Jamie Holder and Gernot Maier University of Delaware/ McGill University A summary of other eventdisplay analysis results from Fall 2006 and some other stuff wot I hav dun. VERITAS Collaboration Meeting, Tucson, January 2007

Results for November dark run Some other stuff Overview

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 Observations

SourceCategoryMean Elevation Wobble offset Exposure (hours) TychoSNR56°0.3°11.7 PSR J2021Pulsar/PWN60°0.3°8.5 PSR J2229Pulsar/PWN57°0.3°11.3 1ES 0806AGN66°0.3°5.8 1ES 0647AGN73°0.5°12.4 Details of the sources will be presented this afternoon

Analysis 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 θ 2 < (θ<0.158°)

Results: Ring Background SourceON eventsOFF events (normalisation) Significance Tycho (0.23)1.0 PSR J (0.23)0.3 PSR J (0.23)1.3 1ES (0.23)1.3 1ES (0.23)1.0 Ring Background Details: Ring Radius = 0.5° Ring Width = 0.15°

Results: Reflected Region SourceON eventsOFF events (normalisation) Significance Tycho (0.33)1.0 PSR J (0.33)-0.1 PSR J (0.33)0.8 1ES (0.33)0.8 1ES (0.20)-0.5 Reflected Region Details: Fixed number of regions 3 for 0.3° offset 5 for 0.5° offset

Sky maps: Tycho Ring Background Reflected Region Background

Sky maps: PSR J2021 Ring Background Reflected Region Background

Sky maps: PSR J2229 Ring Background Reflected Region Background

Sky maps: 1ES 0806 Ring Background Reflected Region Background

Sky maps: 1ES 0647 Ring Background Reflected Region Background

Point source upper limits Source3σ (99.87% CL) Upper Limit (Counts) % Crab FluxPrevious limits (may not be the best) Tycho %3.3% (HEGRA) PSR J %20% (Fegan) PSR J %21% (Fegan) 1ES %8% (de la Calle) 1ES %8% (HEGRA) Using Helene method Using Reflected Region results Crab % calculated using Crab rate at the mean elevation of the observations.

Swift Observations of LSI BAT keV XRT keV UVOT nm

Observations September October November December 24 observations so far (as of December 19 th ) Total exposure ~50ksecs Observations ongoing

XRT Results Strong detection with each exposure

XRT Results Clear variability in light curve (factor of 5)

UVOT Images taken with a range of filters Mostly at shorter wavelengths

UVOT Example image with a blue filter LSI is one of the brightest objects in the frame

Summary 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 TeV source candidates VERITAS Collaboration Meeting, Tucson, January 2007

Wolf-Rayet stars generate strong stellar winds Integrated over their lifetime, the wind energy output is ~10 37 ergs/s In Wolf-Rayet binary systems (e.g. WR20a) winds from two 70M sol 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) Introduction

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 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 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 × photons s -1 cm -2 requires >50 hours, but in the light of HESS result, who knows? Northern 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: σ 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 hours in January would give us a strong upper limit on this new candidate source class. NGC 2024 The flame nebula