Optical/Infrared Observations for
Gravitational Wave Astronomy- 重力波天文学と連携した光赤外観測の提案 光赤天連シンポジウム
2020年代の光赤外天文学-将来計画の再構成

Masaomi Tanaka
田中 雅臣(National Astronomical Observatory of Japan)

New astronomy with gravitational waves
2017 - Advanced LIGO (US)- Advanced VIRGO (Europe)- KAGRA (Japan)

NS-NS merger
with 200 Mpc~ 30 events/yr(~0.3-300)

KAGRA

Hotokezaka+13

spectral sensitivity (strain per root Hz)

-15

BH
-BH

-16

(10 6Mo ) at

-17-18

LISA-19

BH-B

H(z=110 6+10-20-21Mo ) at

z=1

BH-BH (10Mo) at 100 Mpc
NS-BH (10Mo) at 200 Mpc-22

NS-NS at 200 Mpc-23-24-25-6

GEO600LIGO
VIRGO
AdLIGOET

Andersson10-5-4-3-2-1
0
1
2
3gravitational-wave frequency (log10 f /1Hz)45

2 degKiso 1m Schmidt
telescope~ 200 galaxies / 4deg2(< 200 Mpc)

GW alert error box
e.g. 10 deg x 10 deg~ 5000 galaxies(< 200 Mpc)

No electromagnetic counterpart,No gravitational-wave astronomy!

2 deg

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EM signature fromNS-NSmergerspecific stellarpopulations). Because
merger counterparts

strophysical Journal, 746:48 (15pp), 2012 February 10

redicted to be faint, obtaining a spectroscopic redshift
allenging (cf. Rowlinson et al. 2010), in which caseroscopy of the host galaxy is the most promising means
taining the event redshift.
s important to distinguish two general strategies for conng EM and GW events. One approach is to search for a
signal following an EM trigger, either in real time or att-processing stage (e.g., Finn et al. 1999; Mohanty et al.
). This is particularly promising for counterparts predicted
cur in temporal coincidence with the GW chirp, such as-duration gamma-ray bursts (SGRBs). Unfortunately, mostpromising counterparts (none of which have yet been
endently identified) occur hours to months after coales.6 Thus, the predicted arrival time of the GW signal willn uncertain, in which case the additional sensitivity gained
this information is significantly reduced. For instance, if
me of merger is known only to within an uncertainty ofurs (weeks), as we will show is the case for optical (radio)
erparts, then the number of trial GW templates that mustarched is larger by a factor ∼104 –106 than if the merger
is known to within seconds, as in the case of SGRBs.
second approach, which is the primary focus of this paper,
M follow-up of GW triggers. A potential advantage in thisis that counterpart searches are restricted to the nearby
rse, as determined by the ALIGO/Virgo sensitivity range

Metzger & Berger

Jet ISM Shock (Afterglow)
Optical (hours days)
Radio (weeks years)• On-axis short GRB• Off-axis radio/optical

Ejecta ISM ShockRadio (years)

GRB(t ~ 0.1 1 s)

Kilonova

Optical (t ~ 1 day)afterglow•Radioactive emission(r-process nuclei)- kilonova- macronova- mini SNobsjMerger Ejecta
Tidal Tail & Disk Windv ~ 0.1 0.3 c

BHMetzger & Berger 2012,
Figure 1. Summary of potential electromagnetic
counterpartsof NS–NS/ApJ,746,
48
NS–BH mergers discussed in this paper, as a function of the observer angle

θobs . Following the merger a centrifugally supported disk (blue) remains aroundthe central compact object (usually a BH). Rapid accretion lasting !1 s
powers a collimated relativistic jet, which produces a short-duration gamma
ray burst (Section 2). Due to relativistic beaming, the gamma-ray emission
is restricted to observers with θobs ! θj , the half-opening angle of the jetExpected emission

Timescale

Luminosity

tpL

1 day

M
0.01M

1042 erg s 1

energydepositionenergydeposition

1/2

M
0.01M

v
0.2c
1/2

~ 20 mag at 200 Mpc

v
0.2c

1/2

1/2

0.1 cm2 g 1
1/2

1/2

0.1 cm2 g 1Li & Paczynski 98
Metzger+10

Survey with 1m-class wide-field telescopes

Numerical relativity
simulation

3D radiative transfer
simulation

Hotokezaka et al. 2013

MT & Hotokezaka 13, ApJ, in press(arXiv:1306.3742)

1. Opacity of r-process-dominated ejecta?
(κ ~ 0.1 cm2 g-1 for SNe)

2. Characteristic feature of NS merger?

As in10has a hopacity54). T
NSM-all(cm2 g-171) ha2 )-1
κ=0.1 cm g
opacityκ = 0.1
κ=1.0 cm2 g-1
that, hκ = 12 -1
the opa
κ=10 cm gκ = 10Figu
41
NSM-a10is red b(2) a h
Full simulation
opticalmaticareddersistentKasen
4010Since
110ments,
ulationDays after the merger
includeFig. 2.— Bolometric light curve of model NSM-all (black, multicuss thHigher
opacity
byfactorof100(!)
frequency simulations). It is compared with the light curves for thespectra
model
but with the grayapproximationby
of UVOIR
transferof 10
Faintersame
thanpreviously
expectedafactorafter th(κ =0.1, 1, and 10 cm2 g−1 for blue, purple, and red lines, respec(seeresult
also Kasen+13,Barnes& Kasen
all thetively). Theof multi-frequency
transferare 13)
most similar to-1

UVOIR Luminosity (erg s )42Tanaka & Hotokezaka

Log flux (Fλ) + constant

6JUB V R IH
1.5 days
5.0 days10.0 days

54
3
2
1

5000

10000

15000

20000

Wavelength (A)R spectra of model NSM-all at t = 1.5, 5.0, and 10.0 days after the merger. The spectra are almost f
are possible absorption troughs, which result from Y i, Y ii, and Lu i in our simulations. However,incompleteness of the line list in the NIR wavelengths.

