StarCAT: A CATALOG OF SPACE TELESCOPE IMAGING SPECTROGRAPH ULTRAVIOLET ECHELLE SPECTRA OF STARS

Abstract

StarCAT is a catalog of high resolution ultraviolet spectra of objects classified as stars, recorded by Space Telescope Imaging Spectrograph (STIS) during its initial seven years of operations (1997-2004). StarCAT is based on 3184 echelle observations of 545 distinct targets, with a total exposure duration of 5.2 Ms. For many of the objects, broad ultraviolet coverage has been achieved by splicing echellegrams taken in two or more FUV (1150-1700 A) and/or NUV (1600-3100 A) settings. In cases of multiple pointings on conspicuously variable sources, spectra were separated into independent epochs. Otherwise, different epochs were combined to enhance the signal-to-noise ratio (S/N). A post-facto correction to the pipeline data sets compensated for subtle wavelength distortions identified in a previous study of the STIS calibration lamps. An internal fluxing procedure yielded coherent spectral energy distributions (SEDs) for objects with broadly overlapping wavelength coverage. The best StarCAT material achieves 300 m s–1 internal velocity precision; absolute accuracy at the 1 km s–1 level; photometric accuracy of order 4%; and relative flux precision several times better (limited mainly by knowledge of SEDs of UV standard stars). While StarCAT represents a milestone in the large-scale post-processing of STIS echellegrams, a number of potential improvements in the underlying final pipeline are identified.