GAMMA RAY BINARIES WITH FERMI Chandreyee Maitra Crystal Nuansa Aini Harsha Raichur Partha Sarathi Pal Instructors Robin Corbet, Mariano Mendez

Outline of the Talk X-Ray and Gamma Ray binaries Sources of Gamma Ray emission in binaries Gamma Ray Binaries detected by LAT Analysis Technique Results Discussion References

X-Ray Binaries Stellar system in which one is a normal star and the other a compact object.  High Mass X-Ray binary (M c 1M sun )  Low Mass X-ray binary (M c 10M sun )

Gamma ray Binaries Binary systems including a compact object (Neutron star or Black hole ) having sufficient detectability in gamma rays..

Emission Mechanism Interaction between two binary components: Interaction of the pulsar wind or the relativistic jets emitted by the compact object with the wind from the companion

Gamma Ray Binaries detected by LAT LSI +61º303 LS 5039 Cygnus X-3

LSI +61º303 HMXB Companion Be star; Compact object nature not known ; P orb = ± days & e= ; Shows strong emission from radio-X-ray to Tev energies ; Radio observations gives a super orbital period P sup =1667 ± 8 days 23 sources within 7 o ROI

LS 5039 HMXB ; Companion O 6.5 V star; Both black hole and neutron star supported as compact object. eccentric orbit ~0.35 with P orb = ± days 54 point sources within the 10 o ROI

LS 5039 PSRJ

Cygnus X-3 HMXB ; Companion Wolf Rayet star Compact object most probably a black hole; Short orbital period P orb = 4.8 ± hrs detected in X-rays and infrared. Gamma rays detected in flares in coherence with radio flares in the soft x-ray state of the system. 60 sources in 10 o ROI

PSR PSR J PSR J

Analysis Technique Aperture Photometry Likelihood Analysis Off pulse Analysis Technique Measurement of flux collected in the particular region of sky. Model independent Optimum choice of aperture enhances the signal to noise ratio. GTSELECT with 1 degree radius --->> GTMAKETIME, GTBIN (extract the light curve) GTEXPOSURE calculated the exposure of time bins to calculate the exposure weighted error. GTSELECT with event data followed by good time interval selection by GTMKTIME Count MAP created to visualize the extraction region using GTBIN. Exposure map created by GTLTCUBE followed by GTEXPMAP. UNBINNED likelihood analysis performed using GTLIKE Model file includes point sources, diffuse galactic and extragalactic background. Suitable number of sources and their models chosen in the ROI to optimize the fit. GTSELECT for the pulsar with small radius followed by GTMKTIME. GTPPHASE take the ephemeris data base and assigns spin phase to the data 1D histogram of phase shows off pulse period. GTPPHASE on entire dataset where the ephemeris solution is valid with previous specifications assigns the pulse phase GTSELECT on entire data set with phasemin phasemax selects the required phase

Pulsar Phase Analysis Pulse phase diagram of J which is in the vicinity of LS 5039 Pulse phase diagram of PSR J which is near by to the Cygnus X-3

Aperture Photometry of LSI +61º303 Light curve with one orbital period time bin Power spectrum of the light curve with time resolution one day Folded light curve to show the orbital modulation

Aperture Photometry of LS 5039 Light curve with 2 orbital period time bin Power spectrum of the 0.5 day time resolution light curve Folded light curve to show orbital modulation

Aperture Photometry of Cygnus X-3 Light curve with 2 times of the orbital period time bin Power spectrum of the 1000 sec time resolution light curve

Likelihood analysis of LSI+61 o 303 Super Exponential Cutoff: N0 = 0.19X /-0.06X = /- 0.2 Cut-off = 6.4 GeV Frozen TS = 14590

Likelihood Analysis of LS5039 Data for entire duration( 540 days) Data with PSR in off- pulse(13 1 days) Powerlaw 2 Index = / Integral = ( / ) X TS= Power law 2 Index = / Integral = / X TS =

Likelihood analysis of Cygnus X-3 Power law 2 Index = /- 0.2 Flux= e-07 TS = 116.2

Likelihood light curve of LSI +61º303

Likelihood light curve of LS 5039

Likelihood light curve of Cygnus X-3 Light curve obtained from likelihood analysis with 4 days time bin Variation of spectral index obtained from likelihood analysis

Discussions LSI +61 o 303 Flux wrt time has changed --> look for change in corresponding spectral state. Super orbital period observed only in radio --> Longer time data base will detect this in gamma rays ???? LS 5039 spectral variability wrt orbital phase reported --> Further investigation required. Looking for correlations between gamma ray emission with other energy bands. Cygnus X-3 analysis including both the flaring states. More detailed analysis is required because of the complexity of the region.

References Modulated High Energy Gamma Ray Emission from the microquasar Cygnus X-3, The fermi LAT Team, Science, 326, 1512, Fermi LAT observations of LS 5039, The Fermi LAT team,ApJ,706,L56,2009. Fermi LAT observations of LS +61º 303,ApJ,701,L123,2009

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