すばる望遠鏡/HSCを用いた
重力波対応天体の探査

大神 隆幸(甲南大学)J-GEM Collaboration
24-27 Aug. 2020
第50回 天文・天体物理若手夏の学校 @ zoomオンライン

自己紹介•大神 隆幸•略歴•-2018/3 山口大学大学院理工学研究科•2018/4-2019/3 大同大学ポスドク(学振PD)•2019/4-

甲南大学ポスドク•研究•ブラックホール擬似天体の観測における強い重力効果を使った理論的アプローチ-ワームホールシャドウ、グラバスターシャドウ•天の川銀河中心の巨大BHの持つ重力場の検証

物理（相対論）-S2の運動の観測データと理論のフィッティング•GWの電磁波対応天体の探査・調査-すばる望遠鏡/HSCを使ったfollow-up観測

天文（観測）

Gravitational Waves
Propaga5on of space-5me
distor5ons as predicted by
Einstein.

Gravita2onal Waves
GW observations

重力波
アイ ン シ ュ タイ ン に よ って予想された、時空の歪みの伝搬。
電磁波 → 電場・磁場
重力波 → 時空LIGOの二台の検出器によって20115年に初検出+ mode× modehttps://science.gsfc.nasa.gov/663/images/gravity/GWspec.jpg

Takayuki OHGAMI

すばる望遠鏡/HSCを用いた重力波対応天体の探査

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Gravita2onal Waves
PRL 116, 061102 (2016)

Selected for a Viewpoint in Physics
P H Y S I C AGW150914
L REVIEW LETTERS

week ending
12 FEBRUARY 2016

Observation of Gravitational Waves from a Binary Black Hole Merger
B. P. Abbott et al.*(LIGO Scientific Collaboration and Virgo Collaboration)(Received 21 January 2016; published 11 February 2016)

PHYSICAL

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave
Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards infrequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0 × 10−21 . It matches the waveformpredicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of theresulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and afalse alarm rate estimated to be less than 1 event per 203 000 years, equivalent to a significance greaterþ0.03
than 5.1σ. The source lies at a luminosity distance of 410þ160−180 Mpc corresponding to a redshift z ¼ 0.09−0.04 .
þ4In the source frame, the initial black hole masses are 36þ5
−4 M ⊙ and 29−4 M ⊙ , and the final black hole mass is
þ0.5
2
62þ4
−4 M ⊙ , with 3.0−0.5 M ⊙ c radiated in gravitational waves. All uncertainties define 90% credible intervals.
week endingR
E Vobservations
I E W demonstrate
L E T T EtheRexistenceS
Theseof binary stellar-mass 12
blackhole systems. 2016
This is the first direct
FEBRUARY
detection of gravitational waves and the first observation of a binary black hole merger.

DOI: 10.1103/PhysRevLett.116.061102
combined signal-to-

erving at the time of I. INTRODUCTION
The discovery of the binary pulsar system PSR B1913þ16
was being upgraded,by Hulse and Taylor [20] and subsequent observations of
In 1916, the year after the final formulation of the fieldly sensitive
to detectits energy loss by Taylor and Weisberg [21] demonstrated
equationsof general relativity, Albert Einstein predicted
the existence of gravitational waves. This discovery,
ot in observational
the existence of gravitational waves. He found thatalong with emerging
astrophysical understanding [22],62M
29M⊙ had wave36M
linearizedisweak-field equations
solutions:e sourcetheposition
⊙
⊙
led
to
the
recognition
that direct observations of thetransverse
wavesofspatialstrainthat
travel
at
the
speed
of
ve arrival time andamplitude and phase of gravitational waves would enable
light,
generatedbytimevariations
of
the
mass
quadrupole
2
Takayuki
すばる望遠鏡/HSCを用いた重力波対応天体の探査
tely
600 OHGAMI
deg (90%studies of additional relativistic systems and provide new 5

Gravita2onal Waves
PRL 119, 161101 (2017)

Selected for a Viewpoint in Physics
P H Y S I C AGW170817
L REVIEW LETTERS

week ending
20 OCTOBER 2017

GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
B. P. Abbott et al.*(LIGO Scientific Collaboration and Virgo Collaboration)(Received 26 September 2017; revised manuscript received 2 October 2017; published 16 October 2017)
On August 17, 2017 at 12∶41:04 UTC the Advanced LIGO and Advanced Virgo gravitational-wave
detectors made their first observation of a binary neutron star inspiral. The signal, GW170817, was detectedwith a combined signal-to-noise ratio of 32.4 and a false-alarm-rate estimate of less than one per
8.0 × 104 years. We infer the component masses of the binary to be between 0.86 and 2.26 M ⊙ , inagreement with masses of known neutron stars. Restricting the component spins to the range inferred inbinary neutron stars, we find the component masses to be in the range 1.17–1.60 M ⊙ , with the total mass of2
the system 2.74þ0.04−0.01 M ⊙ . The source was localized within a sky region of 28 deg (90% probability) andhad a luminosity distance of 40þ8−14 Mpc, the closest and most precisely localized gravitational-wave signal
yet. The association with the γ-ray burst GRB 170817A, detected by Fermi-GBM 1.7 s after the
coalescence, corroborates the hypothesis of a neutron star merger and provides the first direct evidence of alink between these mergers and short γ-ray bursts. Subsequent identification of transient counterparts
across the electromagnetic spectrum in the same location further supports the interpretation of this event asa neutron star merger. This unprecedented joint gravitational and electromagnetic observation provides
insight into astrophysics, dense matter, gravitation, and cosmology.

