Gamma-ray burst physics
with MAGIC and CTA LST
Koji Noda (ICRR)
25 May 2018
ICRR seminarSelf introduction•

PhD in ICRR, Univ. Tokyo in 2010, for astro-particle neutrinophysics (Ashra experiment on Hawaii Island)•

2-yr postdoc in INFN Catania, Italy, working in a collider
experiment (LHCf), for particle shower physics•

4-yr postdoc in Max-Planck-Institutefor Physics, Munich, Germany, forVery High Energy gamma-ray astroparticle physics (MAGIC & CTA)

•1.2 yrs in IFAE, Barcelona, Spain,
as a Marie-Curie fellow, continuing
MAGIC & CTA, with GRB physics•Back to ICRR since the last Feb

Gamma-Ray Bursts (GRBs)•

Discovered in 1960’s by a military satellite:“short, fading gamma-ray emissions from Universe”•Location unknown until 1990’s:“in our Galaxy, or extra-Galactic?”••

BATSE on CGRO satellite founda uniform distribution (1992).
Extra-Galactic, probably.

BeppoSAX and its followup almost confirmed a (partial)
supernova association (GRB980425 & SN1998bw)•finally done by HETE-II et al. with GRB030329 = in 2003.

•next GRB-dedicated satellite! Swift (2004 - now)

New class of objects in the 21st century

GRB classification
Quick localization and alert totelescopes on the ground••Tons of studies for >10 yrs

Classification of GRBs•

(See e.g. the 3rd Swift BAT GRB catalog,
Lien et al. arXiv:1606.01956)•Long GRBs (typ. duration >2 s, ~70%, soft)
associated with core-collapse SNe = death of a massive starStudied well, (almost) no controversy now•

Short GRBs (typ. duration <2 s, ~30%, hard)
Probably a merger of neutron stars (NS), or NS - Black hole
We need GW to confirm it. First example (?) in 2017

Physical mechanism?

(C) NASA

Even if we know origins, we don’t know why gamma-rays are emitted• Afterglow (>~104s): well-known late emissions in X-ray, optical and radio• jet + interstellar matter = shock wave. Accelerated e’s emit synchrotron.

• Prompt emission (<~102s): is GRB “itself”, but is unknown.

• Very efficient (complicated?) mechanism is required in the jet ejecta
5

“Standard” (X-ray) lightcurve
Panaitescu (2006)

Connection between prompt and afterglow is much unclear
even in X-ray. Slow decay is a rather common feature.
After the end of prompt emission, something is happening.

GeV GRBs•’Gamma-Ray’ above is < ~MeV. We need more information.
How about higher energy (100 MeV ~ 10 GeV) ?

•EGRET on CGRO••

>100 MeV γs from 4 GRBs consistent with synchrotron•

but, GRB941017 has another HE component (<200 MeV),
with a delay of ~200 s (reported only in 2003)

LAT on Fermi observed 35 GRBs with >20 MeV in 2008 - 2011.
~140 GRBs as of now. E.g.,•090510: Even short GRB has a prompt HE emission (~30 GeV)

•090902B: 3 γs >10 GeV with a delay up to 80 s•

and,,, “the” GRB130427A

GRB130427A

Ackermann et al. (2014)••15 γs >10 GeV. 73 GeV (19 s), 95 GeV (4 min), 32 GeV (~9 h) !
•VHE γs are emitted mostly in the late prompt - early afterglow,
even later than the slow decay phase (if any)?

•Naturally, not from the main component, but how?

“faster obs is better”, but nice to know a short delay is acceptable8Mechanism?
•one of candidates: “Refreshed shocks”•Assumption: mixture of shell speeds(consistent with multi-peak prompt)

fastershell•(C) NASA

slower Interstellar
shellmatter

Shock made byslower shell

will be re-energized byfollowing faster shells

E.g., Veres & Meszaros (2014) calculate
GeV-TeV γs from short GRB, with thismechanism•~10 GeV will have a peak at ~300 s•

With a long activity in the central
engine, higher E can endure evenfor ~103-4 s

Veres &Meszaros (2014)9Imaging Air CherenkovTelescopes (IACTs)

Very High Energy (>10 GeV)
“IACT regime”•

In >10 GeV, IACTs like MAGIC
are more sensitive than satellites,as the collection area is much larger.

