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Astron. Astrophys. 353, 147-152 (2000)


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Near-infrared photometry of the intermediate age open clusters IC 166 and NGC 7789 *

Antonella Vallenari 1, Giovanni Carraro 2 and Andrea Richichi 3

1 Padova Astronomical Observatory, vicolo dell' Osservatorio 5, 35122 Padova, Italy
2 Department of Astronomy, Padova University, vicolo dell'Osservatorio 5, 35122 Padova, Italy
3 Arcetri Astrophysical Observatory, Largo E. Fermi, 50110 Firenze, Italy (vallenari, carraro@pd.astro.it; richichi@fi.astro.it)

Received 1 July 1999 / Accepted 22 October 1999

Abstract

We present and discuss new photometric data obtained with an IR camera in the J and K pass-bands for the intermediate age open clusters IC 166 (936 stars in total) and NGC 7789 (1030 stars in total). IC 166 is a poorly studied open cluster for which no IR data was available previously, while NGC 7789 is a well studied open cluster.

We show that IC 166 is of intermediate age (about 1.0 Gyr), with a reddening E(V-K) [FORMULA] (corresponding to E(B-V) = 0.50) and a true distance modulus [FORMULA]. These values are significantly different from previous determinations.

NGC 7789 is found to be a 1.4 Gyr open cluster. The metallicity derived with the method developed by Tiede et al (1997) is found to be closer to the spectroscopic estimate than previous photometric studies.

Key words: techniques: photometric – Galaxy: open clusters and associations: general – Galaxy: open clusters and associations: individual: IC 166 – Galaxy: open clusters and associations: individual: NGC 7789

* Based on observations taken at TIRGO

Send offprint requests to: Antonella Vallenari (vallenari@pd.astro.it)

© European Southern Observatory (ESO) 2000

Online publication: December 8, 1999

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