5th science agile workshop, june 2008 1 observations of pulsars with magic marcos lópez...
Post on 16-Dec-2015
215 Views
Preview:
TRANSCRIPT
5th Science AGILE Workshop, June 2008
1
Observations of pulsars with MAGIC
Observations of pulsars with MAGIC
Marcos López (INFN/Padova)
on behalf of the MAGIC collaboration
5th Science AGILE Workshop, June 2008 2
MAGIC
OutlineOutline
Importance of detecting pulsars with CTs
Results from first MAGIC observations
A new trigger concept
Crab pulsar detection !QuickTime™ and a
decompressorare needed to see this picture.
5th Science AGILE Workshop, June 2008 3
MAGIC
What we learnt from EGRETWhat we learnt from EGRET
Typically 2 peaks, and interpulse emission.Typically 2 peaks, and interpulse emission.
Crab only pulsar which same behaviour at all wavelengths !Crab only pulsar which same behaviour at all wavelengths !
~2000~2000 pulsars known, but only pulsars known, but only 77(+3)(+3) at at -rays !-rays !
5th Science AGILE Workshop, June 2008 4
MAGIC
Crab pulsar as seen by EGRETCrab pulsar as seen by EGRET
above 100 MeV: Two peaks,
broad structures
above 5 GeV: First peak seems to
disaperarTwo 100Two 10050 50
GeVGeVphotons!photons!
5th Science AGILE Workshop, June 2008 5
MAGIC
EGRET pulsars: Multi-wavelength spectraEGRET pulsars: Multi-wavelength spectra
Maximum of emission Maximum of emission in the hard X- and in the hard X- and --ray rangeray range
Spectra are very Spectra are very different above 1 GeV different above 1 GeV
Che
renk
ov T
eles
cope
sC
here
nkov
Tel
esco
pes
High energy spectral High energy spectral cutoffscutoffs
5th Science AGILE Workshop, June 2008 6
MAGIC
Acceleration of electronsCooling mechanisms
a) Curvature radiation
b) Synchrotron, I.C. of X-rays
-rays interact with magnetic field, via Magnetic pair production
−+ +→+ eeBr
γ
Polar Cap ModelPolar Cap Model Sturrock (1971); Ruderman & Sutherland (1975); Harding (1981); Daugherty & Harding (1982)
Polar Cap model predicts super-exponential cutoff in high energy -ray spectra !
Models of -ray emission in Pulsars
)/1exp( pp BEB κ −⋅∝
5th Science AGILE Workshop, June 2008 7
MAGIC
-ray emission occurs near LC
Charges accelerated in vacuum gap
-rays via Curv. rad.B not strong enough for
pair-production. But, curvature photons interact with non-thermal X-rays
Outer Gap model Outer Gap model Cheng, Ho & Ruderman (1986); Romani (1996)
€
→ e+e−
Electrons may up scatter IR photons to TeV Gamma-rays !
Softer exponential cutoff in the high energy -ray spectra !
Models of -ray emission in Pulsars
5th Science AGILE Workshop, June 2008 8
MAGIC
Discrimination between models Different models predict different spectral cutoff. Measuring the spectral tail is possible to distinguish between
models.
Where do Where do -rays come from? Outer gap or polar cap?-rays come from? Outer gap or polar cap?
MA
GIC
Sum
Trig
MA
GIC
Sum
Trig CherenkovCherenkov
TelescopeTelescope(original (original MAGIC)MAGIC)
5th Science AGILE Workshop, June 2008 9
MAGIC
First Crab observationsFirst Crab observations Data taken in Oct-Dec 2005. 16 hours of optimal quality
A hint of a signal found– 2.9 in phase with EGRET
Derived upper limits– Eo<27 GeV (exp. case)– Eo<60 GeV (super-exp case)
QuickTime™ and a decompressor
are needed to see this picture.
