The Nature of Supernovae Progenitors and Interstellar Dust: Light Echoes Around Type Ia Supernovae

Abstract

Incomprehensive knowledge on dust is hindering our study of the universe. For example, the type Ia supernovae (SNe) cosmology requires better estimation of interstellar extinction to reduce systematic uncertainties. The extinction properties measured towards type Ia SNe suggest the properties of extragalactic dust may be incompatible with the Galactic dust, resulting in a systematic uncertainty in the intrinsic luminosity and distances to the type Ia SNe. Additionally, the exact progenitor systems of type Ia SNe and explosions remain unknown.

We present the results of our multi-band polarimetric monitoring of SN 2014J at five epochs between 277 days and 983 days after the B-band maximum light. The polarization measured at day 277 shows conspicuous deviations from other epochs and this can be identified as due to at least ∼10^(−6M)⊙ of dust located at a distance of ∼5×10^17 cm away from the SN. The presence of this circumstellar dust may set strong constraints on the progenitor system that led to the explosion of SN 2014J. We also detected different wavelength-dependencies of scattering in different ISM components through the resolved interstellar light echoes around SN 2014J. We found a steeper extinction law in a dense dust layer and a Milky Way-like extinction law in a diffuse cloud. This reveals the extinction law fluctuation of the extragalactic dust on parsec scales, and we consider systematically steeper extinction laws towards type Ia SNe do not have to represent the average behavior of the extinction law in the host galaxy. We also preformed high-precision photometry with HST for SN 2014J from 277 days to 985 days past the B−band maximum light. We found the reprocessing of electrons and X-rays emitted by the radioactive decay chain ^(57)Co→^(57)Fe are needed to explain the significant flattening of both the F606W-band and the pseudo-bolometric light curves. The flattening confirms previous predictions that the late-time evolution of type Ia supernova luminosities requires additional energy input from the decay of ^(57)Co (Seitenzahl et al., 2009).

Antarctic sites appear to be excellent sites for optical, NIR, and THz astronomical observations. To understand and make the use of the long ‘winter night’ as well as other remarkable observation conditions is one of the essential topics for future astronomy. Related to my PhD thesis, taking advantages of the long “winter night” as well as characterizing other remarkable observation conditions are specifically important to carry out future SN and other time-domain surveys at Dome A. We present here the measurements of sky brightness with the Gattini ultra-large field of view (90° × 90°) in the photometric B-, V -, and R-bands, cloud cover statistics measured during the 2009 winter season, and an estimate of the sky transparency. These values were obtained around the year 2009 with minimum aurora, and they are comparable to the faintest sky brightness at Mauna Kea and the best sites of northern Chile.