Observations of the Optical Transient in NGC 300 with AKARI-IRC: Possibilities of Asymmetric Dust Formation - Astrophysics > Solar and Stellar AstrophysicsReport as inadecuate




Observations of the Optical Transient in NGC 300 with AKARI-IRC: Possibilities of Asymmetric Dust Formation - Astrophysics > Solar and Stellar Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: We present the results of near-infrared NIR multi-epoch observations of theoptical transient in the nearby galaxy NGC300 NGC300-OT at 398 and 582 daysafter the discovery with the Infrared Camera IRC onboard AKARI. NIR spectra2-5 um of NGC300-OT were obtained for the first time. They show no prominentemission nor absorption features, but are dominated by continuum thermalemission from the dust around NGC300-OT. NIR images were taken in the 2.4, 3.2,and 4.1 um bands. The spectral energy distributions SED of NGC300-OT indicatethe dust temperature of 810 +-14 K at 398 days and 670 +-12 K at 582 days.We attribute the observed NIR emission to the thermal emission from dust grainsformed in the ejecta of NGC300-OT. The multi-epoch observations enable us toestimate the dust optical depth as larger than about 12 at 398 days and largerthan about 6 at 582 days at 2.4 um, by assuming an isothermal dust cloud. Theobserved NIR emission must be optically thick, unless the amount of dust grainsincreases with time. Little extinction at visible wavelengths reported inearlier observations suggests that the dust cloud around NGC300-OT should bedistributed inhomogeneously so as to not screen the radiation from the ejectagas and the central star. The present results suggest the dust grains are notformed in spherically symmetric geometry, but rather in a torus, a bipolaroutflow, or clumpy cloudlets.



Author: R. Ohsawa, I. Sakon, T. Onaka, M. Tanaka, T. Moriya, T. Nozawa, K. Maeda, K. Nomoto, N. Tominaga, F. Usui, H. Matsuhara, T. Nakag

Source: https://arxiv.org/



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