早期で発⾒されたII型超新星
SN 2024acnの可視光追観測
Ryotaro Koshi

The Univ. of Tokyo (D1)
8 th March, 2024
OISTER Workshop

0. Contents• Observation of SN 2024acn (24acn) plays a role asØA case study of Type II(n) supernovaeØAn example of follow-up observations for transient objects found by theTomo-e Gozen project

Table of contents
1. Type II Supernovae (SNe II)

1.1 Type II supernovae
1.2 Mass-loss of SN II progenitors

2. Detecting early SNe with Tomo-e Gozen

2.1 The Tomo-e Gozen camera
2.2 Transient surveys with Tomo-e Gozen
2.3 Recent improvement of transient detection
2.4 Discovery of SN 2024acn

3. Follow-up observations of SN 2024acn
3.1 Follow-up observations with OISTER
3.2 Follow-up status of SN 2024acn
3.3 Photometry of SN 2024acn
3.4 Spectroscopy of SN 2024acn
3.5 Comparison with other SNe
3.6 Future observation plans

4. Summary11.1 Type II supernovae (SNe II)• SNe II are supernovae that occur
from core-collapse of massive stars(>8M☉)

Ø Strong hydrogen lines in spectra(progenitor has a hydrogen envelope)• SNe II can be further classified fromtheir light curves / spectraØ SN IIP: “P”lateau phase in light curveØ SN IIL: “L”inear decline in light curveØ SN IIn: “n”arrow lines in spectrum

Branch & Wheeler 17

A typical spectrum of SNe II

SN IIPSN IILu Dense circumstellar material (CSM) aroundthe SN → heavy mass-loss of progenitor

Ø SN IIb: emergence of He I in spectrum

Wheeler 90

Light curves of SN IIP and IIL2

1.1 Type II supernovae (SNe II)• SNe II are supernovae that occur
from core-collapse of massive stars(>8M☉)

Ø Strong hydrogen lines in spectra(progenitor has a hydrogen envelope)

Branch & Wheeler 17

A typical spectrum of SNe II• SNe II can be further classified fromtheir light curves / spectraØ SN IIP: “P”lateau phase in light curveØ SN IIL: “L”inear decline in light curveØ SN IIn: “n”arrow lines in spectrum

u Dense circumstellar material (CSM) aroundthe SN → heavy mass-loss of progenitor

Ø SN IIb: emergence of He I in spectrum

Leonard+00

Spectrum of SN IIn (SN1998S)

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1.2 Mass-loss of SN II progenitors• Wide-field surveys have enabled early SNobservations, deepening our understandings• Many SN II progenitors experience intense
mass-loss just before explosion (not just SNeIIn)Ø SN 2013fs: a SN IIP showing narrow lines for ~5days (Yaron+17)
Ø Implies the existence of CSM near the SN

6.2h-5.3dHαHα8.8d-57.2d• There is a diversity of mass-loss rates within
SNe IIØ We need a larger sample (e.g. SNe in between
SNe IIP and SNe IIn) to understand this diversityØ SNe should be observed as early as possible

Spectra of SN2013fsYaron+174

2.1 The Tomo-e Gozen camera• The Tomo-e Gozen camera is an
instrument mounted on the 1.05m Kiso
Schmidt telescope• A wide-field camera consisting of 84 CMOSsensorsØØØØField of view of 20 square deg
2 fps images~10 TB of data per nightNo filters

The Tomo-e Gozen camera →東京⼤学 ⽊曽観測所

Kiso Schmidt telescope

Wide field × high time resolution × quick data handling= a powerful tool to study short timescale phenomena
52.2 Transient surveys with Tomo-e Gozen• We are conducting survey programs with the Tomo-e Gozen camerato discover short timescale phenomena (e.g. supernovae)
Ø All-sky survey
Ø High-cadence survey
Features

ValueFeatures

ValueCadence

1 day

Cadence

0.5 hrDepth~ 18 magDepth~ 18 magField coverage per day

13,000 square deg

Field coverage per day

3,000 square deg

Exposure time

0.5s * 18 frames

Exposure time

0.5s * 12 frames

Othersurveys
18+ manual ToO observations

All-sky survey

19

20

21

High-cadence survey

22

23

24

1

2

3

Example of an observation schedule of Tomo-e Gozen

4566

2.3 Recent improvement of transient detection• Using machine learning, an alert system has recently been developed
to discover and notify about new transients

⾮公開

⾮公開

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2.4 Discovery of SN 2024acn
1/13• 24acn was detected at
17.57±0.11 mag (Tomo-e)

1/14• We received an alert• 2nd observation: detection andbrightening was confirmed(MITSuME Akeno)

1/15

ReferenceNew

Subtracted

Image of first detection of 24acn• Object was reported to theTransient Name Server (TNS) as
AT 2024acn
Ø Second object to be reported byTomo-e Gozen (after SN2019cxx)

Discovery report of 24acn83.1 Follow-up observations with OISTER
1/15

1/16
1/17

• Spectroscopy andphotometry (Seimei)• 24acn was classified as a SN
II at z=0.031 (~130Mpc)• Spectroscopy andphotometry (Seimei)• A proposal was submitted toand accepted by OISTER• Follow-up observations byOISTER were commenced

He IIHβHαA quicklook spectrum of 24acn taken on
1/15 by Seimei (KOOLS-IFU, VPH-blue)

93.2 Follow-up status of SN 2024acn
Follow-up observation is currently in progress with 5 observatories

Kiso (not from OISTER)Ø Photometry
NayutaØ BVRcIc photometry

MITSuME Akeno
Ø g’RcIc photometry

KanataØ BVRI photometry

SeimeiØ gri photometry
Ø Spectroscopy (4100-8900Å)

Photometry
Photometry+ Spectroscopy

103.3 Photometry of SN 2024acn

Koshi et al., in prep.

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3.4 Spectroscopy of SN 2024acn

Koshi et al., in prep.

12

3.5 Comparison with other SNe

Koshi et al., in prep.

13

3.6 Future observation plans

Koshi et al., in prep.

14

4. Summary• SN 2024acn is a Type II supernova that was found in its early phase by
Tomo-e Gozen• It has a SN IInP like light curveØ Beginning to show broad hydrogen lines
Koshiet al.,ininSNe
prep(that maybe seenIIP)
Ø More observation is needed to discuss
properties and progenitor candidates• Observation with several telescopes
enables obtainment of good data
• More SNe is expected to be found by
Tomo-eØ Follow-up with OISTER will maximize thevalues of these discoveries

Discovery report of SN 2024ahe, a SN Ia
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