Very High Energy Gamma Ray Observations with the MAGIC ...scipp.ucsc.edu › seminars › experimental › archive_sumq07 › MAGIC_UCSC.pdfA. Nepomuk Otte Max-Planck-Institut für

Very High Energy Gamma Ray Observations with the MAGIC

Telescope(a biased selection)

Nepomuk Ottefor the MAGIC collaboration

2A. Nepomuk Otte Max-Planck-Institut für Physik / Humboldt Universität Berlin

• Imaging air shower Cherenkov technique– The MAGIC telescope

• Observation of the AGN 3c279

• Observation of Neutron Stars with MAGIC

• The Crab nebula and Pulsar (young pulsar) [astro-ph/0705.3244] • PSR B1951+32 (middle aged pulsar) [astro-ph/0702077]• PSR B1957+20 (millisecond pulsar)• LS I 61+303 [Science 2006]

• Where to go next?


The non-thermal universe in VHE gamma-rays

GRBsAGNs

Origin ofcosmic rays

CosmologyDark matter

Space-time& relativity

Pulsarsand PWN

SNRs Micro quasarsX-ray binaries


VHE gamma-ray sources status ICRC 2007

Rowell

71 known sources

detections from ground


Imaging Air Cherenkov Technique

~ 10 kmParticleshower

~ 1o

Cher

enko

vlig

ht

~ 120 m

Gammaray

Cherenkov light image of particle shower in telescope camera

• fast light flash (nanoseconds)• 100 photons per m² (1 TeV Gamma Ray)

reconstruct: arrival direction, energy

reject hadron background


CANGAROO III(Australia & Japan)

4 telescopes 10 meters Ø

Woomera, Australia

Windhoek, NamibiaHESS

(Germany & France)4 telescopes12 meters Ø

Roque delos Muchachos, Canary Islands

MAGICMAGIC(Germany, Spain, Italy)(Germany, Spain, Italy)1 telescope 17 meters 1 telescope 17 meters ØØ

MontosaCanyon,Arizona

VERITAS(USA & England)4 (7) telescopes

10 meters Ø

Current generation Current generation CherenkovCherenkov telescopestelescopes

MAGICVeritas

H.E.S.S.

Cangaroo III


The MAGIC site


A recent view of MAGIC

MAGIC I

MAGIC II

counting house

picture by R.Wagner


Current Status of MAGIC

First telescope in regular observation mode since fall 2004

– 236 m2 mirror area (17m Ø)– Fast repositioning (40 sec) for GRB

follow-up observations– Upgrade: 2GSamples/s FADCs

– Trigger threshold: ~ 50 GeV– Sensitivity: 2 % Crab (5σ,50h)

for E>200GeV– Using timing parameters after

installation of new 2GSamples/s FADC:=> Sensitivity improved to 1.5% Crab

MAGIC-I

http://wwwmagic.mppmu.mpg.de/gallery/pictures/La_Palma_July_2004/MAGIC10.JPG


Central Pixel for Optical Measurements

• Modified central pixel for optical measurements

• simultaneous with Gamma-ray observations

Crab pulsar in optical by MAGIC

view from back


Event Parameterization

muon ringhadronhadrongamma candidate

event parameterization with principal components

commonly known as Hillas parameters


Background Rejection

hadron shower (background)

gamma shower

Main background:- cosmic ray (hadron)showers

- >103 times more numerous than γ-ray showers

- reject based on showershape (hadrons are broader)


Gamma / Hadron Separation

differences between gammas and background events compressed into one variable:

HADRONNESS

determined with the method of Random Forests

Breimann 2001

analysis for Sizes < 200 phe is difficult

background

gamma rays


Extragalactic Sources: Active Galactic Nuclei

Jet

BlackHole

ObscuringTorus

LineRegion

LineRegion

Disk

Narrow

Broad

Accretion

Urry & Padovani (1995)

blazar


EBL CherenkovTelescope

BL-Lac object

Red shifted stellar light Red shifted dust light

2.7K

Attenuation of VHE γ-rays

−+→ eeEBLHE γγ Eγγ ≈1.8* 2mec2( )

