TY - JOUR
T1 - Circumstellar Light Echo as a Possible Origin of the Polarization of Type IIP Supernovae
AU - Nagao, Takashi
AU - Maeda, Keiichi
AU - Tanaka, Masaomi
N1 - Funding Information:
The authors thank Lifan Wang for stimulating discussion to initiate this project and an anonymous referee for constructive comments. The authors also thank Lluís Galbany for organizing the workshop “Supernova is In Da House,” where this work was initiated. The participation of T.N. and K.M. to this workshop was supported by a JSPS Open Partnership Bilateral Joint Research Project between Japan and Chile (K.M.). The authors thank the Yukawa Institute for Theoretical Physics at Kyoto University. Discussions during the YITP workshop YITP-T-16-05 on “Transient Universe in the Big Survey Era: Understanding the Nature of Astrophysical Explosive Phenomena” were useful to complete this work. The authors thank Keiichi Ohnaka for his useful comments on the geometry of CS dust around RSGs. T.N. thanks Takashi Kozasa and Takaya Nozawa for giving much advice on the Monte Carlo code to calculate polarization by dust scattering. The simulations were in part carried out on the PC cluster at the Center for Computational Astrophysics, National Astronomical Observatory of Japan. This research has made use of the Spanish Virtual Observatory (http://svo.cab.inta-csic.es) supported from the Spanish MINECO through grant AyA2014-55216 for the filter profiles. The work has been supported by Japan Society for the Promotion of Science (JSPS) KAKENHI Grant 17J06373 (T.N.), 26800100 and 17H02864 (K.M.), 15H02075 (M.T.), MEXT KAKENHI Grant 15H00788 (M.T.), and Inoue Foundation for Science (M.T.).
Publisher Copyright:
© 2017. The American Astronomical Society. All rights reserved.
PY - 2017/10/1
Y1 - 2017/10/1
N2 - Type IIP supernovae (SNe IIP) are the most common class of core-collapse SNe. They often show a rapid increase of polarization degree in the late phase. This time evolution is generally believed to originate from the emergence of an inner aspherical core, while the effect of polarized-scattered echoes by circumstellar (CS) dust around the SN may also substantially contribute to this polarization feature. In this study, we examine the effects of the scattered echoes on the SN polarization through radiative transfer simulations for various geometries and amounts of CS dust. It is found that asymmetrically distributed CS dust, which is generally inferred for red supergiants, can reproduce the observed polarization features. We have applied our results to SNe 2004dj and 2006ov, deriving the geometry and amount of CS dust to explain their observed polarization features in this scenario. For both SNe, the blob-like or bipolar distribution of CS dust rather than the disk-like distribution is favored. The derived dust masses Mdust in the blob model (the bipolar CS dust model) for SNe 2004dj and 2006ov are ∼7.5 × 10-4 M⊙ (∼8.5 × 10-4 M⊙) and ∼ 5.2 × 10-4 M⊙ (∼ 1.3 × 10-3 M⊙) respectively. Even in the case where this process would not play a dominant role in the observed polarization signals, this effect should in principle contribute to it, the strength of which depends on the nature of the CS dust. Therefore, this effect must be taken into account in discussing the multi-dimensional structure of an SN explosion through polarimetric observations.
AB - Type IIP supernovae (SNe IIP) are the most common class of core-collapse SNe. They often show a rapid increase of polarization degree in the late phase. This time evolution is generally believed to originate from the emergence of an inner aspherical core, while the effect of polarized-scattered echoes by circumstellar (CS) dust around the SN may also substantially contribute to this polarization feature. In this study, we examine the effects of the scattered echoes on the SN polarization through radiative transfer simulations for various geometries and amounts of CS dust. It is found that asymmetrically distributed CS dust, which is generally inferred for red supergiants, can reproduce the observed polarization features. We have applied our results to SNe 2004dj and 2006ov, deriving the geometry and amount of CS dust to explain their observed polarization features in this scenario. For both SNe, the blob-like or bipolar distribution of CS dust rather than the disk-like distribution is favored. The derived dust masses Mdust in the blob model (the bipolar CS dust model) for SNe 2004dj and 2006ov are ∼7.5 × 10-4 M⊙ (∼8.5 × 10-4 M⊙) and ∼ 5.2 × 10-4 M⊙ (∼ 1.3 × 10-3 M⊙) respectively. Even in the case where this process would not play a dominant role in the observed polarization signals, this effect should in principle contribute to it, the strength of which depends on the nature of the CS dust. Therefore, this effect must be taken into account in discussing the multi-dimensional structure of an SN explosion through polarimetric observations.
KW - circumstellar matter
KW - dust extinction
KW - polarization
KW - radiative transfer
KW - stars: mass-loss
KW - supernovae: general
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U2 - 10.3847/1538-4357/aa8b0d
DO - 10.3847/1538-4357/aa8b0d
M3 - Article
AN - SCOPUS:85031100518
VL - 847
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 2
M1 - aa8b0d
ER -