New Astronomy 56 (2017) 28–49 Contents lists available at ScienceDirect New Astronomy journal homepage: www.elsevier.com/locate/newast NIR properties of Be stars in star clusters in the Magellanic Clouds Paul K. T. a,∗ , Annapurni Subramaniam b , Blesson Mathew c , Shruthi S. B. a a Department of Physics, Christ University, Bangalore, India b Indian Institute of Astrophysics, Bangalore, India c Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Mumbai, India h i g h l i g h t s • We studied the NIR properties of Be star candidates in clusters in the LMC and SMC. • New diagnostic area is suggested in the CCD for the Classical Be stars in the MCs. • We found 14 Be stars with high NIR excess suspected to be in HAeBe or sgB[e] phase. a r t i c l e i n f o Article history: Received 25 August 2016 Revised 13 March 2017 Accepted 5 April 2017 Available online 6 April 2017 Keywords: Stars Emission-line Be—infrared Stars—galaxies Magellanic Clouds a b s t r a c t Magellanic Clouds are the nearby galaxies which are ideal to study the properties of metal poor stellar population. In this study, we explore the near-IR properties of optically identified classical Be stars in 19 star clusters in the Magellanic Clouds. From an optically identified sample of 835 Be stars we obtained the J, H, K magnitudes of 389 stars from the IRSF MCPS catalog. Among these, 247 stars (36.4%) are found in 9 clusters in the Large Magellanic Cloud and 142 stars (55.5%) in 10 clusters in the Small Magellanic Cloud. After correcting for reddening, we studied their NIR properties in the (H – K) 0 vs (J – H) 0 diagram. We identified 14 stars with abnormally large near IR excesses, which were removed from the analysis, there by restricting our study to 355 classical Be stars. We propose an extended area in the near-IR (H - K) 0 vs (J - H) 0 diagram as the diagnostic location of Classical Be stars in the Magellanic Clouds. We identified 14 stars to have near-IR excess, higher than those seen in classical Be stars. From the analysis based on spectral energy distribution and luminosity estimate, we found that 8 candidate Be stars may be Herbig Ae/Be stars. We identified a new sample of 6 sgB[e] stars, which when added to the sparse existing sample of 15 sgB[e] stars in the Magellanic Clouds can provide insight to understand the evolutionary link between sgB[e] stars and Luminous Blue variables. © 2017 Elsevier B.V. All rights reserved. 1. Introduction Classical Be stars (CBe) are non-supergiant B-type stars that show or have shown, Balmer emission lines in their spectra at least once in their lifetime (Porter and Rivinius, 2003; Rivinius et al., 2013). The term classical has been used to distinguish them from Herbig Ae/Be (HAeBe) stars, which are intermediate mass pre-main sequence (PMS) candidates with circumstellar accretion disk. From here onwards, we denote CBe/Be to represent classi- cal Be stars. CBe stars are characterised by their rapid rotation and decretion disks (see Rivinius et al. (2013) for a recent re- view). There are several ways to identify Be stars. The first pos- sibility is to use the photometric techniques. Combining different color/color diagrams (CCDs) or color/magnitude diagrams (CMDs) ∗ Corresponding author. E-mail address: paul.kt@christuniversity.in (P. K. T.). would help to pre-classify the stars and detect potential Be star candidates. Wisniewski and Bjorkman (2006) studied the B, V, R, and Hα photometry of clusters in the SMC, the LMC, the MW and use CCDs to identify candidate Be star populations in these clusters. Keller et al. (1999) provide examples of CMDs with given thresholds above which the Be stars could fall. They also show that Be stars tend to form a redder sequence than normal B stars. Dachs et al. (1988) have shown that the infrared excess is related to the circumstellar disk of Be stars. It is also linked to the Hα equivalent width. In the Galaxy, there are different surveys to find Be stars, in- cluding the photometric survey by McSwain and Gies (2005) and the slitless spectroscopic survey by Mathew et al. (2008). Slitless spectroscopic survey of the SMC by Meyssonnier and Azzopardi (1993), Martayan et al. (2010) and Martayan et al. (2008) are also examples of surveys to find Be stars. Spectroscopic survey of massive stars particularly, of B and Be stars in the Galaxy and http://dx.doi.org/10.1016/j.newast.2017.04.004 1384-1076/© 2017 Elsevier B.V. All rights reserved.