VERITAS Collaboration Recent Results:

1
VERITAS CollaborationRecent Results
March, 13 2002

• Frank Krennrich (Iowa State University)
• for the VERITAS collaboration

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Outline

• - Whipple 10m ground-based g-ray astronomy
• - Recent results from Whipple 10m
• - VERITAS impact on science to come
• - Summary

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History of the Whipple 10m

• Imaging Camera

0.01 100 TeV
Area 100,000 m2 E 0.2 100 TeV Dq/q
0.2 o
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Cosmic Ray Rejection Technique

• g-ray images
• - narrow, short, smooth
• Hadronic images
• - broad, long
• - local muons, patchy
• hadron rejection 99.7 (10-3)

g-ray
proton
Courtesy W.Hofmann
Crab Nebula 7 s in 1hour
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Science Highlights Whipple 10m

• 1997 Flare of Mrk 501
• z 0.034

• 1989 Discovery of TeV
• photons from the Crab

Weekes et al. 1989, ApJ, 342, 379
37
151
Catanese et al. 1997, ApJ, 487, L143

• 2001 Discovery of
• 1H1426428
• (z 0.129)

• 1992 TeV photons from
• the blazar Mrk 421
• z 0.031

Horan et al. 2002, ApJ, in press
Punch et al. 1992, Nature, 358, 477
109
489

• 2001 Flare Mrk 421

• 1996 Giant short flare
• from
• Mrk 421

489
Gaidos et al. 1996, Nature, 383, 319
Krennrich et al. 2001, ApJL, 560, L45
109
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Mrk 501 Flare in 1997
Whipple

• - X-ray peak at E gt 100 keV
• ? extreme BL Lac

• dN/dE
• E-1.95 K 0.07 e (E/E )
• E 4.6 K 0.8 TeV

0
0
HEGRA

• dN/dE
• E-1.92 K 0.03 e (E/E )
• with E 6.2 K 0.4 TeV

0
0
Origin of cutoff? IR-background, intrinsic to
source etc.
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Mrk 421 spectrum (2001)

• - 23,000 photons above 260 GeV
• - average g-ray rate 3.7 Crab

Whipple average spectrum in high
state

• dN/dE E-2.14 K 0.03 e (E/E )
• with E 4.3 K 0.3 TeV
• (- 1.4 1.7 TeV)syst

0
0
Krennrich et al. 2001, ApJL, 560, L45
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Spectral Variability of Mrk 421
Flux-Index correlation
Spectra _at_ Fluxes 1 10 Crab
preliminary
preliminary

• dN/dE E-a e (E/E ) E 4.3 TeV

0
0
VERITAS collaboration (in preparation)
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X-ray/TeV correlation Mrk 421
TeV lightcurve TeV spectral variation
X-ray/TeV lightcurve
preliminary
preliminary
preliminary
VERITAS collaboration (in preparation)
Courtesy of G. Fossati , J. Buckley M. Jordan
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Recent Results 1H1426428

• - z 0.129
• - ltrategt 100 mCrab

• - X-ray peak at E gt 100 keV
• ? extreme BL Lac

• dN/dE E-3.44 K 0.36

Horan et al. 2000, HEAD Meeting, Honolulu, No.
32, 05.03
Aharonian et al. 2002, AA, in press
Horan et al. 2002, ApJ, in press
Petry et al. 2002, ApJ, in preparation
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VERITAS

• - 7x Davis-Cotton
  110 m2
• - focal length 12 m
• - steel structure
• - ground-glas mirrors
• - 499 pixels
  0.15o
• - distance 80 m
• - 500 MHz FADC
• - Front-end/moonlight
  operation
• - Sub-arrays

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Improvements with VERITAS

• Combine stereoscopic view with improved
• 10m type telescope
• improved angular resolution
• enhanced background suppression
• lower energy threshold
• improved energy resolution
• cross-calibration with GLAST
• ? absolute energy calibration

VERITAS

• - 50 GeV 50 TeV
• - Dq/q 0.03o _at_1TeV
• 0.09o _at_100GeV
• - Flux sensitivity
• 15 mCrab _at_100GeV
• 5 mCrab _at_300GeV

80 m
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Scientific Objectives

• Active Galactic Nuclei

• (Diffuse) Galactic Plane

• Infrared Background

• Pulsars

g g ? e e -

• Gamma Ray Bursts

• Supernova Remnants

• Neutralino Annihilation,
• Primordial Black Holes,
• Quantum Gravity,

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Summary

• - spectral cutoffs for Mrk 421, Mrk 501 (1-10
  Crab)
• ? IR cutoff? IC-peak? KN-cross section?
• - spectral variability of Mrk 421
• cutoff variable?
• - detection of blazars with redshift up to z
  0.129
• but background dominated, steep spectrum

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Sensitivity
VERITAS-4
- 100 GeV 50 TeV - Dq/q 0.04o _at_1TeV
0.12o _at_100GeV - Flux sensitivity
200 mCrab _at_100GeV 6 mCrab _at_300GeV
VERITAS-7

• - 50 GeV 50 TeV
• - Dq/q 0.03o _at_1TeV
• 0.09o _at_100GeV
• - Flux sensitivity
• 15 mCrab _at_100GeV
• 5 mCrab _at_300GeV

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Sensitivity of Telescope Arrays