HighSpec: A High-Resolution Spectrograph for the MAST Telescope Array

TL;DR

HighSpec is a high-resolution spectrograph designed for the MAST telescope array, optimized for faint stellar objects like white dwarfs, with high efficiency and multiple observing modes for detailed spectral analysis.

Contribution

This paper presents the design and optimization of HighSpec, a novel high-resolution spectrograph tailored for the MAST array, enhancing capabilities for faint object spectroscopy.

Findings

Achieves peak efficiency of over 85% in two bands

Supports multiple observing modes for key spectral features

Optimized for faint stellar object studies, especially white dwarfs

Abstract

We present the updated design of HighSpec, a high-resolution $\mathcal{R} \sim 20,000$ spectrograph designed for the Multi Aperture Spectroscopic Telescope (MAST). HighSpec offers three observing modes centered at the Ca II H&K, Mg b triplet, and H$\alpha$ lines. Each mode is supported by a highly optimized ion-etched grating, contributing to an exceptional instrument peak efficiency of $\gtrsim85\%$ for the two latter bands ($\gtrsim55\%$ for the Ca II H&K band). Optimizing throughput over wavelength coverage ($\Delta \lambda=10-17$ nm), HighSpec enables the precise measurement of spectral lines from faint targets. This approach is especially relevant for stellar object studies, specifically of WDs, which are intrinsically faint and have few spectroscopic lines. Each observing mode was tailored to target spectral features essential for WD research. Its integration with MAST, an array of 20 custom-designed telescopes that can function as a single large telescope (equivalent to a $2.7$ m telescope in collecting area) or multiplexing over the entire sky, provides unique adaptability for extensive and effective spectroscopic campaigns. Currently in its final assembly and testing stages, HighSpec's on-sky commissioning is scheduled for 2025.