Be star candidates in the Large Magellanic Cloud: the catalogue and comparison with the Small Magellanic Cloud sample

Sabogal, B. E.; Mennickent, R. E.; Pietrzyński, G.; Gieren, W.

doi:10.1111/j.1365-2966.2005.09261.x

Cited by 40 publications

(79 citation statements)

References 20 publications

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“…A portion is shown here for guidance regarding its form and content. than in the LMC (Sabogal et al 2005). The bumpers and the fading events reported in the LMC last up to 800 and 600 days, respectively.…”

Section: Irregular Variablesmentioning

confidence: 99%

“…As a result, the fraction of earlyBe stars in the SMC is found to exceed the fraction in the Galaxy and the Large Magellanic Cloud (LMC; McSwain & Gies 2005;Wisniewski & Bjorkman 2006;Martayan et al 2010), specifically in the second half of their main-sequence lifetimes. In addition, the duration and amplitude of the outbursts as ejections of matter from Be stars, appear longer and larger in the SMC than in the LMC (Sabogal et al 2005).…”

Section: Introductionmentioning

confidence: 99%

“…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.…”

Section: Introductionmentioning

confidence: 99%

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

Kourniotis

Bonanos

Soszyński

et al. 2014

A&A

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We present a variability study of 4646 massive stars in the Small Magellanic Cloud (SMC) with known spectral types from the catalog of Bonanos et al. (2010) using the light curves from the OGLE-III database. The goal is to exploit the time domain information available through OGLE-III to gain insight into the processes that govern the evolution of massive stars. This variability survey of massive stars with known spectral types is larger than any previous survey by a factor of 7. We find that 60% of our sample (2766 stars) show no significant variability and 40% (1880 stars) exhibit variability distributed as follows: 807 stars display low-amplitude stochastic variability with fluctuations in the I-band of up to 0.05 mag, 443 stars present irregular variability of higher amplitude (76% of these are reported as variables for the first time), 205 are eclipsing binaries (including 101 newly discovered systems), 50 are candidate rotating variables, 126 are classical Cepheids, 188 stars exhibit short-term sinusoidal periodicity (P < 3 days) making them candidate "slowly pulsating B stars" and non-radial Be pulsators, and 61 periodic stars exhibit longer periods. We demonstrate the wealth of information provided in the time domain, by doubling the number of known massive eclipsing binary systems and identifying 189 new candidate early-type Be and 20 Oe stars in the SMC. In addition, we find that ∼80% of Be stars are photometrically variable in the OGLE-III time domain and provide evidence that short-term pulsating stars with additional photometric variability are rotating close to their break-up velocity.

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Section: Irregular Variablesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Kourniotis

Bonanos

Soszyński

et al. 2014

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“…The final column indicates the Massey et al (2006) survey consists of UBVRI and various narrow band coverage of the entire optical D 25 ellipse of M 31 down to a limiting magnitude of V = 24.9. To search for optical counterparts to our 18 HMXB candidates we adapted the criteria for Galactic luminous Be stars from Sabogal et al (2005). Galactic Be stars have V-band absolute magnitudes between M V − 6 and 0, as well as both −0.4 < B − V < 0.8 and −0.35 < V − I < 0.8 colour restrictions.…”

Section: Spectral Propertiesmentioning

confidence: 99%

An X-ray spectral survey of the disc of M 31 with XMM-Newton

Greening¹,

Barnard²,

Kolb³

et al. 2009

A&A

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Aims. We present the results of a complete spectral survey of the X-ray point sources detected in five XMM-Newton observations along the major axis of M 31 but avoiding the central bulge, aimed at establishing the population characteristics of X-ray sources in this galaxy. Methods. We obtained background subtracted spectra and lightcurves for each of the 335 X-ray point sources detected across the five observations from 2002. We also correlate our source list with those of earlier X-ray surveys and radio, optical and infra-red catalogues. Sources with more than 50 source counts are individually spectrally fit in order to create the most accurate luminosity functions of M 31 to date. Results. Based on the spectral fitting of these sources with a power law model, we observe a broad range of best fit photon index. From this distribution of best fit index, we identify 16 strong high mass X-ray binary system candidates in M 31. We show the first cumulative luminosity functions created using the best fit spectral model to each source with more than 50 source counts in the disc of M 31. The cumulative luminosity functions show a distinct flattening in the X-ray luminosity L X interval 37.0 log L X erg s −1 37.5. Such a feature may also be present in the X-ray populations of several other galaxies, but at a much lower statistical significance. We investigate the number of AGN present in our source list and find that above L X ∼ 1.4 × 10 36 erg s −1 the observed population is statistically dominated by the point source population of M 31.

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“…Figure 1 shows examples of these morphological types. Sabogal et al (2005) also found these morphological behaviour of BeSC in the Large Magellanic Cloud (LMC). Despite the diversity of the shape of their light curves, these stars are collectively classified as BeSC.…”

Section: Introductionmentioning

confidence: 93%

Machine learning techniques to select Be star candidates

Pérez-Ortiz

García-Varela

Quiróz

et al. 2017

A&A

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Context. Optical and infrared variability surveys produce a large number of high quality light curves. Statistical pattern recognition methods have provided competitive solutions for variable star classification at a relatively low computational cost. In order to perform supervised classification, a set of features is proposed and used to train an automatic classification system. Quantities related to the magnitude density of the light curves and their Fourier coefficients have been chosen as features in previous studies. However, some of these features are not robust to the presence of outliers and the calculation of Fourier coefficients is computationally expensive for large data sets. Aims. We propose and evaluate the performance of a new robust set of features using supervised classifiers in order to look for new Be star candidates in the OGLE-IV Gaia south ecliptic pole field. Methods. We calculated the proposed set of features on six types of variable stars and also on a set of Be star candidates reported in the literature. We evaluated the performance of these features using classification trees and random forests along with the K-nearest neighbours, support vector machines, and gradient boosted trees methods. We tuned the classifiers with a 10-fold cross-validation and grid search. We then validated the performance of the best classifier on a set of OGLE-IV light curves and applied this to find new Be star candidates. Results. The random forest classifier outperformed the others. By using the random forest classifier and colours criteria we found 50 Be star candidates in the direction of the Gaia south ecliptic pole field, four of which have infrared colours that are consistent with Herbig Ae/Be stars. Conclusions. Supervised methods are very useful in order to obtain preliminary samples of variable stars extracted from large databases. As usual, the stars classified as Be stars candidates must be checked for the colours and spectroscopic characteristics expected for them.

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Be star candidates in the Large Magellanic Cloud: the catalogue and comparison with the Small Magellanic Cloud sample

Cited by 40 publications

References 20 publications

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

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

An X-ray spectral survey of the disc of M 31 with XMM-Newton

Machine learning techniques to select Be star candidates

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