The spectra of late-type dwarfs and sub-dwarfs in the near ultraviolet. III. an atlas of MG II H and K profiles.

Abstract

Using a radically new suite of data extraction routines, IUEARM, high resolution IUE spectra of six F and G stars, taken at regular intervals since 1978 are analysed. The salient features of the new routines are: reduction of interorder scattering via two-dimensional deconvolution of the echelle spectrograph image plane, with high frequency filtering, to reduce the effects of the instrument function; enhanced spectral resolution by data extraction using a small pseudo-slit; improved "ripple correction" yielding mutually consistent inter-order overlap regions; and an improved absolute calibration. Rigorous limits, twice as precise as any previously available, are set on weak spectral features, and on possible variability of the h and k chromospheric emission cores in the G stars. The authors show how the interstellar Mg II components of the stars can be abstracted and used to examine a sector of the local interstellar medium.