• Absorption leads to cutoff in AGN spectrum

• Measurement of spectral features allows to constrain EBL Models


known extragalactic VHE-sources (19)Source Redshift Sp. Types Discovery Observation

M 87 0.004 2.9 FR-I HEGRA HESS

Mkn 421 0.031 2.2 HBL Whipple many


1ES 2344+514 0.044 2.9 HBL Whipple MAGIC

Mkn 180 0.045 3.3 HBL MAGIC

1ES 1959+650 0.047 2.4 HBL 7TA many

PKS 0548-322 0.069 HBL HESS

BL Lac 0.069 3.6 LBL MAGIC

PKS 2005-489 0.071 4.0 HBL HESS

PKS 2155-304 0.116 3.3 HBL Durham many

1ES 1426+428 0.129 3.3 HBL Whipple HEGRA

1ES 0229+200 0.139 HBL HESS

H 2356-309 0.165 3.1 HBL HESS

1ES 1218+304 0.182 3.0 HBL MAGIC VERITAS

1ES 1101-232 0.186 2.9 HBL HESS

1ES 0347-121 0.188 HBL HESS

1ES 1011+496 0.212 4.0 HBL MAGIC

3C 279 0.538 FSRQ MAGIC

PG 1553 ? 4.0 HBL HESS/MAGIC


Detection of 3C279

80-220 GeV

E> 220 GeV

PreliminaryPreliminary

PreliminaryPreliminarySky map around 3C279Sky map around 3C279




big jump into the deep universe

may deliver stringent constraint on EBL and acceleration models

Pulsars and & pulsar nebulae

ExploringExtreme electrodynamics& GRRelativistic windsAcceleration in shocks


The Pulsar Wind Nebula Complexon the example of the Crab

magnetized, spinning neutron star (pulsar)

energy carried away by electromagnetic radiation and particles (~1038 erg/s)

particle acceleration in:

1. light cylinder2. shock front

massive object in center:

from Aharonian et al


The Crab Nebula resolved in X-Rays

NASA/CXC/ASU/J.Hester et al.

7 still images of Chandra observations taken between November 2000 and April 2001.

rich and dynamic structure in X-rays:

• wisps• knots• jets


The Crab-PWN: Broadband Emission

Aharonian & Atoyan (1998)

synchrotron emission

IC-emission

• little known at energies around the peak of the IC-emission

morphology?

variability?

spectrum?

pulsar?

studied with MAGIC at energies >60 GeV

Pulsar

Nebula Synchrotron IC


Crab Nebula: Spectral Energy Distribution

• good agreement with other Cherenkov telescopes above 400GeV

• spectrum well described within SSC-framework

• first time determination of the IC-peak at 77±47statGeV


Crab Nebula: Morphology

• emission region compatible with point-like source

- emission region


Crab Nebula: Variability

no variability (>200 GeV) on time scales of:

• minutes (


The Crab Pulsar Wind Nebula Complex

from Aharonian et al

turning to the central object

the pulsar


Gamma-Ray Emission from Pulsars

• three sites favored for particle acceleration

• emission appears pulsed; lighthouse model

• complex electrodynamics; challenging for theory

spin axis magnetic dipole moment

Harding

• no pulsar detected above ~100 GeV

spectral cutoff; challenging for experiment


Crab Pulsar in Gamma-Rays

shaded: regions of pulsed emission defined by EGRET measurements above 100 MeV (P1, P2)

significance of pulsed emission:no prior assumption about pulse profile: 1.2σguided by EGRET >100 MeV profile: 2.9σ

