The HST Treasury "Advanced Spectral Library" (ASTRAL) Programs

TL;DR

The ASTRAL project provides high-resolution, high-quality UV spectra of prototypical stars across the HR diagram, enabling diverse astronomical research for decades.

Contribution

This paper details the observing programs and strategies for the ASTRAL spectral library, including target selection and data quality optimization.

Findings

Spectra of 8 evolved late-type stars obtained.

Spectra of 21 early-type stars spanning O to A types collected.

Initial scientific analyses demonstrate the utility of the spectra for stellar and interstellar studies.

Abstract

The "Advanced Spectral Library (ASTRAL)" Project (PI = T. Ayres) consists of two Treasury Programs: the Cycle 18 "Cool Stars" (GO-12278) Program and the Cycle 21 "Hot Stars" (GO-13346) Program. The primary goal of these programs is to collect, for the use of the astronomical community over the coming decades, a definitive set of representative, high-resolution (R~30,000-100,000), high signal/noise (S/N>100) spectra, with full UV coverage (~1150 - 3100 A) of prototypical stars across the HR diagram, utilizing the high-performance Space Telescope Imaging Spectrograph (STIS). The Cycle 18 program obtained spectra of 8 F-M evolved late-type stars, while the Cycle 21 program is in the process of observing 21 early-type stars, which span a broad range of spectral types between early-O and early-A. All of these data will be available from the HST archive and, in post-processed and merged form, at http://casa.colorado.edu/~ayres/ASTRAL/. These data will enable investigations of a broad range of problems -- stellar, interstellar, and beyond -- for many years into the future. We describe here the details of the observing programs, including the program targets and the observing strategies utilized to optimize the quality of the spectra, and present some illustrative examples of the on-going scientific analyses, including a study of the outer atmospheres and winds of the two evolved M stars in the sample and a first look at a "high definition" UV spectrum of a magnetic chemically peculiar "Ap" star.