Abstract
We present a series of ground-based photometry and spectroscopy of the superluminous Type IIn supernova (SN) ASASSN-15ua, which shows evidence for strong interaction with pre-existing dense circumstellar material (CSM). Our observations constrain the speed, mass-loss rate, and extent of the progenitor wind shortly before explosion. A narrow P Cygni absorption component reveals a progenitor wind speed of ∼100 km s-1. As observed in previous SNe IIn, the intermediate-width H α emission became more asymmetric and blueshifted over time, suggesting either asymmetric CSM, an asymmetric explosion, or increasing selective extinction from dust within the post-shock shell or SN ejecta. Based on the CSM radius and speed, we find that the progenitor suffered extreme eruptive mass-loss with a rate of 0.1-1 M· yr-1 during the ∼12 yr immediately before the death of the star that imparted ∼1048 erg of kinetic energy to the CSM. Integrating its V-band light curve over the first 170 d after discovery, we find that ASASSN-15ua radiated at least 3 × 1050 erg in visual light alone, giving a lower limit to the total radiated energy that may have approached 1051 erg. ASASSN-15ua exhibits many similarities to two well-studied superluminous SNe IIn: SN 2006tf and SN 2010jl. Based on a detailed comparison of these three, we find that ASASSN-15ua falls in between these two events in a wide variety of observed properties and derived physical parameters, illustrating a continuum of behaviour across superluminous SNe IIn.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 7767-7780 |
| Number of pages | 14 |
| Journal | Monthly Notices of the Royal Astronomical Society |
| Volume | 527 |
| Issue number | 3 |
| DOIs | |
| State | Published - Jan 1 2024 |
Funding
This work is supported by the international Gemini Observatory, a programme of NSF’s NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation, on behalf of the Gemini partnership of Argentina, Brazil, Canada, Chile, the Republic of Korea, and the United States of America. Observations reported here were obtained at the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution. Observations using Steward Observatory facilities were obtained as part of the observing programme AZTEC: Arizona Transient Exploration and Characterization, which received support from NSF grant AST-1515559. This work was supported through a NASA grant awarded to the Arizona/NASA Space Grant Consortium and by the Rolf Scharenberg Graduate Summer Research Fellowship. Support was also provided by the National Aeronautics and Space Administration (NASA) through HST grant AR-14316 from the Space Telescope Science Institute, operated by AURA, Inc., under NASA contract NAS5-26555. Some data reported here were obtained at the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution.
Keywords
- circumstellar matter
- stars: evolution
- stars: winds, outflows
- supernovae: general
- supernovae: individual: ASASSN-15ua
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science