Near-infrared variability in the star-forming region RCW 38

Aims. We want to study the content of young stellar objects in the RCW38 cluster by means of multi-epoch variability studies. Methods. We performed a three-month near-infrared (NIR) monitoring campaign of the young cluster RCW38 using the 80 cm IRIS telescope near Cerro Armazones, Chile. Variability data with a median sampling of 1 day was gathered for 1026 sources, while a total of 3433 sources in JHK could be studied in the co-added, deep images with a completeness limit of K < 15 mag. Results. We find that 139 sources were identified as variable with amplitudes above 10% in H and K, and 47% of these variables have been classified as candidate young stars by previous X-ray and mid-infrared studies. Although the majority of the variable sources show no K-excess, their high extinction and concentration towards the cluster center, together with their irregular variability behavior, suggest that they are also candidate young stellar objects. Most of them are likely low-mass sources with variability amplitudes typical of T Tauri stars. The majority of previously suggested OB candidates appear to be intermediate-mass pre-main sequence sources on the basis of their JHK properties. Conclusions. NIR variability is an efficient tool for detecting new, embedded, young stellar objects that have escaped previous X-ray and mid-infrared studies.