Results On VHE Gamma Ray Sources from ACTs and Air Shower Arrays

• HESS

• CANGAROO

• STACEE

• CELESTE

• MILAGRO

• TIBET – III Future Case Study from Other Sources

Results from Northern Sources from HESS

CELESTEBussons Gordo 2004Energy calibration under review!

H.E.S.S.H.E.S.S.

Significance Map

Object H.E.S.S. status

Crab Nebula ~50 (3 h), flux and spectrum agree

Mkn 421 ~80 (12 h), flux and spectrum ok

Mkn 501 not seen (~2 h); not detected by Whipple either at that time

Index 1.8Cutoff 2.4 TeV

H.E.S.S. & the “old” sources

PKS 2155

NGC 253

Gal. center

RX J 1713

SN 1006

Vela

PSR 1706-44

Object

H.E.S.S.: not detected at level of old fluxCANGAROO I I I : > 30 h of data under analysis

“A”

H.E.S.S.: not detected at level of old flux“B”

H.E.S.S.: 11 , spectrum differs

H.E.S.S.: 45 , spectrum & flux reasonable“B”

H.E.S.S.: 20 , spectrum & flux not incompatible“B+”

H.E.S.S.: not detected at level of old fluxCANGAROO I I I : > 30 h of data under analysis

“B”

H.E.S.S.: not detected at level of old flux“C”

Current status

Southern hemisphere TeV sources

PSR 1706-44• Spindown lum. ~ 1% of Crab

• X-ray lum. ~ 0.01% of Crab

• TeV emission detected by Durham and CANGAROO-I,II

Kifune et al. 1995Chadwick et al. 1998Kushida et al., ICRC 2003

PreliminaryICRC 2003

Crab Flux

E –2.2

E -1.2

Kifune, ICRC 2003

IC prediction ~0.001 CrabSefako & de Jager 2003, 2004

PSR 1706-44

Signalregion

2 (Degr.2)

14 h 2-telescope datataken during commissioningphase

H.E.S.S.assumingpoint source

preliminary

10-13

10-12

10-11

10-10

0,1 1 10

F [c

m-2

s-1]

E [TeV]

Integral Flux

CANGAROOYoshikoshi et al.

1997

DurhamChadwick et al.2000

H.E.S.S.2004assumingpoint source

E-1.5

VELA

• CANGAROO source 0.13o off pulsar

• H.E.S.S. limits similar for both CANGAROO and pulsar location

Chandra

preliminary

Classical southern SNRs

CANGAROO SN 1006

Kifune ICRC 2003

H.E.S.S. significance map

preliminary

Tanimori et al., ApJ 497 (1988) L253.8 m telescope+ conference proceedings

10-13

10-12

10-11

0,1 1 10 100

Inte

gral

Flu

x [c

m-2

s-1]

Energy [TeV]

CANGAROO 1996/97

HEGRA CT1 1999-2001

H.E.S.S. 99% UL2003 Datafor CANGAROO hotspot

with CANGAROO psf (0.23o)

H.E.S.S. flux limitsTime dependence ?

Size of SNR ~50 LYBut small scale shocks < 1 LY (Chandra)Need O(mG) fields to cool electrons quickly enough

Problem with theory ?(Berezhko, Völk)

Fields > 100 G reduce IC below limit Density < 0.1 cm-3 reduces o component below limit

Classical southern SNRs

CANGAROO RXJ1713.7-3946

Kifune ICRC 2003

H.E.S.S.

RJX1713 Spectrum, HESS analysed 18 hrs of 2003 data, Hard Cuts and No

Background Subtraction

H.E.S.S.: full remnant

CANGAROO: hotspot

Index 2.2±0.07±0.1

preliminary

Index 2.84±0.15±0.20

TeV gamma rays from GC

Whipple 1995 – 20033.7

CANGAROO2001/2002> 10

Tsuchiya et al.200467 h on

Kosack et al. 200426 h

H.E.S.S.17 h datatight cutsno backgr.subtraction

CANGAROO Results on GC

Comparison of Spectrum from Different Experiments

on

off

Point source (size < 3‘ or 7 pc)

H.E.S.S.psf

H.E.S.S.Whipple(95%)

CANGAROO (80%)

none of the individual experiments sees variability

HESS and WHIPPLE see less flux than extrapolated

EGRET flux

PSR B1259-63 / SS 2883 System Outline

Star► Bright and massive Be-star:

L* = 3 .1030 W, M = 10 M ► Stellar disk, mass outflow

Pulsar► Radio pulsar with

P = 48 ms► Spin down luminosity

Lp = 8 .1028 W

Orbit► Period 3.4 years► Periastron 23 R*

► Apastron 331 R*

► Inclination 35°► Distance1.5 kpc point source► Last periastron 7th of March 2004

Only known object of this class in our galaxy! (not really true ????) (see Tavani’s talk in HD’04)

.

