The metamorphosis of SN 2019yvr: late-time interaction

Lic. Lucía Ferrari ^1,2

Supervisors: Dr. Gastón Folatelli ^1,2, Dr. Hanindyo Kuncarayakti ^3,4

¹ Instituto de Astrofísica de La Plata, Argentina

² Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Argentina

³ Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland

⁴ Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Finland

SN 2019yvr

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• Discovered on 12/27/2019, LC peak on Jan 3rd, 2020
• Host galaxy: NGC 4666; Z = 0.005; D = 14.7 ± 1.4 Mpc
• Originally classified as Ib, the SN begins to show signs of interaction with the CSM at around 70 days post B-band maximum

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Observations: ePESSTO+ & NUTS collaborations

Facilities: VLT/FORS2, NOT/ALFOSC, NTT/EFOSC2, LCOGT, Subaru/HDS

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Previous case: SN 2014C

• Host galaxy NGC 7331; distance 14.7 ± 0.6
• Initially classified as Type Ib, it evolved into a Type IIn at later times
• Ordinary H-poor SN embedded in a non-standard H-rich environment

Milisavljevic et al. 2015

Margutti et al. 2017:

• SN 2014C bridges the gap between ordinary SNe Ib/c and type-IIn SNe
• Distance to the CSM: ~6 x 10¹⁶ cm
• Short WR phase of its progenitor (single) star, lasting only ~20 years , and a very large mass-loss rate during the previous RSG phase of ~7 x 10^-4 M_⊙ yr^-1
• SN 2014C violates several expectations from evolutionary models

SN 2019yvr

• Previous work
• Progenitor candidate analysis (Kilpatrick et al. 2021)
• Analysis of the environment and the progenitor candidate (Sun et al. 2022)
• This work
• Analysis of interaction signatures on light curves and spectra
• Mass-loss rate estimation
• Progenitor properties
• Our future work
• Optical, NIR and high-resolution spectra analysis
• Further analysis on CSI effects
• HST program recently approved will observe the site (PI: Charles Kilpatrick)

Spectra and light curves evolution

Interaction signatures begin at ~70-90 days post peak light (75-105 days from explosion)

H𝛼 emission line appearance

LC flattening

Nebular spectra

H𝛼 is asymmetric, blue-shifted by ~300 km s⁻¹, width ~2000 km s^-1

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[O I] shows a double-peaked profile with a ~1300 km s⁻¹ blueshift and a FWHM of ̣~2000 and ~2500 km s⁻¹ for the bluer and redder component respectively

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Unusually strong Ca II triplet

Properties of the CSM

By adopting a maximum ejecta velocity of ~10,000 km s⁻¹ → distance of ~6.5 − 9.1 × 10¹⁵ cm

If the CSM was expelled by stellar winds of 50 − 100 km s⁻¹, the mass loss must have occurred up until ~20 − 60 years prior to the explosion

From H𝛼 luminosity in the nebular phase and considering shock velocity of ~10,000 km s⁻¹ → mass-loss rate of ~3 − 7 x 10⁻⁵ 𝑀_⊙ 𝑦𝑟⁻¹

Upper limit for the mass-loss rate considering a shock velocity of 2 000 km s⁻¹ → ~4 − 8 x 10^-3 𝑀_⊙ 𝑦𝑟⁻¹

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Progenitor properties: hydrodynamical model

1D Lagrangian hydrodynamic code (Bersten et al. 2011) model the bolometric light curve and the photospheric velocity. Free parameters: explosion energy, ejecta mass, mass of synthesized ⁵⁶Ni and the extent of outward mixing of ⁵⁶Ni. The energy is deposited at a certain mass coordinate, 𝑀_cut.

He mass between 3.3 − 4.0 𝑀_⊙ → ZAMS mass of 13 - 15 𝑀_⊙

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Progenitor properties: model nebular spectra

The flux ratio of nebular [O I] to [Ca II] lines has been suggested as an indicator of the pre-SN mass. We calculated these ratios on the EFOSC2 spectra and compared with the grid of models published in Dessart et al. (2023a) where the spectral evolution between 100 and 400 d is calculated for a wide range of initial He masses.

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He mass between 3.0 − 3.5 𝑀_⊙

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Progenitor properties: oxygen doublet flux

Estimation of the oxygen core minimum mass responsible for [O I] doublet flux.

Procedure presented by Jerkstrand et al. 2014.

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This flux could be contaminated by CSI effects, so we consider this result as an upper limit.

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T = 3000 K → 1.1 𝑀_⊙

T = 3500 K → 0.4 𝑀_⊙

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ZAMS mass between 15 - 20 𝑀_⊙

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SN 2019yvr

Kilpatrick et al. 2021: pre-explosion light curve (HST). No variability detected. Not conclusive on the progenitor system.

Sun et al. 2022: SED fitting, proposes a hot and compact star (SN progenitor) and a cool YHG (dominates pre-explosion emission). M_ej≃ 2 M_⊙; M_ZAMS≃ 10.4 M_⊙

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Summary

• Late-time interaction showed for the first time
• A progenitor with no hydrogen, indicated by the early spectra, evolves into a H-rich SN at later times
• Kilpatrick et al. (2021) suggested two progenitor scenarios: a massive star that went through a series of eruptions in a LBV phase, or a binary system that led to mass-loss episodes timed years to decades ahead of core collapse
• Sun et al. (2022) suggested a hot and compact progenitor in a binary system with a cool and inflated YHG companion
• Based on the mass estimations, our results are compatible with the binary progenitor scenario and do not favor a single star going through an LBV phase

Thank you!

luciaferrari@fcaglp.unlp.edu.ar

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