中性子星連星からの重力波の初検出

DOI: 10.1103/PhysRevLett.119.161101

Kilonova

will observe between one BNS merger every few years to
I. INTRODUCTION
中性子星が合体する時にrプロセスによって作られた元素が放射性崩壊を起こ
hundreds per year [14–21]. This detector network currently

On August 17, 2017, the LIGO-Virgo detector network
includes three Fabry-Perot-Michelson interferometers that
し、そのエネルギーが電磁波となって爆発的に放射される現象。
observed a gravitational-wave signal from the inspiral ofmeasure spacetime strain induced by passing gravitational
two low-mass compact objects consistent with a binary
waves as a varying phase difference between laser lightneutron star (BNS) merger. This
discovery comes four
Takayuki OHGAMI
すばる望遠鏡/HSCを用いた重力波対応天体の探査
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Multi-messenger Astrophysics
複数のメッセンジャーを用いて天体現象を総合的に解明する天文学のこと。(天文学辞典)

Multi-messenger Astrophysics
Coordination between GW and EM wave
Japanesecollaboration
forforGravitational-wave
Electro-Magnetic
follow-up
J-GEM(Japanesecollaboration
Gravitational-wave Electro-Magnetic
follow-up)
J-GEM - Optical, Nere Infrared and Radio

5

Takayuki OHGAMI

すばる望遠鏡/HSCを用いた重力波対応天体の探査

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8

Multi-messenger Astrophysics
Purpose of J-GEM★ Purpose•

重力波源の光学的な対応天体を同定・観測•

マルチメッセンジャー観測を通して重力波イベントの物理的背景を解明★ Requirements•

広い領域の探査(>10 deg 2 )•できるだけ早い段階での観測・同定★ Approach•

たくさんの日本の望遠鏡を使用し、できるだけ広い範囲を探査観測•

Takayuki OHGAMI

候補天体が見つかり次第、様々な波長帯で追観測

すばる望遠鏡/HSCを用いた重力波対応天体の探査

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Two types of telescope
Multi-messenger Astrophysics
Two types of telescope

Normal Telescope (FoV < 1 deg^2)• Kanata • OAO WFC• B&C• IRSF• MITSuME• SaCRA• Nayuta Akeno/Okayama • Seimei

Galaxy-targeted survey
Takayuki OHGAMI

Telescope having large FoV (FoV > 1 deg^2)• Subaru
・MOA-II• Kiso Tomo-e

Wide-ﬁeld survey

すばる望遠鏡/HSCを用いた重力波対応天体の探査

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Multi-messenger Astrophysics
Scheme ofTransient
SurveyGalaxy-targetedsurvey①

J-GEM

Web System
planner②
OAOWFC
Okayama Astrophysical Observatory Wide Field Camera• Make galaxy list
• Serve realtime info③
• Observe• Reduce

2015/12/07

Takayuki OHGAMI

奛㷔塭伖㈨埻WS

7

④

Image
Server• Save/show obtained images• Calculate limiting ﬂux• Subtract image

すばる望遠鏡/HSCを用いた重力波対応天体の探査

11

Multi-messenger Astrophysics
planner and Image Server

User interface: planner

Galaxy ID Probability

Galaxy Info

Observational Information• List candidate galaxies from GLADE catalog.
• Share information to avoid a duplication of observations
Takayuki OHGAMI

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Multi-messenger Astrophysics
planner and Image Server

User interface: Image ServerObs. Image

Ref. Image

Sub. Image

Blinking gif• Show an observing and reference image (PanSTARRS and
2MASS).
• Image subtraction• Compare between obtained and reference images using
subtracted image and blinking gif image.

Takayuki OHGAMI

すばる望遠鏡/HSCを用いた重力波対応天体の探査

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Multi-messenger Astrophysics
Scheme ofTransient
Surveyplannerand Image Server
①

J-GEM

Web System
planner②
OAOWFC
Okayama Astrophysical Observatory Wide Field Camera• Make galaxy list
• Serve realtime info③
• Observe• Reduce

2015/12/07

Takayuki OHGAMI

奛㷔塭伖㈨埻WS

7

④

Image
Server• Save/show obtained images• Calculate limiting ﬂux• Subtract image

すばる望遠鏡/HSCを用いた重力波対応天体の探査

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Multi-messenger Astrophysics
First BNS event•

Distance: 155 45 Mpc•

90% area: 7461 sq. deg•

Observe 23 galaxies listed in
GLADE catalog•

Percentage of coverage: 1.1%•

The ToO observations were
performed by Subaru/FOCAS.

•

GCN circular; #24192, 24230,
24328

Abs. mag•mag (AB)BNS Event:S190425z
BNS Event: S190425z

14
18
22
-22
-18
-14
0

Takayuki OHGAMI

1

すばる望遠鏡/HSCを用いた重力波対応天体の探査

2

3

4

(Day)
15

Multi-messenger Astrophysics
BNS Event: S190425z

154 galaxies obtained by Subaru/FOCAS
Takayuki OHGAMI

すばる望遠鏡/HSCを用いた重力波対応天体の探査

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Multi-messenger Astrophysics
Wide-field survey

GWイベントのいくつかの例
Event

Source category

90% credible
regionLuminosity
distance

GW190425(S190425z)

BNS

7461 deg2

156 Mpc

S190426c

BNS [49%], NSBH[13%]1131 deg2377 Mpc

S190510g

BNS[98%]→ Terrestrial[58%], BNS[42%]1166 deg2

227 Mpc

S190814bv

NSBH [99%]23 deg2

267 Mpc

GW170817

BNS

28 deg2

40 Mpc

とても遠く、とても広い
重力波望遠鏡は到来方向の位置決定精度が低く、数1000deg 2 に及ぶこともある。また、遠いGWイベントも検出可能。広い視野を持つ大口径望遠鏡での観測が重要となる。
Takayuki OHGAMI

すばる望遠鏡/HSCを用いた重力波対応天体の探査

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Multi-messenger Astrophysics
Etendue of optical telescopes
1000

10
532.0

Etandue [m^2 deg^2]

Wide and Deep

8.4

8.2

100

8

93.5

6
53.2
37.7
22.9
17.3

10
8.2

7.4

4

4.0

Aperture [m]Etandue = FoV x mirror area

3.6
10.1

2
1.8
1.4

1.2

1.1

1.0

すばる望遠鏡/HSCを用いた重力波対応天体の探査

)
R

O

SC
ST

(V

H

F
ZT

am
D

EC

1
PS

e
o-

FH
C

To
m

J-GEM collabo.

