CTAとマルチメッセンジャー観測で明らかにする
ガンマ線バーストとその他トランジエント天体	

井上進（東大宇宙線研）	

井上芳幸、格和純、山崎了、山本常夏、村瀬孔太、	

当真賢二、浅野勝晃、井岡邦仁、吉越貴紀、手嶋政廣、	Jim Hinton、Rhaana Starling、Valerie Connaughton、	Paul O’Brien、Jonathan Granot、ほか�CTA Consortium	

スペクトル	

光度曲線	

検出率	

short GRB	その他	

Astroparticle Physics special issue	

著者23人中11人が日本人�ガンマ線バースト (GRB)	 宇宙最大・最強・最速の爆発	

宇宙最遠方級の天体	

long GRB (T>~2s): 	

大質量星崩壊時に超相対論的速度ジェット発生	

ジェット内部から即時放射＋外部衝撃波から多波長残光放射	

adapted from Meszaros 01	

中心駆動天体？�ジェット形成機構？�粒子加速・放射機構？	

異なる種族 (short GRB, T~<2s) の起源？�宇宙論的進化？	

宇宙で最も謎めいた天体の一つ	

CTAによるGRB観測	

1. 10 GeVに迫るエネルギー閾値 (<<現行IACT)	

-> 宇宙背景放射光 (EBL) によるγγ吸収を受けにくい	

2. 高速指向性能：180deg/20sec for LST (MAGIC2と同等)	

-> long GRBの即時放射中に観測開始	

3. 莫大な有効面積：>104m2@30GeV (Fermiの1万倍)	

-> 圧倒的な光子統計、詳細なスペクトル・時間変動の情報	

Fermi LAT GRB 080916C�
>100	MeV�> 10 GeV photon	

>1GeV�
Fermi数発 ->	

CTA 数百-数千発！	

Abdo+ 09�

CTAによるGRB観測で目指すサイエンス	

GRBの起源�- 放射体運動速度の確実な測定（内部γγ吸収カットオフ）	

- 即時放射機構、残光の物理の解明	

�（多波長スペクトル・時間変動）	

宇宙線の起源�- 最高エネルギー宇宙線・高エネルギーν生成の兆候	�（陽子・原子核シンクトロトロン、カスケード成分…）	

観測的宇宙論�- 遠方宇宙背景放射の精査（γγ吸収カットオフ）	

- 銀河間弱磁場の精査（pair echo=二次ガンマ線）	

基礎物理学	

- Lorentz不変性破れ、新粒子への制限…	

GRB 080916C, z=4.3	

t0=35 sec (interval d)	

array E, exposure 20 sec	

EBL: Y. Inoue	

By Y. Inoue & S. Inoue using	D. Mazin’s simulation tool	

for the CTA collaboration	

1262	 1321	/2�
/1� 1804	/1�
439	/1�
10	/1�

total excess/bkgd	

=4836/5	

NB: array sensitivity~<200 GeV almost due to LSTs alone	GRB 080916C, z=4.3	

t0=35 sec (interval d)	

array E, exposure 20 sec	

EBL: Kneiske best fit	264	/2� 139	 293	/1�
/1�

By Y. Inoue & S. Inoue using	D. Mazin’s simulation tool	

for the CTA collaboration	

total excess/bkgd	

=701/5	

effective probe of high-z EBL:	

unique info on cosmic star formation/galaxy formation�

GRB 080916C, z=1.0	

t0=50 sec (interval f-like)	

array E, exposure 30 sec	

EBL: Franceschini	

By Y. Inoue & S. Inoue using	D. Mazin’s simulation tool	

for the CTA collaboration	

53555	

59104	

95618	

/4�/1�/2� 86269	

39413	/1�
/1�
7528	

/0�

total excess/bkgd	

=343204/9	

1516	/0�185	/0�
13	/0�

hugh photon statistics! detailed spectral variability info	

lower E threshold seems possible	

GRB 080916C, z=6.5	

t0=50 sec (interval d-like)	

array E, exposure 50 sec	

EBL: Y. Inoue	

By Y. Inoue & S. Inoue using	D. Mazin’s simulation tool	

for the CTA collaboration	

622	 661	/5�
/3� 890	/3�
198	/2�

total excess/bkgd	

=2372/15	

GRB 080916C, z=6.5	

t0=50 sec (interval d-like)	

array E, exposure 50 sec	

EBL: S. Inoue + Y. Inoue	

23	/5�

132	

46	 /2�
/2�

By Y. Inoue & S. Inoue using	D. Mazin’s simulation tool	

for the CTA collaboration	

total excess/bkgd	

=206/12	

unique info on cosmic dawn (cosmic reionization)!�

GRB 080916C, z=10	

t0=50 sec (interval d-like)	

