Strongly Bipolar Inner Ejecta of the Normal Type IIP Supernova ASASSN-16at

Abstract

We report distinctly double-peakedH-alpha and H-beta emission lines in the late-time, nebular-phase spectra (>~200 d) of the otherwise normal at early phases (<~ 100 d) 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 Co56 decay, so the observed line-profile bifurcation suggests a strong bipolarity in the Ni56 distribution or in the line-forming region of the inner ejecta. The strongly bifurcated blue- and red-shifted peaks are separated by ~3x10^3 km/s 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 d 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 d.

arXiv commentPublished in ApJL

References in corpus (37)

• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• The Leiden/Argentine/Bonn (LAB) Survey of Galactic HI: Final data release of the combined LDS and IAR surveys with improved stray-radiation corrections
• The Man Behind the Curtain: X-rays Drive the UV through NIR Variability in the 2013 AGN Outburst in NGC 2617
• Explosion Mechanisms of Core-Collapse Supernovae
• Spectropolarimetry of Supernovae
• The Distance to SN 1999em in NGC 1637 from the Expanding Photosphere Method
• Jet-Induced Explosions of Core Collapse Supernovae
• Photometry and Spectroscopy of the Type IIP SN 1999em from Outburst to Dust Formation
• The Landscape of the Neutrino Mechanism of Core-Collapse Supernovae: Neutron Star and Black Hole Mass Functions, Explosion Energies and Nickel Yields
• Dust and the type II-plateau supernova 2004et
• Production of dust by massive stars at high redshift
• Massive-Star Supernovae as Major Dust Factories
• Multi-wavelength Observations of the Enduring Type IIn Supernovae 2005ip and 2006jd
• On the source of the late-time infrared luminosity of SN 1998S and other type II supernovae
• Optical and near infrared coverage of SN 2004et: physical parameters and comparison with other type IIP supernovae
• From Spitzer Galaxy Photometry to Tully-Fisher Distances
• X-ray, Optical, and Radio Observations of the Type II Supernovae 1999em and 1998S
• Massive stars exploding in a He-rich circumstellar medium III. SN 2006jc: IR echoes from new and old dust in the progenitor CSM
• Comparison of progenitor mass estimates for the type IIP SN 2012A
• What are Published X-ray lightcurves telling us about Young Supernova Expansion?
• Hubble Space Telescope and Ground-Based Observations of SN 1993J and SN 1998S: CNO Processing in the Progenitors
• The Type IIb SN 2011dh - Two years of observations and modelling of the lightcurves
• Supernova 2012aw - a high-energy clone of archetypal type IIP SN 1999em
• The Type IIP SN 2007od in UGC 12846: from a bright maximum to dust formation in the nebular phase
• Dust and the type II-Plateau supernova 2004dj
• Constraining the physical properties of Type II-P supernovae using nebular phase spectra
• The first year of SN 2004dj in NGC 2403
• The ASAS-SN Bright Supernova Catalog -- III. 2016
• SN 2013ab : A normal type IIP supernova in NGC 5669
• Properties of Newly Formed Dust Grains in The Luminous Type IIn Supernova 2010jl
• Optical observations of type IIP supernova 2004dj: Evidence for the asymmetry of ${}^{56}$Ni ejecta
• After the Fall: Late-Time Spectroscopy of Type IIP Supernovae
• The spectacular evolution of Supernova 1996al over 15 years: a low energy explosion of a stripped massive star in a highly structured environment
• SN 2016X: A Type II-P Supernova with A Signature of Shock Breakout from Explosion of A Massive Red Supergiant
• Asymmetry of ${}^{56}$Ni ejecta and polarization in type IIP supernova 2004dj
• Luminous type IIP SN 2013ej with high-velocity Ni-56 ejecta
• Failure of a neutrino-driven explosion after core-collapse may lead to a thermonuclear supernova

Cited by in corpus (11)

• An elliptical accretion disk following the tidal disruption event AT 2020zso
• The Iron Yield of Normal Type II Supernovae
• Emission peaks in the light curve of core collapse supernovae by late jets
• Resolving the puzzle of type IIP SN 2016X
• The ASAS-SN Bright Supernova Catalog -- V. 2018-2020
• ASASSN-18am/SN 2018gk : An overluminous Type IIb supernova from a massive progenitor
• Jet-shaped geometrically modified light curves of core collapse supernovae
• Direct evidence of two-component ejecta in supernova 2016gkg from nebular spectroscopy
• Simulating the inflation of bubbles by late jets in core collapse supernova ejecta
• Type IIP supernova SN 2016X in radio frequencies
• Modelling light curves of bipolar core collapse supernovae from the equatorial plane