Fierro, 1998

events with Size


Upper limit on cutoff energy

1. assume EGRET spectrum with exponential cutoff

2. convolute spectrum with MAGIC response

3. calculate number of expected pulsed excess events

4. compare with upper limit on pulsed excess events

5. reiterate with different cutoff energy until match

MAGIC response after cuts (Size


Crab Pulsar II

• no detection/hints of pulsed emission in differential bins of energy

• upper limits compatible with results from other experiments


PSR B1951+32 / CTB 80

pulsar detected by EGRET up to 20 GeV

at 10 GeV similar luminosity as the Crab pulsar

A different pulsar than Crab

• 100 times older (~105 years)• 10 times lower surface magnetic

field (~5x1011 G)• moves 2 times faster through ISM

(240km/s)• 100 times lower spin down

luminosity (~1036 erg/s)

radio

optical

radio and synchrotron nebula CTB80 + VHE gamma-ray predictions

a good candidate to observe with MAGIC


In the surroundings of PSR B1951+32

No displaced gamma ray emission level of few % Crab (point source 0.1° RMS radius)

reduced sensitivity for more extended emission region


PSR B1951+32 / CTB 80

• model calculations do not take pulsar motion into account

emission smeared outover a larger volume?

• magnetic field larger than assumed

pulsar wind not particle dominated?

• can exclude flux level predicted by Bednarek & Bartosik(2003)


PSR B1951+32 Pulsar

• no pulsed emission detected

• constrain on the cutoff energy


Evolution of Pulsars in Binary systems

Lorimer, 2005

spin up of old pulsars by accretion of mass from companion star

millisecond period pulsars

Lower magnetic field:reduced screening of Gamma-rayslower acceleration voltage


PSR B1957+20: The black widow

• second fastest known pulsar (1.607 ms)

• recycled pulsar

• binary system (eccentricity


PSR B1957+20: search for steady gamma-ray emission

can not exclude predicted gamma-ray flux from pulsar [Bulik (2000)]

more sensitive pulsed analysis not possible because of invalid ephemeris of the binary system


PSR B1957+20: Search in orbital phase

no evidence for gamma ray emission

light curve flux limits


LSI+61 303

LSI+61 303:

• high mass x-ray binary• Be star companion with

circumstellar disc• high eccentricity (~0.7)• radio and x-ray emission

modulation: 26.5 days (orbit)

• radio jets (100AU)

Massi et al 2004


LSI+61 303: MAGIC observations

Albert et al., SCIENCE 2006Albert et al., SCIENCE 2006

• 54 h observation from November 2005 till March 2006• 9 σ detection of point-like source (E > 200 Gev)• Spectral index = -2.6 ± 0.2 (stat) ± 0.2 (syst)• Flux clearly variable• Average emission has maximum (~16% Crab) at phase 0.6.


LSI+61 303: models

• Microquasar: rel. electrons (& hadrons) from accretion powered jetsor• Binary Pulsar: rel. electrons from rotational energy of pulsar

Mirabel 2006


Summary and Conclusion

• MAGIC in full production

• ~1 new source every two month

• many exciting results like 3C279 or LSI 60+303

• detailed studies possible: Crab nebula in the energy range between 60GeV and 400GeV– within experimental resolution:

• emission region is point like;


Outlook into the Future

• The gamma-ray window between 10 GeV and 100 GeVis still closed

• GLAST will be a pathfinder mission but can not answer all questions– the strength of Cherenkov telescopes is a large collection area

(~104 m²)high sensitivity to transients

• short time flaring in AGNs• test stability of pulsed emission at the highest energies• ….