array E, exposure 50 sec	

EBL: Y. Inoue	

158	 174	/7�
/2� 225	

42	/3�
/2�

By Y. Inoue & S. Inoue using	D. Mazin’s simulation tool	

for the CTA collaboration	

total excess/bkgd	

=602/14	GRB 080916C
Fermi results	

Abdo+ 09�

>100	

MeV�
>1GeV�

GRB 080916C
Fermi results
+CTA simulation	

- normalize to GBM	light curve	

- extrapolate	

GBM+LAT spectra	with Y. Inoue EBL 	- simulate with	

D. Mazin’s tool	

T. Yamamoto, Y. Inoue,	

R. Yamazaki, SI�

Abdo+ 09�

>100	

MeV�
>1GeV�
>30GeV�GRB 080916C
Fermi results
+CTA simulation	

Abdo+ 09�

>30GeV, 0.5 sec bin�- normalize to GBM	light curve	

- extrapolate	

GBM+LAT spectra	with Y. Inoue EBL 	- simulate with	

D. Mazin’s tool	

T. Yamamoto, Y. Inoue,	

R. Yamazaki, SI�

>100	

MeV�
>1GeV�
>30GeV�GRB 080916C
Fermi results
+CTA simulation	

Abdo+ 09�

>30GeV, 0.5 sec bin�- normalize to GBM	light curve	

- extrapolate	

GBM+LAT spectra	with Y. Inoue EBL 	- simulate with	

D. Mazin’s tool	

T. Yamamoto, Y. Inoue,	

R. Yamazaki, SI�

>100	

MeV�
>1GeV�
>30GeV�GRB 080916C
Fermi results
+CTA simulation	

Abdo+ 09�

>30GeV, 0.1 sec bin�- normalize to GBM	light curve	

- extrapolate	

GBM+LAT spectra	with Y. Inoue EBL 	- simulate with	

D. Mazin’s tool	

T. Yamamoto, Y. Inoue,	

R. Yamazaki, SI�

>100	

MeV�
>1GeV�
>30GeV�GRB 080916C
Fermi results
+CTA simulation	

- normalize to GBM	light curve	

- extrapolate	

GBM+LAT spectra	with Y. Inoue EBL 	- simulate with	

D. Mazin’s tool	

T. Yamamoto, Y. Inoue,	

R. Yamazaki, SI�

Abdo+ 09�

0.5 sec bin�

>100	

MeV�
>1GeV�
>30GeV�science from detailed light curves	

1. extract physics from E-dependent variability	- decipher UHECR signatures from variability timescales 	- distinguish intrinsic vs EBL cutoffs	

…�
2. devise GRB-optimized analysis methods utilizing timing	signatures	

-> lower E threshold + increase low-E sensitivity�

from K. Asano	GRB detection rate	

Kakuwa, Yamazaki, Toma, Murase, SI+�alert rate	 GRB facility	

×� sky coverage	 0.25x2	 ×� duty cycle	 0.1(->0.15)	

spectrum,T,luminosity,
zdist.	

90×� slewing+detection efficiency	

EBL attenuation	

↓�
prompt: 0.37 (T90>Tdelay=100s) x0.15-0.37 (detect)	

afterglow: 0.34-0.79 (detect)�
assume:	Fermi/GBM	 alert 50/yr (loc.< 3.5 deg) 	

z & peak L. dist. 	 Wanderman	

Band spec. extension	

& Piran 10�
Ep-Eiso corr.	

prompt: no structure, Tdur dist.	

afterglow: fν~ ν-1t-1.5	

EBL: Razzaque (z<5 only)�
array I integral sensitivity	

prompt: 0.1-0.3/yr	 x2.5 with better loc.�
afterglow: 0.7-1.6 yr 	

SVOM	 alert 80/yr x1.6 anti-solar bias 	

prompt: 0.3-0.7/yr	

afterglow: 1.7-4.0 yr 	

Swift	 alert 95/yr x 1.4 anti-solar bias x0.6 sky 	 GBM+SVOM	

prompt: 0.2-0.5/yr	

prompt: >~0.5-1/yr	

afterglow: 1.1-2.5 yr 	afterglow: >~2-6 yr 	

redshift & photon count distribution 	

photon count�
prompt�afterglow�GRB detection rate�

A. Bouvier +colleagues	more questions	- Should MSTs/SSTs also be slewed?	

When, how many, how soon and how fast? 	

- How do we deal with large GBM error circles? Offset LSTs?	

-> under study by MC group	- How much can the duty cycle be increased under moonlight?	

- How can we increase the alert rate?	

JANUS/Lobster -> GUNDAM?	

HAWC/LHAASO?	

CTA-dedicated satellite?	

- Can we detect some (short) GRBs from t=0 during	a wide-field survey mode?	

- How can we obtain redshifts for all CTA GRBs?	

On-site optical/near-IR telescope?�-> collab. with MOA?	

…	Fermi/GBM bursts with CTA	fluence�GBM localization accuracy�

from V. Connaughton�
error (deg)�

from A. Bouvier�short GRBs	 compact binary merger=GW source?�
Fermi GRB 090510�

Γbulk? emission mechanism?	

CR acceleration? LIV test? -> CTA!�

short GRBs with CTA: wide field mode?	

under study	by J. Hinton+�

short GRBs	

long GRBs from T=0	

unbiased transient search�
GRB detection rate ~<few/yr?�

short GRBs with CTA: GW alert?	

inspiral phase�

merger�

BH ringdown�

localization ~5 deg after merger �-> localize before+alert? inclination?�
Bohdan Paczynski, on discovery of microlensing by MACHO:	

“It is a real tribute to the high-energy physicists, who did know	that it cannot be done, so they did it.”�

まとめ	

CTAによるGRB観測	

- GRBは宇宙で最も謎めいた天体の一つ	

CTAによる>10 GeVガンマ線観測で新境地開拓	��大きな光子数統計�����������	- 予想検出数は年間当たりGRB数発	がGRB毎の詳細なスペクトル・時間変動データ	

- 多様なサイエンス：	

��GRBの起源、宇宙線の起源、観測的宇宙論、基礎物理学…	

- 日本がサイエンスを主導：	LST（大口径望遠鏡）チーム、MCグループと連携	

- wide field modeによるshort GRB+トランジエント探査	- 重力波アラートによるshort GRB観測？