r. m. wagner: agn observations with magic – p.1 r. m. w agner max-planck-institut für physik,...

R. M. Wagner: AGN observations with MAGIC – p.1

R. M. WAGNERMax-Planck-Institut für Physik, München

on behalf of the MAGIC COLLABORATION

AGN Observations in the GeV/TeV Energy Range

with the MAGIC Telescope


Contents

Blazars & jets – how can TeV observations help?

MAGIC blazar observation activitiesBlazars observed by MAGIC, some highlights

• Markarian 421• 1ES 1959+650• 1ES 1218+304• PG 1553+113• Markarian 501• Markarian 180• 1ES 2344+514• BL Lacertae

Conclusions

16 sources (incl M87) to date and counting

seen in VHE -rays


Jets observed under small angle• Rapid variability at all wavelengths• Most violent and rapid often in VHE• High Doppler factors: amplified

emission, deep insight into jet

Kino et al.

synchrotronpeak

Inverse Compton

peak

(Buckley 1999)

Hadronic

TeV Blazars | E>100 GeV

Mkn 501 HEGRA, Kranich 2001

How can TeV observations help? -rays are crucial messengers:• Dynamics of emission regions in the jets• Study acceleration & energy loss timescales • Decide: leptonic vs hadronic acceleration?

- Hadronic models challenged by observed X/VHE correlations and by very rapid -ray variability

- Variability needs to be explained: Matter crossing the jet? sub-shocks? ...jet structure

• Decide SSC/EIC


The MAGIC Telescope

• 17m Imaging Air Cherenkov Telescope: currently largest single-dish instrument

• 3.5° FOV

Optimized for extragalactic point-like sources

• Trigger threshold: 50 – 60 GeV Analysis thresh: 70 – 100GeV

• Energy resolution 30% at 150 GeV

• Sensitivity: 2.5% Crab Nebula in 50 hours at E=250 GeV

• Enhanced duty cycle (moon observations)

• 2nd telescope under construction

Major Atmospheric Gamma-ray Imaging Cherenkov Telescope

Extensive blazar observation program: approx. 500 hours/year

Simultaneous optical monitoring during observations MWL campaigns with Suzaku and other satellite experiments (results: see ICRC’07)

Numerous ToO agreements with optical; X-ray, -ray satellites; telescopes, and

Global Network of Cherenkov Telescopes initiative

simultaneous observations w/HESS: wider energy coverage

sequential observations w/VERITAS: ext’d time coverage

Ongoing blazar monitoring of known bright sources: low state, flare statistics, blazar duty cycle

MAGIC | AGN & blazar observation activities


Mkn 421 | z=0.030 | Nov 2004 - Apr 2005

• 25.6 h observations, clear diurnal signal

• Energy threshold: 150 GeV• Source-inherent cutoff 1.40.3 TeV

ApJ 663 in press

astro-ph/0603478

historical

TeV spectra

MAGIC


Mkn 421 | z=0.030 | Nov 2004 - Apr 2005

• Variable fluxes on day-to-day scale, 0.5–2 Crab, but no flares shorter than 1h

ApJ 663 in press

astro-ph/0603478

F(E>200GeV)

2-10 keV

optical

Intra-night, 10 min bins:

6 nights, night-by-night

• Clear TeV/X-ray correlation,slope hardens with intensity: IC favored


Mkn 501 | z=0.034 | June/July 2005ApJ submitted

astro-ph/0702008

• Clear signal each night: > 85 • Energy threshold 150 GeV• No strong evidence for correlated optical/X/VHE emission

June 30 July 09Clear variability in -rays

<F>Mkn501 ~ 0.5 Crab (‘low’)

Unprecedented

fast variations!

(<3 min)Emission region

severely constrained!June 30 July 09

<F>Mkn 501

2 min bins 2 min bins

Obs during moontime!


Mkn 501 | Intra-night flaresApJ submitted

astro-ph/0702008

• Two flares behave rather differently• June 30 flare: No high (>600 GeV) energies• July 09: all energies, “pre-flare“?

June 30 July 09

150-250 GeV

250-600 GeV

600-1200 GeV

1200 GeVand above


Constant fit : 2/ndf = 76.6/25 (P=4×10-7)

Spectrum hardens with increasing flux

Peak Peak

Peak in VHE distribution clearly observed in high-flux nights

Peak location seems to depend on the source luminosity

Mkn 501 | Spectral variations

EBL corrected EBL corrected(Kneiske et al. 2004 “low IR”)

(Kneiske et al. 2004 “low IR”)

measured

measured

ApJ submitted

astro-ph/0702008

Flux-Spectral index correlation

SED

MAGIC


1ES 2344+514 | z=0.044 | Aug 2005 – Dec 2005ApJ 663 in press

astro-ph/0612383

First time-resolved observation of the low blazar emission state

Energy spectrum• Discovery: Whipple, Flare Dec 1995, F(>350GeV) = 63% Crab Catanese et al. 1997

• UL from Whipple (1997, 2000), HEGRA (1998-2002), TACTIC (2004-2005)

• MAGIC: observation Aug-Dec 2005 F(>350GeV)=6% Crab

• 11 - Clear detection

• Only marginal hints of variability


PG 1553+113 | z>0.09 ApJL 654 (2007) 119

Blazar at unknown distance• No emission lines: Jet outshines core? Very close alignment of jet axis to observer?• High z? Small host galaxy? • Discovery by H.E.S.S. & MAGIC• Steepest observed –ray spectrum: spectral slope =4.2±0.3 – how much absorption is intrinsic?

MAGIC VHE

KVA optical

2005

2005

2006

2006

SSC modeling:• Models based on different z: Disfavor z>0.56 on 4.5 level

• Light curve: No correlation with optical flare. Time lag?