• Opening the 10 GeV - 100 GeV window from ground will be necessary

lower threshold Cherenkov telescopes are needed


Very near future: This Crab season

• trigger threshold of MAGIC is limited by accidental triggers caused by PMT afterpulses

• current trigger requires a 4 next neighbor coincidence

• investigate new trigger idea:– analog signals are clipped above ~6phe– analog sum of ~10 pixels– discriminate sum signal at ~20 phe

First tests on MAGIC are very encouraging


Trigger tests on La Palma


midterm future (2008): MAGIC II

second telescope: MAGIC-II

”Improved clone”– Most fundamental parameters identical

to MAGIC-I– Use improved technology where

available:• High QE photosensors• Fast sampling readout

MAGIC-I

MAGIC-II

85m

Aim:• Increase sensitivity (particularly below 100 GeV)• Lower energy threshold further


MAGIC II Monte Carlo Studies

Stereo Analysis:• observe shower simultaneously

with 2 telescopes

• 3D shower reconstruction• Additional shower parameters:

– Impact parameter– Shower maximum (hmax)– Eliminate ambiguity on arrival

direction

• Better reconstruction of energy and arrival direction

• Improved background rejection


Improved Reconstruction

• Energy resolution– MAGIC-I: ~25%– MAGIC-II: 14-20%

(2 telescopes)

• Angular resolution– Substantial (~50%) improvement

since source position is obtained from intersection point of both showers


Improved Sensitivity

using Stereo Analysis• better background rejection down to low energies • increase sensitivity by up to factor 3

=> reduce observation time by factor 9• Large gain in sensitivity at low energies (< 100 GeV)


New photon detectors: The G-APD

a promising photon detector concept invented in Russia in the 80’s

P. Buzhan et al. http://www.slac-stanford.edu/pubs/icfa/fall01.html

• sensors with ~60% efficiency become available• internal gain ~105 -106• compact and robust• …

advantages

disadvantages

• small sizes (


Test on La Palma with MAGIC

4 MPPC-33-050C from Hamamatsu:

sensor size: 3x3mm²single cell size: 50x50µm²nominal bias: 70.4Vdark rate at nominal bias: ~2MHzgain at nominal bias: 7.5*105crosstalk at nominal bias: 10%

peak photon detection efficiency 55% needs to be confirmed

Array of 4 MPPCs:light catchers with factor 4 concentration; 6x6mm² onto 3x3mm²

MAGIC Pixel Size


Array mounted onto the MAGIC camera entrance window for two nights


position of MPPC array

1 phe

MPPCs

PMTs

2 phe 4 phe 1 phe

70 phe 35 phe 35 phe 15 phe


Shower Signals: MPPC vs PMT

event selection:two PMTs next to MPPCs with more than 15 photoelectrons in each tube

signals are correlated

coun

ts

~300 events from ~30 min data

on average MPPCs detect 1.6 times more light


End


Light recorded from Calibration Runs

UV-LEDs 375nm

Pedestal

1 phe

2 phe

3phe

…

single phe-resolution degraded due to light

from night sky background

easy calibration

some recorded showers


Key technological elements for MAGIC

17 m diameter parabolic reflecting surface (236 m2 )

Analog signal transport via optical fibers IPE

IPEIPECENET

2-level trigger system& FADC system

Active mirror control(PSF: 90% of light in 0.1o inner pixel)

high reflective diamond milled aluminum mirrors Light weight Carbon fiber

structure for fast repositioning

- 3.5o FOV camera - 576 high QE PMTs

(QEmax= 30%)


Data Set

• October – December 2005

• 16 hours ON source / 19 hours OFF source

• zenith angle 500 GeV

alpha plot for energies >200 GeV


The Crab Pulsar Wind Nebula

• standing reverse shock

• acceleration of electrons up to 1016 eV

• synchrotron emission (radio to gamma -rays) downstream of shock

• inverse Compton scattering (VHE gamma-rays)

other possible VHE gamma-ray components are pi0-decay or bremsstrahlung

influence on VHE gamma-ray spectrum, morphology and variability


3C 279

• EGRET brightest AGN– Gamma-ray flares in 1991 and 1996– Apparent luminosity ~ 1048erg/s– First time variation △T ~ 6hr in 1996 flare

• Typical OVV quasar (Optically violent variable)– Categorized as a FSRQ (Flat Spectrum Radio

Quasar)

