A&A Supplement series, Vol. 122, May I 1997, 415-432
Received February 29, accepted August 9, 1996
monitoring of 12 southern hemisphere
Long Period Variables
P. de Laverny
-
H. Geoffray 
-
L. Jorda 
-
M. Kopp 
Send offprint request: P. de Laverny (Uppsala Observatory)
Uppsala Astronomical Observatory, Box 515, S-751 20 Uppsala, Sweden
GRAAL, Université Montpellier II, F-34095 Montpellier Cedex 05, France
ESO, Casilla 19001, Santiago 19, Chile
ARPEGES, Observatoire de Paris, place J. Janssen, 92195 Meudon Principal
Cedex, France
DAEC, Observatoire de Paris, place J. Janssen, 92195 Meudon Principal
Cedex, France
A program of 
photometric observations of twelve southern
hemisphere Long Period Variables (LPV or Miras) has been carried out
at the European Southern Observatory.
Each star was observed on at least 11 occasions up to 29
over a 4-year period.
A determination of their spectral types from the (V-
) and (
)
colours was also performed using the
method described by Celis (1986b). We therefore
present for the first time spectral
type variations together with visible and
colour light-curves for at least three successive cycles.
New photometric parameters as visible and spectral type extrema are
given. Spectral type variations are found in the range 1.3-4.5
subclasses.
The variations during a cycle and from cycle-to-cycle are discussed and
short-term declines with large amplitude are reported for R Oct and RY Hyi.
We finally estimate the distance of these stars using a
(
, P, Spectral type) relation. It is shown that rather
good distances (mean error less than 30%) can be determined
if the period of the stars is known and good UBVRI data are collected
at the maximum of luminosity.
keywords: stars: late-type -- stars: AGB and post-AGB -- stars: variables -- stars: distances