BL Lacertae | z=0.069 | Aug – Dec 2005

LBL-type blazar: Synchrotron peak in the optical:Expect steep slope at VHE profit from low energy threshold!

First LBL discovered in VHE –rays!

Relatively steep –ray spectrum: spectral slope =3.6±0.5

ApJL submitted

astro-ph/0703084

Leptonic model, no EIC components necessary as required to explain 1997 flare seen by EGRET

Epeak=250 GeV216 Excess eventsSignificance: 5.1

Sky map

Ravasio et al. 2002

O/VHE correlation?


Summary & Conclusions• There are now 16 blazars observed in -rays above 100 GeV with more

observations & detections in the pipeline • VHE observations are crucial for modeling non-thermal emission

regions in jets, but...• Will need full time-dependent modeling & MWL observations• Increased instrumental sensitivity helps precision observations

of bright blazars Mkn 421, Mkn 501, 1ES 2344.

• Leptonic nature of acceleration?flux-hardness correlation, IC peak detected

• Fast blazar flaring: First time minute-scale variability in VHE!• Low blazar emission state was mostly elusive before:

• now removing observational bias towards flaring sources in the VHE regime

1) Many new sources discovered with interesting properties:• Mkn 180: source detected upon optical trigger • 1ES 1218: high redshift (now confirmed by VERITAS)• PG 1553: probably very close alignment to jet axis• BL Lacertæ: First LBL -ray source


Backup slides


Detection of E>100 GeV -rays

showers

• Narrow images

• Aligned towards source direction

, 100 GeV Proton, 100 GeV• Cosmic rays initiate extensive air showers

• Cherenkov light is emitted by relativistic particles in the shower

• Showers induced by -rays and hadronic cosmic rays (104 times more numerous) develop differently in the atmosphere

• Image parametrization

• Background suppression: Cuts in image parameters

candidate eventsfrom pointing direction

hadronic showers

• Spread images

• Isotropic arrival direction


Kino et al.

synchrotronpeak

Typical Spectral Energy Distribution

Inverse Comptonpeak

(Buckley 1999)

• Inverse Compton scattering on different possible target photon fields

• In particular in blazars: Synchrotron Self-Compton model: synchrotron photons target field for IC process

• Natural explanation of X-ray / -ray correlated variability

Acceleration and VHE productionPrimary acceleration by diffusive shock acceleration in jetsPower law

• Electrons emit synchrotron radiation

Electron

Electron

• Protons: 0 decay from photo-pion production or synchrotron emission from protons

• Difficult to accomodate X-ray / -ray correlations

• Should observe simultaneous -emission

Hadronic acceleration models:


Low-level blazar emission

1ES 2344+514 Discovery: Flare during the night of 1995/12/21

• Up to now VHE -ray observations biased towards flaring states: • What are the properties of blazars at non-flare times?

• MAGIC: Clear 11 signal from 23 observation nights

MAGIC 2005VHE -ray light curve

• and with previous <5observations

• Profit from MAGIC’s higher sensitivity

• Integral flux 5.7 times lower than during 1995 flare

• Light curve well compatible with low emisson state of the source

All-time VHE -ray light curve

1995 flare

MAGICsignificance well below 5

1995 flare data & 2005 MAGIC low emission data could be modeled using a one-zone SSC model.

ApJ in press

astro-ph/0612383


PG 1553 probablydistant source!

Possibility to constrain redshift by assumptions on EBL and acceleration mechanism:

z < 0.42 (Mazin & Goebel 2007)Once distance is known: Source probably

decisive for EBL determination!

Attenuation of VHE -rays in the universePG 1553+113 blazar with unknown distance• Simultaneous discovery by MAGIC, H.E.S.S. • MAGIC: 8.8 signal from 19 h observations• Steepest observed –ray spectrum:

spectral slope =4.20.3

MAGICH.E.S.S.

Crab nebula

Modification of spectrum due to Extragalactic Background Light (EBL)

VHE + EBL e+e–

VHE is “lost” to observer

IR(dust)

Vis(starlight)

Peak in e+e– GeV energies probe a specific energy range of the EBL spectrum

Net effect in the >100 GeV range: Steepening of (power-law) spectra


Mkn 180 | z=0.045 | 2006 March 23-31

New sources discovered by IACT:

Mkn 180• Successful optical trigger• 11.1 h, 5.5 ,

F(>200GeV) = 11% Crab,

spectral slope =3.3 ± 0.7rather hard spectrum

• Earlier UL at comparable level• No significant variability• Need to understand whether

O/VHE correlation

ApJL 648 (2006) 105

SEDModel: FO98

Model: CG02


1ES1218+304 | z=0.182

• Whipple: F(>350GeV)<8% C.U.

• HEGRA: F(>750GeV)<12% C.U.

• MAGIC: DISCOVERY!

• Jan 2005, 8.2 h

• 6.4 , F>120GeV = 13% C.U., spectral slope =–3.0 ± 0.4

2 plot sky map

ApJL 642 (2006) 119

SED


• High-peaked BL Lac objects

Cycle-I: 181 hours, 13 source candidates

Cycle-II: 99 hours• Low-peaked BL Lac objects

Cycle-I: 76 hours

Cycle-II: 86 hours• Monitoring of TeV-bright blazars

Cycle-II: 38 hours (70% done)

• Time-of-Opportunity observations (externally triggered)

Cycle-II: 11 hours

Upper limit publication of cycle-I HBLs upcoming...

MAGIC blazar observations

r. m. wagner: agn observations with magic – p.1 r. m. w agner max-planck-institut für physik,...

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