• Superluminal motion, γ~ 20~30• z = 0.538, Ld ~ 3Gpc


3C 279 Flare in 1996


SSC+EC / Hadronic

MAGIC


EBL Absorption

Pair Creation; γHE＋γEBL e+ + e-


MAGIC Telescope

MAGIC-II is under construction and will becompleted in the fall of the next year

Improve sensitivity by a factor of threeEffectively lower the threshold energy

New technologiesto lower the threshold energy

17m diameter world largest cherenkov tel.0.1°High resolution cameraHemispherical PMT with enhanced QEAnalogue signal fiber transmission

Current MAGIC-I Performance

Fast rotation for GRB < 40secsTrigger threshold ~50GeVSensitivity ~2% of Crab (50hrs)Angular resolution ~0.1 degreesEnergy Resolution 20-30%

85m


Observation of 3C 279 with MAGIC

• Observation– In the period of January - April 2006– Observation of 9.5hrs– Zenith angle range is between 32 and 40

degrees relatively high threshold of 80GeV

• Analysis– 4 independent analyses have been done– Standard analysis and standard quality cut– Preliminary results will be presented here


Sky-map and alpha ploton 23rd Feb 2007

80-220 GeV

E> 220 GeV



Sky map around 3C279Sky map around 3C279





3C279 VHE gamma-ray light curve

Intra-night LC



Optical light curve


Extragalactic VHE-sources (19)

Source Redshift Sp. Types Discovery ObservationM 87 0.004 2.9 FR-I HEGRA HESS


Mkn 501 0.034 2.4 HBL Whipple many1ES 2344+514 0.044 2.9 HBL Whipple MAGIC

Mkn 180 0.045 3.3 HBL MAGIC1ES 1959+650 0.047 2.4 HBL 7TA manyPKS 0548-322 0.069 HBL HESS

BL Lac 0.069 3.6 LBL MAGICPKS 2005-489 0.071 4.0 HBL HESSPKS 2155-304 0.116 3.3 HBL Durham many1ES 1426+428 0.129 3.3 HBL Whipple HEGRA1ES 0229+200 0.139 HBL HESS

H 2356-309 0.165 3.1 HBL HESS1ES 1218+304 0.182 3.0 HBL MAGIC VERITAS1ES 1101-232 0.186 2.9 HBL HESS1ES 0347-121 0.188 HBL HESS1ES 1011+496 0.212 4.0 HBL MAGIC

3C 279 0.538 FSRQ MAGIC

PG 1553 ? 4.0 HBL HESS/MAGIC

New HBL 1ES1011+496 See the presentation by D. Mazin

Big progress in AGN studyfrom z ~ 0.2 to z = 0.538


Summary

• VHE gamma-ray emission from 3C 279 was discovered by MAGIC– New class of source FSRQ, OVV-quasar

• The VHE flare at 100GeV was observed on 23 February in 2006 – 6 sigma below 220GeV, and 5 sigma above 220GeV

• The survey distance is extended up to z = 0.538 by MAGIC telescope– Big jump toward the deep Universe!

• Study of Energy spectrum– may deliver a stringent constraint on EBL and acceleration model– Analysis is ongoing; We need very careful understanding of

systematic uncertainties in the energy determination


Crab nebula emission region in VHE gamma-rays

• emission region determined by:• confinement of electrons by

magnetic fields• synchrotron cooling times

lower energies more extended emission region (few tens of arcseconds)

possible hadronic component (pi0 decay) could result in a more extended emission region

Atoyan & Aharonian


Crab Nebula: Differential Energy Spectrum

• gamma-ray emission measured over two decades of energy60 GeV – 9 TeV

• simple power-law behavior disfavored; χ²: 24/8

• spectrum is well described by a curved power law fit; χ²: 8/7

( )

