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Title: Early Spectroscopy and Dense Circumstellar Medium Interaction in SN 2023ixf
Abstract

We present the optical spectroscopic evolution of SN 2023ixf seen in subnight cadence spectra from 1.18 to 15 days after explosion. We identify high-ionization emission features, signatures of interaction with material surrounding the progenitor star, that fade over the first 7 days, with rapid evolution between spectra observed within the same night. We compare the emission lines present and their relative strength to those of other supernovae with early interaction, finding a close match to SN 2020pni and SN 2017ahn in the first spectrum and SN 2014G at later epochs. To physically interpret our observations, we compare them to CMFGEN models with confined, dense circumstellar material around a red supergiant (RSG) progenitor from the literature. We find that very few models reproduce the blended Niii(λλ4634.0,4640.6)/Ciii(λλ4647.5,4650.0) emission lines observed in the first few spectra and their rapid disappearance thereafter, making this a unique diagnostic. From the best models, we find a mass-loss rate of 10−3–10−2Myr−1, which far exceeds the mass-loss rate for any steady wind, especially for an RSG in the initial mass range of the detected progenitor. These mass-loss rates are, however, similar to rates inferred for other supernovae with early circumstellar interaction. Using the phase when the narrow emission features disappear, we calculate an outer dense radius of circumstellar materialRCSM,out≈ 5 × 1014cm, and a mean circumstellar material density ofρ= 5.6 × 10−14g cm−3. This is consistent with the lower limit on the outer radius of the circumstellar material we calculate from the peak Hαemission flux,RCSM,out≳ 9 × 1013cm.

 
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Award ID(s):
1813466
NSF-PAR ID:
10482201
Author(s) / Creator(s):
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Publisher / Repository:
AAS Journals
Date Published:
Journal Name:
The Astrophysical Journal Letters
Volume:
956
Issue:
1
ISSN:
2041-8205
Page Range / eLocation ID:
L5
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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