Liger for Next Generation Keck Adaptive Optics: Opto-Mechanical Dewar for Imaging Camera and Slicer

Liger is a next generation adaptive optics (AO) fed integral field spectrograph (IFS) and imager for the W. M. Keck Observatory. This new instrument is being designed to take advantage of the upgraded AO system provided by Keck All-Sky Precision Adaptive-optics (KAPA). Liger will provide higher spectral resolving power (R$\sim$4,000-10,000), wider wavelength coverage ($\sim$0.8-2.4 $\mu$m), and larger fields of view than any current IFS. We present the design and analysis for a custom-made dewar chamber for characterizing the Liger opto-mechanical system. This dewar chamber is designed to test and assemble the Liger imaging camera and slicer IFS components while being adaptable for future experiments. The vacuum chamber will operate below $10^{-5}$ Torr with a cold shield that will be kept below 90 K. The dewar test chamber will be mounted to an optical vibration isolation platform and further isolated from the cryogenic and vacuum systems with bellows. The cold head and vacuums will be mounted to a custom cart that will also house the electronics and computer that interface with the experiment. This test chamber will provide an efficient means of calibrating and characterizing the Liger instrument and performing future experiments.Comment: 8 pages, 6 figure

Nucleosynthesis constraints through

Context. Classical novae belong to the most frequent transient events in the Milky Way and are key agents of ongoing nucleosynthesis. Despite their large numbers, they have never been observed in soft γ-ray emission. Measurements of their γ-ray signatures would provide insights into explosion mechanism and nucleosynthesis products. Aims. Our goal is to constrain the ejecta masses of 7Be and 22Na from classical novae through their γ-ray line emissions at 478 and 1275 keV. Methods. We extracted posterior distributions on the line fluxes from archival data of the INTEGRAL/SPI spectrometer telescope. We then used a Bayesian hierarchical model to link individual objects and diffuse emission, and to infer ejecta masses from the whole population of classical novae in the Galaxy. Results. Individual novae are too dim to be detectable in soft γ-rays, and the upper bounds on their flux and ejecta mass uncertainties cover several orders of magnitude. Within the framework of our hierarchical model, we can nevertheless infer tight upper bounds on the 22Na ejecta masses, given all uncertainties from individual objects as well as diffuse emission, of < 2.0 × 10−7 M⊙ (99.85th percentile). Conclusions. In the context of ONe nucleosynthesis, the 22Na bounds are consistent with theoretical expectations and exclude that most ONe novae occur on white dwarfs with masses of about 1.35 M⊙. The upper bounds from 7Be are uninformative. From the combined ejecta mass estimate of 22Na and its β+ decay, we infer a positron production rate of < 5.5 × 1042 e+ s−1, which would mean 10% at most of the total annihilation rate in the Milky Way