We present high S/N GHRS G140M spectra of the nearby stars Altair (alpha Aql, A7 V, d = 5.0 pc, l = 48, b = --9), alpha Cep (A7 V, d = 15 pc, l = 101, b = 9), and alpha Hyi (F0 V, d = 21 pc, l = 289, b = --54), which were obtained as part of a program to study the onset of chromospheric activity in late-type stars. These three stars are valuable probes of the local interstellar medium because they are of sufficiently early spectral type to have a large rotation (v sin i > 150 km s(-1) ), and yet are sufficiently cool to show Lyalpha in emission. The short line of sight toward Altair is particularly interesting because Ca II and UV absorption line studies have indicated the presence of three distinct interstellar components. The GHRS spectrum of each star shows a broad Lyalpha emission cut by interstellar hydrogen and deuterium. We will fit the Lyalpha profiles to derive column densities and broadening parameters along the lines of sight.
American Astronomical Society Meeting Abstracts
- Pub Date:
- December 1996