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Modelling the mid-infrared polarization in dust around young stars

2019; Oxford University Press; Volume: 484; Issue: 3 Linguagem: Inglês

10.1093/mnras/stz231

1365-2966

Gautam Saikia, Rupjyoti Gogoi, Ranjan Gupta, D. B. Vaidya,

Astro and Planetary Science

The presence of crystalline silicates has been detected in the circumstellar environment of several young stars in the recent past and there is evidence of silicon carbide (SiC) detection in the envelope of pre-main sequence star SVS13. In this work, we have attempted to probe the presence of SiC in the dust around protoplanetary discs in a sample of young stars. We have modelled the linear polarization of composite dust grains in the mid-infrared (MIR: 8–13 |$\mu$|m) using silicates as the host with various inclusions of SiC and graphites using the Discrete Dipole Approximation (DDA) and the Effective Medium Approximation (EMA) T-Matrix methods. We have then compared our modelling results with polarimetric observations made in the protoplanetary discs surrounding two Herbig Be stars and one T-Tauri star with particular emphasis towards the 10 |$\mu$|m silicate feature using CanariCam mounted over the Gran Telescopio Canarias (GTC). We report the possible existence of SiC in the outer disc/envelope around one star in our sample which has been interpreted based on the shape, size, composition, and fraction of inclusions by volume in our dust grain models.