Jamie Holder and Gernot Maier University of Delaware/ McGill University

A summary of other A summary of other eventdisplay analysis results eventdisplay analysis results

from Fall 2006 and some from Fall 2006 and some other stuff wot I hav dun.other stuff wot I hav dun.

VERITAS Collaboration Meeting, Tucson, January 2007

• Results for November dark run

• Some other stuff

OverviewOverview

• All Observations taken during the November dark run

• Two-telescope data only

• major noise problems resolved

• relative gain gradient removed

• Loose run selection criteria

• Better than B weather

• No major hardware problems

Summary of ObservationsSummary of Observations

Summary of ObservationsSummary of Observations

Source Category Mean Elevation

Wobble offset

Exposure (hours)

Tycho SNR 56° 0.3° 11.7

PSR J2021 Pulsar/PWN 60° 0.3° 8.5

PSR J2229 Pulsar/PWN 57° 0.3° 11.3

1ES 0806 AGN 66° 0.3° 5.8

1ES 0647 AGN 73° 0.5° 12.4

Details of the sources will be presented this afternoon

AnalysisAnalysis• Eventdisplay/mscw_energy/anasum

• 5.0/2.5 σ pixel cleaning

• doublepass trace analysis

• Cleaning Cuts:• Two images with ≥5 pixels

• Hillas distance <1.2°

• Angle between image axes >10°

• Gamma Selection Cuts:• image size > 400 dc in each image

• mean-scaled width < 0.5

• mean-scaled length < 0.5

• θ2 < 0.025 (θ<0.158°)

Results: Ring BackgroundResults: Ring Background

Source ON events OFF events (normalisation)

Significance

Tycho 183 168.4 (0.23) 1.0

PSR J2021 214 209.8 (0.23) 0.3

PSR J2229 192 172.6 (0.23) 1.3

1ES 0806 89 76.0 (0.23) 1.3

1ES 0647 301 281.9 (0.23) 1.0

• Ring Background Details:

• Ring Radius = 0.5°

• Ring Width = 0.15°

Results: Reflected RegionResults: Reflected Region

Source ON events OFF events (normalisation)

Significance

Tycho 183 168.3 (0.33) 1.0

PSR J2021 214 216.3 (0.33) -0.1

PSR J2229 192 180.0 (0.33) 0.8

1ES 0806 89 80.7 (0.33) 0.8

1ES 0647 301 310.8 (0.20) -0.5

• Reflected Region Details:

• Fixed number of regions

• 3 for 0.3° offset

• 5 for 0.5° offset

Sky maps: Sky maps: TychoTycho

Ring BackgroundReflected Region

Background

Sky maps: Sky maps: PSR J2021PSR J2021

Ring BackgroundReflected Region

Background

Sky maps: Sky maps: PSR J2229PSR J2229

Ring BackgroundReflected Region

Background

Sky maps: Sky maps: 1ES 08061ES 0806

Ring BackgroundReflected Region

Background

Sky maps: Sky maps: 1ES 06471ES 0647

Ring BackgroundReflected Region

Background

Point source upper limitsPoint source upper limits

Source 3σ (99.87% CL) Upper Limit

(Counts)

% Crab Flux Previous limits (may not be

the best)

Tycho 72.3 5.0% 3.3% (HEGRA)

PSR J2021 64.7 5.6% 20% (Fegan)

PSR J2229 71.7 5.1% 21% (Fegan)

1ES 0806 48.6 5.6% 8% (de la Calle)

1ES 0647 72.1 3.5% 8% (HEGRA)

• Using Helene method

• Using Reflected Region results

• Crab % calculated using Crab rate at the mean elevation of the observations.

Swift Observations Swift Observations of LSI+61303of LSI+61303 BAT

15 - 150 keV

XRT0.3 - 10 keV

UVOT170-650nm

ObservationsObservations

September October November December

• 24 observations so far (as of December 19th)

• Total exposure ~50ksecs

• Observations ongoing

XRT ResultsXRT Results

• Strong detection with each exposure

XRT ResultsXRT Results

• Clear variability in light curve (factor of 5)

UVOTUVOT

• Images taken with a range of filters

• Mostly at shorter wavelengths

UVOTUVOT

• Example image with a blue filter

• LSI is one of the brightest objects in the frame

SummarySummary

• This was the multiwavelength state-of-the-art view before this year.

• Mainly non-contemporaneous

• Swift/VERITAS observations will greatly improve this

• We should keep observing LSI!

Jamie Holder University of Delaware

Magnetic Massive Stars as Magnetic Massive Stars as TeV source candidatesTeV source candidates

VERITAS Collaboration Meeting, Tucson, January 2007

• Wolf-Rayet stars generate strong stellar winds

• Integrated over their lifetime, the wind energy output is ~1037ergs/s

• In Wolf-Rayet binary systems (e.g. WR20a) winds from two 70Msol stars collide with a relative speed of ~1000 km/s

• This forms a shock region, where particle acceleration can occur (e.g. Bednarek 2005, Pittard 2006)

IntroductionIntroduction

• HESS have recently detected emission from the region of WR20a (9σ result)

• Extended ~0.2°

• Flux ~10-15% Crab

• Steady emission

• Spectrum ~Crab-like

• Offset w.r.t. WR20a

HESS ResultHESS Result

• WR 20a itself would be a point source

• Westerland 2, a stellar cluster with massive star formation (Chandra sees 500 X-ray sources here).

• Radio observations reveal wind blown "bubbles" around WR20a and WR20b and the core of Westerland 2, and a "blister" to the west, where the "bubble" is expands into a less dense region of the ISM.

HESS InterpretaionHESS Interpretaion

Radio Map (843MHz)

WR20a

WR20b

• Another colliding wind binary (Wolf-Rayet and O-type star)

• RA= 20h 20m, dec=+43 degrees

• Summer source (bad!), but unique to northern hemisphere (good!)

• Pittard & Dougherty:

• Integral predicted flux >1TeV= 1.2 × 10-14 photons s-1 cm-2

• requires >50 hours, but in the light of HESS result, who knows?

Northern hemisphere: WR140Northern hemisphere: WR140

• Most massive stars do not have strong magnetic fields; however, there exist a class of magnetic massive stars

• Bp stars: chemically peculiar (helium rich)

• Magnetic fields of ~ 10,000 Gauss

• These fields can channel the hypersonic, radiation-driven stellar wind into violent collision with itself, generating a shock of similar magnitude to a colliding wind binary system (Townsend and Owocki, 2006).

Northern hemisphere: Northern hemisphere: σσ Ori E Ori E

Northern hemisphere: Northern hemisphere: σσ Ori E Ori E • RA 05h 38m dec -02° 32'

• Visible now, to northern and southern hemispheres

• In the same field of view are star clusters; e.g. NGC 2024

• Chandra sees 283 sources in this star-forming region

• May have some trouble with bright stars...

• 10 hours in January would give us a strong upper limit on this new candidate source class.

NGC 2024The flame nebula