SN 2023ixf : Closest CCSN in Over Two
Decades after SN 2004dj
Captured at Higashihiroshima
Equipment: Nikon Z6, 200-500mm f/5.6

Seimei Users Meeting 2023, Kyoto University
Avinash SinghAssistant Professor, Hiroshima University
In Collaboration with:

Kyoto University (Keiichi Maeda, Kenta Taguchi),NAOJ (Takashi Moriya),
University of Hyogo (Miho Kawabata)
Indian Institute of Astrophysics (D.K. Sahu, Rishabh Teja),
Indian Institute of Technology, Bombay (Varun Bhalerao, Vishwajeet, Ravi)
Team at Hiroshima University : Tatsuya Nakaoka, Anjasha Gangopadhyay, Ryo Imazawa, Koji KawabataOverview
First Paper is Out!
Rishabh Singh Teja et al 2023 ApJL
954 L12
DOI 10.3847/2041-8213/acef20
24 Papers in arXiv!

Collective Team Effort in Follow-up
1) Kanata Telescope
2) Seimei Telescope3) Growth-India Telescope
4) Himalayan Chandra Telescope5) Kottamiya Telescope
6) Steward Observatory7) Subaru

Discovered by Itagaki-san!
Host - M101
(RGB Composite from 2m HCT)
Distance - 6.82 Mpc

Brief Introduction
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Shock breakout ionises the outer ejecta (T >10,000 K)
Envelope expands -> Recombination wave moves inwards inmass (and opacity), staying at roughly the same radius (andtemperature)

1.
2.

Almost constant phase of luminosity - 'PLATEAU'
P-Cygni features of hydrogen visible in their spectra

Arcavi et al. 2016

Ultraviolet-Optical-Infrared Light Curves

Optical (ugriz)
Growth-India Telescope

NIR (JHK)
Kanata Telescope (HONIR)

Ultraviolet
Swift-UVOT

Bolometric Light Curve and Temperature Evolution●Shock Breakout inside a dense CSM. Hence, No shock Cooling phase as in a standard SN ejecta.

SpectroscopicSequence

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2.

3.

6

Flash Spectroscopy (High ionizationfeatures) up until 7 days.
Shows a plethora of featuresindicating CSM interaction. (Willdiscuss in following slides)
Features of Na, Fe, Ba and Sc areseen - Normal as a Type II SN

Evolution of Balmer Features - 1●●In the Spectrum of 7.9-9.9 d, we observe intermediate-widthHα emission at 1000 km/s , in addition to the emergence ofa broad P Cygni-feature with an absorption trough.
This could possibly be due to a residual of ongoinginteraction with the dense CSM along with the presence ofphotospheric emission from the SN ejecta.

Evolution of Balmer Features - 2●●●●●●

Spectra from June 03-06 (which is transitionalfrom Flash Phase to the Photospheric phase)shows multiple broad Gaussian and Lorentzianfeatures
There are two absorption features at theblue-wing of Hα at 8000 km/s and 15000 km/s.
We also detect an analogous proﬁle bluewardof Hβ with a similar velocity as seen in the Hα
proﬁle, indicating that the feature is likely due
to hydrogen.
Using the ejecta velocities, we estimate an
inner radius of 75 AU and an outer radius of 140AU.
Assuming a standard RSG wind, we estimatethat this ejection of mass happened 35-65
years before explosion.

Evolution of Balmer Features - 3●●We see dual Absorption component
in the Blue-wing of Halpha from 15 dto 80 d.
Absorption Feature at -13,200 km/s ofHalpha (Wavelength 6278 Angstrom)present through all the spectra (bothSeimei KOOLS and HCT HFOSC).

Line Velocity Evolution
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2.

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Photospheric velocity shows evolution to a normal Type II SN.
It is similar to an average Type II SN despite a much brighter absolutemagnitude of the SN and several instances of CSM interaction

Polarisation Signatures●●●We see 2 peaks in the polarisation light curve.
one during the ﬂash CSM (peak at 0.9%)
and one during the extended wind CSM (at 0.5%),

Conformation with our spectral signature that we are seeing a
CSM with a complex geometry.

MESA-STELLA Hydrodynamical Modelling
Preliminary model ﬁts suggest:
1) a low-mass progenitor - 10 Msolar2) Explosion energy - 2e51 erg
3) 56Ni mass - 0.06 Msolar4) mass-loss rate - 10-2 Msun/yr
5) Beta = 3.0 (0..084 Msolar)
6) dense CSM extent - 1015 cm.

Discrepancies:
1) Overestimating late-plateau bump
2) UV Luminosity is underestimated at later phase indicating that CSM
interaction is still ongoing and needs to be accounted with an even more
extended CSM.

Summary
SN 2023ixf is one of the nearest Type II SNe in the last 2 decades and it offers us a rare opportunity for comprehensive
observations and progenitor characterization. We plan to submit a paper within a month for the photospheric phase!

Signs of a Inner Dense CSM :●●Presence of Flash features till 7 d
FUV-NIR Bolometric LC rising and temperature increasing indicates shock breakout inside a dense CSM

Extended Wind CSM:●
●CSM inner Radius of 75AU and an outer radius of 110 AU.
Enhanced mass-loss episode 35-65 years before the SN (assuming 10 km/s RSG wind)Type IIL SN and Light Curve Modelling●●●

Light Curve decline rate is 1.5mag/100d, indicating it to be a Type IIL SN
Preliminary modelling suggests a 10 solar mass progenitor having mass-loss rate of 10-2 solar
mass/year with a solar metallicity.
Explosion parameters : 2e51 erg with a mass with 0.06 solar mass of 56Ni synthesizedPolarisation Features●Polarisation light curve has 2 peaks indicating a multi-faceted CSM geometry congruent with ourspectral sequence.

Any Questions?
Comet C/2023 ZTF
Equipment: Nikon Z6, 250mm f/4.9 APO,
SkyGuider Pro,
EXIF: (30s * 257 Frames), Flat and Dark Corrected

Captured From
Higashihiroshima