We present a catalogue with coordinates and photometric data of 2446 Be star candidates in the Large Magellanic Cloud (LMC), based on a search of the OGLE II data base. The I‐band light curves of these stars show outbursts in 24 per cent of the sample (Type‐1 stars), high and low states in 10 per cent, periodic variations in 6 per cent (Type‐3 stars), and stochastic variations in 60 per cent of the cases. We report on the result of the statistical study of light curves of Type‐1 and Type‐3 stars in the LMC, and the comparison with the previously reported results of the Small Magellanic Cloud (SMC) sample. We find a statistically significant difference between amplitude, duration and asymmetry distributions of outbursts in both galaxies. Outbursts of SMC Type‐1 stars are usually brighter, longer and with a slower decline. We find a bimodal distribution of periods of Type‐3 stars in both galaxies, probably related to the recently discovered double periodic blue variables. We find also period and amplitude distributions of Type‐3 LMC stars statistically different from those of the SMC stars. Our findings above suggest that the mechanisms causing the observed photometric variability of Type‐1 and Type‐3 stars could depend on metallicity. Moreover, they suggest that the outbursts are not primarily caused by stellar winds.

We present new L-band spectra of 13 outbursting Be stars obtained with ISAAC at the ESO Paranal observatory. These stars can be classified in three groups depending on the presence/absence of emission lines and the strength of Brα and Pfγ emission lines relative to those of Humphreys lines from transitions 6-14 to the end of the series. These groups are representative of circumstellar envelopes with different optical depths. For the group showing Brα and Pfγ lines stronger than Humphreys lines, the Humphreys decrement roughly follow the Menzel case-B for optically thin conditions. For the group showing comparable Brα, Pfγ and Humphreys emission line strengths, the Humphreys decre-ments moves from an optically thin to an optically thick regime at a transition wavelength which is characteristic for each star, but typically is located around 3.65-3.75 µm (transitions 6-19 and 6-17). Higher order Humphreys lines probe optically thin inner regions even in the optically thicker envelopes. We find evidence of larger broadening in the infrared emission lines compared with optical lines, probably reflecting larger vertical velocity fields near the star. The existence of the aforementioned groups is in principle consistent with the proposed description by de Wit et al. (2006) for Be star outbursts in terms of the ejection of an optically thick disk that expands and becomes optically thin before dissipation into the interstellar medium. Time resolved L-band spectroscopy sampling the outburst cycle promises to be an unique tool for testing Be star disk evolution.

We present the first spectroscopic data for a sample of the recently discovered blue double‐periodic variables in the Magellanic Clouds. The optical spectrum of these objects is dominated by Balmer and helium absorption lines and a continuum with a blue or sometimes flat slope. Spectral classification yields B spectral types and luminosity classes mostly of type III. However, the Hβ absorption line is weaker than expected for the spectral classification in most objects. For two objects, OGLE 05060009‐6855025 and OGLE 05195898‐6917013 we obtained time‐resolved spectroscopy, finding radial velocity variations consistent with binarity. Phasing the short‐term photometric variability of these two systems with their spectroscopic ephemeris, we find that they can be interpreted as ellipsoidal variations of the brighter component in a close binary system. From the analysis of their short‐term light curves and radial velocities, we estimate that the cooler component could be a B‐type dwarf. Our findings support the hypothesis that double‐periodic variables are close binary systems consisting of two B‐type stars. The shorter periodicity in non‐eclipsing systems should be the ellipsoidal variation of the more evolved component. Regarding the long‐term periodicity, we find their origin in or around the brighter star, as the oscillations virtually disappear at primary eclipse. Their nature remains unknown, at the present time. We also report the discovery of three (two of them eclipsing) new double‐periodic variables in the Large Magellanic Cloud. One of them shows a shortening of the long‐term period by approximately 20 per cent in a couple of cycles, which coincides with an increase of the maximum oscillation brightness.

Mennickent et al. and Sabogal et al. identified a large number of classical Be (CBe) candidates (∼3500) in the Large and Small Magellanic Clouds (LMC and SMC) based on their photometric variability using the OGLE II data base. They classified these stars into four different groups based on the appearance of their variability. In order to refine and understand the nature of this large number of stars, we studied the infrared properties of the sample and the spectroscopic properties of a subsample. We cross‐correlated the optical sample with the IRSF‐MCPS catalogue to obtain the J, H, Ks magnitudes of all the four types of stars (∼2500) in the LMC and SMC. Spectra of 120 stars belonging to the types 1, 2 and 3 were analysed to study their spectral properties. Among the four types, the type 4 stars are the dominant group, with ∼60 and ∼65 per cent of the total sample in the LMC and SMC, respectively. The near‐infrared (NIR) colour–colour diagrams suggest that the type 4 stars in the LMC have a subclass, which is not found in our Galaxy or in the SMC. This subclass is ∼18 per cent of the type 4 sample. The main type 4 sample which is ∼49 per cent of the total sample has NIR properties similar to the Galactic CBe stars and the SMC type 4 stars. Though the new subclass of type 4 stars have high E(B−V) ∼ 0.75, they are not located close to regions with high reddening. The type 3 stars (∼6 per cent and 7.3 per cent in the LMC and SMC) are found to have large Hα equivalent width (EW) in the SMC and some are found to have large NIR excess. This small fraction of stars are unlikely to be CBe stars. Three stars among the type 3 stars in the LMC are found to be double periodic variables. The type 2 stars are found in larger fraction in the SMC (∼14.5 per cent), when compared to the LMC (∼6 per cent). The spectroscopic and the NIR properties suggest that these could be CBe stars. The type 1 stars are relatively more in the LMC (∼24 per cent) when compared to the SMC (∼13 per cent). The SMC type 1 stars have relatively large Hα EW and this class has properties similar to CBe stars. The spectroscopic sample of type 1 stars which show Hα in emission and are confirmed as CBe stars are more abundant in the SMC by a factor of 2.6. If the effect of metallicity is to cause more CBe stars in the SMC, when compared to the LMC, then type 1, type 2 and type 4 stars follow this rule, with an enhancement of 2.6, 2.4 and 1.3, respectively.

Aims. We investigate the nature of a sample of 17 long-term periodic variables in the direction of the Small Magellanic Cloud. Methods. Based on new spectroscopic data, we determined spectral types, radial velocities, absolute magnitudes, and colors for these stars. We present a refined discussion of their OGLE light curves along with an analysis of their 2MASS photometry. Results. Most stars turned out to be B-A giants members of the Small Magellanic Cloud. We find a new interacting eclipsing binary with a period of 184 days and two new early-type ellipsoidal variables. One of our objects is the ROSAT source RX J0058.2-7231. We analyzed 11-years of data for this Be X-ray binary finding that their photometric period varies by ∼4% quasiperiodically, on a time scale of ∼1200 days. We find evidence of multiple photometric periods in 2 Ae-type and 1 late-Be type stars. The case of OGLE00445466-7328029 is especially interesting, as this late-type Be star shows a beating phenomenon primarily caused by two closely-spaced frequencies, 0.