Tomo-e Gozen突発天体サーベイと連携した
Rapid Transientの観測

田中 雅臣 (東北大学)
on behalf of Tomo-e Gozen Transient Survey Teamulations. Based on the history of our subject we should noade fromnow,
thatwewerenot
sufficientlyimaginative.
Fron=er of transient sky

LSST Science Book (a.er Rau+09, Kasliwal+,Kulkarni+)

Transient survey
Timescale (sec)
10-1

100

101

102

103

105

2 hr
ASAS-SN

16

1 day

Tomo-e18
Magnitude

104

Discovery
space

20

Tomo-eZTF
PS1

22

DECam
24
26
10-6

HSC
10-5

10-4

10-3
10-2
10-1
Timescale (days)

100

101

12. OctoberEvent rates of therapidly evolving transient from the HSC–SSPof rapidtransients
TheDiscovery
AstrophysicalJournal,
794:23 (23pp), Figure2014
10Transient Survey (red), PS1 (green, Drout et al. 2014), and Dark Energy
Survey (blue, Pursiainen et al. 2018) compared with the event rate of normal
core-collapse SNe (gray, Strolger et al. 2015).

Required
56Ni mass

3 daysPeak Luminosity (erg s-1)

Normal SN

Diﬃcult to be
powered byradioacJvity

Timescale (day)Drout+14

Figure 13. 2 t1 2,rise vs. observed peak luminosity of our rapidly evolving
transients and the rapidly evolving transients from PS1. Lines represent thecorrelation of t1 2,rise and observed peak luminosity at given parametersassuming mass of 56Ni is equal to the mass of ejecta.

Tampo+20

Compared with supernovae:
Motivated by similar analyses by Drout et al. (2014) andArcavi et al. (2016), we discuss the power source of rapidly- Similar luminosity (w/large diversity)
evolving transients using the phase diagram (Figure 13). Thein thephase involved)
diagram has several implications as- Shorter =me scale (=locationsmallmass
discussed below. The dotted lines show the radioactive decay
luminosity for given masses of Ni (Nadyozhin 1994):- ~5 % event rate56⎡⎛ 2 t1 2,rise ⎞⎛ 2 t1 2,rise ⎞ ⎤ogelF
u5v
e
TbineeAaodce
Csint
StpssreOrigin of rapid transients?

•Ultra-stripped envelope SN?

Mej ~ 0.1 Msun

• Mej ~0.1 Msun by binary interacJon(e.g., Tauris+13, Moriya+17)
a route to neutron star merger?

• BH-forming supernovae?

Mej ~ 0.01 Msun

• Disk ouWlow (e.g., Kashiyama+15)
or AccreJon-powered transients?
(e.g., Dexter & Kasen 13)• …?

BH or NS

Moderate samples so far
Drout+14 (PS1, 2m), Pursiainen+18 (DES, 4m), Tampo+20 (Subaru, 8m)=> Diﬃcult to perform spectroscopy
Need nearby, bright objects for spectroscopy

Tomo-e Gozen Transient Survey (2019/4-)• Tomo-e Gozen @ Kiso Schmidt• 84 CMOS sensors, no ﬁlter• 20 deg FOV
2=> MulJ-messenger follow-up(GravitaJonal wave, IceCube neutrino)• Survey strategy• 7000 deg2
• 2 hour cadence• 0.5 sec x 12 = 6 sec exposure

Poin=ng padern- - - -=> 18 mag (5 sigma)• ~ a few rapid transients / 0.5 yr (< 200 Mpc)

• Follow-up with Seimei• 19A-21A (PI: Morokuma) KOOLS-IFU• 21B (PI: Tanaka) KOOLS-IFU + TriCCS

Pedroso, Ikeda, et al. in prep.

Overall speed-up(led by 冨永 望さん)

Data ﬂow
Standard reducJon(+ astrometry)**Raw image(0.5 sec x 12)
30 TB/night**deleted in 1 week

Update of reference images(led by 新納 悠さん)
Image subtracJon(PS1, r-band)

Stack**Reduced image(0.5 sec x 12)

Stacked image(6 sec)Subtractedimage

CatalogCatalog

Measurement
Catalog(0.5 sec)

LimiJng magnitude

Real/bogus classiﬁcaJon
Match w/ minor planet
Update of real-bogus and w/ previous detecJon

Main issues- Too many images to reduce- Too many fake detecJonclassiﬁca=on(led by 高橋 一郎さん)
Update of web interface(led by 瀧田 怜さん)

WebInterface

Challenges in transient detec=on
NewDiﬀerence

Old-=Examples of diﬀerence imagesFakeReal

Imperfect
convolu=on

Cosmic ray
Fake

Satura=on

Fake

Fake

Fake

Cosmic ray

Imperfectalignment

Fake/Real >> 1000=> 1% false posi=ve rate
is not good enough0.967

0.179------

Ini=al development: 浜崎 凌さん (甲南大)
Performance update: 高橋 一郎さん (東北大)Classiﬁca=on with
0.934 0.739 ----Convolu=onal Neutral Network (CNN)

Figure by Ichiro Takahashi

bener

90 % true
posi=ve rate

False posi=ve rate
= 0.0006(at 90 % true posi=verate)Performance of new machine
Figure by Ichiro Takahashi

Updated1 detec=on
2 detec=ons

1/130

1/40

~100,000 images /day=> ~150 transient candidates / day = manageable number!

Deep coadd reference for 20,000 deg2 sky(PS1 => Tomo-e)
Led by 新納 悠さん (東京大)Further improvement in real-bogus classiﬁca=on (iden=cal response)=> automa=c alert for high-conﬁdence candidates
前田さん講演
2430

3744-1550-8.6-2.1

4.5

11

Web interface

Led by 瀧田 怜さん (東京大)Toward higher =me resolu=onTimescale (sec)
10-1
16

100

101

102

0.5 sec

18105

1 day

Tomo-eDiscoveryspace

20104

2 hr
ASAS-SN

Tomo-eMagnitude

103

Tomo-eZTF
PS1

22DECam24
26
10-6

HSC
10-5

10-4

10-3
10-2
10-1
Timescale (days)

100

101

Real=me analysis of “movie”
Watch out 16th frame

ApplicaJon ofobject recogniJon technique(Single Shot MulJbox detector= SSD, arXiv:1512.02325)

SSD: Single Shot M

Summary• Fron=er of transient sky• Rapid transients: new kind of astronomical explosion• Need rapid spectroscopic follow-up• Tomo-e Gozen transient survey• 7000 deg - 2 hr - 18 mag• A number of development work in the past years• Data reducJon pipeline, Real-bogus classiﬁer,
2

Coadded reference images, Web interface,
ReducJon of movie data

• Feed good targets for Seimei• Toward automaJc alert for high-conﬁdence candidates
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