LS

Sk

yM

ap

Si
lla
La
Takayuki OHGAMI

T

0

pe
r

1

18

Multi-messenger Astrophysics
Role of Subaru/HSC

Subaru / Hyper Suprime-Cam
Diameter : 8.2m
FoV : 1.5deg in diameter(1.77deg 2 )Because Subaru telescope has one of the most powerful cameras in
the world, Hyper Suprime-Cam (HSC), it has very important role forthe transient survey. We had qualification to use for a total of 9nights in the last year (4.5 nights ToO in each semesters; S19A-009
and S19B-013, PI M. Yoshida).
Takayuki OHGAMI

すばる望遠鏡/HSCを用いた重力波対応天体の探査

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GW170817
Discovery of op5cal
counterpart for the GW event.

GW170817
The first identification of a EM counterpart
EM対応天体 (SSS17a/AT2017gfo) の発見

This event has been classified as BNS.
The localization with 3 detectors was
as narrow as about 28 deg2 for a 90%
credible region and the distance wasabout 40 Mpc.
28-4

Arcavi, I., McCully, C., Hosseinzadeh, G., et al. 2017, Astrophys. J., 848, L33
Coulter, D. A., Foley, R. J., Kilpatrick, C. D., et al. 2017, Science, 358, 1556

Localization of GW170817

D ́ ıaz, M. C., Macri, L. M., Lambas, D. G., et al. 2017, Astrophys. J., 848, L29
Evans, P. A., Cenko, S. B., Kennea, J. A., et al. 2017, Science, 358, 156
Lipunov, V. M., Gorbovskoy, E., Kornilov, V. G., et al. 2017, ApJL, 850, L1
Soares-Santos, M., Holz, D. E., Annis, J., et al. 2017, Astrophys. J., 848, L16
Tanvir, N. R., Levan, A. J., Gonz ́ alez-Ferna ́ ndez, C., et al. 2017, Astrophys. J., 848, L27

Publications of the Astronomi

Tominaga, N., Tanaka, M., Morokuma, T., et al. 2018, Publ. Astron. Soc. Jap., 70, 28
Valenti, S., Sand, D. J., Yang, S., et al. 2017, ApJL, 848, L24

The Astrophysical Journal Letters, 850:L1 (9pp), 2017 November 20

Lipunov et al.

Tominaga+ 2018

Lipunov+ 2017

Fig. 1. Pointing map for GW170817 overlaid on the probability map3
(Abbott et al. 2017d). The white contour represents the 90% credible
region. Circles represent the field-of-view of HSC; their colors changing
Table 2
すばる望遠鏡/HSCを用いた重力波対応天体の探査
Possible Kilonova Brightness
with an order of observation. Observations have been carried out from

Figure 4. MASTER-composed discovery image started 2017 August 17 at 23:59:54 UT. We used color B, R, I, W ﬁlters, MASTER-OAFA, and MASTER-SAAO
images. The kilonova position is marked by white lines on the left part of composed image. The right (large) image is the MASTER main telescope’s usual FOV.

Takayuki OHGAMI•Localization: 28 sq. deg

with a diameter offrom 18.3 mag to 2
(figure 3 and table
mainly determined
are typically shallo
particular, the dept
August 19 are quite sof detection by a ra
cial point sources w
figure 4). The magni
in time. The large diAugust 19 causes th
on the PSF magnitu
5σ limiting magnitu
completeness magni
As the detected s21

GW170817
Search for an optical counterpart (Tominaga+)
Observations of the optical counterpart (Utsumi+)• Follow-up observation‣ Subaru/HSC‣ MOA-II‣ B&C‣ IRSF

Tominaga+18

LIGO+17

Takayuki OHGAMI‣ 28.9 deg2 corresponding to the 66%
credible region‣ z = 21.3 mag‣ 4 epochs Aug 18, 19, 25 and 27 2017

すばる望遠鏡/HSCを用いた重力波対応天体の探査

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GW170817
Candidate screening

After image subtraction,other time fluctuation
objects also remain (e.g. SN,
GRB).

J-GEM17btc
We have identified only one
object as GW source after
this screening. The key toidentification was thelocation in 3D skymap.
Takayuki OHGAMI

すばる望遠鏡/HSCを用いた重力波対応天体の探査

Tominaga+18

HSC z
IRSF HIRSF Ks
23

GW170817
Probability in the 3D skymap: mean distance to GW170817: LF of galaxies at a rest wavelength λ: abs. mag. of a galaxy with mj at dist. of D
: rest wavelength of λj with a dist. of D
: surface area at a dist. of D
The associated extended objects such as host galaxies have g, r, i, z or ymagnitudes in Pan-STARRS1 catalog. Integrating the luminosity function
with respect to volume, we obtain the probability. As the results ofcalculation, only J-GEM17btc showed high probability of over 60%,
other candidates showed lower than 1%.

