the spectrum of markarian 421 above 100 gev with stacee
DESCRIPTION
The Spectrum of Markarian 421 Above 100 GeV with STACEE. Jennifer Carson UCLA / Stanford Linear Accelerator Center February 2006. Space-based. 10 MeV. 100 MeV. 10 GeV. 100 GeV. 10 TeV. 1 GeV. 1 TeV. 1 MeV. Ground-based. Outline. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/1.jpg)
The Spectrum of Markarian 421 Above 100 GeV with STACEE
Jennifer CarsonUCLA / Stanford Linear Accelerator Center
February 2006
100 MeV
1 GeV 10GeV
100GeV
1 TeV 10 TeV
10 MeV
1 MeV
Space-based
Ground-based
![Page 2: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/2.jpg)
Outline
I. Science goal for -ray detections from active galaxies• Understanding particle acceleration
II. Brief overview of VHE gamma-ray astronomy
III. Ground-based detection techniques• Atmospheric Cherenkov technique• Imaging vs. wavefront sampling
IV. STACEE
V. Markarian 421• First STACEE spectrum• Detection of high-energy peak?
VI. Prospects for the future
![Page 3: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/3.jpg)
Blazars
• bright core
• 3% optical
polarization
• strong multi-wavelength
variability
Radio-loud AGN viewed at small angles to the jet axis
![Page 4: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/4.jpg)
Blazars
• bright core
• 3% optical
polarization
• strong multi-wavelength
variability
• Double-peaked SED:
synchrotron emission + ?
Radio-loud AGN viewed at small angles to the jet axis
What physical processes produce the high-energy emission?
Maraschi et al. 1994
1 eV (IR) 1 keV (X-ray) 1 MeV10-3 eV (radio) 1 GeV
synchrotron
?
![Page 5: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/5.jpg)
Blazar High-Energy Emission ModelsIs the beam particle an e- or a proton?
![Page 6: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/6.jpg)
Blazar High-Energy Emission Models
Leptonic models:• Inverse-Compton scattering off accelerated electrons• Synchrotron self-Compton and/or • External radiation Compton
Is the beam particle an e- or a proton?
![Page 7: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/7.jpg)
Blazar High-Energy Emission Models
Leptonic models:• Inverse-Compton scattering off accelerated electrons• Synchrotron self-Compton and/or • External radiation Compton
Hadronic models:• Accelerated protons• Gamma rays from pion decay or• Synchroton gamma-ray photons
Is the beam particle an e- or a proton?
![Page 8: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/8.jpg)
Blazar High-Energy Emission Models
Leptonic models:• Inverse-Compton scattering off accelerated electrons• Synchrotron self-Compton and/or • External radiation Compton
Hadronic models:• Accelerated protons• Gamma rays from pion decay or• Synchroton gamma-ray photons
Gamma-ray observations around 100 GeV can distinguish between models
Is the beam particle an e- or a proton?
