Time-varying Extinction, Polarization, and Colors of Type Ia Supernovae due to Rotational Disruption of Dust Grains

Abstract

Photometric and polarimetric observations toward type Ia supernovae (SNe Ia) frequently report an unusually low total-to-selective extinction ratio (R V < 2) and small peak wavelength of polarization (λ max < 0.4 µm). Recently, Hoang et al. proposed that the increase in the abundance of small grains relative to large grains near SNe Ia due to RAdiative Torque Disruption (RATD) can explain this puzzle. To test this scenario, we will perform detailed modeling of dust extinction and polarization of SNe Ia accounting for grain disruption by RATD and grain alignment by RAdiative Torques (RATs). For dust clouds at distance d < 4 pc from the source, we find that R V decreases rapidly from the standard value of 3.1 to ∼ 1.5 after a disruption time t disr < 40 days. We then calculate the observed SNe Ia light curve and find that the colors of SNe Ia would change with time due to time-varying extinction for dust clouds at distance d < 4 pc. We also calculate the wavelength-dependence polarization produced by grains aligned with the magnetic fields by RATs. We find that λ max decreases rapidly from ∼ 0.55 µm to ∼ 0.15 µm over an alignment time of t align < 10 days due to the enhanced alignment of small grains. By fitting the theoretical polarization curve with the Serkowski law, we find that the parameter K from the Serkowski law increases when large grains are disrupted by RATD which can explain the K vs. λ max data observed for SNe Ia. Finally, we discover an anti-correlation between K and R V which might already be supported by SNe Ia observational data. Our results demonstrate the important effect of rotational disruption of dust grains by radiative torques on the time-dependent extinction, polarization, and colors of SNe Ia.

An imaging polarimetry survey of Type Ia supernovae: are peculiar extinction and polarization properties produced by circumstellar or interstellar matter?

“…Furthermore, for SNe showing time-variable reddening, Bulla et al (2018b) notice a possible preference for low 𝑅 𝑉 values. This may suggest that cloud-cloud collisions driven by the radiation pressure of SNe produce a high abundance of small dust grains, as proposed by Hoang (2017) (see also Giang et al 2020, who predict time-varying polarization, extinction, and colour of SNe Ia owing to rotational disruption of dust grains). Phillips et al (2013) found a correlation between the strength of the diffuse interstellar band (DIB) at 5780 Å along the sight lines to SNe Ia and extinction 𝐴 𝑉 .…”

Rotational Disruption of Astrophysical Dust and Ice—Theory and Applications

“…Using the RATD theory, Giang et al [91] performed modeling of time-varying disruption, extinction, and polarization. Figure 18 shows our results for dust grains having a maximum tensile strength S max = 10 7 erg cm −3 .…”

“…R V decreases rapidly from their original values from t = t disr to 40 days and then almost saturates when RATD ceases. From Giang et al[91].…”

“…Dotted vertical lines mark alignment time (t align ) and disruption time (t disr ) of silicate grains. From Giang et al[91].…”

“…Symbols show observational data for SNe Ia presented (red symbols) and normal stars in our galaxy (blue symbols). From Giang et al[91].…”