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M. Schultheis 1,
S. Ganesh 2,
I.S. Glass 3,
A. Omont 1,
R. Ortiz 4,9,
G. Simon 5,
J.Th. van Loon 6,
C. Alard 5,1,
J.A.D.L. Blommaert 7,
J. Borsenberger 1,
P. Fouqué 8 and
H.J. Habing 4
Received 21 March 2000 / Accepted 9 May 2000
Repeated DENIS observations (summer 1996 & 1998) in the J (1.25 µm) and the (2.15 µm) bands are used to look for variable stars. We present two catalogues of 1000 probable variables in an area of of the inner galactic bulge. The first one contains variable star candidates which show variability in J and while the second consists of sources only observed to be variable in ( sources), mainly in regions with high interstellar extinction.
Using the extinction map by Schultheis et al. (1999a), most of the variable stars are found to be above the RGB tip and thus belong to the AGB while there is a small fraction of candidates which could be below the RGB tip with rather small "amplitudes" of 0.3-0.4 mag in .
Our catalogue has been cross-correlated with five ISOGAL fields (total area ) in order to study the mid-IR properties of the LPVs. The AGB variables can be distinguished from other M-type giants by their high 7 µm luminosities and redder colours.
Based on a few repeated ISOCAM observations a good correlation is found between near- and mid-IR variability.
Key words: stars: AGB and post-AGB stars: variables: general ISM: dust, extinction Galaxy: general infrared: stars
* This is paper no. 7 in a refereed journal based on data from the ISOGAL project
Send offprint requests to: M. Schultheis (email@example.com)
Online publication: October 30, 19100