A photometric and spectroscopic investigation of star formation in the very young open cluster NGC 6383 ^*,**

GAPHE, Institut d'Astrophysique et de Géophysique, Université de Liège, Allée du 6 Août 17, Bât. B5c, 4000 Liège, Belgium e-mail: rauw@astro.ulg.ac.be

Received: 29 June 2009
Accepted: 26 November 2009

Abstract

Context. The very young open cluster NGC 6383 centered on the O-star binary HD 159176 is an interesting place for studying the impact of early-type stars with strong radiation fields and powerful winds on the formation processes of low-mass stars.

Aims. To investigate this process, it is necessary to determine the characteristics (age, presence, or absence of circumstellar material) of the population of low-mass pre-main-sequence (PMS) stars in the cluster.

Methods. We obtained deep UBV photometric data of the entire cluster as well as medium-resolution optical spectroscopy of a subsample of X-ray selected objects.

Results. Our spectroscopic data reveal only very weak Hα emission lines in a few X-ray selected PMS candidates. We photometrically identify a number of Hα emission candidates but their cluster membership is uncertain. We find that the fainter objects in the field of view have a wide range of extinction (up to A_V = 20), one X-ray selected OB star having .

Conclusions. Our investigation uncovers a population of PMS stars in NGC 6383 that are probably coeval with HD 159176. In addition, we detect a population of reddened objects that are probably located at different depths within the natal molecular cloud of the cluster. Finally, we identify a rather complex spatial distribution of Hα emitters, which is probably indicative of a severe contamination by foreground and background stars.