TeVscmGeVE

dEdF GeVE

⋅⋅⎟⎠⎞

⎜⎝⎛⋅=

−−−

2

300/log26.031.210 1

300106


Crab pulsar in optical

verifies analysis chain

main pulse offset by -252±64 µsto position of main pulse in radio


Search for pulsed Gamma-ray emission

BackgroundExcessQ =

Q vs. upper Size cut

Assuming exponential cutoff of the pulsar at 30 GeV

highest sensitivity for pulsed emission if events with Size


Pulsar: Broadband Emission

Thompson et al. 1999

• synchrotron radiation• curvature radiation• inverse Compton scattering

radiation processes

• no pulsar detected above ~100 GeV

MAGIC

spectroscopy of the cutoff would help to distinguish between theories

spectral cutoff; challenging for experiment


The GeV excess

EGRET observed Gamma-ray flux >1GeV can not be described by SSC

possible explanations:

• DC gamma-ray component from the pulsar

• enhanced Bremsstrahlungemission

SSC-model

GeV excess


The GeV excess explained by Bremsstrahlung

Atoyan & Aharonian 1996

amplified Bremsstrahlung in denser regions of the nebula (knots)

can explain the GeV excess

could result in modified spectrum between 100 GeVand several TeV


Crab Nebula: Spectral Index

• observation of energy dependent spectral index

• no deviation from SSC predictions (blue line)

• disfavor A&A 1996

• model A&A 1998 in agreement with measurement

Very High Energy Gamma Ray Observations with the MAGIC Telescope�(a biased selection)The non-thermal universe in VHE gamma-raysVHE gamma-ray sources �status ICRC 2007Imaging Air Cherenkov Technique The MAGIC siteA recent view of MAGICCurrent Status of MAGICCentral Pixel for Optical MeasurementsEvent ParameterizationBackground Rejection Gamma / Hadron SeparationExtragalactic Sources: Active Galactic NucleiAttenuation of VHE -rays known extragalactic VHE-sources (19)Detection of 3C279Pulsars and �& pulsar nebulaeThe Pulsar Wind Nebula Complex�on the example of the CrabThe Crab Nebula resolved in X-RaysThe Crab-PWN: Broadband EmissionCrab Nebula: �Spectral Energy DistributionCrab Nebula: MorphologyCrab Nebula: VariabilityThe Crab Pulsar Wind Nebula ComplexGamma-Ray Emission from PulsarsCrab Pulsar in Gamma-RaysUpper limit on cutoff energyCrab Pulsar II PSR B1951+32 / CTB 80In the surroundings of PSR B1951+32PSR B1951+32 / CTB 80PSR B1951+32 PulsarEvolution of Pulsars in Binary systemsPSR B1957+20: The black widowPSR B1957+20: search for steady gamma-ray emissionPSR B1957+20: Search in orbital phaseLSI+61 303 LSI+61 303: MAGIC observationsLSI+61 303: modelsSummary and ConclusionOutlook into the FutureVery near future: This Crab seasonTrigger tests on La Palmamidterm future (2008): MAGIC IIMAGIC II Monte Carlo StudiesImproved ReconstructionImproved SensitivityNew photon detectors: The G-APDTest on La Palma with MAGICShower Signals: MPPC vs PMTLight recorded from Calibration RunsKey technological elements for MAGICData SetThe Crab Pulsar Wind Nebula3C 2793C 279 Flare in 1996SSC+EC / HadronicEBL AbsorptionMAGIC TelescopeObservation of 3C 279 with MAGICSky-map and alpha plot�on 23rd Feb 20073C279 VHE gamma-ray �light curveExtragalactic �VHE-sources (19)SummaryCrab nebula emission region �in VHE gamma-raysCrab Nebula: Differential Energy SpectrumCrab pulsar in opticalSearch for pulsed Gamma-ray emissionPulsar: Broadband Emission The GeV excessThe GeV excess explained by BremsstrahlungCrab Nebula: Spectral Index

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Very High Energy Gamma Ray Observations with the MAGIC ...scipp.ucsc.edu › seminars › experimental › archive_sumq07 › MAGIC_UCSC.pdfA. Nepomuk Otte Max-Planck-Institut für