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

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(RI)(c) H alpha 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 Ha emission lines in a few X-ray selected PMS candidates. We photometrically identify a number of H alpha 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 Lambda(V) = 20), one X-ray selected OB star having Lambda(V) similar or equal to 8. 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 H alpha emitters, which is probably indicative of a severe contamination by foreground and background stars.