Off axis counterparts of SGRBs tagged by gravitational waves Kazumi Kashiyama (Penn State) with K.Ioka, T.Nakamura and P. Meszaros.

Off axis counterparts of SGRBs tagged by gravitational waves

Kazumi Kashiyama (Penn State)with K.Ioka, T.Nakamura and P. Meszaros

Why?The era of gravitational wave astronomy will come soon!

The “promising target” : compact binary mergers

Multi-messenger approach

since 2015 〜 20172nd generation network

Distance detectable : 〜 200Mpc, Event rate : 〜 40yr-1 for NS-NS merger

• GW detectors have bad eyesight! Angular resolution of 2nd generation 〜 10deg2

Off-axis X-ray, optical, radio counterpart searches

• SGRBs are the most reliable counterpart, but low-frequent. if θj 〜 0.1, the GW-SGRB simultaneous detection rate 〜 0.1yr-1

Point : “Pre-jet” envelope formation

Mildly relativistic! Optically thick! Neutron-rich!

Hyper-massive neutron star

Pre-jet envelope( Magnetically or Neutrino driven wind )

Tidal mass ejection

Rotational plane of binary

e.g. Lee et al. (2010) , Dessart et al. (2009), Shibata et al. (2011)

Possible off axis emissions from pre-jet envelope

Optical (kilonova) Radio active heating in the envelope (β-decay, fission, 56Ni→56Co→56Fe)

Interaction between the envelope and interstellar medium

Radio (afterglow)

〜 days

〜 years Nakar & Piran (2011)

Li & Paczynski (1998)Metzger et al. (2010)

UV-X-ray Interaction between the envelope and relativistic jets

≤ minutes???

relativistic jet cocoonBlack hole (magnetar) + accretion disk

Jet penetration problem in SGRBs

VS

Jet penetration problem in SGRBs

Faile

d Pe

netra

tion

Non-re

lativ

istic p

enet

ratio

n

Rela

tivisti

c pen

etra

tion

No co

coon

( Fail → jet induced supernovae like? )Succeed penetration → jet+cocoon

Two possible off axis emissions from jet-envelope interaction

relativistic jetcocoon

Black hole (magnetar) + accretion disk

1. Hard X-rays from cocoon breakout2. Soft X-ray quasi-thermal emission from cocoon itself

X-rays from cocoon breakout

Too dim to be detected because of the small rcbo

cocoon

jet

Energy budget of breakout photons:

@

Timescale of the emission:

Jet-cocoon dynamics →

UV-Soft X-rays from cocoon itself

cocoon

@

Adiabatic expansion:

Jet-cocoon dynamics →

Marginally detectable by future facilities?

for ~ minute @ soft X-ray or UV (down scattered)

Summary

• Off axis X-ray counterpart of compact binary mergers could be a key for GW astronomy.

• Consider jet and pre-jet envelope interaction– Cocoon breakout emission → too dim– Emission from cocoon itself• could be soft X-ray transient ~minute• might be detected by future facilities? • need to be modeled more precisely.

– Failed penetration cases could be also interesting.