2021年度せいめいユーザーズミーティング

測光・分光・偏光観測で探る
Ia-CSM型超新星
SN 2020uemのCSM構造
Kohki Uno (Kyoto Univ.)
collaborator:

Keiichi Maeda (Kyoto Univ.), Miho Kawabata, Masayuki Yamanaka,Tatsuya Nakaoka (Hiroshima Univ.), Koji Kawabata,Takashi Nagao (U. Truku), Kentaro Aoki (NAOJ), Tajitsu Akito,
Kentaro Motohara (NAOJ/U. Tokyo), Masaomi Tanaka (Tohoku Univ.)

Introduction: Type Ia Supernovae

せいめいUM 2021/08/11-12

2Type Ia Supernovae (SN Ia): Thermonuclear explosion of white dwarf(s), but …
Classification

Progenitor System
Single Degenerate (SD)Explosion Mechanism
Delayed Detonation

He Ignition

Maeda+10

Fink+10

MS/RS/HeWD(c) STFC/D. Hardy

Double Degenerate (DD)Nakaoka-san→Tanikawa+15

WDWD(c) D. Kasen(c) NASAWD MergerせいめいUM 2021/08/11-12

Introduction: Type Ia Diversity

3

highSN Ia: Standard Candles, but…

Taubenberger 17←Kawabata-san

Peak magNew generation surveys

Much more diversity than expected !

・New insight for Stellar Evolution

low・Too much diversity indicates diﬀerent
progenitor & explosion mechanism.

SN 2020uem is one of the peculiar SN Ia.
slowDecline ratefast

Introduction: Type Ia-CSM Supernovae

せいめいUM 2021/08/11-12

Type Ia-CSM Supernovae (or SN 2002ic-like transients)
・spectrum: high temperature Ia (like 1991T) + narrow H emission lines (c.f, Type IIn SNe)・high and long-lasting luminosity (> 100 days)
HαHβFeMg

FeInteraction between energetic Ia and dense circumstellar matter (CSM)

Where did such a dense CSM come from？

4Type Ia-CSM Supernova: SN 2020uem

せいめいUM 2021/08/11-12

5・Discovery: 16.5 mag on 2020-09-22 (MJD 59114.6) by ATLAS
・Coordinate: RA = 08h24m23.85s, Dec=-3°29′19.1″
・Distance: dL = 173.3 Mpc (z = 0.041)
・Follow UP observation- Photometry:

Kanata 19/21 nignts (HOWpol/HONIR)
Subaru 1 nights (SWIMS)- Spectroscopy: Seimei 8 nights (VPH-blue & VPH-683)
Subaru 3 nights (FOCAS, HDS & SWIMS)- Polarimetry:

Subaru 1 nights (FOCAS)
Tohoku T60 1 nights (Dipol-2)

20uem

What Can We Discuss？
Light Curve Evolution, Mass-Loss History, Spectral Evolution, Asymmetric Hα profile,
Comparison & Classification with Other SNe, Dust Mass Estimation, NIR Echo Estimation,
Evolution of Polarization Degree, CSM Geometry, Progenitor System, Explosion Mechanism…

せいめいUM 2021/08/11-12

Results: Seimei, Kanata & Subaru Observation

6SN2005gj+7+22 (Seimei)

JHKs
Kanata(HONIR)

JKs
Subaru(SWIMS)+34 (Seimei)+47 (Seimei)+62 (Seimei)+69+74 (Seimei)+91 (Seimei)

color: constant→ little/no NIR excess

BVRI
Kanata(HOWPol)+97+103 (Subaru)+110 (Seimei)
Seimei (VPH-683)+ Subaru (HDS/SWIMS)

せいめいUM 2021/08/11-12

Results: Bolometric Luminosity & Mass-Loss Rate
Integrate BVRI flux to bolometric luminosity·Mass-Loss Rate ( M )·M ≈ 0.09

Lopt ~1043 [erg/s]→ consistent with other Ia-CSM/IIn SNeϵ( 0.3 )−1L( 1043 erg s−1 )Vshock×( 5000 km s−1 )−3(Moriya+13)
VwindM⊙yr−1( 100 km s−1 )·→ consistent with typical M of SN IIn
MCSM ∼ a few M⊙

7

Results: Flux Ratio of Balmer Lines
Line Flux Ratio (Hα/Hβ)→ Indication for the CSM density (c.f., Balmer Decrement)
・Type IIn SNe → Ratio ~ 3・Type Ia-CSM SNe → Ratio > 10@ High Density (Optically Thick)n=4n=3n=4n=3n=2

HαHβHα→Hαn=2Hαn=4Paαn=3Hαn=2Hβ→Paα & HαEnergyRedistribution→ Ia-CSM is more dense than IIn.

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せいめいUM 2021/08/11-12

Results: Subaru (FOCAS) Spectropolarimetry
Date: 2021-01-02 (+103 days)
Interstellar Polarization (ISP)

PISP(λ) = Pmax exp [−K ln2 (λmax /λ)] (Serkowski+1975)
K = 0.01 + 1.66λmax (μm)(Whittet+1992)

PISP ∼ 0.7 %Polarization Degree:・PSN ∼ 1.0 − 1.5 % (c.f., SN2002ic: PSN ∼ 0.8 % )・No wavelength dependence

Wang+2004(1) electron scattering is dominant.
- highly dense CSM- CSM geometry: disk/clump/jet？
(2) no dust echo
- little/no dust

9Discussion: How Asymmetric Is The CSM?
PSN ∼ 1.0 − 1.5 %→ Indication for asymmetric CSM geometry

せいめいUM 2021/08/11-12

10sphere・‘Elliptical’ CSM (c.f., Hoflich 91)(1) Photons are emitted from spherical inner boundary.
(2) Polarization in the elliptical CSM (axis ratio = b/a)bθ

observerphotonainnerboundary

Extremely Flat CSM → Disk-Like CSM？

Ratio < 0.2

face onedge on

Discussion: CSM Geometry of SN 2020uem

せいめいUM 2021/08/11-1211(1) Ia component at early phase
optical depth in the line of sight < 11615→ τ(10 cm) ≈ 1 v.s. Rph ∼ 10 cm→ Aspherical CSM Geometry(2) Balmer line ratio > 10more dense CSM than Type IIn SNe··→ MIIn ∼ MIa−CSM→ localized & Confined CSM

observer(3) PSN ∼ 1.0 − 1.5 % @~100 days
axis ratio < 0.2 @elliptical CSM→ Disk-like CSM(4) little/no NIR excess/echo
localized CSM / No CSM after 1017 cmCSMIa ejecta

SN 2020uem has more confined disk-like CSM than general IIn SNe.

Take Away

せいめいUM 2021/08/11-12

12Background

・New generation surveys have revealed the diversity of Ia SNe.
Observation

・Continuous follow up observations for a Ia-CSM SNe; SN2020uem, ware
performed with Seimei, Kanata, and Subaru telescope.
Results

・SN 2020uem may have more dense CSM than typical Type IIn SNe.
・The CSM geometry may be disk-like one.
Further More・Dust echo, Mass-Loss history, Explosion mechanism, Progenitor, …
Many things can (and have to) be discussed
Request・KOOLS-IFU解析のノウハウを教えていただける機会があると嬉しいです。

Thanks to everyone involved with Seimei telescope！ Thank you very much！