•lower duty cycle, so less probability•

IF observed, GRBs will be detectedby IACTs, but(C) A. Carosi•

Telescopes should react fast enough (as FoV is small)No strong need for O(1) s. O(10-1000) s is fine•

Energy threshold should be as low as possible•

GRB should be close enough to avoid the EBL attenuation.
Nobody knows in advance, but less EBL with lower E
11

MAGIC telescopes•

ORM, La Palma, Canaries, Spain. 2200 m a.s.l., 2 x 17 m IACTs since 2009

•Sensitivity (50 h, 5σ, >220 GeV): ~0.66% Crab, Energy resolution: ~15% @1 TeV, ~23% @ 100 GeV, Energy threshold: ~50 GeV, ~30 GeV (SumTrig)•Slewing speed: 7 deg/s (~25 s for 180 deg)

•MAGIC is the best IACT for GRB, but no firm detection yet•“Good GRBs are always with a bad weather or with a bright moon”=> Of course, due to a lower duty cycle. We should not give up.

•“Not only the best instrument”: Strategy should be continuously
updated with newest knowledge.
12

GRB obs. by MAGIC
Delay vs. Zenith angle

histogram of known redshift• 101 (as of May 2018, not all analyzed), 23 started < T0+100 s, 15 stereo• fastest 3: 24 s (160821B), 26 s (in 2013, z=1.30), 29 s (in 2015, z=2.59)
2 more stereo of z<1.5: 55 s (in 2014, z=1.32), 60 s (in 2013, z=1.16)• 2 stereo with z<0.5: 160821B (z=0.16), 160623A (z=0.37, T0+7.6e4 s)

Short GRB 160821B(ICRC 2017, Texas Symposium, etc., MAGIC Coll. in prep. (2018))• Swift-BAT detected. T90 ~0.5 s• Swift-XRT:t < 300 s extended emission +steep decay, t < 30 ks plateau?
• MAGIC covered this period
24 s - 4 hr (14.4 ks)• Fermi-GBM:
T90 ~1 s, Ep ~= 84 keV
S(10-1000 keV) =1.7e-6 erg cm-2
Eiso =1.2e50 erg (with z=0.16)• Fermi-LAT: no detection• Optical (NOT, WHT (z=0.16), GTC, MASTER, Swift-UVOT), Radio (VLA, AMI)
• IR (HST) : constraints on kilonova. Hint in H-band? (Tanvir et al. in prep)

Signal from MAGICPreliminary• Bright moon (dedicated analysis needed), adverse weather up to 1.5 hr• 4 hr data: >4 sigma (pre-trial), 3.1 sigma (post-trial) in >600-800 GeV
Not firm detection (requiring >5 sigma post-trial). A hint of a detection.
• No (apparently) interesting source around• Observed ~1 yr later but nothing found. No unknown steady source

Lightcurve & SED
Swift-XRT

Fermi-LATMAGICainmiler
Pyr

Fermi-LAT ULs

Preliminary

Intrinsic spectrum(EBL de-absorbed)

Good weather
only (1.5-4 hr)

MAGIC SED

• MAGIC & LAT points compatible with a relatively flat LC coinciding witha possible X-ray shallow decay (though not constraining much)• Suggested flat SED is OK with the EBL attenuation. Intrinsic spectrum isrelatively hard (PWL with index 0.8 +/- 0.6). Beyond synchrotron?

Lightcurve models
By S. Inoue. MAGIC Coll. in prep (2018)

10-6

Implusive:
single pulse injection with single ΓNot too bad, but marginal with VHE UL.
Not nice in X-ray (? Jin et al. 2017）

10-8

•

Energy injection: “Refreshed shock”

energy flux (erg cm-2 s-1)

•10-7

••

Anyway, need another explanation for the
X-ray extended emission.
Transient ms pulsar?
Both models work also for SED (backup)

-10

10

Impulsive

XRT (0.3-10 keV)

-11

10

10-12

Energy injection

-13

10-14

impulsive
energy injection

Preliminary

-15
10 -6

1010-1

100

101-1010103

104

105

VHE light curve
SSC

10-8
10-9

102

time since BAT trigger

10-7energy flux (erg cm-2 s-1)

multiple Γ
Slightly better both in VHE and in X, but
inconclusive

-9

1010

(Sari & Meszaros 01, Veres & Meszaros 14)
Additional injection after the main, with

X-ray light curve
Sync.

BAT (5-150 keV)

Impulsive
MAGIC (>500 GeV)

-11

10

Energy injection

-12

10

10-13

impulsive
energy injection

Preliminary

-14

10

10-1

100

101

102

103

time since BAT trigger

104105

By S. Inoue.
MAGIC Coll. in prep (2018)

Standard picture (impulsive injection) + off-axis angle still gives usan interesting implications for GW follow-up observations!