Takayuki OHGAMI

すばる望遠鏡/HSCを用いた重力波対応天体の探査

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GW170817
Light curve of J-GEM17btc

Tominaga+18

4

Publications of the Astronomical Society of Japan, (2014), Vol. 00, No. 0

Fig. 7. Stacked and difference-17 z-band images of J-GEM17btc (a.k.a. SSS17a/DLT17ck) associated-17with NGC 4993 located in the 3D skymap of GW170817.
2
g/V
g/V
The archival HST ACS image is also
The (Yelengthsof ticks are 11 arcsec and the figure size is 56 M
× 56
arcsec. (Ye = 0.25)
M = shown.
0.03 Msun= 0.10-0.40)= 0.03
Msun
-16

r/R
i
z
J
objects
H
K

-16

r/R
i
z
J
OnHthe other
K

Absolute magnitude

Absolute magnitude

GEM17btc is described in the next subsection.
We further exclude sources associated with PS1-15-15282 sources do not have distance measurement
hand, the otherthat is firmly located outsideof the 3D skymap derived fromin the GLADE catalog or NED. After the catalog matching, four
the GW observations (LALInference v2.fits.gz; Abbott et al.
-14-14of the authors remove bogus and high proper motion stars by
2017c), adopting the GLADE v2 catalog and NASA/IPAC
visual inspection (Figure 6). The number of final candidates,
Extragalactic Database (NED)4 . While we primarily employ the-13-13that may be related to GW170817, is 60 (Table 5). We note that
distance in the GLADE catalog, we replace it with the redshift58 candidates -12
are located at the center of extended PS1 objects
independent distance in
NED if the associated PS1 objects or-12and that some of them could be active galactic nuclei (AGN) or
one of a galaxy pair containing the associated PS1 objects
indistinguishable
have information (Tully-11 1988; Willick et al. 1997; Freedman-11 residuals resulting from different instrumental Tanaka+17
0
5
10
15
0
5
10
15
signatures
between
PS1
and
HSC,
but
we
conservatively
hold
et al. 2001; Theureau et al. 2007; SorceDays
et al.
2014;
Springob
after GW170817
Days after GW170817
them as candidates.
et al. 2014), and with the redshift-dependent distance in NED
Fig.
2. 2000)
Opticalifand
near-infrared
light curvesof SSS17aincomparedwith kilonova models with (left) Ye = 0.10 − 0.40 and (right) Ye = 0.25. The optical and(Mouldet al.
no distanceinformation
is available
theTakayuki
OHGAMI
すばる望遠鏡/HSCを用いた重力波対応天体の探査
25
near-infrared data are taken from Utsumi et al. (2017). For the observed data, the line of sight extinction of E( B − V ) = 0.1 mag has been corrected. All theIn O3
S190510g
S191216ap
S200224ca

Multi-messenger Astrophysics
Observing runs (O1 〜 O5)

GW170817

we are here

https://wiki.gw-astronomy.org/OpenLVEM/Telecon20190815

Figure 2: The planned sensitivity
evolution and observing runs of the aLIGO, AdV and
すばる望遠鏡/HSCを用いた重力波対応天体の探査
27

Takayuki OHGAMI

Multi-messenger Astrophysics
GW detection in O3
検出数：56• BBH : 37
• Has NS : 11
- BNS : 6
- NSBH : 5• MassGap : 4• Burst : 1• Terrestrial : 3

2019

Takayuki OHGAMI

2020

すばる望遠鏡/HSCを用いた重力波対応天体の探査28

S190510g
O3での最初のHSCを使用した
follow-up 観測S190510g
Time series‣ Preliminary alert : 13:03 May 10, 2019 (JST) 268 Mpc‣ Initial alert : 14:24 May 10, 2019 (JST)‣ HSC observation start : 14:46 May 10, 2019 (JST)‣ Update Alert : 19:23 May, 10, 2019 (JST)- GCN 24450 “LIGO/Virgo S190510g: HSC Y-band follow-up observation”
We have started the observation with HSC at about 1.7 hour after the firstalert and the observation was carried out smoothly. However, a highprobability region we aimed has disappeared on an updated skymap.
updateTakayuki OHGAMI

すばる望遠鏡/HSCを用いた重力波対応天体の探査30

S190510g
Survey pointings with Subaru/HSC

12%

1.2%

The 90% contour and our survey pointings. We have aimed 12% credible region
on the basis of the initial skymap. The value of probability have become 1/10 on
the updated skymap.
Takayuki OHGAMI

すばる望遠鏡/HSCを用いた重力波対応天体の探査

31

S190510g
Survey pointings with Subaru/HSC• Obs. start : 2019-05-10 05:46:27 (UTC)• Filter : Y-band• Pointings : 120• Obs. Area : 118.8 deg2
• Exp. Time : 30 sec × 2• Lim. Mag. : 22.30 mag

Takayuki OHGAMI

すばる望遠鏡/HSCを用いた重力波対応天体の探査

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S190510g
Methods to find

Reference images
Blue : HSC SSP‣ Area = Obs. ∩ Ref. = 25.9 deg2
‣ Prob. = 0.25%
Green : PS1

深いリファレンスが十分でないので、観測領域を２つに分けて別々に突発天体を探査• 領域１(HSC-SSPのリファレンスがある)：Image subtraction• 領域２(HSC-SSPのリファレンスがない)：PS1カタログとのマッチング

Takayuki OHGAMI

すばる望遠鏡/HSCを用いた重力波対応天体の探査

33

Ref (PS1-y)

S190510g

New (HSC-Y)

Ref (PS1-y)!"#$%&'(New (HSC-Y)!"#$%&'-!"#$%&')!"#$%&'.

領域１

Image subtraction:
Useful to search !"#$%&'*
for transient
objects embedded in host galaxies.

!"#$%&'+!"#$%&('!"#$%&((

Detection criteria★ To remove bogus and cosmic rays

example of bogus!"#$%&',• Detected at least twice on May 10
erage of the HSC-SSP reference images. Blue area shows the• Signal-to-noise ratio > 5σ
HSC-SSP Y -band images we used. Red-filled circles represent•tion pointings.Elongation > 0.65 of point spread function (PSF)• FWHM 0.7-1.3 of PSF•

Residual after PSF subtraction < 3σ Fig. 6. Examples of the final candidates in the fi★ To exclude minor
Sourcesplanets•!"#$%&()

Detected twice664477
at least 1h apart

Takayuki
OHGAMId point
sourceMatcherence images; reference images in PS1-y ban
images with HSC (New).

