Results from Galactic Source Observations with VERITAS

1
Results from Galactic Source Observations with
VERITAS

• Amanda Weinstein
• for the VERITAS Collaboration
• Moriond,
• Feb. 4, 2009

2
Outline

• Introduction to VERITAS
• VERITAS Galactic Science Program
• Overview
• Highlight results
• Summary and future prospects

3
VERITAS at Whipple Observatory
Data, October 2007-June 2008 ? Good weather,
4-telescopes 800 hours ? Moonlight 100hrs ?
35 moonlight data this fall
Since March 2006
T2
109 m
Fall 2006
85 m
T3
82 m
35 m
T4
T1
April 2007
? FLWO,Mt. Hopkins, Az (1268 m asl)
Specifications ? Angular resolution 0.1 ?
Energy resolution 15-20
Sensitivity ? 1 Crab _at_ 5 s 47 hrs ? 5 Crab _at_
5 s 2.5 hrs
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VERITAS Galactic Science Program
SNR/PWN Key Science Project
Composite and shell-type SNR
Strategy search for TeV PWN associated with
pulsars E/d2 gt 1x1035 ergs/s/kpc2
Cygnus Region Sky Survey (Key Science Project)
e.g. HMXBs, LMXBs, magnetars (microquasars)
Combination of dedicated and serendipitous
observations (objects in FOV of other targets,
survey)
Galactic Compact Objects
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Galactic Science
LSI 61303
MGRO J190806
IC443
AGILE 20214024
Geminga
PSR J17401000
PSR J06311036
PSR J02056449
Cas A
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Cas A

• Young (330yrs) SNR at a distance of 3.4 kpc
• Massive star progenitor
• 5 (4.5 pc) diameter (comparable to TeV angular
  resolution)
• Discovered in TeV by HEGRA (232 hrs, 5 s),
  confirmed by MAGIC (47 hrs, 5.3 s)
• Flux 3.3 Crab above 1 TeV
• Power-law index of 2.3 0.2stat 0.2sys
• Well studied SNR in a relatively clean
  environment
• Extensive modeling of cosmic-ray acceleration and
  gamma-ray production exists

• VERITAS wobble-mode observations, 0.5º offset,
  during Oct/Nov 2007 with 4 telescopes
• Exposure 20.3 hr 9.8 s detection
• Flux 3 Crab
• Consistent with a point source

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IC 443

• Middle-aged SNR few 10 kyr
• SNR shell / molecular cloud interaction (beam
  dump)
• PWN (southern edge) spin-down luminosity
  uncertain (1036 erg/s 5 x 1037 erg/s)
• Co-discovered (MAGIC/VERITAS) in TeV in 2007

• Green Radio
• Red Optical
• Blue X-rays

PRELIMINARY

• Observed (wobble, 0.5º offset) during two epochs,
  for 37.1 hrs total livetime
• Feb / Mar 2007 with 3 telescopes, PWN location
• Oct / Nov 2007 with 4 telescopes
• Center of Feb/Mar hot spot
• 06 16.9 22 33
• Flux 3 Crab
• 8.2s peak significance pre-trials

VERITAS position
PWN
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IC 443
2-D Gaussian profile fit Centroid 06 16.9
22 32.4 0.03º(stat) 0.07º(syst) Extension
s 0.17º 0.02º(stat) 0.04º(syst)

• Not coincident w/radio/optical shell to northeast
• Overlap with CO indicating molecular cloud along
  line of sight
• Maser emission suggests SNR shock interacting
  with cloud
• TeV emission could be
• CR-induced pion production in cloud(1,2)
• associated with the pulsar wind nebula to the
  south (relic electrons?)(3)

• Zhang, L. and Fang, J. Ap. J. 675 L21 (2008).
• Torres, D. F. et al. arXiv0804.2526.
• (3) Bartko, H. and Bednarek, W. arXiv0712.2964.