TeV gamma ray production viaInverse Compton Scattering of thestar’s photon field and acceleratedparticle populations from:

1) Unshocked pulsar wind Ball, Kirk 2000

2) Pulsar wind termination shock induced by star’s photon field Ball, Dodd 2001

3) Interaction region of star mass outflow and pulsar wind Kawachi et al. 2004

CANGAROO Observations HESS Observations Schedule

Pre-periastron:► 26.2. - 2.3.2004► Livetime: 7.8 h► 3 telescopes only► Zenith angle: 42

deg► Threshold: 360

GeV

Post-periastron:► 19.3. - 29.3.2004► Livetime: 17.4 h► Zenith angle: 44

deg► Threshold: 380

GeV

Preliminary Analysis Results - Signal

Pre-periastron, 7.8 h:► Significance: 9.1 σ► Excess rate:

(0.39 ± 0.04) /min

Post-periastron, 17.4 h:► Significance: 6.3 σ► Excess rate:

(0.22 ± 0.03) /min

Significance Skymap:► FoV = 2 deg radius► Clear excess at pulsar

position

Spectrum Fit:► Spectral index:

-2.8 ± 0.3 (stat)► Flux level:

5% Crab► Spectral index of post-

periastron spectrum is compatible

► HESS sees variability with RXT Observations

unshocked pulsar wind

log

(Flu

x [a

.u.])

days

shocked pulsar wind

aligned stellar disc

misaligned stellar disc

► Data does not favour continuous flux decrease within 21 days after periastron

► Systematics still under investigation

Lightcurve Shape –Data vs. Models

Looking For Other Sources in the Field of View

Results from the CELESTE Experiment

Results from the STACEE Experiment

Results from Air Shower ArraysMILAGRO and TIBET-III

(88.8,30.2)

Crab

Mrk421

DEC.

R.A.

Crab and MKn421 seen at significance of 4.9 and 5.3 sigma resp.Upper limits for several sources given

List of sky cells with clustered directions (24)having statistic significance larger than 4.0

TIBET-III

Large scale anisotropy of CR intensity with a magnitude of 0.1% has been observed

All Sky Coverage by MILAGRO

Full (northern)sky surveys

Energy Threshold ~ 1 TeVCrab and Mkn421 seen

For more details see the Milagro Talk at Heidelberg, 04

Old story we know

MILAGRO Observations Contd…….

Galactic Plane Survey

Galactic Centre obs showed 91 objectsthat accounts for 90% of > 20 KeV bgd

towards the centre of galaxy

For more details, see talk by R.Much at HD’04

Some Thoughts for the Future Sources

High Energy Processes from MicroquasarsRadio Emitting X-ray binaries

A few sources detected simultaneously in X-ray/radio bands

Merck et al ( 1996) studied spectral characteristics of unidentified galactic EGRET sources

Most of them have hard spectrum and extend to GeV energies

Could be Pulsar like !!!!!!Spectra does not seem to be identical to the identified pulsars

High galactic diffuse background make analysis difficult

Be Binary system LS I +61deg 303 (associated with GT 0236 +610)Possible emission with 100 MeV gamma ray source, 2CG135 +01

Simultaneous radio and RXTE obsRadio bursts on 26.5 day orbital circle

Modulation of X-ray emission on orbital timescales confirmedMost likely IC of stellar photons off electrons accelerated

at the shock boundary bet. relativistic wind of young pulsarand Be star wind.

Multiwavelength Studies of AGNs

There were quite a few talks, but no new results or theories as such

People still want more data and more co-ordinated observations to distinguish between ‘hadronic’ and ‘leptonic’ model

(see papers by Costamante and Ghisellini, A&A, 384, 56-71(2002)

High Energy Components of GRBs

• GRB association with SNe is confirmed in at least a few cases ( GRB0300329-Sn2003dh )

• Physics of jet creation, acceleration, propagation and evolution to be understood

• Correlations of MeV energy with global jet parameters imply MeV to be dominant

• However in the standard scenario a large fraction of energy is expected in the afterglow phase

• And in several GRBs powerful >> MeV components are observedHurley et al. 1994 discover high energy component with EGRET

High energy photons last much longer than MeV emission

Also Gonsalez et al(2003) discovered in EGRET archive a GRB whose prompt Energy emission is dominated by E>> 200 MeV, MILAGRO discovered a TeV burst at 3.0 sigma level

Can one do cosmography with GRBs ? Check for possible evolution of cosmological constant??