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Astron. Astrophys. 362, 215-222 (2000)

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DENIS and ISOGAL properties of variable star candidates in the Galactic Bulge * ** ***

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

1 Institut d'Astrophysique de Paris, CNRS, 98bis Bd Arago, 75014 Paris, France
2 Physical Research Laboratory, Navarangpura, Ahmedabad 380009, India
3 SAAO, South Africa
4 Leiden Observatory, Leiden, The Netherlands
5 DASGAL CNRS UMR 8633, Observatoire de Paris, France
6 Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK
7 ISO Data Centre, ESA, Villafranca, Spain
8 ESO, Santiago, Chile
9 Departamento de Fisica, UFES, Av. Fernando Ferrari s/n, 29060-900, Vitoria, Brazil

Received 21 March 2000 / Accepted 9 May 2000


Repeated DENIS observations (summer 1996 & 1998) in the J (1.25 µm) and the [FORMULA] (2.15 µm) bands are used to look for variable stars. We present two catalogues of [FORMULA] 1000 probable variables in an area of [FORMULA] of the inner galactic bulge. The first one contains [FORMULA] variable star candidates which show variability in J and [FORMULA] while the second consists of sources only observed to be variable in [FORMULA] ([FORMULA] 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 [FORMULA] 0.3-0.4 mag in [FORMULA].

Our catalogue has been cross-correlated with five ISOGAL fields (total area [FORMULA]) 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 [FORMULA] 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
** Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with the participation of ISAS and NASA
*** Based on observations collected at the European Southern Observatory, La Silla Chile

Send offprint requests to: M. Schultheis (schulthe@iap.fr)

© European Southern Observatory (ESO) 2000

Online publication: October 30, 19100