The Character of High Energy Emission From The Galactic Binary LS Andy Smith Smithsonian Astrophysical Observatory (for the VERITAS collaboration)

LS High Mass X-ray Binary -BH or NS? day period -periodic outbursts in X-ray, radio, GeV, and TeV gamma rays!

LS Archival X-ray Outbursts (ROSAT,RXTE,XMM-Newton)

LS TeV Emission (MAGIC)

LS TeV Emission (MAGIC, VERITAS LS Radio Emission (VLA, GBI)

Microquasar or Binary Pulsar?

LS Pulsar Model given support by VLBA monitoring No X-ray or radio pulsations detected, but… Dhawan et al 2006 However, identification of system still an open issue- multiwavelength observations (with TeV) help to constrain rise time of high energy emission in different bands

VERITAS LS I Observations: - New TeV Array in S. Arizona (see T.Weekes on Sat) -Sensitive in range 100 GeV->20 TeV -44h of data from September 2006-February Observations covered phase bins >10 sigma detection in “active” phase bins ( )

Phases0.5->0.8

TeV activity coincides with near-apastron passage

Multiwavelength Monitoring ToO observations approved for SWIFT and RXTE in late 2006 ToO observations approved for SWIFT and RXTE in late 2006 RXTE: 2-10 keV monitoring in October RXTE: 2-10 keV monitoring in October SWIFT keV monitoring Sep->Dec (PSU data reduction: A.Falcone,D.Morris) SWIFT keV monitoring Sep->Dec (PSU data reduction: A.Falcone,D.Morris) Flares observed by both instruments around phases 0.6->0.7 Flares observed by both instruments around phases 0.6->0.7

Contemporaneous observations during Tev/X-ray flaring states

Very high flux seen in both bands on same night- spectral analysis forthcoming

Contemporaneous observations during X-ray flaring states

X-ray emission elevated, but not maximal Local X-ray Peak Local TeV Peak TeV emission elevated, but not maximal

Active X-ray Regions Active TeV regions

Summary so far… VERITAS observations confirm detection of LS as variable TeV source VERITAS observations confirm detection of LS as variable TeV source One of 3 known “TeV” binaries- new class of sources One of 3 known “TeV” binaries- new class of sources Multiwavelength observations show elevated TeV emission correlated with elevated X-ray behavior (not necessarily bijective....) Multiwavelength observations show elevated TeV emission correlated with elevated X-ray behavior (not necessarily bijective....) SWIFT observations show secondary X-ray peak near pre- periastron passage- no TeV observations yet for this region. SWIFT observations show secondary X-ray peak near pre- periastron passage- no TeV observations yet for this region.

X-ray Peaks TeV Emission Latest Observations……

Microquasar Scenario: Accretion driven emission during and after density peaks. X-ray Accretion Disk- ->Radio Loud Jets ->Upscatter stellar photons to TeV energies Supporting Evidence: -MERLIN Imaging -TeV emission agreeable with “Second Peak” TeV Emission Cons: No spectral evidence for accretion Where is primary peak?

Or…….. Binary Pulsar Scenario: Shock acceleration at interface between pulsar and stellar wind drives X-ray/TeV emission- radio emission from cometary tail Observational Evidence: -VLA imaging strongest evidence -Close rise time of X-ray/TeV emission Cons: -No evidence for pulsations -Is stellar wind stronger than pulsar wind? -Difficult to say without greater understanding of orbital geometry

X-ray Peaks TeV Emission Secondary X-ray Peak?

Summary Latest high energy observations of LS show evidence for correlation between X-ray and TeV behavior Latest high energy observations of LS show evidence for correlation between X-ray and TeV behavior No clear indication of fundamental identification of system No clear indication of fundamental identification of system Regardless of nature (MQ vs BP), it is evident that “local“ compact systems are able to accelerate (most likely) electrons to TeV energies. Regardless of nature (MQ vs BP), it is evident that “local“ compact systems are able to accelerate (most likely) electrons to TeV energies. TeV binaries represents ideal laboratories for observations of high energy emission in the presence of strong gravity stellar environments. TeV binaries represents ideal laboratories for observations of high energy emission in the presence of strong gravity stellar environments.

Watch this space RXTE monitoring approved for bi-nightly observations from September >February 2008 RXTE monitoring approved for bi-nightly observations from September >February 2008 This, combined with TeV monitoring from VERITAS, will allow first multiwavelength observations taken between phases 0.9->0.2: more accurate measurement of full cycle behavior This, combined with TeV monitoring from VERITAS, will allow first multiwavelength observations taken between phases 0.9->0.2: more accurate measurement of full cycle behavior If LS1 is a black hole, will add to study of BH dynamics. If it is a binary pulsar, will add to study of pulsar wind acceleration If LS1 is a black hole, will add to study of BH dynamics. If it is a binary pulsar, will add to study of pulsar wind acceleration