High Energy Neutrinos andTransient Phenomena
Kazumi Kashiyama (U. of Tokyo)

Outline• High energy neutrinos• Why important?
• How to produce?
• Very quick overview of IceCube neutrinos• High energy neutrinos from transient phenomena• Some general arguments about IceCube targets• What have been done so far• What “we” can do

High energy neutrinos

Multi-messenger astronomy

Image: Juan Antonio Aguilar and Jamie Yang. IceCube/WIPAC

High-E neutrino production ; pp & pγ

Eν ~ 0.04 Ep  PeV neutrinos ⇔ a few 10 PeV protons

The Waxman-Bahcall bound: meson production efficiency: source redshift evolution: cosmic-ray generation rate per volume
If CR injection rate is comparable to that of ultra-high energy cosmic rays;

and the pion production is efficient,IceCube neutrinos
Aartsen+16

 The atm. background-only hypothesis is rejected at 3.6σ.
 The flux is comparable to the Waxman-Bahcall bound.
 Low energy excess at ~ 10 TeV?
 High energy cutoff at ~ PeV?

High energy neutrinos fromtransient phenomena

Some general arguments
about IceCube targets

How many neutrinos per event?

With IceCube – signal type“track” (detected)“shower” (detected)~15% energy res.
~ 10 deg ang. res.
~2 energy res.
< deg ang. res.

“double-bang” (not detected)

can be observed @ higher energies

With IceCube – for detection, in general

Very roughly,• Let us detect a nearby bigshot• or we can also stackevents

With IceCube – vs atm. background
Very roughly,or Less than ~ 1 % are expected to be of cosmic origin @ ~TeV.
 > 100 TeV  likely astrophysical• For stacking,What we can learn, in generalEM surveys
to find source candidates

EM surveys or followups
to detect EM counterparts
indirect in most cases(leptonic origins)

indirectCR obs.

IceCube(non-)detections of neutrinos
origins of IceCube neutrinos,
origins of cosmic rays,
acceleration and emission mechanism, …

Target candidates•↑

Brighter transients↑with non-thermal signatures↑in a “dense” environment

likeand their relatives

Multi-messenger obs. strategies
 For bigshot(s)should not miss nearby events;
A wide field-of-view is more essential.

EM surveys
 For stacking

EM surveys

IceCubeν alert quickly after the detection,
rapid EM followup

IceCubeFind as many as possible.

What have been done

Multi-messenger obs. strategies
 For bigshot(s)EM surveys

IceCube For stacking

EM surveys

IceCubeStacking ~1000 GRBs

Exclude GRBs as the dominant source of the observed IceCube neutrinos.

(Long) Gamma-Ray Bursts• A standard picture？
？ ？

Meszaros 2001

• What we do not know
→ BH and magnetar formation– Central engine?
Physics of the jet→– Prompt emission?
Origin of UHECRs– Progenitor? → GRB-SN connection

Q. What is the GRB mechanism?
“Band” function〜 broken power law
 @ low energy

 @ high energy
Abdo+2010 non-thermal features → particle acceleration?
 polarization? (e.g., Yonetoku+2012) → magnetic fields?

GRB prompt neutrinos

with@ Δ-resonanceMeson production efficiency (large astrophysical uncertainties)

The GRB-UHECR hypothesis• If not only electrons but protons are accelerated,
Waxman 1995

• If,withWanderman & Piran 2003

Consistent with the UHECR observations

Stacking ~1000 GRBs

Emission mechanism, the GRB-UHECR hypothesis, and so on are being tested.

Way to go!

Multi-messenger obs. strategies
 For bigshot(s)EM surveys

IceCube For stacking

EM surveys

IceCube“The brightest GRB ever since 2010”

Shan, KK, Meszaros 2013

Multi-messenger obs. strategies
 For bigshot(s)EM surveys

IceCube For stacking

EM surveys

IceCubeAlerts from IceCube
 Not to be ”cry wolf too often” …

1. High energy events
2. Multiplets i.e. two or more neutrinos from the same direction within 100 s
 The real-time search“In case of automatic forwarding,the median latency for triggering follow-up observatories is ∼ 1 min. ”

High energy events
Aartsen+16

So far no association with any transient source reported,but only one single association means huge, keep on going!

Follow-up of a neutrino multiplet
A ~ TeV ν doublet+ SN IIn (~160 days after exp.)

Let’s see…

“Too ν bright to be true”

The significance of the chance detection is 2.2σ

Follow-up of a neutrino multiplet
A ~TeV ν triplet candidateLet’s see…

No EM counterpart detected

The probability to detect one triplet
from atm. backgrounds is 32%.

Stringent constraint on
nearby energetic explosionsHE ν & transients so far (my personal view)
GRB stacking~ TeV ν multiplet
 EM followup

High-energy ν EM followup

John MacDougall/AFP/Getty Images

What “we” can do(or what have not been done)• GRB stacking is working very well.

They are rare but EM bright and detected efficiently
thanks to e.g., Swift and Fermi.

• Next target will be relatively dim in the γ-ray bandsbut still energetic or abundant transients, e.g.,• Low luminosity GRBs
• Failed GRBs or choked jet events• Pulsar-driven supernovae• Interaction-powered supernovae• Tidal disruption events•…

• For stacking, EM survey strategies including target
selection can be optimized based on the νmodeling and source distribution of each transient.

• EM followup of high energy ν events is useful.

 So far in vain, but one single association means huge.
 Rapid and followup of ~1 deg2 and ~10 deg2 fields fortruck and shower events, respectively
 The primary target is nearby bigshots.

• HSC can give a unique contribution.
(Tanaka-san’s talk) Even for track events(?)
 When HSC follows up the ~ 1 deg2 field for ~30 mins,
there always ~ 10 CCSNe at z ~< 0.4.
 Only a minor fraction (~ 30 min/month ~ 1/1000)
explode just after the trigger.
 Effective especially for relatively rare, EM dim (so that
not to be detected by other surveys), but ν bright ones(e.g., choked jet HNe)• EM followup of ν multiplets is also interesting.
It is even more biased to nearby bright sources.
Relatively shallow surveys e.g., by ASAS-SN suffice?
No need for HSC?

• There may be very ν-bright but EM-dim transients.
(It’s fun to think about it …)
 how about failed SNe with choked jets, resulting inmassive BH formation?
 motivated by GW astronomy
 Theoretical challenge:
possible to make them “very ν-bright but EM-dim”
 Observational challenge:
not much info about the low luminosity end of SNe
 H!S!C!