GW burst-GRB delay Shiho Kobayashi (Liverpool JMU)
Time delay between GW signal and GRB trigger • GRB-trigger search for GWs by LIGO/Virgo targets both the chirp signal in the case of short GRBs and short unmodeled pulses of GWs. • On-source time windows of few mines (Long GRBs) and few seconds (Short GRBs) • Any astrophysical implications?
Collapsar Model for Long GRBs Massive Star Core collapse accreting disk relativistic jet
GRB Progenitor GW Signals: Collapsar (S.K. & Mészáros 2003) breakup(optimistic) d=270 Mpc, solar mass blobs at disk size r=107 cm (b) (Solid: dot-dash: merger; circle :bar inst; spike: ring-down); shaded : rate/dist uncertainty Dashed: adv LIGO sensitivity
Long GRBs • The time delay is possibly dominated by the time necessary for the jet to push through the stellar envelope. • For low luminosity GRBs, the break time is longer, and the head velocity is newtonian: beta <<1 • Possible Correlation between GRB luminosity and time delay(GW-GRBs) • Luminosity, temporal profile (shock breakout), spectrum
t Time delay: EM and GW onset of afterglow External shock ~week prompt gamma-rays Internal shock model ~hr relativistic jet observer’s world line almost null geodesic GW burst R 10^16-17cm 10^13-14cm
Two photons from a source with relativistic velocity 2R R photon1 photon2 photon1 1st photon propagates Separation: Arriving time difference:
Summary • Possible Correlation between GRB luminosity and time delay(GW-GRBs) • Luminosity, temporal profile (shock breakout), spectrum • Other contributions to the delay between GW burst and GRB? • Precursor, some GRBs : dimmer peaks at the beginning • Uncertainty in GW production: GW and jet form together?