More MAGIC GRB
papers to come•Stack (?) ULs of stereo GRBs (2013~): draft in prep•

LAT GRBs in 2016-2017: analyses mostly ready•Some more recent interesting GRBs: data taken
Anyway,,, stay tuned!

and more to come,,,next to the stable
MAGIC telescopes,,,

CTA LST will come soon

It is a computer
generated image

In reality now

11 May 201823 May 2018
181 mirrors
installed!

Mechanics status

CSS & Camera access in June

Optics status•

181 mirrors alreadyinstalled, 17 more in Jul•

Mirror adjustment(Active Mirror Control)
being prepared, to beinstalled in Aug

Camera status•

Moved from CIEMAT (Madrid) toIFAE (Barcelona) for assembly.

•~ half of PMT modules installed.

•Final assembly of the light guides
in Aug. Installation in Sep.

LST features for GRBs••

Fast movement (180 deg / 20 s)•Improved telescope motor drive
less oscillation during/after slewing•

Additional pointing monitor
correct for remained fast oscillations•Active Mirror Control (AMC)
dynamic mirror alignment for a shortduration performanceLow energy threshold (>20 GeV)•

Built-in analog sum trigger(Not yet standard in MAGIC GRB obs.)•Trigger exchange (‘OR’) among LSTs
25

DAQ, analysis, MC,,,:CTA North IT center•

We should and will focus more on data-related devs
(DAQ, analyses, MC), to achieve physics results
CTA-N IT centerprocured by Japan
2000 cores
3 PBytes
Discussions ledby ICRR members

Performance for GRBs/transients•~1 prompt obs. / month"Science with the Cherenkov
Telescope Array",
astro-ph:1709.07997•If observed, much more sensitive(S. Inoue et al., 2013)# popular plot

# new CTA-official plot

Expected GRB physics•(First) Firm detections of VHE gammas from GRBs•

Detailed LC of gammas, together with X-ray satellites.
time correlation => implication to mechanism•

If together both with X-rays and GeV (Fermi-LAT):
spectrum extended to VHE? 2nd component?
=> understanding of the mechanism (Sync vs. IC)

Triggers by Swift-BAT (or similar satellites) &Fermi-LAT obs needed: we should hurry up•

Short nearby GRBs: together with GW signals?
=> confirmation of (one of) the origins
Better GW localization: we need KAGRA

Summary•

Even with IACTs like MAGIC, still a lot left for GRB physics•

SGRB 160821B: detection hint, but interpretation inconclusive•

CTA LST will start to understand its mechanism and origins

Inauguration of LST-1 on 10 Oct 2018 !!!

BackupAbstract•

Gamma-Ray Bursts (GRBs) are the most luminous
objects in the Universe. Their origins are considered tobe a collapsing death of a massive star, or a neutron starmerging with another neutron star or with a blackhole.
However, the physical processes happening in theobjects are not yet revealed well. A long-awaited
detection by Cherenkov telescopes will be a key
ingredient to elucidate the GRB emission mechanism. In
this seminar, observations of GRBs with MAGIC
telescopes are reviewed, and the expected physics
cases with Large Size Telescopes of Cherenkov
Telescope Array project are introduced.

If the light curves are flat
10-6

Based on “refreshed shock” scenario
energy flux (erg cm-2 s-1)

(Sari & Meszaros 01, Veres & Meszaros 14)
blastwave with additional energy injection• Extended emission by transient ms pulsar• Collapse to BH, outflow with multiple Γ• model SED is compatible with MAGIC(but impulsive model as well)

10-7

10-9
XRT (0.3-10 keV)
-10

10

10-11
10-12
1010

impulsive
energy injection

VHE spectrum
SSC
impulsive

10-1

10-12
MAGIC (1.5-4 hr)

10-13

Preliminary

34 5 6 7

102

2

3

4 5 6 7E (GeV)103

2

3

4 5 6 7

104

102

103

104

105

time since BAT trigger

VHE light curve
SSC

10-910-10

MAGIC (>500 GeV)
-1110-121010

Preliminary101

10-8-13

2100

10-7

Energy injection

10-14
101

Energy injection-13-1510 -6energy flux (erg cm-2 s-1)

E2df/dE (TeV cm-2 s-1)

10-8

10-14

10-10

10-11

X-ray light curve
Sync.

BAT (5-150 keV)

10-14
10-1

Energy injection
impulsive
energy injection
100

Koji Noda (IFAE), 29th Texas Symposium @ Cape Town, 4 December 2017

101

Preliminary
102

103

time since BAT trigger

104

105

32

• impulsive• uniform ISM• Ekin=1051 erg, n=0.1 cm-3
• εe=0.1, εB=0.01, p=2.1, θj=0.1• EBL Dominguez+ 11
Jin+ 17

Koji Noda (IFAE), 29th Texas Symposium @ Cape Town, 4 December 201733