FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Brian Humensky
for the VERITAS Collaboration
December 10, 2009University of Chicago
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
27 Source Detections in 6 source classes, at least 10 in the Galactic Plane
http://tevcat.uchicago.edu
1ES 0502+675
1ES 0229+200
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Survey of the Cygnus region in TeV: At < 3% Crab flux Discovery of new source VER
J2019+407 Detection of TeV J2032+4130
Discovery of IC 443 in TeV: Classic SNR / MC interaction system Wonderful laboratory to explore
cosmic-ray interaction / diffusion
Discovery of SNR G106.3+2.7 in TeV: Extended TeV source –associated with PWN or SNR/MC interaction?
Discovery of SNR G54.1+0.3 in TeV: Young Crab-like PWN
Detailed study of Cassiopeia A: Young, nonthermal X-ray SNR VHE spectrum is a power law to 5
TeV
Study of gamma-ray binaries: LSI: clear detection only at
apastron. Investigation of GeV/TeV differences.
HESS J0632+057: VERITAS established variability. A new TeV binary system?
Cyg X-3: Convincing -ray detections from AGILE, Fermi → VERITAS follow-up in spring 2010
Detailed study of Crab Nebula: 5detection ~ 70 seconds Search for correlation with giant
radio pulses (with Green Bank) Stability of TeV flux (with MAGIC)
Unidentifieds HESS J1857+026 and HESS
J1858+020 in the W44 region MGRO J1908+063 AGILE transient J2021+4024
Northern PWN Survey Limits 3C 58, Geminga, others
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
VER J2019+407
Eff
ective e
xposure
tim
e [m
in]
0.8˚
1.0˚1.75˚
Preliminary Flux Limits above 200 GeV (99% CL, all points in survey below 3σ)
<3.0% Crab (point source)
<8.5% Crab (0.2˚ radius extended source)
Possible indication that population in Cygnus region differs from inner galaxy
HESS survey: of 14 sources in -30˚<l< 30˚, saw 12 sources with fluxes ≥ 5% Crab above 200 GeV → expect ~2-3 in VERITAS survey – see zero
Un-biased indication of source population
112 hrs base survey, 56 hrs follow-up to date
VER J2019+407: New VERITAS source
TeV J2032+4130: known source, first detected by HEGRA
Likely associated: MGRO J2031+41, 0FGL J2032.2+4122 (LAT pulsar)
Detection: >5σ at nominal position (no trials)
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
In northwest region of Cygni SNR (G78.2+2.1) → What exactly is it?
PWN?
core ~0.5˚ away from Fermi pulsar
Association seems unlikely
VERITAS emission does overlap well with radio contours in northwest
Shock-cloud interaction?
Plenty of CO in southeast, little in northwest
Two partial shells in HI, one in northwest (Ladouceur and Pineault 2008, A&A 490, 197)
Cloudlets? Enough mass in HI?
Speculation:
SNR expanded in progenitor’s wind-blown bubble → now encountering surrounding swept-up shell
VERITAS excess map
1420 MHz CGPS Radio contours
No visible -ray emission to the southeast
LAT PSR
J2021+4026
VERITAS
1σ ellipse
PRELIMINARY
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
SNR / MC Interaction + PWN
Discovered in GeV by EGRET
Now AGILE, Fermi
Discovered in TeV in 2007 by VERITAS & MAGIC
VERITAS: 8.3 , extended emission
TeV emission may be
CR-induced pion production in cloud
associated with the pulsar wind nebula to the south
GeV and TeV emission spatially separated? (both extended)
Broad-band morphological evolution distinguishes between scenarios (not all PWN)
Window into propagation / diffusion of Cosmic Rays in interstellar medium
Abdo et al. submitted
Red: Optical (DSS)Green: CO (Lee et al. 2010, in prep.)Yellow: VERITAS significance (4, 6 )
Troja et al. 2006
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
VERITAS observations resolve TeV emission overlapping the radio shell of G106.3+2.7
7.3 σ detection in 33 hours (6.0 σ post-trials)
TeV emission is extended
Spans a 0.4 0.6 region
Peak is 0.4 (~6 pc) from PSR
Overlaps region of high CO density
Energy Spectrum – power law
Index: 2.3 ± 0.3stat ± 0.3sys
Flux (> 1 TeV) ~ 5% Crab
Extrapolation of spectrum is consistent within errors with Milagro point at 35 TeV
Excess Map Purple - 12CO Emission (FCRAO)Yellow star – 1AGL J2231+6109
Black – Radio (DRAO)Circle – FGST Error Box
Dot – Pulsar Position
Acciari et al. 2009, ApJ 703 L6
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Power-law spectrum: Index: 2.40 ± 0.24stat ± 0.3sys
Flux (> 1 TeV) ~ 2.5% Crab
L / E-dot ~ 0.15% Similar to other young TeV PWNe,
eg G0.9+0.1, Kes 75
VHE -rays from freshly injected electrons
“Cousin of the Crab”
X-ray jet/torus, no thermal shell
Age ~ 2900 years
E-dot = 1.2 × 1037 erg/s
Distance ~ 6.2 kpc
Location compatible with pulsar
Consistent with point source
Lu et al. 2002 (Chandra/ACIS)
Acciari et al. (2009), in prep.
