The Character of High

Energy Emission From The

Galactic Binary LS 1 +61

303Andy Smith

Smithsonian Astrophysical

Observatory

(for the VERITAS

collaboration)

LS 1 +61 303LS 1 +61 303

-High Mass X-ray Binary-High Mass X-ray Binary

-BH or NS?-BH or NS?

-26.496 day period-26.496 day period

-periodic outbursts in -periodic outbursts in

X-ray, radio, GeV,X-ray, radio, GeV,

and TeV gamma rays!and TeV gamma rays!

LS 1 +61 303LS 1 +61 303

Archival X-ray Archival X-ray

OutburstsOutbursts

(ROSAT,RXTE,(ROSAT,RXTE,

XMM-Newton)XMM-Newton)

LS 1 +61 303LS 1 +61 303

TeV EmissionTeV Emission

(MAGIC)(MAGIC)

LS 1 +61 303LS 1 +61 303

TeV EmissionTeV Emission

(MAGIC, VERITAS(MAGIC, VERITAS

LS 1 +61 LS 1 +61

303303

Radio Radio

EmissionEmission

(VLA, GBI)(VLA, GBI)

Microquasar or Binary Microquasar or Binary

Pulsar?Pulsar?

LS 1 +61 LS 1 +61

303303

Pulsar Model given support byPulsar Model given support by

VLBA monitoringVLBA monitoringNo X-ray or radio pulsations No X-ray or radio pulsations

detected, but…detected, but…Dhawan et al 2006Dhawan et al 2006

However, identification of However, identification of

system stillsystem still

an open issue- an open issue-

multiwavelength multiwavelength

observations observations

(with TeV) help to constrain (with TeV) help to constrain

rise time of rise time of

high energy emission in high energy emission in

different bandsdifferent bands

VERITAS LS I +61 303 Observations:VERITAS LS I +61 303 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 2007

-Observations covered phase bins

0.2-0.9

->10 sigma detection in “active”

phase bins (0.5-0.8)

PhasesPhases

0.5->0.80.5->0.8

TeV activity coincides

with near-apastron

passage

Multiwavelength Multiwavelength

MonitoringMonitoring ToO observations approved for ToO observations approved for

SWIFT and RXTE in late 2006SWIFT and RXTE in late 2006

RXTE: 2-10 keV monitoring in RXTE: 2-10 keV monitoring in

OctoberOctober

SWIFT 0.2-10 keV monitoring Sep-SWIFT 0.2-10 keV monitoring Sep-

>Dec (PSU data reduction: >Dec (PSU data reduction:

A.Falcone,D.Morris) A.Falcone,D.Morris)

Flares observed by both instruments Flares observed by both instruments

around phases 0.6->0.7around phases 0.6->0.7

Contemporaneous observationsContemporaneous observations

during Tev/X-ray flaring statesduring Tev/X-ray flaring states

Very high flux seen in both bandsVery high flux seen in both bands

on same night- spectral analysison same night- spectral analysis

forthcomingforthcoming

Contemporaneous observationsContemporaneous observations

during X-ray flaring statesduring X-ray flaring states

X-ray emission elevated, X-ray emission elevated,

but not maximalbut not maximal

Local X-ray PeakLocal X-ray Peak

Local TeV PeakLocal TeV PeakTeV emission elevated,TeV emission elevated,

but not maximalbut not maximal

Active X-ray RegionsActive X-ray Regions

Active TeV regionsActive TeV regions

Summary so far…Summary so far… VERITAS observations confirm detection of LS 1 VERITAS observations confirm detection of LS 1

+61 303 as variable TeV source+61 303 as variable TeV source

One of 3 known “TeV” binaries- new class of One of 3 known “TeV” binaries- new class of

sourcessources

Multiwavelength observations show elevated TeV Multiwavelength observations show elevated TeV

emission correlated with elevated X-ray behavior emission correlated with elevated X-ray behavior

(not necessarily bijective....)(not necessarily bijective....)

SWIFT observations show secondary X-ray peak SWIFT observations show secondary X-ray peak

near pre-periastron passage- no TeV observations near pre-periastron passage- no TeV observations

yet for this region. yet for this region.

X-ray Peaks

TeV

Emission

Latest Observations……

MicroquasarMicroquasar

Scenario:Scenario:

Accretion Accretion

driven emission driven emission

during and during and

after density after density

peakspeaks. .

X-ray Accretion Disk-X-ray Accretion Disk-

->Radio Loud Jets->Radio Loud Jets

->Upscatter stellar photons->Upscatter stellar photons

to TeV energiesto TeV energies

Supporting Evidence:Supporting Evidence:

-MERLIN Imaging-MERLIN Imaging

-TeV emission agreeable with -TeV emission agreeable with

““Second Peak”Second Peak”

TeV

EmissionCons:Cons:

No spectral evidence for accretionNo spectral evidence for accretion

Where is primary peak?Where is primary peak?

Or……..Or……..

Binary Pulsar Binary Pulsar

Scenario:Scenario:Shock acceleration at interface between Shock acceleration at interface between

pulsar and stellar wind drives X-ray/TeV pulsar and stellar wind drives X-ray/TeV

emission- radio emission from cometary tailemission- radio emission from cometary tail

Observational Evidence:Observational Evidence:

-VLA imaging strongest evidence-VLA imaging strongest evidence

-Close rise time of X-ray/TeV emission-Close rise time of X-ray/TeV emission

Cons:Cons:

-No evidence for pulsations-No evidence for pulsations

-Is stellar wind stronger than pulsar wind?-Is stellar wind stronger than pulsar wind?

-Difficult to say without greater understanding-Difficult to say without greater understanding

of orbital geometryof orbital geometry

X-ray Peaks

TeV

Emission

Secondary X-ray Peak?Secondary X-ray Peak?

SummarySummary Latest high energy observations of LS 1 +61 303 Latest high energy observations of LS 1 +61 303

show evidence for correlation between X-ray and show evidence for correlation between X-ray and

TeV behaviorTeV behavior

No clear indication of fundamental identification of No clear indication of fundamental identification of

systemsystem

Regardless of nature (MQ vs BP) , it is evident that Regardless of nature (MQ vs BP) , it is evident that

“local“ compact systems are able to accelerate “local“ compact systems are able to accelerate

(most likely) electrons to TeV energies .(most likely) electrons to TeV energies .

TeV binaries represents ideal laboratories for TeV binaries represents ideal laboratories for

observations of high energy emission in the observations of high energy emission in the

presence of strong gravity stellar environments.presence of strong gravity stellar environments.

Watch this space.......Watch this space....... RXTE monitoring approved for bi-nightly RXTE monitoring approved for bi-nightly

observations from September 2007-->February observations from September 2007-->February

20082008

This, combined with TeV monitoring from This, combined with TeV monitoring from

VERITAS, will allow first multiwavelength VERITAS, will allow first multiwavelength

observations taken between phases 0.9->0.2: observations taken between phases 0.9->0.2:

more accurate measurement of full cycle more accurate measurement of full cycle

behaviorbehavior

If LS1 is a black hole, will add to study of BH If LS1 is a black hole, will add to study of BH

dynamics. If it is a binary pulsar, will add to dynamics. If it is a binary pulsar, will add to

study of pulsar wind accelerationstudy of pulsar wind acceleration