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E>30 GeV?. ?. Some more science considerations/thoughts …. P. Coppi, Yale. vs. E>5 GeV?. ?. Real population statistics and fully observed SED peaks would be very useful …. Don’t forget absorption by infrared/optical background!.
Some more science considerations/thoughts ….
P. Coppi, Yale
Real population statistics and fully observed SED peaks would be very useful …
Mkn 421 2002 X-ray/TeV campaign
(Dieter Horns, preliminary)
X-ray hardness ratio (spectrum)
Lesson from ASCA/X-ray monitoring days…. Need complete time sampling!
(HAWC won’t do this. Would be nice to have similarthreshold to GLAST so see same sources. )
Long burst w/optical flash detected by ROTSE, BATSE flux > 99.6% BATSE bursts
Energy Flux at MeV Peak
Integration Time for Spectrum ~ 32 s
Assume same energy flux at 1 GeV,
Great GeV energy spectrum forthis burst, and reasonable spectrafor bursts ~ 50x fainter.A MAJOR improvement
BUT … this is a time
Look at what BATSE saw during those 32 sec
Briggs et al. 1999
Awesome statistics, even for
64 msec time bins.
Allows detection of significantspectral variability on < 1 sectimescales.
Just as for blazars, fitting
time-integrated spectra when thissort of variability is going on is
NOT a good idea.
Can GLAST match this
(N.B. OSSE detected 16 msec variability for this burst at ~ 1 MeV.)
Another key component of GRB studies is the AFTERGLOW.
Can GLAST study this?
[Afterglow is much easier because there is no rapid time variability.]
Bottom line: Unless we’re lucky with physics, GLAST will only seebrightest bursts at ~ 1 GeV, and there is not much margin for error.
Hey, there are some interesting nearby objects – jet emission (synch X-ray? => TeV e-/e+)!
M87 – FRI (weak jet)
Mostly synchrotron emission?
Resolved X-ray emission -> in situ acceleration!?
M87 jet is not wimpy!!!
the GeV-TeV extragalactic diffuse background.
Why so interesting?
GeV-TeV+ gamma-rays only produced in extreme environments or
by “exotic” processes: e.g., black hole jets, supernova blast waves,
cosmic strings, relict particle decays, or matter-antimatter annihilation.
Background is sum of all nearby GeV-TeV activity
in the Universe + all > GeV activity at z > 1.
[ Gamma-ray pair production and
cascading on intergalactic photon fields
GLAST = calorimeter for
(best limits on BAU/matter-antimatter domains from gamma-rays) ]
a la Stecker & Salamon 1996
Including IR/O absorption
Coppi & Aharonian 1997
Be careful in
of spectral featuressuch as “bumps” and break energies!
Can get spectral indexharder than 0.5!
[N.B.: Getting strong
TeV emission not so easy!]
Moderski et al. 2005
CDM particles, trace large scale structure/shocks…
look for clustering signal!
Bromm et al. 2003
GLAST AGN follow-up
Diffuse gamma-ray background (extragalactic and galactic)
GLAST “hotspot” follow-up
GRB, high energy components
Microquasars (NIR jet emission detected)
SNR/Cosmic Ray accelerators
Pulsed emission from plerions (pulsars )
Star formation-related cosmic ray emission from other galaxies
What if your “low energy” threshold is 30 GeV?
Don’t go halfway or risk
losing GLAST-related science!
And do a bad of “TeV” science…
??? Serendipity: Exciting particle physics?
Aside: really pounding away at >1 TeV relatively easy and interesting too…
(cosmic ray, SNR, probe EBL in 10-60 micron region – most poorly constrained by direct counts & impacts star formation history
Rule of thumb: give a theorist a spectrum consistent with a power law
(e.g., due to insufficient statistics) and he can fit any model/EBL you like.
Need to detect curvature! Ideally measure both sides of
low and high energy peaks, simultaneously w/good
(< hour-month) time-sampling: UV-MeV, 100 MeV-TeV
coverage. [Also very good to get below IR/O absorption
There will always be some special objects,
e.g., Mkn 501, not accessible from a given
Want good population statistics ….
One “super” telescope not enough – want tightly coordinated
space and ground-based telescopes.
As gamma-rays enter realm of mainstream astronomy, similar considerations