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Solid: VERITAS
Dashed: HEGRA
Dotted: MAGIC
Index: 2.61 ± 0.24stat ± 0.2sys
Flux (> 1 TeV) ~3.5% Crab
No sign of a cut-off at high energy.
Fermi spectrum connects at lower energy
Electrons or hadrons?
Young (~330 yr) shell-type SNR
Discovered in TeV by HEGRA (232 hrs, 5 ), confirmed by MAGIC (47 hrs, 5.3 )
VERITAS: 22 hr data in 2007, 8.3
Consistent with point source
Acciari et al. 2009, submitted
Stage et al. 2006
Chandra
5’
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
First detected by MAGIC (2006)
Intensively observed by VERITAS, 2006-2009
Orbital modulation: GeV/TeV anticorrelation
Competition between IC and absorption?
Spectrum: Fermi cutoff ~6 GeV, VERITAS only 3 since Fermi launch
Magnetospheric emission?
Stellar weather?
Mirabel (Science 309, 714, 2006)
Accretion-powered Wind-driven
Fermi
VERITAS
FermiMAGIC/VERITAS
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
AGILE, Fermi report -ray activity from Cyg X-3
Fermi detects orbital period
AGILE detects 4 -ray flares, connects to jet formation
VERITAS will follow up in Spring!
VERITAS establishes -ray variability of HESS J0632+057
Unidentified TeV source in the Galactic plane – unresolved!
X-ray & radio sources coincident with a Be star (MWC148)
Swift: long-term X-ray variability
VERITAS, HESS leading MWL campaign to identify sourceAbdo et al. 2009 Science Express
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
IC 443: Extended and complicated Strong Fermi source: broadband spectral, morphological evolution
will be illuminating
SNR G106.3+2.7/Boomerang: Fermi, VERITAS, MILAGRO
Cas A: Best TeV spectrum to date Boon to modelers, especially combined with Fermi spectrum
Cygni: Emission not associated with large cloud to south Encountering increasing density to north?
LS I +61 303: GeV / TeV differences cooling mechanisms? GeV: detected at all phases, peaks at periastron
TeV: only clearly detected at apastron
HESS J0632+057: VERITAS established variability A new TeV binary system ?
Overall: Lack of strong (>5% Crab) sources (eg, PWNe) Sky survey is addressing this quantitatively
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Broad-band -ray studies with VERITAS & Fermi Joint analysis (morphology, cross-correlation studies) with Fermi
data (funded GI Cycle II proposal)
Monitoring of LS I +61 303 (funded GI Cycle II proposal)
Deep observations & detailed studies of sources IC 443, SNR G106.3+2.7/Boomerang, Cygni, Cassiopeia A
MWL monitoring of known and candidate binary systems Cyg X-3, HESS J0632+057, LS I +61 303
Exploratory observations of candidate TeV emitters Supernova remnants interacting with molecular clouds
Nebulae associated with energetic pulsars
Follow-up of Fermi galactic sources Unidentifieds – use VERITAS angular resolution, lack of diffuse
Transients – very few so far!
