Recent TeV Observations of Blazars & Connectionsto GLAST

Frank Krennrich

Iowa State University

VERITAS Collaboration

GSFC, October 24, 2002

AGN

204/20/23

VERITAS Collaboration:

Frank Krennrich (krennrich@iastate.edu)

for the VERITAS collaboration

Collaboration members:Iowa State U.Leeds U. (U.K.)McGill University (Canada)Purdue U.Smithsonian Astrophysical ObservatoryUCLAUniversity College, Dublin (Ireland)U. of ChicagoU. of Utah Washington U.

304/20/23

Outline

Introduction

atmospheric Cherenkov imaging technique

brief overview of TeV blazars Astrophysics results with Whipple 10m telescope

Mrk 421 2000/2001, Mrk 501 1997 spectra

H1426+428, 1ES1959+650 Next generation instrument: VERITAS VERITAS – GLAST connection Summary

404/20/23

History of the Whipple 10m

Imaging Camera 0.01 – 100 TeV

Area ~ 100,000 m2

E ~ 0.2 – 100 TeV

~ 0.2 o

100 optical photons/m2 TeVwithin a few ns

504/20/23

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

-ray proton

Cosmic Ray Rejection Technique

Crab Nebula 7 in 1hour

Courtesy W.Hofmann

604/20/23

Science Highlights: Whipple 10m• 1989 Discovery of TeV photons from the Crab

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

• 1997 Flare of Mrk 501 z = 0.034

• 2001 Discovery of H1426+428 (z = 0.129)

• 2001 Flare Mrk 421

37

109

151

489

489

Weekes et al. 1989, ApJ, 342, 379

Punch et al. 1992, Nature, 358, 477

Gaidos et al. 1996, Nature, 383, 319

Catanese et al. 1997, ApJ, 487, L143

109

• 1996 Giant & short flare from Mrk 421

Krennrich et al. 2002, ApJL, 575, L9 Krennrich et al. 2001, ApJL, 560, L45 ~10 Crab

Horan et al. 2002, ApJ, 571, 753 Petry et al. 2002, ApJ, in press

> 70 “EGRET” blazars at 1 GeV Redshift z = 0.03 – 2.28

zH1426+428Mrk 421

Mrk 501

1ES1959+650

1ES2344+514

3C66

1ES2155-304

TeV blazar

“Whipple”

blazars

at 300 GeV

Mrk 421 0.031

Mrk 501 0.034

1ES2344 0.044

1ES1959 0.048

H1426 0.129

804/20/23

PK

S 2

155-

304 Search for new TeV Blazars:

Mrk

501

Mrk

421

H14

26+

428

1ES1959+650

1ES

2344

+51

4

Costamante, L. & Ghisellini, G. 2001, A&A, 384, 56

904/20/23

Mrk 421 z = 0.031 X-ray BL Weak GeV > 86 TeV

Mrk 501 z = 0.034 X-ray BL Marginal GeV > 40 TeV

1004/20/23

Multiwavelength spectra

Peak: 100 keV/200 GeV X-ray/TeV correlation

Mrk 501 Mrk 421 Peak at 1 keV/~50 GeV X-ray/TeV correlation

Catanese et al., ??? Catanese & Weekes, PASP, 111, 3191193 (1999)

1104/20/23

Mrk 421 in 2000/2001:

23,000 -rays at E> 300 GeV

Courtesy of J. Holder (see also Holder et al., 2001, Proc. 27th ICRC, Hamburg)

1204/20/23

Mrk 421/Mrk 501 spectra

Mrk 501

Mrk 421

dN/dE ~ E- e –(E/ E )

with E0 = 4.6 0.8 TeV

dN/dE ~ E- e –(E/E )

with E0 = 4.3 0.3 TeV

(- 1.4 + 1.7 TeV)syst

Samuelson et al. 1998, ApJL, 501, L17

Krennrich et al. 1999, ApJ, 511, 149

Krennrich et al. 2001, ApJL, 560, L45

0

0

1304/20/23

Mrk 421 <spectral variability>

on average, -ray luminosity peakshifts to larger energieswith increasing flux!

Krennrich, F. et al. 2002, ApJL, 575, L9

1404/20/23

<Mrk 501> 1997 vs. Mrk 421 high state

Mrk 501 1997 average

Mrk 421 high state (set I)

spectral index varies but cutoff region remains stable!

imagine instrument with 20 times the sensitivity of Whipple separate constant from variable component

IR-background density

1504/20/23

Mrk 421: spectral variability:

Property of a specific blazar or emission mechanism?

