GRB Science with Next Generation Instrument

1
GRB Science with Next Generation Instrument

• Abe Falcone
• (Penn State University)

2
Science Group Members

• Dingus
• Falcone
• Horan
• Krawczynski
• Meszaros
• Williams
• (Other contributions will be welcomed)

3
Direct GRB Studies

• 3 basic categories
• lt10 s (bulk of nominal prompt emission)
• 10-1000 s (extended prompt injection phase
  early afterglow flares)
• gt1000 s (afterglow flares)

Other Studies

• Lorentz invariance violation
• GRB remnants
• Cosmic Ray acceleration

4
Nominal prompt emission

• Initial prompt emission is generally thought to
  be from internal shocks
• IC of MeV-keV emission should create GeV/TeV
  emission
• Can measure VHE cutoff energy and bulk Lorentz
  factor
• GLAST will beat us to this for GeV (1
  burst/year) Current ACTs ltlt 1/year
• Wide range of Lorentz factors expected
  (100-1500)
• ground-based needed for GRBs with very high
  (gt500) Lorentz factor
• All sky or VERY fast slewing needed to even look
  at many, AND probably need sens. gt10x V/H/M (of
  course, with a low threshold)

5
10 - 1000 sec

• 4 Mechanisms
• More prompt emission thought to be from internal
  shocks
• external shock blast wave (i.e. nominal
  afterglow)
• prolonged energy injection
• Flares
• Again IC of MeV-keV emission should create
  GeV/TeV emission can measure VHE cutoff energy
  and bulk Lorentz factor
• Can map out jet/shock parameters --gt
  refute/confirm current model
• NEED sens. gt10x V/H/M to have a hope of seeing
  many bursts and to get a lightcurve
• Requirements on FOV and slew speed are somewhat
  relaxed, but bigger/faster gives more detections

6
Pre-Swift Anticipated X-ray Afterglow
Behavior(GRB 050922C, XRT observation)
Simple power law decay
Expected interesting behavior in spectra
7
Typical XRT afterglow(Nousek et al. 2006, ApJ)
Steep decline common (gt60 of afterglows)
Temporal break around 1000 s
8
The Canonical GRB Afterglow(Zhang et al. 2005)
1
2
3
4
9
Swift Lightcurves the Movie
BAT
XRT
OBrien et al. 2006
10
Giant X-ray Flare GRB 050502B
500x increase!
GRB Fluence 8E-7 ergs/cm2 Flare Fluence 9E-7
ergs/cm2
Falcone et al. 2006, ApJ Burrows et al. 2005,
Science
11
10 - 1000 sec

• 4 Mechanisms
• More prompt emission thought to be from internal
  shocks
• external shock blast wave (i.e. nominal
  afterglow)
• prolonged energy injection
• Flares
• Again IC of MeV-keV emission should create
  GeV/TeV emission can measure VHE cutoff energy
  and bulk Lorentz factor
• Can map out jet/shock parameters --gt
  refute/confirm current model
• NEED sens. gt10x V/H/M to have a hope of seeing
  many bursts and to get a lightcurve
• Requirements on FOV and slew speed are somewhat
  relaxed, but bigger/faster gives more detections

12
gt1000 s

• 2 Mechanisms
• More late flares
• external shock blast wave
• IC still dominant, but pion decay could be
  significant
• Less flux, but higher likelihood that slewing
  instrument will react fast enough
• Probably need sensitivity gt10 V/H/M slewing at
  1deg/s would be good enough high duty factor
  from something like HAWC would help catch more
• Definitely need low threshold

13
Lorentz Invariance Violation

• Energy dependent delays of simultaneously emitted
  photons can limit (or measure) Lorentz invariance
• Best lower limits to-date are from GRBs at
  keV/MeV energies
• 0.0066Epl 0.661017 GeV
• Our major disadvantage we can't see the distant
  GRBs due to IR absorption
• Our major advantage High and broad energy range,
  especially if we measure a delay between GLAST -
  TeV
• Everyone's disadvantage Inherent energy
  dependent delays
• With a detection of 1 TeV photons by a gt10x
  V/H/M sensitivity instrument and a detection by
  GLAST, the limit could be increased by 100x (to
  Epl), asumming a GRB like 050502B at z0.5 !!!
  (caveat I need to check this calculation in more
  detail)
• Need a very sensitive (gt10x V/H/M) instrument to
  create light curves

14
GRB remnants
from Atoyan, Buckley, Krawczynski 2005

• Could be unique science to ground-based gamma ray
• V/H/M will answer some of these questions first
• However, increased spatial and energy resolution
  could provide new science

15
Cosmic Ray Source

• While most GeV/TeV emission is expected to be IC,
  there is some component from p synchrotron, p?
  initiated cascades, and inelastic np initiated
  cascades. The latter is thought to be dominant.
• If there is significant UHECR acceleration, then
  we could detect these
• BUT, like blazars, it will be difficult to break
  degeneracy between IC and hadronic
• Have the advantage of better constraints on
  Lorentz factor and smaller timescales/regions
• May still need neutrinos

16
Conclusions

• Most agree that we need more than just a single
  GRB detection to make a big science impact a
  reasonable goal is 10 GRBs/year
• Nearly all science goals require gt10x V/H/M
  sensitivity AND low thresh.
• Nominal impulsive emission can only be captured
  with all sky (such as HAWC-like) or with a very
  fast (5-10o/s) slewing ACT
• There are many possible sources of IC emission
  after the nominal prompt emission not just the
  afterglow
• Detection after the first 10 sec is best served
  by a very sensitive (gt10 x V/H/M) low threshold
  instrument
• CR acceleration can be addressed by the future,
  but firm conclusions may be hindered by
  IC/hadronic ambiguity
• Lorentz Invariance violation can be addressed at
  Epl by catching time variable emission with a
  gt10x V/H/M sensitive instrument
• GRBRs have potential to be a unique source type
  that can be mapped out and spectrally
  characterized by a high sensitivity instrument