response to SGR outbursts now following GRB protocol - fast
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
VERITAS Telescope Array
VERITAS: Four 12-m diameter atm. Cherenkov telescopes
F.L. Whipple Observatory (1.3 km altitude), AZ, USA
Staged construction, full sensitivity after Sept. 2007
Whipple 10m telescope on Mt. Hopkins (2.2 km altitude) 7km away
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Instrument design:
Four 12-m telescopes, 3.5 FoV
FLWO, Mt. Hopkins, Az (1268m)
Fully operational Sept 2007
Performance:
3-level trigger (250 Hz rate)
~ 800 hrs/yr dark time, ~ 200 hrs/yr moon time
Energy threshold ~150 GeV (zenith)
Energy resolution ~ 15-20 %
Angular resolution ~ 0.1°
7km away
T1
Sep 2009
Sensitivity:
1% Crab < 50 hours (before T1 move)
1% Crab < 30 hours (after T1 move)
See poster by J. Perkins VERITAS T1 Relocation
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Discovered by Whipple 10m in 1989
VERITAS: 5 in ~ 1 minute
Science Goals
Measure/limit extent of TeV emission
Stability of Crab emission (w/ MAGIC)
Probe correlated variability with Giant Radio Pulses (w/ ?)
Confirm pulsed emission
Measure spectrum to high energies
Point-source Sensitivity
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Energy Range: 100 GeV – 30 TeV
(spectra >150 GeV)
Energy Resolution: 15% – 20%
Crab Rate ~ 40 / min (trigger)
Sensitivity: 5% Crab in < 2.5 h
1% Crab in < 50 h
Angular Resolution: r68 < 0.1o
Pointing Accuracy: < 50’’
Effective Area (std. cuts)
Energy Resolution
Angular Resolution
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Currently the most sensitive VHE instrument in the world!
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Energetic pulsar + wind nebula discovered in the error box of source 3EG J2227+6122.
Age ~ 10,000 years
E-dot = 2.2 × 1037 erg/s
Likely part of the larger SNR G106.3+2.7
Distance ~ 800 pc (Kothes et al. 2001)
Fermi: 0FGL J2229+6114
MILAGRO: Extended emission at ~35 TeV
1420 MHz: Effelsberg (Kothes et al.)
Boomerang PWN
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Observations made in 2008 resolve TeV emission overlapping the radio shell of G106.3+2.7
7.3 σ detection in 33 hours (6.0 σ post-trials)
TeV emission is extended
Spans a 0.4 0.6 region
Peak is 0.4 away from PSR
Overlaps with region of high CO density
Excess Map
Black – Radio (DRAO)Circle – FGST Error BoxDot – Pulsar PositionPurple - 12CO Emission (FCRAO)Yellow star – 1AGL J2231+6109
Acciari et al. 2009, ApJ 703 L6.
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Energy Spectrum
Integrate over 0.32 radius centered on emission peak
Well fit by a pure power law
Index: 2.3 ± 0.3stat ± 0.3sys
Flux (> 1 TeV) ~ 5% Crab
Extension of spectrum is consistent within errors with Milagro point at 35 TeV
Spectrum may favor hadronic origin?
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Shell interacting with massive cloud
Age ~20-30 kyr, 0.75º
diameter
PWN at southern edge of shell
Discovered in GeV by EGRET
Now AGILE, Fermi
Discovered in TeV in 2007
by MAGIC (5.7 in 29 hrs)
by VERITAS (7.1/6.0 pre/post-trials in 15.9 hrs)
• Green – Radio
• Red – Optical
• Blue – X-rays
Troja et al. (2006)
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Total live time: 37.9 hrs.
8.3 σ peak significance pre-trials
Power-law fit 0.3 – 2 TeV: Index: 2.99 ± 0.38stat ± 0.3sys
Flux (> 300 GeV) ~ 3.2% Crab
TeV emission may be
CR-induced pion production in cloud
associated with the pulsar wind nebula to the south
GeV and TeV emission spatially separated? (both extended)
Broad-band morphological evolution distinguishes between scenarios (not all PWN)
Window into propagation / diffusion of Cosmic Rays in interstellar medium
2-D Gaussian profile fit: Centroid: 06 16.9 +22 32.4 ± 0.03ºstat ± 0.07ºsys
Extension: σ ~ 0.16º ± 0.03ºstat ± 0.04ºsys
Red: Optical (DSS)Green: CO (Lee et al. 2010, in prep.)Yellow: VERITAS significance (4, 6 )
Acciari et al. 2009, ApJ 698 L133
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
TeV emission may be
CR-induced pion production in cloud
associated with the pulsar wind nebula to the south
GeV and TeV emission spatially separated? (both extended)
Broad-band morphological evolution distinguishes between scenarios (not all PWN)
Window into propagation / diffusion of Cosmic Rays in interstellar mediumAbdo et al. submitted
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Efficient method of searching for new sources over a large region
Un-biased indication of source population
Southern hemisphere well-surveyed HESS Galactic plane survey: ~14 sources in initial survey
Best limits in northern hemisphere sky : HEGRA’s Galactic plane survey -2˚ < l < 85˚, flux upper limits: 15% Crab to several Crab
Size and choice of region based on VERITAS sensitivity and FOV Material distribution, density of potential TeV γ-ray emitters (SNRs,
PWNe, high E-dot pulsars, EGRET unidentified sources...)
