The Variability of R,N,C Stars from HIPPARCOS and AAVSO Data

Abstract

Accurate photometry was obtained for all programme stars during the 3.3-year HIPPARCOS mission. The final observing programme included several hundred Mirae (M), semiregular (SR) long-period and irregular (L) variables. A detailed calibration of the aging of the optics allowed the evaluation of very precise magnitudes over the whole range of star colours. Since the time coverage of the satellite observations was not sufficient to describe the behaviour of M, SR, or L type variables, smooth curves were fitted statistically to the dense AAVSO observations. These curves were then transformed to the HIPPARCOS system in order to complement the HIPPARCOS photometry and thus produce precise light curves with fuller time coverage, for a set of several hundred late-type variables, including most Carbon stars brighter than V = 12.4 at minimum luminosity. A preliminary discussion of the behaviour of C stars, as observed from the space in the broad Hp band, is given.