![Page 9: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/9.jpg)
Exploring the Gamma-ray Spectrum
Atm. Cherenkov Single Dish Imaging
Compton Gamma Ray Observatory
100 MeV
1 GeV 10GeV
100GeV
1 TeV 10 TeV
10 MeV
Energy
1 MeV
Atm. Cherenkov Wavefront Sampling
Air shower arrays
GLAST
Atm. Cherenkov Wavefront Sampling
Atm. Cherenkov Imaging Arrays
Pas
tP
rese
nt/F
utur
e
![Page 10: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/10.jpg)
Atmospheric Cherenkov Technique
ray
~ 1.5oe+
e+
e+
e-
e-
…
e+
![Page 11: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/11.jpg)
Single-dish Imaging Telescopes
ray
~ 1.5o
Whipple 10-meter
![Page 12: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/12.jpg)
Wavefront Sampling Technique
ray
~ 1.5o
![Page 13: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/13.jpg)
Wavefront Sampling Technique
ray
~ 1.5o
![Page 14: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/14.jpg)
Exploring the Gamma-ray Spectrum
Atm. Cherenkov Single Dish Imaging
Compton Gamma Ray Observatory
100 MeV
1 GeV 10GeV
100GeV
1 TeV 10 TeV
10 MeV
Energy
1 MeV
Atm. Cherenkov Wavefront Sampling
Air shower arrays
GLAST
Atm. Cherenkov Wavefront Sampling
Atm. Cherenkov Imaging Arrays
Whipple 10-meter
Pas
tP
rese
nt/F
utur
e
![Page 15: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/15.jpg)
Exploring the Gamma-ray Spectrum
Atm. Cherenkov Single Dish Imaging
100 MeV
1 GeV 10GeV
100GeV
1 TeV 10 TeV
10 MeV
Energy
1 MeV
Atm. Cherenkov Wavefront Sampling
Air shower arrays
GLAST
Atm. Cherenkov Wavefront Sampling
Atm. Cherenkov Imaging Arrays
Whipple 10-meter
STACEE
CELESTE
![Page 16: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/16.jpg)
Exploring the Gamma-ray Spectrum
Atm. Cherenkov Single Dish Imaging
100 MeV
1 GeV 10GeV
100GeV
1 TeV 10 TeV
10 MeV
Energy
1 MeV
Atm. Cherenkov Wavefront Sampling
Air shower arrays
GLAST
Atm. Cherenkov Wavefront Sampling
Atm. Cherenkov Imaging Arrays
Pre
sent
/Fut
ure
STACEE
![Page 17: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/17.jpg)
Exploring the Gamma-ray Spectrum
100 MeV
1 GeV 10GeV
100GeV
1 TeV 10 TeV
10 MeV
Energy
1 MeV
GLAST
Atm. Cherenkov Wavefront Sampling
Atm. Cherenkov Imaging Arrays
HESS
VERITAS
Pre
sent
/Fut
ure
STACEE
![Page 18: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/18.jpg)
The High-Energy Gamma Ray Sky
1995 3 sources
Mrk421
Mrk501
Crab
R.A.OngAug 2005
Pulsar Nebula
SNR
AGN
Other, UNID
(2)(1)
(0) (0)
![Page 19: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/19.jpg)
The High-Energy Gamma Ray Sky
2004 12 sources
Mrk421 H1426
Mrk501
1ES1959
1ES 2344
PKS 2155
Cas A
RXJ 1713
CrabTeV 2032
M87
GC
R.A.OngAug 2005
Pulsar Nebula
SNR
AGN
Other, UNID
(7)(1)
(2) (1,1)
![Page 20: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/20.jpg)
The High-Energy Gamma Ray Sky
2005 31 sources!
Mrk421 H1426
Mrk501
1ES1959
1ES 2344
PKS 2155
Cas A
RXJ 1713
CrabTeV 2032
M87
PKS 2005
PSR B1259
RXJ 0852
MSH 15-52
SNR G0.9
HessJ1303
GC
R.A.OngAug 2005
Pulsar Nebula
SNR
AGN
Other, UNID
H2356
1ES 1218
1ES 1101
LS 5039Vela X
+ 8-15 add. sourcesin galactic plane.
