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Astron. Astrophys. 349, 825-833 (1999)


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Near-infrared photometry of the young open clusters NGC 1893 and Berkeley 86 *

A. Vallenari 1, A. Richichi 2, G. Carraro 3 and L. Girardi 3

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

Received 23 March 1999 / Accepted 5 August 1999

Abstract

We present photometry in the J and K near-infrared bands for two regions centered on the young open clusters NGC 1893 and Berkeley 86. We study 700 stars down to K = 17 in the field of NGC 1893, and about 2000 stars in the field of Berkeley 86 down to K[FORMULA] 16.5, for which near-infrared photometry was insofar not available. Coupling J-K data with UBV photometry taken from literature, we produce reddening corrected colour-magnitude diagrams. We find that our data are consistent with previous determinations: the clusters are roughly coeval with an age between 4 and 6 million years. The mean reddening (measured as E(J-K)) values turn out to be 0.35 and 0.50 for NGC 1893 and Berkeley 86, respectively.

Using colour-colour plots we discuss the presence of candidate pre-main sequence stars showing infrared excess. Candidates are found in both cluster regions, confirming the young age of these clusters.

Key words: techniques: photometric – Galaxy: open clusters and associations: general – Galaxy: open clusters and associations: individual: Berkeley 86 – Galaxy: open clusters and associations: individual: NGC 1893 – infrared: stars

* Based on observations taken at TIRGO

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

© European Southern Observatory (ESO) 1999

Online publication: September 13, 1999

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