Tomo-e Gozen High-Cadence Transient Survey
Tomoki Morokuma (Univ. of Tokyo, IoA; tmorokuma@ioa.s.u-tokyo.ac.jp),
Nozomu Tominaga (Konan Univ.), Masaomi Tanaka, Ichiro Takahashi(Tohoku Univ.), Keiichi Maeda (Kyoto Univ.), Shigeyuki Sako, Ryou
Ohsawa, Satoshi Takita (Univ. of Tokyo, IoA), Tomo-e Gozen Supernova
WG members

Related talks
Day 1 大澤亮(東京大学): 東京大学・木曽観測所の活動報告
Day 2 紅山仁(東京大学): 微小地球接近小惑星の即時動画/多色測光観測
Day 2 吉田二美(産業医科大学): Tomo-e Gozenデータを用いた既知小惑星の位相角曲線の研究

Kiso Schmidt Telescope@Nagano, Kiso
105 cm Schmidt telescope
Ohsawa-san’s talk@Day 1

Tomo-e Gozen
84 CMOS sensors
effective area: 20 deg2 (9 deg in diameter)
1k x 2k ~ 22.4 x 39.7 arcmin2
no filter2 fps readout (nominal): up to ~200 Hz
Tomo-e Gozen High-Cadence Transient Survey

11th OISTER WS

2020/11/10-122

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11th sixOISTER
2020/11/10-123

Very Early Phases of Core-Collapse Supernovae
Bersten+2018, Nature(^) SN 2016gkg@NGC 613: Discovered by Victor Buso@Argentine, 16-inch telescope
possible detection with Gaia (Garnavich+2016, Rubin+2016)
serendipitous detections (SN 2008D): Swift/XRT (Soderberg+2008), GALEX(Schawinski+2008)no early excess for individual TESS SNe, but some excess for stacked LCs (Vallely+2020)
almost no detailed follow-ups for previous detections because of low S/N (high-z),
discovery latency, insufficient follow-up time (large telescopes)4<== overcome by Tomo-e
Tomo-e+ OISTER
Gozen High-Cadence Transient Survey
11th OISTER WS
2020/11/10-12Northern Sky Transient Survey w/ Tomo-e Gozen
7,000 deg2 - 2 hr cadence - 18 mag depth 2019 (initial phase)
7,000 deg2 - one visit - 18 mag depth
2020==> 2,000 deg2 - 0.5 hr cadence - 18 mag depth(now)==> 7,000 deg2 - one visit - 18 mag depth
no filter: effectively g+r bands
1 visit: 6 sec exposure = [0.5 sec exposure] x 12 (~18-19 mag)
~60 deg2 w/ 2x2 (or 2x3) dithering to fill the gaps between sensors
cadence: ~2 hours ==> ~0.5 hours (around midnight)
survey area:~7,000 deg2/2hrs ==> ~2,000 deg2/0.5hrs ==> ~7,000 deg2/2hrssurvey planning: Pedroso, Ikeda, TM+ et al. in prep.
recent (FY2019 winter) changes:
2020/01: cadence change (see above)
2020/10: 24 contiguous frames instead of 12 @ 1st roundnear-future changes:
reference for image subtraction: [PS1/r] ==> [Tomo-e]
Tomo-e footprint@lastnight
achieve better subtraction
around bright nearby galaxies
Tomo-e Gozen High-Cadence Transient Survey

11th OISTER WS

2020/11/10-125

Northern Sky Transient Survey w/ Tomo-e Gozen
7,000 deg2 - 2 hr cadence - 18 mag depth 2019 (initial phase)
7,000 deg2 - one visit - 18 mag depth
2020==> 2,000 deg2 - 0.5 hr cadence - 18 mag depth(now)==> 7,000 deg2 - one visit - 18 mag depth
no filter: effectively g+r bands
1 visit: 6 sec exposure = [0.5 sec exposure] x 12 (~18-19 mag)
~60 deg2 w/ 2x2 (or 2x3) dithering to fill the gaps between sensors
cadence: ~2 hours ==> ~0.5 hours (around midnight)
survey area:~7,000 deg2/2hrs ==> ~2,000 deg2/0.5hrs ==> ~7,000 deg2/2hrssurvey planning: Pedroso, Ikeda, TM+ et al. in prep.
recent (FY2019 winter) changes:
2020/01: cadence change (see above)
2020/10: 24 contiguous frames instead of 12 @ 1st roundnear-future changes:
reference for image subtraction: [PS1/r] ==> [Tomo-e]achieve better subtraction around bright nearby galaxies
Tomo-e Gozen High-Cadence Transient Survey

11th OISTER WS

2020/11/10-12

6

Transients in Transient Name Server (TNS)
Dec > -3 deg & 2019/01/01 - 2020/3/31 (discovery date@TNS)
Detected before TNS discovery date : 86 transients
Deeper than discovery magnitude : 29 transientsSNSN 2019gcc
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Tomo-e Gozen High-Cadence Transient Survey11th OISTER WS

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7

Target Handling System: web I/F

CNN (Hamasaki 2020, master thesis/Konan U.)==> automatic alert for bright transients

will be open in a few months

link to SDSS (if available)link to SDSS, PS1, TNS, MPChecker

link to visibility plot (IAC)

link to Tomo-e Gozen fits

light curve in magnitude unit
(light curve in linear scale below)

image cutout

Photometry for Tomo-e
imagesbeforeTransient
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Survey subtraction will be also
Seimei available.
UM 2020

2020/08/17-198

OISTER Follow-Up Observations
Discoveries, identification, & characterization of a few rapidly evolving transients# expectation: ~15 candidates per semester w/ ~> 1 mag day-1“flash” follow-up (<1 hour) w/ MITSuME (automated), …
“flash” spectroscopy (<1 day) w/ Seimei/KOOLS-IFU(, TriCCS), …
daily follow-up: multi-band imaging, spectroscopy(, polarization, radio, …)

Tomo-e Gozen High-Cadence Transient Survey

Figure 4 T
Tomo-e Goz
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Gemini-N/GMz = 0.025.
9
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11th OISTER WS

2020/11/10-12

Summary
Let’s find young supernovae in early-phase (right after explosions).
Northern Sky Transient Survey from Nov. 2018 w/ (partial) Tomo-e Gozen.
full operation w/ completed Tomo-e Gozen started in Oct. 2019.
7,000 deg / 2 hours, 18 mag ==> 2,000 deg2 / 0.5 hours, 18 mag~10,000 deg2 area is observed at least once during a night.
survey planning w/ statistical approach (Joao, Ikeda, TM, et al. in prep.)+consider weather conditions (avoid cloudy region/choose clear region)
Development of automatic data reduction pipeline+web I/F: almost done.
Machine-learning technique (CNN) to pick up only real sources
quick follow-up observations in OISTER
imaging w/ MITSuME etc.
spectroscopy w/ Seimei, Kanata, etc. (OISTER), Gemini, etc.
Collaborative transient surveys with UV wide-field satellite (Yatsu-san)fully utilize “2 Hz” data (see our pilot study in Richmond+2020)
Contact us (Morokuma, Ohsawa, Sako) if you are interested in survey.

Tomo-e Gozen High-Cadence Transient Survey

11th OISTER WS

2020/11/10-1210