J. Albert et al., Astrophys. J. 674,1037 (2008)
5th Science AGILE Workshop, June 2008 10
MAGIC
PSR B1951+32PSR B1951+32
31 hours taken in July-Sept. 2006
No signal found Constrained cutoff energy to:
Eo<32 GeV
J. Albert et al., Astrophys. J. 669,1143 (2007)
Part III: Gamma-ray Pulsars with MAGIC. Optical Crab observations 11
MAGIC
MAGIC PMTs designed to detect fast Cherenkov pulses 2ns
Need to be adapted to low frequency observations
A PMT was modified to be set at the camera center for optical observations
Electronic Chain Cpix signal is split in 2:
To 16 bits ADC, rate 2-20 kHz MAGIC FADC
Allows Allows and optical and optical
simultaneous observationssimultaneous observations
Motivation:Motivation: Check that MAGIC electronic+software are Check that MAGIC electronic+software are reliable for reliable for -ray pulsar searches-ray pulsar searches
Optical observations of CrabOptical observations of Crab
F. Lucarelli et al., NIM A 589, 415 (2008)
5th Science AGILE Workshop, June 2008 12
MAGIC
MAGIC Crab campaign observed in optical and simultaneously
Optical observations of CrabOptical observations of Crab
Made Crab result robust !
5th Science AGILE Workshop, June 2008 13
MAGIC
Summary first MAGIC pulsar campaignSummary first MAGIC pulsar campaign
No pulsed signal found from any of the observed pulsars
But obtained the lowest upper limit so farConclusion:
– Even the low energy threshold of MAGIC (50-60 GeV) was not enough for catching pulsars
– Solution: Develop a new trigger threshold concept The MAGIC SumTrigger
5th Science AGILE Workshop, June 2008 14
MAGIC
PULSED SPECTRUM (EGRET)
A(E)
NO
EGRET CUTOFFS: POLAR CAP = FAST OUTER GAP = SLOW
FL
UX
or
CO
LL
EC
TIO
N A
RE
A
ENERGY
YESYES
Difficulty of triggering pulsars with CTsDifficulty of triggering pulsars with CTs
New trigger
5th Science AGILE Workshop, June 2008 15
MAGIC
A new trigger conceptA new trigger concept
Idea– clusters of several pixels– sum up analog signals from
individual pixels– discriminate on the summed
signal– Built at MPI (Munich) in
summer 2007 Advantages:
– Small signals contribute to the trigger signal Lower threshold
– Improved signal/noise ratio.
QuickTime™ and a decompressor
are needed to see this picture.
5th Science AGILE Workshop, June 2008 16
MAGIC
A new trigger conceptA new trigger concept
Improvements Size distribution peak shifts to
lower energies Higher coll. area at low energies Sum- & std trigger data taken in
parallel
Improvement Trigger threshold decreased in a factor ~2
5th Science AGILE Workshop, June 2008 17
MAGIC
Crab pulsar detection !!!Crab pulsar detection !!!
Data sample– Observations with new trigger between Oct07
and Feb08– 24 h. of optimal data at low zenith angle
Analysis 3 different analysis show clear signal > 5
– 2 independent timing software: barycenter correction+folding+periodicity tests
– 4 different image cleaning algorithms
5th Science AGILE Workshop, June 2008 18
MAGIC
Results– Clear signal above 25 GeV at 6.3 in phase with EGRET– Observed 8500 pulsed -ray events
Crab pulsar detection !!!Crab pulsar detection !!!Astronomical Telegram #1491
(28th April 2008)
A publication is being prepared, which details about the cutoff
energy
P1 clearly visible,
conversely to EGRET
First Surprise !
Sorry, wait until the publication for getting the
plots
5th Science AGILE Workshop, June 2008 19
MAGIC
ConclusionsConclusions
Pulsars seemed impossible to detect with current CTs,
due to low spectral cutoffs, but we insisted…
First MAGIC pulsar observation campaign already show a
hint of Crab pulsar. New trigger built to confirm it.
First detection of Crab pulsar with a CT after 20 years
chasing it
– Both peaks visible !
– Cutoff higher than expected !
MAGIC opens the road to new discoveries…
5th Science AGILE Workshop, June 2008 20
MAGIC
Outlook: The coming futureOutlook: The coming future
•HESSII under constructionHESSII under construction
•MAGIC II nearly ready…MAGIC II nearly ready… first light in Sept. 2008first light in Sept. 2008
•AGILE successfully in space AGILE successfully in space since more than 1 year since more than 1 year
QuickTime™ and a decompressor
are needed to see this picture.
•GLAST just launchedGLAST just launchedMore than 100 new More than 100 new –ray pulsars –ray pulsars could be discovered !could be discovered !
Full coverage of the Full coverage of the -sky from -sky from 100 MeV to 10 TeV100 MeV to 10 TeV
QuickTime™ and a decompressor
are needed to see this picture.
top related