No match
すばる望遠鏡/HSCを用いた重力波対応天体の探査

34

S190510g
criteria
Publications of the Astronomical 領域１：Additional
Society of Japan, (2018),
Vol. 00, No. 0
After Image subtraction+ detection criteria

Matched point
source in PS1
catalog (< 1”)

Match
228

Sources1000

既知の星を除去

No match772

3.2 Selection in fie
images母銀河からのNext, we examine th
距離で分類
ence images. We con
single exposure imag
Center of extended
Off-center
No close objects
Associated withextended object
object (θsep < 1”)(1” < θsep < 15’’)(θsep > 15”)
3次元スカイマップのscribedin Section 3.1
in PS1 catalog
369
113
290
中か外かで分類
transientsin the sin
Location
InsideOutsideInsideOutsideNo Info
No Info
P3Dの計算in 3D skymap
Weperform a forced(>50%)(<50%)(>50%)(<50%)
1
12
(P3D)
12
356
1
100
images with the hsc
criteria: (i) extende
Visual inspection
1
73
0
0
6
0
3
object) and (ii) dete
最後は目で見て確認
Fig. 2. Flowchart of the candidate screening and the classification process
1 hour. Additionallyfor the objects in the difference images.83個の候補
Numbers in each boxes represent< 21.3 mag for mat
the number of remaining objects at each step. Thick boxes indicate final
log, which correspon
candidates after the visual inspection.
Takayuki OHGAMI
すばる望遠鏡/HSCを用いた重力波対応天体の探査
35 surPS1 3π steradianS190510g
領域１：Example of candidates

Publications of the Astronomical Society of Japan, (2018), Vol. 00, No. 0

6
Ref (SSP)

New

Diﬀ/01

Ref(SSP)
203456678/01

New
203456678
9:33

Diﬀ
9:33
/01

Ref
(SSP)
203456678/01

New
203456678
9:33

Diﬀ
9:33

Ref (SSP)

New

Diﬀ

!"#$%&'(!"#$%&'(!"#$%&',!"#$%&',!"#$%&(+!"#$%&(+!"#$%&+(!"#$%&+(!"#$%&')!"#$%&')!"#$%&'-!"#$%&'-!"#$%&(-!"#$%&(-!"#$%&,+!"#$%&,+!"#$%&'*!"#$%&'*!"#$%&('!"#$%&('!"#$%&.(!"#$%&.(!"#$%&-)!"#$%&-)!"#$%&'+!"#$%&'+!"#$%&((!"#$%&((!"#$%&*'!"#$%&*'!"#$%&;(!"#$%&;(

20′′!!× 20′′!!

Fig. 3. Examples of the final candidates obtained in the fields with HSC-SSP reference images with the image subtraction; HSC-SSP reference images (Ref),
our observation images (New) and difference images (Diff).

3次元スカイマップの内側にある確率が高い

その他の天体は3次元スカイマップの外側(65%)が、AGNである可能性が大きい。

Ref (PS1-y)Takayuki OHGAMI

または母銀河の等級が不明
New (HSC-Y)!"#$%&'(New (HSC-Y)!"#$%&'-!"#$%&')!"#$%&'.

すばる望遠鏡/HSCを用いた重力波対応天体の探査

Ref (PS1-y)

Ref (PS1-y)

New (HSC-Y)!"#$%&)-!"#$%&/'

36

Ref (PS1-y)

S190510g

New (HSC-Y)

Ref (PS1-y)!"#$%&'(New (HSC-Y)!"#$%&'-!"#$%&')!"#$%&'.

領域２

Catalog matching:
Useful to search !"#$%&'*
for transient
objects embedded in host galaxies.

!"#$%&'+!"#$%&('!"#$%&((

Detection criteria★ To remove extended objects and cosmic rays!"#$%&',!"#$%&()

erage of the HSC-SSP reference images. Blue area shows the• extendedness = 0 (i.e. point-like object)
HSC-SSP Y -band images we used. Red-filled circles representtion pointings.★

To exclude minor planets•

Detected twice at least 1h apartFig. 6. Examples of the final candidates in the fi
erence images; reference images in PS1-y ban
images with HSC (New).

★ To matching objects with PS1 catalog

Takayuki
OHGAMId point
source•Sourcesmag < 21.3
664477Match

No match
すばる望遠鏡/HSCを用いた重力波対応天体の探査

37

Fig. 4. Coverage of the HSC-SSP reference images. Blue area shows the
footprint of HSC-SSP Y -band images we used. Red-filled circles represent
our observation pointings.

S190510g

領域２：Catalog matching
Sources
664477After detection criteria
Match647557No match
16920

Associated withextended object
in PS1 catalog(θsep < 15”)

No close
objects
6644

Associated10276

Center ofextended object(θsep < 1”)Center6843

Off-center
3433

Matched point source
in PS1 catalog (< 1”)

Locationin 3D skymap(P3D)

Visual inspection

40

Inside(>50%)
159

Outside(<50%)
2842

No
information
432

2

7

1

Fig. 6. Examples of the final ca
erence images; reference imag
images with HSC (New).
既知の星を除去

Fig. 5. Flowchart of the candidate screening and classification process forthe selection from the single-exposure images
in the fields without HSC-SSP
50個の候補reference images.
Takayuki OHGAMI

すばる望遠鏡/HSCを用いた重力波対応天体の探査

母銀河からの4距離で分類Discussion

4.1 Contamination fro
銀河中心は判別困難なので無視
These
candidates inclu
event such as supernov
3次元スカイマップの
determine their nature
中か外かで分類
servations. Thus, we c
P3Dの計算number of SN detection
from them. Here, we ad
troduced in Niino et al.
estimated by summing u
最後は目で見て確認
magnitudes correspondi
redshift weighted with c
38SN
We assume Type-Ia

20′′!!× 20′′!!

