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Recent TeV Observations of Blazars & Connections to GLAST. Frank Krennrich Iowa State University VERITAS Collaboration. GSFC, October 24, 2002. AGN. VERITAS Collaboration:. Frank Krennrich ([email protected]) for the VERITAS collaboration. Collaboration members:

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Recent TeV Observations of Blazars & Connections to GLAST

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Recent TeV Observations of Blazars & Connectionsto GLAST

Frank Krennrich

Iowa State University

VERITAS Collaboration

GSFC,

October 24, 2002

AGN


VERITAS Collaboration:

Frank Krennrich ([email protected])

for the VERITAS collaboration

Collaboration members:

Iowa State U.

Leeds U. (U.K.)

McGill University (Canada)

Purdue U.

Smithsonian Astrophysical Observatory

UCLA

University College, Dublin (Ireland)

U. of Chicago

U. of Utah

Washington U.


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


History of the Whipple 10m

0.01 – 100 TeV

Imaging Camera

Area ~ 100,000 m2

E ~ 0.2 – 100 TeV

Dq/q~ 0.2 o

100 optical photons/m2 TeV

within a few ns


Cosmic Ray Rejection Technique

g-ray

proton

  • g-ray images:

    - narrow, short, smooth

  • Hadronic images:

    - broad, long

    - local muons, patchy

  • hadron rejection: 99.7% (10-3)

Courtesy W.Hofmann

Crab Nebula

7 s in 1hour


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

Catanese et al. 1997, ApJ, 487, L143

151

  • 2001 Discovery of

  • H1426+428

  • (z = 0.129)

  • 1992 TeV photons from

  • the blazar Mrk 421

  • z = 0.031

Horan et al. 2002, ApJ, 571, 753

Petry 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

~10 Crab

Krennrich et al. 2001, ApJL, 560, L45

489

Gaidos et al. 1996, Nature, 383, 319

Krennrich et al. 2002, ApJL, 575, L9

109


  • “Whipple”

    blazars

    at 300 GeV

    Mrk 421 0.031

    Mrk 501 0.034

    1ES2344 0.044

    1ES1959 0.048

    H1426 0.129

  • > 70 “EGRET” blazars at 1 GeV

  • Redshift z = 0.03 – 2.28

z

Mrk 421

H1426+428

Mrk 501

1ES1959+650

1ES2344+514

3C66

1ES2155-304

TeV blazar


Search for new TeV Blazars:

PKS 2155-304

Mrk 501

Mrk 421

H1426+428

1ES1959+650

1ES2344+514

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


Mrk 501

  • z = 0.034

  • X-ray BL

  • Marginal GeV

  • > 40 s TeV

Mrk 421

  • z = 0.031

  • X-ray BL

  • Weak GeV

  • > 86 s TeV


Multiwavelength spectra

Mrk 501

Mrk 421

  • Peak at 1 keV/~50 GeV

  • X-ray/TeV correlation

  • Peak: 100 keV/200 GeV

  • X-ray/TeV correlation

Catanese et al., ???

Catanese & Weekes, PASP, 111, 3191193 (1999)


Mrk 421 in 2000/2001:

  • 23,000 g-rays at

    E> 300 GeV

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


Mrk 421/Mrk 501 spectra

Mrk 501

dN/dE ~ E-1.95K 0.07 e –(E/ E )

  • with E0 = 4.6 K 0.8 TeV

0

Samuelson et al. 1998, ApJL, 501, L17

Krennrich et al. 1999, ApJ, 511, 149

Mrk 421

dN/dE ~ E-2.14K 0.03 e –(E/E )

  • with E0 = 4.3 K 0.3 TeV

  • (- 1.4 + 1.7 TeV)syst

0

Krennrich et al. 2001, ApJL, 560, L45


Mrk 421 <spectral variability>

 on average, g-ray

luminosity peak

shifts to larger energies

with increasing flux!

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


<Mrk 501> 1997 vs. Mrk 421 high state

Mrk 501 1997 average

 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

Mrk 421 high state (set I)


Mrk 421: spectral variability:

VHE-g-ray

X-ray

Krennrich et al. 2002, ApJL, 575, L9

Property of a specific blazar or emission mechanism?

Fossati et al. 2000, ApJ, 541, 166

Krennrich et al. 1999, ApJ, 511, 149


½ Hourly Spectral Variability:

Feb. 2

Feb. 27

Feb. 1

P = 3.4 x 10-3

March 19

March 25

March 27

P = 8.5 x 10-4

P = 4.0 x 10-3


½ Hourly Spectral Variability

VERITAS collaboration (in preparation)


X-ray/TeV correlation: Mrk 421

X-ray/TeV lightcurve

TeV lightcurve &

TeV spectral variation

preliminary

preliminary

preliminary

VERITAS collaboration (in preparation)

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


weak signal ~ 80mCrab

H1426+428:

2000

2000

2001

2001

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


H1426+428 spectrum:

Whipple 2001:

dN/dE ~ E-3.50K 0.35 K 0.05

Petry et al. 2002, ApJ, in press

HEGRA 2001:

dN/dE ~ E-2.60K 0.6 K 0.05

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

Whipple+HEGRA:

dN/dE ~ E-3.54K 0.27 K 0.05

Petry et al. 2002, ApJ, in press


2002 Flares from 1ES1959+650:

IAU circular 7903 (VERITAS collaboration), 2002

Holder et al. 2002, in preparation


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 sKN~ E-1 (when ghnsoft > me c2)

  • Spectral variability (Mrk 421):

     g-ray luminosity peak shifts with <flux> increase

     a-flux correlation holds over 5 years!

  • Rapid variability (Mrk421):

     tvariability ~ 15 min.  g ~ 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-3.54K 0.27 K 0.05

  • Future:

    source list steadily growing (5 Whipple blazars)  VERITAS


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


Arrays of Imaging Telescopes I

VERITAS

- 50 GeV – 50 TeV

- Dq/q~ [email protected]

~ [email protected]

- Flux sensitivity:

15 mCrab @100GeV

5 mCrab @300GeV

80 m


DESIGN

12 m Reflectors

500 PMT

Cameras

3.5o FOV

7-telescope Array


Telescope: mount, mirrors

Camera: PMTs, amps

Electronics:

FADCs, trigger

DAQ:

High speed

Readout & analysis

TECHNICAL PROGRESS


TELESCOPE

Pedestal

Overall Optical Support Structure

Accomodates 12m mirror


CAMERA

PMT Installation

Camera Box Construction

Cabling inside


FRONT-END

PMT Assembly

Amplifiers

Current Monitoring


Point Source Sensitivity

VERITAS

Stacee

HESS

MAGIC

Cangaroo III


GLAST/VERITAS cross-calibration: Crab Nebula

  • Overlap: 50 GeV – 100 GeV - 1 TeV

  • GLAST:

  • DE/E ~ 5-10% @ 10 GeV –100 GeV

  • VERITAS:

    DE/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

GLAST

VERITAS

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


GLAST

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 mm – 0.01 mm

  • 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 mm – 50 mm

  • Blazar spectra

     50 GeV – 50 TeV


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