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Made possible by good off-axis sensitivity
Region covered: 67˚ < l < 82˚, -1˚ < b < 4˚
Available observing period: Apr-Jun, Sep-Nov
Effective exposure: ~6 hrs in base survey
112 hours in base survey + 56 hours followup.
Prior to Fall 2009
Eff
ective e
xposure
tim
e [m
in]
0.8˚
1.0˚
1.75˚
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
• Partial survey map, generated with standard threshold extended source analysis
• Includes all data in survey region taken to this point
• Exposure uneven due to followup (more intensive followup around VER J2019+407
than around TeV J2032+4130)
VER J2019+407
New VERITAS source
TeV J2032+4130
known source, first
detected by HEGRA
Likely associated: MGRO
J2031+41, 0FGL
J2032.2+4122 (LAT pulsar)
Detection: >5σ at nominal
position (no trials)
VER J2019+407
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Early follow-up candidate
Recent (last 2 months) follow-up treated as an independent search 0.25˚ radius search region 0.6˚ wobble, position
indicated by earlier data
8.5σ (~7.5σ) pre- (post-) trials in Fall 2009 data alone
Position: RA: 304.97˚ ± 0.017˚stat Dec: 40.79˚ ± 0.023˚stat
Extension: 0.16˚ ± 0.028˚ (0.11˚ ± 0.027˚) for the major (minor) axis 2-d Gaussian fit to uncorrelated excess map (Fall 2009 data only)
Flux ~ few % Crab
Fall 2009 data only
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
No hotspots above 5σ post-trials in base survey
Preliminary Flux Limits (99% CL, all points in survey below 3σ) <3% Crab above 200 GeV (point source) <8.5% Crab above 200 GeV (0.2˚ radius extended source)
Possible indication that population in Cygnus region differs from inner galaxy HESS survey: out of 14 sources in -30˚<l< 30˚, saw 12 sources with fluxes ≥ 5%
Crab above 200 GeV expect ~2-3 in this survey
Detection of 2 sources with VERITAS survey technique and followup observations Discovery: VER J2019+407 TeV J2032
Further followup observations in survey region ongoing
Prospects for future: Spectra and energy-dependent morphology (VER J2019+407, TeV J2032+4130) Joint analysis (morphology, cross-correlation studies) with Fermi data
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
• Uchiyama et. al. ApJ, 571:866-875, 2002
– Soft X-ray emission belt (1-3 keV) from north to southeast
• shock interacting with cavity wall of ambient clouds?
– Suggests hard sources in north are shocked dense cloudlets
• Nonthermal bremsstrahlung of GeV electrons
Core of VERITAS excess
In 4-10 keV band, pair of faint hard X-ray
sources under core (part of C2, Uchiyama et
al.)
Uchiyama et. al.
ASCA X-ray map
4.85 GHz radio contours
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Detection of 2 sources with VERITAS survey technique and followup observations Discovery: VER J2019+407
TeV J2032
Further followup observations in survey region ongoing.
Prospects for future: Spectra and energy-dependent morphology studies (VER J2019+407,
TeV J2032).
Joint analysis (morphology, cross-correlation studies) with Fermi data in the region.
