fermi lat observations of galactic x-ray binaries

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Adam Hill R. Dubois (SLAC), R. Corbet (UMBC/NASA, GSFC), G. Dubus (LAOG), T. Tanaka (SLAC), D. Torres (ICREA, Barcelona) on behalf of the Fermi-LAT collaboration. Fermi LAT Observations of Galactic X-ray binaries. The Fermi instruments. Fermi was successfully launched June 2008 LAT: - PowerPoint PPT Presentation

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  • Adam Hill

    R. Dubois (SLAC), R. Corbet (UMBC/NASA, GSFC), G. Dubus (LAOG), T. Tanaka (SLAC), D. Torres (ICREA, Barcelona)on behalf of the Fermi-LAT collaboration

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    Fermi was successfully launched June 2008LAT:20 MeV 300 GeV1 PSLA for bright sources2 str FOVIn survey mode scans the whole sky every 3 hoursGBM:8 keV- 30 MeVViews whole unocculted sky

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    A number of X-ray binaries have been detected at > 1 TeV:

    PSR B1259-63Radio pulsar in 3.5 yr orbit of Be starHESS detection at periastron LS 5039HESS detects 3.9 day orbital periodLS I +61303Be HMXB shows periodic radio flaresMAGIC & VERITAS see VHE emission modulated on 26 day orbital period

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    3EGJ0241+6103 has been associated with LS I +61303 but position is uncertain.Hartman et al. (1999)Evidence of variability found but no periodicity.Tavani et al. (1998)

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    3EG1824-1514 is coincident with LS 5039 but has a 0.5 error box and no indication of variabilityHartman et al. (1999)

    SED of LS 5039 including the spectra of EGRET & HESS. The 2 X-ray measurements are from RXTE & XMM.de Naurois. (2005)

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    LS I +61303 has been fitted to R.A.=40.076, Dec.=61.233 with 95% error radius of 1.8. This location is consistent with the known position of the optical counterpart.Flux variability is also clearly evident

    PRELIMINARY

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    We detect a periodicity in the LS I +61303 light curve at 26.40.5 days

    Folded light curve indicates peaks of emission around periastron.PRELIMINARYPRELIMINARY

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    Investigating signs of orbit to orbit variability

    As more orbits are observed evidence will become clearerJ.Casares et al (2005)N.B. The light curve is not background subtractedPRELIMINARY

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    Veritas observations in 2006-2007 showed a strongly variable flux at 300 GeV 5 TeV.Maximum flux is found during most orbital cycles at apastron.Acciari et al. (2008)

    MAGIC observations in 2005-2006 also showed variable emission (200 GeV 4 TeV).See significant flux increase at phase 0.45-0.65Albert et al. (2006)

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    Unbinned likelihood fitting of the Fermi flux to a power law yields F = A E-:

    Flux (E>100 MeV) = 0.83 0.04 (stat) 0.21 (syst) 10-6 ph/cm2/s

    = 2.41 0.03 (stat) 0.17 (syst)

    (Paper in preparation)

    (N.B. The TeV spectral data is not contemporaneous and is not phase averaged)

    Points: Fitted energy binsRed: Fermi unbinned power law fitGrey: EGRETBlue: MAGIC (Only phase 0.4-0.7) Veritas data points overlaid(systematic errors not shown)PRELIMINARY

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    MAGIC reported a flare at VHE from Cyg-X1 in 2006.

    We are monitoring 68 sources on a daily basis.

    Challenging work due to the high contribution of diffuse emission in the galactic plane.

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    The LAT has and will discover new unknown sources; some of which could potentially be gamma-ray binaries.2 bright transients detected in the Galactic Plane (ATels 1771 &1788).

    3EG J0903-35313EG J0903-3531Fermi J0910-5041PRELIMINARY

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    First detection in the GeV domain of flux modulation on the 26.5 day orbital period.Definitive detection of LS I +61303 by Fermi.LS 5039 to be investigated.More binaries to look for both persistent and flaring. Lots more work to do...

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    Sources seen by traditional X-ray missions, by INTEGRAL up to 100 keV.Seen by MAGIC, HESS & VERITAS at VHE.Why not at MeV-GeV energiesMost radiation emitted above 10 MeV*ASCA 2-10keV image with EGRET 68% and 95% confidence contours*Data until January 2009*