S190510g

ained in the fields with HSC-SSP reference images with the image subtraction; HSC-SSP reference images (Ref),e images (Diff).

領域２：Catalog matching
Ref (PS1-y)

New (HSC-Y)

Ref (PS1-y)

Ref (PS1-y)

New (HSC-Y)!"#$%&'(New (HSC-Y)!"#$%&'-!"#$%&')!"#$%&'.

!"#$%&/'!"#$%&'*!"#$%&('!"#$%&/-!"#$%&'+!"#$%&((!"#$%&*-!"#$%&',!"#$%&()!"#$%&*.

!"#$%&)-

3次元スカイマップの内側にある確率が高い。
• Cand-B01 : 85%• Cand-B02 : 73%

e images. Blue area shows theed. Red-filled circles represent
20′′ × 20′′

Takayuki OHGAMI

Fig. 6. Examples of the final candidates in the fields without HSC-SSP ref-39
すばる望遠鏡/HSCを用いた重力波対応天体の探査

S190510g
Contamination from supernovae

領域１(Image subtrac5on)

領域２(Catalog matching)

Takayuki OHGAMI

すばる望遠鏡/HSCを用いた重力波対応天体の探査40

S190510g
GROWTH team : DECam

Draft version July 24, 2019
Typeset using LATEX twocolumn style in AASTeX62

DECam Follow-up of S190510g

arXiv:1906.00806v2 [astro-ph.HE] 22 Jul 2019

GROWTH on S190510g: DECam Observation Planning and Follow-Up of a Distant Binary Neutron Star Merger
Candidate
Igor Andreoni1 and Daniel A. Goldstein1, ⇤these authors contributed equally to this work
Shreya Anand,1 Michael W. Coughlin,1 Leo P. Singer,2, 3 Tomás Ahumada,4 Michael Medford,5, 6
Erik C. Kool,7 Sara Webb,8, 9 Mattia Bulla,10 Joshua S. Bloom,6, 11 Mansi M. Kasliwal,1 Peter E. Nugent,5, 6
Ashot Bagdasaryan,1 Jennifer Barnes,12, † David O. Cook,13 Jeff Cooke,14, 8 Dmitry A. Duev,1U. Christoffer Fremling,1 Pradip Gatkine,4 V. Zach Golkhou,15, 16, ‡ Albert K. H. Kong,17 Ashish Mahabal,1, 18
Jorge Martı́nez-Palomera,6 Duo Tao,1 and Keming Zhang ( Ô ) 6
1 Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125, USA
2 Astrophysics Science Division, NASA Goddard Space Flight Center, MC 661, Greenbelt, MD 20771, USA
3 Joint Space-Science Institute, University of Maryland, College Park, MD 20742, USA
4 Department of Astronomy, University of Maryland, College Park, MD 20742, USA
5 Computational Science Department, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 50B-4206, Berkeley, CA 94720,

USA
6 Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA
7 The Oskar Klein Centre & Department of Astronomy, Stockholm University, AlbaNova, SE-106 91 Stockholm, Sweden
8 Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, VIC, 3122, Australia
9 ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav), Australia
10 The Oskar Klein Centre, Department of Physics, Stockholm University, AlbaNova, SE-106 91 Stockholm, Sweden
11 Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 50B-4206, Berkeley, CA 94720, USA
12 Columbia Astrophysics Laboratory, Columbia University, New York, NY 10032, USA
13 IPAC, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125, USA
14 Australian Research Council Centre of Excellence for Gravitational Wave Discovery (OzGrav), Hawthorn, VIC, 3122, Australia
15 DIRAC Institute, Department of Astronomy, University of Washington, 3910 15th Avenue NE, Seattle, WA 98195, USA
16 The eScience Institute, University of Washington, Seattle, WA 98195, USA
17 Institute of Astronomy, National Tsing Hua University, Hsinchu 30013, Taiwan
18 Center for Data Driven Discovery, California Institute of Technology, Pasadena, CA 91125, USA

ABSTRACTThe first two months of the third Advanced LIGO and Virgo observing run (2019 April–May) showedthat distant gravitational wave (GW) events can now be readily detected. Three candidate mergers
containing neutron stars (NS) were reported in a span of 15 days, all likely located more than 100 Mpc
away. However, distant events such as the three new NS mergers are likely to be coarsely localized,
which highlights the importance of facilities and scheduling systems that enable deep observations
over hundreds to thousands of square degrees to detect the electromagnetic counterparts. On 201905-10 02:59:39.292 UT the GW candidate S190510g was discovered and initially classified as a BNS
merger with 98% probability. The GW event was localized within an area of 3462 deg2 , later refined
to 1166 deg2 (90%) at a distance of 227 ± 92 Mpc. We triggered Target of Opportunity observations
with the Dark Energy Camera (DECam), a wide-field optical imager mounted at the prime focus of
the 4m Blanco Telescope at CTIO in Chile. This Letter describes our DECam observations and ourreal-time analysis results, focusing in particular on the design and implementation of the observing
strategy. Within 24 hours of the merger time, we observed 65% of the total enclosed probabilityof the final skymap with an observing efficiency of 94%. We identified and publicly announced 13
candidate counterparts. S190510g was re-classified 1.7 days after the merger, after our observations
were completed, with a “binary neutron star merger” probability reduced from 98% to 42% in favorof a “terrestrial” classification.
andreoni@caltech.edu

Takayuki OHGAMI

Figure 1. Preliminary BAYESTAR (top, The LIGO Scientific Collaboration and the Virgo Collaboration 2019a) and refi
LALInference (bottom, The LIGO Scientific Collaboration and the Virgo Collaboration 2019c) localization probability skymof the GW event S190510g. Circles show the DECam coverage, approximating the DECam FoV using a radius of 0.9 deg2 .