CygnusDiffuse
(11)(4+2)
(3+4) (3,3+1)
![Page 21: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/21.jpg)
Wavefront Sampling DetectorsSTACEE & CELESTE
e+
e+
e+
e-
e-
…
e+
Cherenkov light intensity on ground energy of gamma ray
Cherenkov pulse arrival times at heliostats direction of source
![Page 22: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/22.jpg)
STACEE
64 heliostats
5 secondary mirrors & 64 PMTs
National Solar Thermal Test FacilityAlbuquerque, NM
Solar Tower Atmospheric Cherenkov Effect Experiment
![Page 23: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/23.jpg)
STACEE
64 heliostats
5 secondary mirrors & 64 PMTs
National Solar Thermal Test FacilityAlbuquerque, NM
Solar Tower Atmospheric Cherenkov Effect Experiment
• PMT rate @ 4 PEs: ~10 MHz
• Two-level trigger system (24 ns window): - cluster: ~10 kHz - array: ~7 Hz
• 1-GHz FADCs digitize each Cherenkov pulse
![Page 24: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/24.jpg)
STACEE Advantages / Disadvantages
• 2-level trigger system good hardware rejection of hadrons
• GHz FADCs pulse shape information
• Large mirror area (6437m2) low energy threshold
Ethresh = 165 GeV
![Page 25: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/25.jpg)
STACEE Advantages / Disadvantages
• 2-level trigger system good hardware rejection of hadrons
• GHz FADCs pulse shape information
• Large mirror area (6437m2) low energy threshold
But…• Limited off-line cosmic ray rejection limited sensitivity: 1.4/hour on the Crab Nebula
• Compare to Whipple sensitivity: 3/hour above 300 GeV
Ethresh = 165 GeV
![Page 26: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/26.jpg)
STACEE Data
Observing Strategy: Equal-time background observations for every source observation (1-hour “pairs”)
Cuts for data quality
Correction for unequal NSB levels
Cosmic ray background rejection
Analysis:
Significance/flux determination
![Page 27: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/27.jpg)
Energy Reconstruction Idea
Utilize two properties of gamma-ray showers:
1. Linear correlation: Cherenkov intensity and gamma-ray energy
2. Uniform intensity over shower area
200 GeV gamma ray 500 GeV proton
![Page 28: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/28.jpg)
New method to find energies of gamma rays from STACEE data:1. Reconstruct Cherenkov light distribution on the ground from PMT charges2. Reconstruct energy from spatial distribution of light
Energy Reconstruction Method
Results:
fractional errors < 10%
energy resolution ~25-35%
![Page 29: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/29.jpg)
STACEE
• Nearby: z = 0.03• First TeV extragalactic source detected (Punch et al. 1992)• Well-studied at all wavelengths except 50-300 GeV• Inverse-Compton scattering is favored• High-energy peak expected around 100 GeV• Only one previous spectral measurement at ~100 GeV (Piron et al. 2003)
Markarian 421
Blazejowski et al. 2005
Krawczynski et al. 2001
log (Energy/eV)
log
(E2 d
N/d
E /
erg
cm-2
s-1)
?
STACEE
![Page 30: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/30.jpg)
STACEE Detection of Mkn 421
Pairwise distribution of
• Observed by STACEE January – May 2004• 9.1 hours on-source + equal time in background observations• Non – Noff = 2843 gamma-ray events• 5.8 detection• 5.52 0.95 gamma rays per minute• Energy threshold ~198 GeV for = 1.8
Eth = 198 GeV = 1.8
![Page 31: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/31.jpg)
Rat
e (p
hoto
ns s
-1 G
eV-1)
Aef
f(E)
(m2 )
Energy (GeV)
Spectral Analysis of Mkn 421
Gamma-ray rate (photons s-1 GeV-1) Effective area (m2)
• Six energy bins between 130 GeV and 2 TeV• Find gamma-ray excess in each bin• Convert to differential flux with effective area curve
Energy (GeV)
![Page 32: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/32.jpg)
Spectral Analysis of Mkn 421
= 1.8 0.3stat
First STACEE spectrum
![Page 33: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/33.jpg)
Spectral Analysis of Mkn 421
= 1.8 0.3stat
First STACEE spectrum
Flat SED
![Page 34: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/34.jpg)
2004 Multiwavelength Campaign
January February March April
TeV
X-ray
PC
A data courtesy of W
. Cui, B
lazejowski et al. 2005
![Page 35: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/35.jpg)
2004 Multiwavelength Campaign
January February March April
TeV
X-ray
STACEEobservations
PC
A data courtesy of W
. Cui, B
lazejowski et al. 2005
• STACEE coverage: 40% of MW nights• ~90% of STACEE data taken during MW nights• STACEE combines low and high flux states
![Page 36: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/36.jpg)
Multiwavelength Results
Blazejow
ski et al. 2005
![Page 37: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/37.jpg)
Multiwavelength Results
STACEE region
Blazejow
ski et al. 2005
![Page 38: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/38.jpg)
STACEE + Whipple Results
![Page 39: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/39.jpg)
STACEE + Whipple Results
![Page 40: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/40.jpg)
Science Interpretation
• STACEE’s first energy bin is ~90 GeV below Whipple’s.