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Name Edot Dist Lg LX Lg/Edot LX / Edot LX /Lg
(erg/s) (kyr) (kpc) (10^34 erg/s) (10^35 erg/s) (%) (%)
Crab Nebula 460 1.2 2 8.6 190 0.02 4 220
G0.9+0.1 43 5.3 8.5 4.4 3.6 0.1 0.8 8
G21.5-0.9 33 4.85 4.7 0.72 2.2 0.02 0.7 30
G54.1+0.3 12 2.9 6.2 1.8 0.12 0.15 0.1 0.7
Kes75 8.1 0.7 7.5 2.5 2.4 0.3 19 18
Comparing properties to other young TeV pulsare wind nebulae:
Lg: Luminosity in 0.2-10 TeV band
LX: Luminosity in 0.5-8 keV band (Kargaltsev & Pavlov 2008)
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Results: Unidentified Source
The Monoceros Loop SNR? Rosette Nebula region
Molecular gas,
NANTEN Galactic
plane survey
Radio observations
8.35 GHz
Green’s Catalog
position of SNR
30-150 kyrs old
Distance ~1.5 kpc
Interaction with the
Rosette nebula?
Puehlhofer et al. 2007 - First GLAST Symposium
HESS J0632+057: Only unidentified TeV source that is point-like
MWC 148
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Results: Unidentified Source
Prob. that VERITAS upper flux limits is consistent with HESS flux is 0.007% (~4 )
Ongoing analysis work: Is there a signal in energy range below 1 TeV?
Interpretation: Binary system? Coincident with Be star MWC 148
No companion yet detected; no information on period
Variable X-ray emission (Hinton 2009)
Acciari et al. 2009, in prep.
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Results: Unidentified Source
• Unidentified sources detected in
same FoV as the composite SNR
W44
– 9.1 hrs wobbling on W44
position, 4 hrs wobbling on UIDs
– J1857+026 possibly associated
with newly discovered radio
pulsar PSR J1856+0245
• W44: UL ~5% Crab
• J1857+026: 4-5 Sigma
• J1858+020: 7-8 Sigma
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Results: Unidentified SourceTransient (E> 100 MeV) AGILE J2021+4024
Observations (initially under moonlight) triggered by AGILE. 3 Atels (#1492, 1547, 1585) issued on Apr 28, May 27, and Jun 23 2008 by AGILE
7 hour exposure (Apr 29 – May 6)
99% upper limit at 2% Crab flux above 300 GeV.
3EG J2020+4017
IGR J2018+4043
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Results: Cas A
The non-thermal X-ray emission predominantly originates from filaments and knots in
the reverse-shock region of Cas A (Helder & Vink 2008).
The presence of a large flux of high-energy electrons in the reverse-shock region,
responsible for the non-thermal radio to X-ray emission, will also produce high-energy -
ray emission through non-thermal bremsstrahlung and IC scattering (Atoyan 2006).
Based on that leptonic emission, Cas A would appear in VERITAS data as a disk or ring-
like source with outer radius 2.5′ (Uchiyama & Aharonian 2000).
If, on the other hand, the VHE γ -ray emission from Cas A were dominated by 0 decay
produced in inelastic collisions of relativistic protons, the location of the particle-
acceleration site is less constrained by data in other wavebands.
The question of whether or not there is
a sufficiently high flux of Galactic
nuclear CRs resulting in a steady flux of
VHE –rays, remains one of the most
stimulating scientific questions of
ground-based –ray astronomy.
(Berezhko et al. 2003)
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Results: Geminga
VERITAS Observations: 13.3 hours at high elevation
Upper Limit to steady emission(>300 GeV): <2x10-8 γ/m2/s (~1% Crab flux)
Upper Limit to pulsed emission(>300 GeV): <1x10-8 γ/m2/s (~0.5% of Crab flux)
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Results: MGRO J1908+06HESS J1908+063
Needed a test case for Sky Survey extended source search, chose MGRO J1908+06/HESS J1908+063
MGRO unidentified source
80% of Crab Nebula Flux, <2.6diam. extension at 20 TeV
Detected in HESS galactic plane survey
14% Crab flux > 300 GeV
Source extension 0.21 0.07 (stat) 0.05 (sys)
VERITAS
Data taken under aegis of sky survey
~22h of 4-telescope data
4.85σ detection
~0.19 0.04 extension
position in agreement with HESS J1908+063
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Published papers: 5 LS I +61 303 data from 2006/7 season , LS I +61 303 MWL (TeV
+ X-ray) 2007/8 season
IC 443, SNR G106.3+2.7/Boomerang
HESS J0632+057 variability
Submitted papers: 1 Cassiopeia A
Drafted papers: 1 PSR J1930+1852
Papers in preparation: 4 Sky Survey, Cygni , TEV J2032+4130
W44 / HESS J1857+026 / HESS J1858+020 region
Papers in development: 2 Supernova Remnant upper limits
Pulsar Wind Nebula upper limits
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Two Key Science Projects:
Survey of Cygnus Region
Studies of Supernova Remnants and Pulsar Wind Nebulae
Merger of several inter-related science groups:
Sky Survey
SNRs & PWNe
Compact Objects
Unidentified Sources
Telecons ~ monthly to discuss observing proposals, results, papers, …
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
IC 443
SNR G106.3+2.7 / Boomerang
SNR G54.1+0.3 / PSR J1930+1852
Cassiopeia A
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Summary
VERITAS is operating very well (> 95% uptime) with
two+ good years of data in hand.
