A catalogue of Be stars in the direction of the Galactic Bulge

Abstract

Context. Detailed studies of Be stars in environments with different metallicities like the Magellanic Clouds or the Galactic Bulge are necessary to understand the formation and evolution mechanisms of the circumstellar disks. However, a detailed study of Be stars in the direction of the bulge of our own galaxy has not been performed until now. Aims. The aim of this work is to report the first systematic search for Be star candidates in the direction of the Galactic Bulge. We present the full catalogue, give a brief description of the stellar variability seen, and show some light curve examples. Methods. We searched for stars matching specific criteria of magnitude, color and variability in the I band. Our search was conducted on the 48 OGLE II fields of the Galactic Bulge.Results. This search has resulted in 29053 Be star candidates, 198 of them showing periodic light variations. Nearly 1500 stars in this final sample are almost certainly Be stars, providing an ideal sample for spectroscopic multi-object follow-up studies.

Variability of massive stars with known spectral types in the Small Magellanic Cloud using 8 years of OGLE-III data

“…Over the past two decades, the microlensing experiments MACHO (Alcock et al 1993), the Optical Gravitational Lensing Experiment II (OGLE-II; Udalski et al 1997), and EROS (Aubourg et al 1995) have provided a database of light curves of a large number of massive stars located in the Magellanic Clouds and the Galaxy, motivating detailed studies of Be stars (Keller et al 2002;Mennickent et al 2002;de Wit et al 2003;Sabogal et al 2005Sabogal et al , 2008 and other types of massive stars. Furthermore, surveys with the All Sky Automated Survey (ASAS ;Pojmanski 2002) and the Hipparcos mission have motivated a couple of studies on variability as a function of spectral type.…”

Searching for Be star candidates within large databases

“…This process conducted us to a catalog of about 29000 BeSC. We found that 198 of these stars exhibit a periodic behavior ( [7]). …”

Machine learning techniques to select Be star candidates

“…The first comes from OGLE-III and Sabogal et al (2008). We use this data set to train and test our classifiers.…”

“…These variability classes and the number of stars in each class are shown in Table 1. Additionally, we selected the OGLE-III I band light curves of 475 BeSC reported by Sabogal et al (2008) in the direction of the GB, and of 200 BeSC reported by Sabogal et al (2005) in the LMC. These 675 BeSC are included in our training sample since they clearly exhibit the five morphological types shown in Fig.…”

“…(1) Sabogal et al (2008); (2) measurements as opposed to their non-robust counterparts. The robustness of a statistic is usually measured with the so-called breakdown point.…”