Study of candidate Be stars in the Magellanic Clouds using near-infrared photometry and optical spectroscopy
- Title
- Study of candidate Be stars in the Magellanic Clouds using near-infrared photometry and optical spectroscopy
- Creator
- Paul K.T.; Subramaniam A.; Mathew B.; Mennickent R.E.; Sabogal B.
- Description
- 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 OGLEII 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, K s 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 H? 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 H? EW and this class has properties similar to CBe stars. The spectroscopic sample of type 1 stars which show H? 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. 2012 The Authors Monthly Notices of the Royal Astronomical Society 2012 RAS.
- Source
- Monthly Notices of the Royal Astronomical Society, Vol-421, No. 4, pp. 3622-3640.
- Date
- 2012-01-01
- Subject
- Circumstellar matter; Magellanic Clouds; Stars: emission-line, Be; Techniques: spectroscopic
- Coverage
- Paul K.T., Department of Physics, Christ University, Bangalore 560029, Karnataka, India; Subramaniam A., Indian Institute of Astrophysics, II Block Koramangala, Bangalore 560034, Karnataka, India; Mathew B., Indian Institute of Astrophysics, II Block Koramangala, Bangalore 560034, Karnataka, India, Astronomy and Astrophysics Division, Physical Research Laboratory, Ahmedabad, Gujarat, India; Mennickent R.E., Department of Astronomy, University of Concepcion, Concepcion, Chile; Sabogal B., Departamento de Fica, Universidad de los Andes, Edificio Ip, Bogot Cra. 1 No. 18A-10, Colombia
- Rights
- All Open Access; Bronze Open Access; Green Open Access
- Relation
- ISSN: 13652966; CODEN: MNRAA
- Format
- Online
- Language
- English
- Type
- Article
Collection
Citation
Paul K.T.; Subramaniam A.; Mathew B.; Mennickent R.E.; Sabogal B., “Study of candidate Be stars in the Magellanic Clouds using near-infrared photometry and optical spectroscopy,” CHRIST (Deemed To Be University) Institutional Repository, accessed February 23, 2025, https://archives.christuniversity.in/items/show/17391.