spectrometer in development at the UC Berkeley Space Sciences Laboratory for the W.M. Keck Observatory. KPF is designed to characterize exoplanets via Doppler spectroscopy with a goal of a single measurement precision of 0.3 m s-1 or better, however its resolution and stability will enable a wide variety of astrophysical pursuits. Here we provide post-preliminary design review design updates for several subsystems, including: the main spectrometer, the fabrication of the Zerodur optical bench; the data reduction pipeline; fiber agitator; fiber cable design; fiber scrambler; VPH testing results and the exposure meter.