Elongation along cloud
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LSI 61303
J.Casares et al (MNRAS 360, 1105 (2005))
MW Fermi
25hrs
21hrs
45hrs
50 moonlight data MW Swift/RXTE
VERITAS phases 0.2-0.9 MW Swift, RXTE
Microquasar? Binary pulsar?
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LSI61 303 2006-2008
RXTE(2-10keV)
2007-2008
2006-2007
SWIFT(0.2-10keV)
8.4s detection
7.3s detection
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LSI61 303 2006-2008
2007-2008 Consistent with 2006-2007 spectrum
2006-2007 only Consistent with MAGIC

• G2.40 0.16 (stat) 0.2 (sys)

• G2.6 0.6 (stat) 0.2 (sys)

Phase-resolved (0.5-0.8)
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LSI 61303
2008-2009
2007-2008
2006-2007
apastron
PRELIMINARY
4.5s detection
8.4s detection
No strong excess (2.6s)
periastron
PRELIMINARY
3.6s pre-trials
Strong indication of orbit-to-orbit variability
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Nov 2008 In Context
Fermi data (Dubois, AAS, 2009)
Nov. 2008 data part of a MWL campaign
detects the source continuously Emission peaks at
periastron
PRELIMINARY
orbit-orbit variability(?)
Sees clear periodicity
VERITAS data 99 upper flux limit F(Egt500
GeV)lt 1.26x10-12 cm-2s-1 (2.1 Crab)
?
Apastron, 2006-2007
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VERITAS Sky Survey

• Partial survey of Cygnus region
• -1 lt b lt 4 and 67 lt l lt 82
• Completed this fall (along with a small/moderate
  amount of followup)
• At least 6 hrs acceptance-corrected exposure at
  each point in the survey
• Survey analysis ongoing (release pending
  additional observations in April)

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MGROJ190806 / HESS J1908063

• Needed a test case for Sky Survey extended source
  search, chose MGRO J190806/HESS J1908063
• MGRO unidentified source
• 80 of Crab Nebula Flux, lt2.6 diam. extension
  at 20 TeV
• Detected in HESS galactic plane survey
• 14 Crab flux gt 300 GeV
• Source extension 0.21 0.07 (stat) 0.05(sys)

PRELIMINARY
Significance Map (smoothed)

• VERITAS
• Data taken under aegis of sky survey
• 22h of 4-telescope data
• 4.85s detection
• 0.19 0.04 extension
• position in agreement with HESS J1908063

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AGILE 20214024

• Observations (initially under moonlight)
  triggered by AGILE atels
• 7 hour exposure
• 99 upper limit at 2 Crab flux above 300 GeV.

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Future prospects

• A new guide

• new Fermi pulsars, or sources w/PWNe
  associations ? PWN searches, searches for pulsed
  emission from gamma-ray loud pulsars (if cutoff
  is favorable), new Fermi XRBs
• GeV-TeV connection ? disentangling nature of
  object, emission (e.g LSI, IC443)
• Coordinated GeV-TeV observations

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Summary

• VERITAS Galactic science program in first 2 years
  has been fruitful
• SNR/PWN detections Crab, CasA, IC443
• UnID detections MGRO J190806/HESS J1908063
• Long-term observations (MWL) of LSI 61303 have
  contained some suprises
• Expect updated analyses of SNR detections (Cas
  A, IC443)
• Expect a number of new results by summer,
  including the Sky Survey
• Moving T1 will improve our sensitivity to
  galactic sources
• Fermi data and VERITAS Sky Survey results will
  likely modify our observing strategy for the
  coming year

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EXTRA/ BACKUP
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The Crab A Standard Candle
Measured sensitivity to the Crab Nebula at
high elevation (gt65) HESS 1 Crab in 25
hours (but mirror reflectivity now degraded)
MAGIC 2 Crab in 50 hours
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Geminga

• VERITAS Observations 13.3 hours at high
  elevation
• Upper Limit to steady emission(gt300 GeV)
  lt2x10-8 ?/m2/s (1 Crab flux)
• Upper Limit to pulsed emission(gt300 GeV)
  lt1x10-8 ?/m2/s (0.5 of Crab flux)

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IC443
IC443

• Green Radio
• Red Optical
• Blue X-rays

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IC 443

• Middle-aged SNR few 10 kyr
• SNR shell / molecular cloud interaction (beam
  dump)
• PWN (southern edge) spin-down luminosity
  uncertain (1036 erg/s 5 x 10 1037 erg/s)
• Co-discovered (MAGIC/VERITAS) in TeV in 2007

• Observed (wobble, 0.5º offset) during two epochs,
  for 37.1 hrs total livetime
• Feb / Mar 2007 with 3 telescopes, PWN location
• Oct / Nov 2007 with 4 telescopes
• Center of Feb/Mar hot spot
• 06 16.9 22 33
• Flux 3 Crab
• 8.2s peak significance pre-trials

PRELIMINARY
PWN