すばる望遠鏡/HSCを用いた重力波対応天体の探査

41

S191216ap
localiza5onが良い
MassGap → BBH

S191216ap
property

Takayuki OHGAMI

すばる望遠鏡/HSCを用いた重力波対応天体の探査

43

S191216ap
Follow-up observation• Filter : z-band• Obs. Area : 2.3 deg2
• Lim. Mag. : 25.2
HAWC (gcn:26507)の候補天体3つを入れて１視野分

Takayuki OHGAMI

すばる望遠鏡/HSCを用いた重力波対応天体の探査

44

S200224ca
Localiza5onが非常に狭いという好条件
ただBBH。。。

S200224ca
property

Takayuki OHGAMI

すばる望遠鏡/HSCを用いた重力波対応天体の探査

46

S200224ca
Publications of the Astronomical Society of Japan, (2018), Vol. 00, No. 0
Follow-up
observation

UTC.

83.4%

80.8%

this event, the Japanese collaboration fortional wave ElectroMagnetic follow-up (J-GEM)• Filter : z-band, r2-band
formed optical observations to survey the EM• Pointings: 60 25, 28 and Mar. 23,
part of GW
source on Feb.
2
• Obs.
Area : 57.8
deg
TC with hyper
Suprime-Cam(HSC;
Miyazaki
et al.
which is a wide-field imager installed on the prime
the Subaru telescope, in HSC-r2 and HSC-z band.
d of view (FoV) of 1.77 deg2 is the largest among
ently existing 8 m-class telescopes, and it is thefficient instrument for the optical survey. We chose
Fig. 1. Preliminary (left, BAYESTAR; The LIGO Scientific Collaboration andthe Virgo Collaboration 2020a) and refined (right, LALInference; The Jey pointings that cover 57.8 deg2 corresponding
GEM collaboration 2020) localization probability skymaps of the S200224ca.
2/25
2/28
3/23
3.4% credible regionDate
in the(UTC)BAYESTAR skymap
Contour line and red-filled circles show the 90% credible regions and ourin the LALInference skymap). The exposure
survey pointings with Subaru/HSC, respectively. We have conducted theobservation on the basis of the BAYESTAR map.
r each pointings are 30 seconds and we revisited
35 sec × 2 (z)
Exp.
TIme
30 sec × 2
30 sec × 2
intings about one hourapartin each observation
50 sec or 70 sec (r2)
The first exposure was started at about 12.3
had been installed before the starting of our observation.
ter the GW detection (The J-GEM collaboration
23.6 (z) The first
23.2(z) in first epoch
23.8
exposurehas (z)been started at Feb.

Lim. Mag.

24.6 (r2)25.5 (r2)
25, 10:43:07
UTC, which corresponds
to about 12.3 hours
his paper, we report the detail of the observaafter the GW detection. Because overlaps between the obh Subaru/HSC and GTC, the classification of observed images exist when NSIDE = 64, there are the areas
解析中。。。
ources and the list of final candidates. Throughout
observed three times or more. Therefore, the overlap areas
er, we correct the Galactic reddening (Schlafly &may be observed repeatedly in less time than one hour.
Takayuki OHGAMI
すばる望遠鏡/HSCを用いた重力波対応天体の探査
1

25.3 (r2)47

Future prospects
S190519gでの観測を踏まえた
O4以降のObserving runの展望Future prospects
8Comparison with kilonova model

5σ depth of PS1 catalog( PS1-y )Difference images( 30sec, HSC-Y )Publications

radiative transfer model(Banerjee+2020)
Mej = 0.05M⊙
Ye = 0.30 − 0.40

30sec x 2 exposures( HSC-z )30sec x 2 exposures( HSC-i 2 )Takayuki OHGAMI

すばる望遠鏡/HSCを用いた重力波対応天体の探査

49 9.
Fig.

Future prospects

30sec x 2 exposures( HSC-i 2 )8Comparison with kilonova model

5σ depth of PS1 catalog( PS1-y )Difference images( 30sec, HSC-Y )Publications

radiative transfer model(Banerjee+2020)
Mej = 0.05M⊙
Ye = 0.30 − 0.40

30sec x 2 exposures( HSC-z )30sec x 2 exposures( HSC-i 2 )Fig. 8. Multi-color (i-, z- and Y -band) light curve of the kilonova model withan ejecta mass Mej = 0.05M! and an electron fraction Ye = 0.30 − 0.40
(The i- and z-band cases are shown in Banerjee et al. (2020)), under an as-

Takayuki OHGAMI

すばる望遠鏡/HSCを用いた重力波対応天体の探査

50 9.
Fig.

