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Bose, S, Dong, S, Elias-Rosa, N, Shappee, BJ, Bersier, D, Benetti, S, Stritzinger, MD, Grupe, D, Kochanek, CS, Prieto, JL, Chen, P, Kuncarayakti, H, Mattila, S, Morales-Garoffolo, A, Morrell, N, Onori, F, Reynolds, TM, Siviero, A, Somero, A, Stanek, KZ , Terreran, G, Thompson, TA, Tomasella, L, Ashall, C, Gall, C, Gromadzki, M and Holoien, TW-S (2019) Strongly Bipolar Inner Ejecta of the Normal Type IIP Supernova ASASSN-16at. The Astrophysical Journal Letters, 873 (1). ISSN 2041-8205
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Strongly Bipolar Inner Ejecta of the Normal Type IIP Supernova ASASSN-16at.pdf - Accepted Version Download (1MB) | Preview |
Abstract
We report distinctly double-peaked Hα and Hβ emission lines in the late-time, nebular-phase spectra ( 200 days) of the otherwise normal at early phases ( 100 days) type IIP supernova ASASSN-16at (SN 2016X). Such distinctly double-peaked nebular Balmer lines have never been observed for a type II SN. The nebular-phase Balmer emission is driven by the radioactive 56Co decay, so the observed line profile bifurcation suggests a strong bipolarity in the 56Ni distribution or in the line-forming region of the inner ejecta. The strongly bifurcated blueshifted and redshifted peaks are separated by ~3 × 103 km s−1 and are roughly symmetrically positioned with respect to the host-galaxy rest frame, implying that the inner ejecta are composed of two almost-detached blobs. The red peak progressively weakens relative to the blue peak, and disappears in the 740 days spectrum. One possible reason for the line-ratio evolution is increasing differential extinction from continuous formation of dust within the envelope, which is also supported by the near-infrared flux excess that develops after ~100 days.
| Item Type: | Article |
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| Uncontrolled Keywords: | 0201 Astronomical and Space Sciences |
| Subjects: | Q Science > QB Astronomy Q Science > QC Physics |
| Divisions: | Astrophysics Research Institute |
| Publisher: | American Astronomical Society |
| Related URLs: | |
| Date Deposited: | 23 May 2019 09:26 |
| Last Modified: | 04 Sep 2021 09:21 |
| DOI or ID number: | 10.3847/2041-8213/ab0558 |
| URI: | https://researchonline.ljmu.ac.uk/id/eprint/10756 |
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