Krennrich et al. 1999, ApJ, 511, 149 Krennrich et al. 2002, ApJL, 575, L9 Fossati et al. 2000, ApJ, 541, 166

X-rayVHE--ray

½ Hourly Spectral Variability:

Feb. 1 Feb. 2 Feb. 27

March 19 March 25 March 27

P = 3.4 x 10-3

P = 4.0 x 10-3 P = 8.5 x 10-4

1704/20/23

½ Hourly Spectral Variability

VERITAS collaboration (in preparation)

1804/20/23

X-ray/TeV correlation: Mrk 421

preliminary

TeV lightcurve & TeV spectral variation

X-ray/TeV lightcurve

Courtesy of G. Fossati , J. Buckley & M. Jordan

preliminarypreliminary

VERITAS collaboration (in preparation)

1904/20/23

H1426+428: weak signal ~ 80 mCrab

2000 2000

20012001

from Horan et al. 2002, ApJ, 571, 753

2004/20/23

H1426+428 spectrum:Whipple 2001:dN/dE ~ E-3.50 0.35 0.05

Petry et al. 2002, ApJ, in press

HEGRA 2001:dN/dE ~ E-2.60 0.6 0.05

Whipple+HEGRA:dN/dE ~ E-3.54 0.27 0.05

Aharonian et al. 2002, A&A, 384, L23

Petry et al. 2002, ApJ, in press

2104/20/23

2002 Flares from 1ES1959+650:

IAU circular 7903 (VERITAS collaboration), 2002

Holder et al. 2002, in preparation

2204/20/23

Conclusion from blazar observations

Spectral cutoffs for Mrk 421/501 at ~ 4 TeV: possible evidence for absorption from IR background

or due to internal break due to KN~ E-1 (when hsoft > me c2 )

Spectral variability (Mrk 421): -ray luminosity peak shifts with <flux> increase -flux correlation holds over 5 years! Rapid variability (Mrk421):

tvariability ~ 15 min. ~ 10 emission region 10-4 - 10-5 pc H1426+428: first detection of blazar with z ~ 0.129 at E >300 GeV steep spectrum: dN/dE ~ E-3.54 0.27 0.05

Future: source list steadily growing (5 Whipple blazars) VERITAS

2304/20/23

VERITAS: Very Energetic Radiation Imaging Telescope Array System

50 GeV – 50 TeV Area: = 100,000 m2 (1 TeV) = 40,000 m2 (300 GeV) = 1,000 m2 (50 GeV) Angular res.: 0.03o – 0.14o Energy resolution: 10-18% Observation strategy: pointed exposures

2404/20/23

Arrays of Imaging Telescopes I

- 50 GeV – 50 TeV

- ~ 0.03o @1TeV

~ 0.09o @100GeV

- Flux sensitivity:

15 mCrab @100GeV

5 mCrab @300GeV

80 m

VERITAS

2504/20/23

DESIGN

7-telescope Array

12 m Reflectors

500 PMTCameras3.5o FOV

2604/20/23

TECHNICAL PROGRESS

Telescope: mount, mirrors

Camera: PMTs, amps

Electronics: FADCs, trigger

DAQ:High speed Readout & analysis

2704/20/23

TELESCOPE

Overall Optical Support StructureAccomodates 12m mirror

Pedestal

2804/20/23

CAMERA

PMT Installation

Camera Box Construction

Cabling inside

2904/20/23

FRONT-END

Amplifiers

PMT Assembly

Current Monitoring

3004/20/23

Point Source Sensitivity

Cangaroo III

HESS MAGIC

Stacee VERITAS

3104/20/23

GLAST/VERITAS cross-calibration: Crab Nebula

Hillas et al., ApJ, 503, 744 (1998)

GLASTVERITAS

Overlap: 50 GeV – 100 GeV - 1 TeV GLAST: E/E ~ 5-10% @ 10 GeV –100 GeV VERITAS: E/E ~ 20-10% @ 50 GeV-1000 GeV 20-25% uncertainty in the absolute energy of IACTs! fix with GLAST/VERITAS cross- calibration using overlap! GLAST (40 days exposure) 150 (10) photons above 10 (100) GeV 10% accuracy in absolute E

3204/20/23

Connections:

Unified AGN picture

~ several 103 GeV blazars

blazar classification studies

(GeV blazars) Jet models

broad studies

daily-yearly flux variations EBL cutoff

probe 0.1 m – 0.01 m Blazar spectra

20 MeV – 100 GeV

Unified AGN picture

~ 102 sub-TeV blazars

classification studies

(extreme blazars) Jet models

detailed studies

min. - yearly spectral variations EBL cutoff

probe 0.1 m – 50 m Blazar spectra

50 GeV – 50 TeV

GLAST