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

¹ Astronomisches Institut, Ruhr-Universität Bochum, Universitätsstraße 150, 44801 Bochum, Germany
e-mail: chini@astro.rub.de
² Instituto de Astronomía, Universidad Católica del Norte, Antofagasta, Chile

Received: 30 August 2012
Accepted: 11 March 2013

Abstract

Aims. We want to study the content of young stellar objects in the RCW 38 cluster by means of multi-epoch variability studies.

Methods. We performed a three-month near-infrared (NIR) monitoring campaign of the young cluster RCW 38 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.