- Very red SED (peak at NIR)
- Extremely broad-line (feature-less) spectra(Identification of r-process elementsdifficult)
6. seems
IMPLICATIONSFOR OBSER

1.2 + 1.5

6.1. Follow-up Observations of EMmaging of the location of GRB 130603B. The host is well resolved and displays a disturbed, late-type morphology. The location at which thedetermined from ground-based imaging) is marked as a red circle. The left-hand panel shows the higher resolution optical (F606W) image,s little sign of any emission which could be associated with the GRB. The right-hand panel is the nIR (F160W) image, and although poorer
ws evidence of a compact source coincident with the GRB location.

Radioactive emission in short GRB
2Berger, Fong, & Chornock

F IG . 1.— Images of the afterglow and host galaxy of GRB 130603B. Left: Magellan/IMACS r-band image at 8.1 hr, with the bright afterglow marked. Middle:
HST/ACS/F606W image at 9.4 days. Right: HST/WFC3/F160W image at 9.4 days. In all three panels the circle marks the position of GRB 130603B, with aradius of 10 times the rms of the astrometric match between the Magellan and HST images (1σ ≈ 34 mas). A source coincident with the GRB position is clearlyvisible in the WFC3/F160W image, with no corresponding counterpart in the ACS/F606W image.

Golenetskii et al. 2013). The spectral lags are 0.6 ± 0.7
ms (15 − 25 to 50 − 100 keV) and −2.5 ± 0.7 ms (25 − 50to 100 − 350 keV), and there is no evidence for extendedemission (Norris et al. 2013). The combination of theseproperties indicates that GRB 130603B is a short-hard burst.
Swift/X-ray Telescope (XRT) observations commenced
about 59 s afterour
the burst
and led to the identification
modelof a fading source, with a UVOT-enhanced position ofMej = 0.01 Msun
RA=11h 28m 48.15s, Dec=+17◦04" 16.9"" (1.4"" radius, 90%containment; Evans et al. 2013).
Ground-based observations starting at about 2.7 hr revealed a point source slightly offset from a galaxy
visible in Sloan Digital Sky Survey (SDSS) images(Levan et al. 2013; de Ugarte Postigo et al. 2013; Foley et al.
2013; Sánchez-Ramírez et al. 2013; Cucchiara et al. 2013a).
The point source subsequently faded away indicating that it

tainty is 34 mas (1σ). The WFC3/F160W observations reveal
a point source coincident with the afterglow position, with nocorresponding source in the ACS/F606W observation (Figure 1).
To measure the brightness of the source we use pointspread-function (PSF) photometry with the standard PSFfitting routines in the IRAF daophot package. We model
the PSF in each image using 4 bright stars to a radius of 0.85"" ,and apply the WFC3/F160W PSF to the point source using a0.15"" radius aperture and a background annulus immediately
surrounding theposition of the arXiv:
point source1306.3960
to account forBerger+13
the raised background level from the host galaxy. Using theTanvir+13
tabulated zeropoint, we obtain
mF160W = 25.8 ± 0.2 AB mag.
To determine thelimit at the corresponding
position in the(Nature,arXiv:1306.4971)
ACS/F606W observation, we use the PSF to add fake sourcesof varying magnitudes at the afterglow position with the IRAF

200Observing strategy
20ndMpcnd51015Days after the merger

At 200 Mpc

Observed magnitude

212220i bandoptical
200 Mpc
i band
1m1m

10 min5 sigma

234m

244m

25

5days
268m8m27
20051015
Days after the merger

20 Best with i band (0.8 um)
NIR ?? (~21 AB mag in NIR)
J band20

2Field of view (deg )100
101ZTFLa SillaPTF
CRTS
KISS

0.1
0.01
0.001

~ 8-10m~ 4m~ 1-2mLSSTPSDES

SDSS CFHT

Subarutypicaltypical
4m
8-10m
HST

18 19 20 21 22 23 24 25 26 27
Limiting magnitudeGW alert error box 8m LSSTe.g. 10 deg x 10 deg~ 5000 galaxies(< 200 Mpc)

3.5 deg

Pan STARRS 1.8m
3.0 deg

8m Subaru
Hyper Suprime-Cam

PTF 1m

1.5 deg

2 deg
Typical 8-10m
telescope
0.3 deg
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Big challenge
BeforeAfter(SDSS)(KISS)

BeforeAfter

KISS: Kiso Supernova Survey• Need all-sky reference image!

1 deg(with i ~ 25 mag)=> ~350 nights with Subaru/HSC... (half sky)

• Or detection of declining object?

=> Spectroscopy of <26 mag objects (=> TMT!)Toward the Dawn of GW Astronomy• GW detectors in 2017 • NS merger at < 200 Mpc• Localization ~ 100 deg
2• EM counterpart is crucial• Short GRBs are not always expected• Radioactive emission• Observing strategy• Wide field search with 22-25 mag (i band)of declining object?
• Detection(or all sky reference image with i=25 mag)
• Extremely broad line spectrum• Subaru/HSC => TMT