Many new results, including:
• Discovery of -ray emission from starburst galaxy M82.
•New information on origins of cosmic rays.
• Stringent limits from Galactic plane survey.
• Detection of new TeV source near Cygni SNR, VER J2019+407
• Detection of 2 new PWN/SNR: G106.3+2.7, G54.1+0.3.
• Detailed studies of SNRs: IC 443 and Cas-A.
VERITAS Upgrade will significantly improve sensitivity.
T1 Relocation already has!
Broad-band studies (GeV – TeV) underway – much more to come.
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
IC 443: Extended and complicated Hints of energy-dependent morphology in TeV band
Strong Fermi source: broadband spectral, morphological evolution will be illuminating
Cas A: Best TeV spectrum to date Boon to modelers
Cygni: Emission not associated with large cloud to south Cloudlets to the north?
LS I +61 303: GeV / TeV differences cooling mechanisms? GeV: detected at all phases, peaks at periastron
TeV: only clearly detected at apastron
Rapid X-ray variability (doubling times short as 2 seconds!)
General: Lack of strong (>5% Crab) sources (eg, PWNe) Sky survey is addressing this quantitatively
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Many of our sources show significant extent IC 443, Boomerang, MGRO J1908…
This matches HESS experience: Almost all Galactic sources (minus Crab, Cas A, binaries) are extended
Observing: Default 0.5º wobble may not be appropriate for Galactic sources where extent is a priori unknown Issue both for detection (potentially) and spectra (definitely)
Larger wobbles? Mini surveys?
Moonlight is fruitful for Galactic sources
PSR J1930, LS I +61 303
Analysis: More effort needed on extended sources Background models for detection, spectra
Handling of bright stars, angular resolution
Likelihood methods for extended sources?
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Young (~330 yr), well studied shell-type SNR
Distance ~3.4 kpc
5-arcmin diameter
Comparable to TeV PSF
Discovered in TeV by HEGRA (232 hrs, 5 ), confirmed by MAGIC (47 hrs, 5.3 )
Stage et al. 2006 (Chandra, 7.3’ by 6.4’)
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Solid: VERITAS
Dashed: HEGRA
Dotted: MAGIC
Index: 2.61 ± 0.24stat ± 0.2sys
Flux (> 1 TeV) ~3.5% Crab
No sign of a cut-off at high energy.
Fermi spectrum connects at lower energy
Electrons or hadrons?
VERITAS: 22 hr data in 2007, 8.3
Consistent with point source
Acciari et al. 2009, submitted
To be replaced by spectrum
including Fermi points
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
“Cousin of the Crab” X-ray jet/torus, no thermal shell
Age ~ 2900 years
E-dot = 1.2 × 1037 erg/s
Distance ~ 6.2 kpc
Lu et al. 2002 (Chandra/ACIS)
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Hint of signal in 2007 moonlight data.
2008/09 follow-up yields a 7-σ detection in 31 hours
Location compatible with pulsar
Consistent with point source.
Acciari et al. (2009), in prep.
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Cassiopeia A is a young SNR, ~ 320 yrs old
X-ray synchrotron (like SN 1006)
First SNR detected in TeV gamma rays! By HEGRA in 2001
since detected by VERITAS and MAGIC as well
Does it accelerate ions, or just electrons?
Chandra X-ray image
~ 5 arcmin
m m m m
FLWO, December 10, 2009 Galactic Science with VERITAS B. Humensky, U. of Chicago
Introduction
Survey of the Cygnus Region
Detections of SNRs and PWNe
-ray Binaries
Summary
Unidentifieds
HESS J1857+026 and HESS J1858+020 in the W44 region
MGRO J1908+063
AGILE transient J2021+4024
Northern PWN Survey Limits
3C 58, Geminga, others