• STACEE result:
is consistent with a flat or rising SED.
suggests that the high-energy peak is above ~200 GeV.
slghtly is inconsistent with most past IC modeling.
• Combined STACEE/Whipple data suggest that the peak is around 200-500 GeV.
• SED peak reflects peak of electron energy distribution.
![Page 41: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/41.jpg)
Prospects for the Future
• STACEE will operate for another year
Air Cherenkov Single Dish Imaging
100 MeV
1 GeV 10GeV
100GeV
1 TeV 10 TeV
10 MeV
Energy
1 MeV
Compton Gamma Ray Observatory
Air Cherenkov Wavefront Sampling
Gamma-ray spectrum
![Page 42: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/42.jpg)
Prospects for the Future
• STACEE will operate for another year
• Imaging arrays coming online, Ethreshold 150 GeV - HESS: 5 Crab detection in 30 seconds! - VERITAS: 2 (of 4) dishes completed
Air Cherenkov Imaging Arrays
100 MeV
1 GeV 10GeV
100GeV
1 TeV 10 TeV
10 MeV
Energy
1 MeV
Compton Gamma Ray Observatory
Air Cherenkov Wavefront Sampling
Gamma-ray spectrum
![Page 43: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/43.jpg)
VHE Experimental World
STACEE
MILAGRO
TIBETARGO-YBJ
PACT
GRAPES
TACTIC
VERITAS
MAGIC
HESS CANGAROO
TIBETMILAGRO
STACEE
TACTIC
![Page 44: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/44.jpg)
Compton Gamma Ray Observatory
Prospects for the Future
100 MeV
1 GeV 10GeV
100GeV
1 TeV 10 TeV
10 MeV
Energy
1 MeV
Air Cherenkov Wavefront Sampling
GLAST
Gamma-ray spectrum
Air Cherenkov Imaging Arrays
• STACEE will operate for another year
• Imaging arrays coming online, Ethreshold 150 GeV - HESS: 5 Crab detection in 30 seconds! - VERITAS: 2 (of 4) dishes completed
• GLAST launch in 2007!
![Page 45: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/45.jpg)
GLAST
• Two instruments: LAT: 20 MeV – >300 GeV GBM: 10 keV – 25 MeV
• LAT energy resolution ~ 10%
• LAT source localization < 0.5’
GLAST Large Area Telescope (LAT)
Burst Monitor (GBM)
![Page 46: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/46.jpg)
EGRET Sources
![Page 47: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/47.jpg)
GLAST Potential
![Page 48: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/48.jpg)
• Gamma-ray observations of AGN are key to understanding particle acceleration in the inner jets
• Many new VHE gamma-ray detectors & detections
• STACEE - “1st-generation” instrument sensitive to ~100 GeV gamma rays - Energy reconstruction is successful - 5.8 detection of Markarian 421 - Preliminary spectrum between 130 GeV and 2 TeV - Second spectrum of Mkn 421 at 100-300 GeV - High-energy peak is above ~200 GeV
• Bright future for gamma-ray astronomy
Conclusions
![Page 49: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/49.jpg)
Cosmic Ray Background Rejection
What we have:
• Hardware hadron rejection (~103)
• Off-source observations for subtraction
• 2 from shower core reconstruction (‘templates’)
• Timing information & 2 from wavefront fit
• RMS on average # photons at a heliostat
• Limited directional information
- reconstruction precision ~0.2°, FOV ~0.6°
Some initial success with the Crab nebula…
• 5.4 hours on-source after data quality cuts
• 3.0 before hadron rejection
• Cut on core fit 2 + wavefront fit 2 + direction: 5.7!