Future prospects

blications of the Astronomical Society of Japan, (2018), Vol. 00, No. 0
Comparison with detecter’s range
O1

O2

O3

O4

O5

すばる望遠鏡/HSCを用いた重力波対応天体の探査
Fig. 9. BNS range during
each observing run shown in Abbott et al. 2018. 51

Takayuki OHGAMI

Future prospects
Expected number of BNS events★ BNS-GW event rate (Abbott et al. 2019)•110 〜 3840 Gpc -3 yr -2★ LIGOの感度で検出されるBNSイベントの期待数•

4.9 〜 172.4 (O4)•

41.4 〜 1445.1 (O5)

★ HSCでfollow-up観測できそうなイベント数✓ 全イベントの9% (Elevation>20°, ToOできる確率30%)

Takayuki OHGAMI•

0.4 〜 15.2 (O4)•

3.7 〜 127.7 (O5)

すばる望遠鏡/HSCを用いた重力波対応天体の探査

52

Conclusion★ GW170817 (初のBNS-GWイベント)•

EM対応天体を発見し、kilonovaを伴うことを発見★ O3では56イベントがLIGO&Virgoにより検出•

BBH 37, BNS 6, NSBH 5, MassGap 4, Burst 1, Terrestrial 3★ ３つのイベントでSubaru/HSCのfollow-up観測

S190510g : BNS → Terrestrial• S191216ap : MassGap → BBH• S200224ca : BBH➡ EMの対応天体は見つからなかった•➡ 他のイベントでも発見報告はない★ O4以降の展望•

S190510gでの観測を踏まえ、数回から百回程度のイベントを
follow-upできそうTypical localization area
Typical localization area

Takayuki OHGAMI

すばる望遠鏡/HSCを用いた重力波対応天体の探査

54

GW170817

GW170817
GW170817

Abbott +2017

Time series• LIGO/Virgo detected the GW on• LIGO/Virgo detected the GW on
17 Aug. 2017.
17 Aug. 2017.
• GW170817 was identiﬁed as the• GW170817 was identiﬁed as the
EM counterpart in the entire
EM counterpart in the entire
wavelength.
wavelength.
•• Detected
in allall wavelengths
wavelengths
Detected in•• Gamma-ray
Gamma-ray•• X-ray
X-ray•• Opticaland NIR
NIR
Optical and•• Radio
Radio
•• No
in IceCube
IceCubeNo Detection
Detection in
neutrino.
neutrino.

Takayuki OHGAMI

すばる望遠鏡/HSCを用いた重力波対応天体の探査

55

GW170817
Light curves in Optical and NIR
Light curves in Optical and NIR
101-5
101-3

NIR : ~ 10 days

Publications

Publications of the Astronomical Society of Japan (2017), Vol. 69, No. 6

2 J-GEM Observations

A broad geometrical distribution of observatories was
required to observe SSS17a because it was visible fora limited amount of time after sunset in the northernhemisphere. J-GEM facilities were suitable for observing
this target because they are distributed all over the Earthin terms of the longitude, which included the southern
Publications of the Astronomical Societyhemisphereof Japan (2017),
Vol.
69,visibility
No. 6
where
the
was better. We used thefollowing facilities to perform follow-up optical obserFig. 1. Three-color composite images of 2
SSS17ausing Observationsz-, H-, and Ks vations of GW170817: 8.2 m Subaru/HSC (Miyazaki
J-GEM
band images. The size of the image is 56!! × 56!! . From left to right, theet al. 2012) and MOIRCS (Suzuki et al. 2008) at Mauna
A takenbroad
geometrical
distribution of observatories was
combined images created from the images
betweent = 1.17 andKea in the United States; 2.0 m Nayuta/NIC (near-infrared
1.70 d and between t = 7.17 and 7.70 d arerequired
shown. to observe SSS17a because it was visible forimager) at the Nishi-Harima Astronomical Observatory ina limited amount of time after sunset in the northern
Japan; 1.8 m MOA-II/MOA-cam3 (Sako et al. 2008; Sumi
hemisphere. J-GEM facilities were suitable for observing
et al. 2016) and the 61 cm Boller & Chivens telescope
this target because they are distributed all over the Earth(B&C)/Tripol5 at the Mt. John Observatory in New
in terms of the longitude, which included the southern
Zealand; 1.5 m Kanata/HONIR (Akitaya et al. 2014) at theelements in the Universe as emission
properties
hemisphere
where reflect
the visibility was better. We used theHigashi-Hiroshima Astronomical Observatory in Japan;
the ejected mass and abundancesof r-processelements
following
facilities
to perform follow-up optical obser1.4 m IRSF/SIRIUS (Nagayama et al. 2003) at the Southosite imagesof SSS17a
H-, andBarnes
Ks (e.g.,
Kasen using
et al.z-,2013;&
Kasenof2013;
Tanaka 8.2 m Subaru/HSC (Miyazaki
vations
GW170817:
African Astronomical Observatory; and 50 cm MITSuME!! × 56!! . From left to right, thethe image&is 56
Hotokezaka
2013; Tanaka etet al.
Metzger& (Suzuki et al. 2008) at Maunaal. 2014;
2012) and
MOIRCS
Utsumi+ 2017
(Kotani et al. 2005) at the Akeno Observatory in Japan.
from the images taken between t = 1.17 andFernández
2014;
Kasen
et
al.
2015).
Kea in the United States; 2.0 m Nayuta/NIC (near-infrared
17 and 7.70 d are shown.
We reduced all the raw images obtained using the aforeOn 2017 August 17, 12:41:04imager)
GMT, theLIGO(Laserat theNishi-Harima
Astronomical Observatory in
Takayuki OHGAMI
すばる望遠鏡/HSCを用いた重力波対応天体の探査
mentioned
instruments
in aofstandard
manner.
Aftercolorelim- is 56
Fig. 2. Light curves
and colorevolution
SSS17a.
The face

Optical : < 5 days

S200224ca
Completeness of Image subtraction

02-25

Takayuki OHGAMI

02-28

すばる望遠鏡/HSCを用いた重力波対応天体の探査

57

2020-02-28

r2
24.61
25.13
23.98
z
23.21
23.76
22.54
2020-03-23
r2
25.53
26.25
24.64
Limiting magnitudeof subtracted
images
z
23.83
24.64
22.85

HSC-r2

S200224ca

HSC-z

Takayuki Fig.
OHGAMI
2. Map (top) andすばる望遠鏡/HSCを用いた重力波対応天体の探査
histogram (bottom) of the 5σ limiting magnitudes inFig. 3first (tpleten58