The solar-stellar spectrograph: Project description, data calibration, and initial results

Abstract

The Solar-Stellar Spectrograph (SSS) is a project initiated in the 1980s by scientists from the High Altitude Observatory, Lowell Observatory, the Pennsylvania State University, and the Sacramento Peak Observatory. The instrument is comprised of two spectrographs: one is an echelle covering the wavelength range λλ5000-9200, while the second is a Littrow spectrograph covering the Ca II H and K region around λ3950. This project is designed to address a broad range of outstanding questions regarding the nature of stellar activity cycles. The unique capability of the spectrograph is its ability to record both solar and stellar spectra, allowing more accurate placement of the Sun in the stellar context than has been feasible previously. In this report we discuss the motivation for this project, the instrumental characteristics, the observing programs, the methods being used to reduce, calibrate, and analyze the data, and the connection of our database to extant databases. A central part of the discussion is the connection of the Sun with the stars both in terms of existing solar and stellar activity indices as well as physical flux. This work resolves a long-standing discrepancy in this area and establishes a protocol for relating the large set of observations from the Mount Wilson Ca II H and K project to physical flux, in preparation for future comparison to our observations and results from theory.