![Page 50: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/50.jpg)
Field Brightness CorrectionExtra light in FOV from stars will increase trigger rate due
to promotions of sub-threshold cosmic rays
![Page 51: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/51.jpg)
Field Brightness CorrectionExtra light in FOV from stars will increase trigger rate due
to promotions of sub-threshold cosmic rays
Correct using information from FADCs to equalize light levels
After correction
![Page 52: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/52.jpg)
STACEE Atmospheric Monitor
• Goal: measure atmospheric
transmission and detect
clouds.
• Meade 8'' S-C scope,
Losmandy equatorial
mount with PC-controlled
“goto” pointing/tracking,
SBIG CCD camera
for pointing and
photometry.
• Two IR radiometers
(cloud detectors).
• Full Weather station.
![Page 53: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/53.jpg)
Methods for Finding the Shower Core
2. ‘Template’ method• # PEs vs. shower core position• One template per PMT and energy• Fit core and energy with maximum likelihood estimator• Pros: - precise - 2 for hadron rejection• Con: ‘black box’
x-position of core
y-po
sitio
n of
cor
e
1. Finding the centroid• If we sampled the entire shower, we could find its centroid.• The early part of the shower is contained within the array.• Use the first few nanoseconds of the shower to find the centroid.
Sample template
![Page 54: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/54.jpg)
Calibrating the Detector
Air shower simulations &Atmospheric monitoring
STACEE Atmospheric Monitor
![Page 55: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/55.jpg)
Calibrating the Detector
Trasmission measurementsSTACEE Atmospheric Monitor
Heliostat
Secondary
PMT
DTIRC
![Page 56: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/56.jpg)
Calibrating the Detector
PMT Gain Calibration
electronics
![Page 57: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/57.jpg)
STACEE AGN Targets
3C 66A• z = 0.444 • Strong source at energies < 10 GeV• One questionable measurement at TeV energies• High redshift heavy absorption• STACEE flux limit (Bramel et al. 2005)
Which objects are most scientifically promising?
R.A.OngMay 2005
Pulsar Nebula
SNR
AGN
Other, UNID
The Very High Energy Sky
3C 66A
![Page 58: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/58.jpg)
STACEE AGN TargetsWhich objects are most scientifically promising?
R.A.OngMay 2005
Pulsar Nebula
SNR
AGN
Other, UNID
The Very High Energy Sky
Mkn 421
Mkn 421• z = 0.031• Well-studied at TeV energies• Target of multi- variability studies• One previous measurement at 50-300 GeV• High-energy peak is at ~100 GeV• Potential to constrain the optical EBL• STACEE detection (Carson 2005)
![Page 59: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/59.jpg)
STACEE AGN TargetsWhich objects are most scientifically promising?
R.A.OngMay 2005
Pulsar Nebula
SNR
AGN
Other, UNID
The Very High Energy Sky
W Comae • z = 0.102• Hard EGRET spectrum: = 1.73• Limits only at TeV energies• STACEE observations can test model predictions• STACEE flux limit (Scalzo et al. 2004)
W Comae
![Page 60: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/60.jpg)
Models of W Comae
Leptonic modelsno emission predicted above 100 GeV
Predicted differences around 100 GeV
Hadronic modelssignificant emission above 100 GeV
![Page 61: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/61.jpg)
STACEE Measurement of W Comae
< ~ 2.5 10-10 cm-2 s-1 for hadronic models above 165 GeVSTACEE flux limit constrains hadronic emission models
Scalzo et al. 2004
![Page 62: The Spectrum of Markarian 421 Above 100 GeV with STACEE](https://reader035.vdocument.in/reader035/viewer/2022070418/56815964550346895dc6a19e/html5/thumbnails/62.jpg)
Scalzo et al. 2004
STACEE Measurement of W Comae
< ~ 2.5 10-10 cm-2 s-1 for hadronic models above 165 GeVSTACEE flux limit constrains hadronic emission models