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Gamma-ray Nova V407 Cyg and Fermi-LAT Galactic Plane Transients

Gamma-ray Nova V407 Cyg and Fermi-LAT Galactic Plane Transients. C.C. Teddy Cheung (NRC Research Associate*) on behalf of the Fermi-LAT Collaboration *resident at Naval Research Lab. Heidelberg Galactic Binaries – 2010 Dec 3. Fermi-LAT Galactic Plane Transients.

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Gamma-ray Nova V407 Cyg and Fermi-LAT Galactic Plane Transients

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  1. Gamma-ray Nova V407 Cyg and Fermi-LAT Galactic Plane Transients C.C. Teddy Cheung (NRC Research Associate*) on behalf of the Fermi-LAT Collaboration *resident at Naval Research Lab Heidelberg Galactic Binaries – 2010 Dec 3

  2. Fermi-LAT Galactic Plane Transients Low Galactic latitude blazars in 1st LAT AGN Catalog LAT Galactic plane (|b|<10o) transients from daily search* *Excludes flaring from known sources like Cyg X-3 and Crab 2010 Dec 3 - Cheung

  3. Counterpart Search - Fermi J0910-5041 • Fermi J0910-5041 • (Cheung et al. ATel #1788) • Gal. latitude, b = -1.2o • October 15, 2008 (10σ), 2 day gamma-ray flare • Gamma-ray flare 10x larger than average flux • Swift TOO within 1 day 68% 68% LAT 95% error circle contains Swift XRT source (Landi et al. ATel #1822) coincident w/ flat-spectrum radio source in AT20G & SUMMS (Sadler ATel #1843) • Background blazar? Blazar gamma-ray activity typically more ‘long lived’ • Galactic origin? More follow-up necessary 2010 Dec 3 - Cheung

  4. Counterpart Search - 3EG J0903-3531 • 3EG J0903-3531 • (Hays et al. ATel #1771) • Gal. latitude, b = +7.7o • October 5, 2008 (10σ), 3 day gamma-ray flare • 5x above 3EG flux • Swift TOO within 2 days 68% 68% Updated LAT 95% error circle (8 months) contains a flat-spectrum radio source that is detected with Swift/XRT • Other bright Galactic plane transients • Fermi J1057-6027 (Yasuda et al. Atel #2081) – no ID • Fermi J0109+6134 (Vandenbroucke et al. 2010) - blazar Preliminary 2010 Dec 3 - Cheung

  5. Fermi-LAT Discovery of a Nova • Fermi J2102+4542 (6-8σ) March 13-14(Cheung et al. Atel #2487) • Excellent γ-ray localization (r=3.7’), consistent with symbiotic binary V407 Cyg • Subsequent analysis found initial LAT detection on March 10, same day as nova discovery • First g-ray detection of a nova • White dwarf in binary system LAT 0.2-100 GeV PSR J2021+4026 1FGL J2111.3+4607 Nova 2010 V407 Cygni Abdo et al. 2010 Science, 329, 817 (arXiv:1008.3912) Corresponding authors: Cheung, A.B. Hill, P. Jean, S. Razzaque, K.S. Wood 2010 Dec 3 - Cheung

  6. V407 Cygni: a variable star Symbiotic binary: small white dwarf (WD) star and large red giant (RG) star orbiting each other closely Variability can come from the binary motion, pulsations of the red giant (IR/optical), accretion disk around the white dwarf (UV) Nova thermonuclear runaway on WD surface Nova discovery by Nishiyama & Kabashima IAUC 2199 (2010); H. Maehara (Kyoto) 2010 Dec 3 - Cheung

  7. Panchromatic Lightcurves • Optical peaks first • First γ-ray detection day of nova optical discovery • peak 3-4 days later • duration ~15 days • X-rays peak at ~30 days; substantial rise after γ-rays below detectability • Bright evolving radio source (3-140 GHz): ATel #2506, 2511, 2514, 2529, 2536, 2741, 2905 • ★ • Asymmetric distribution of Red giant and wind radiation as seen by nova shell 2010 Dec 3 - Cheung

  8. V407 Cyg Binary System • Evolved Red Giant (M6 III) with: • Mira-like pulsations (745 day period) • SiO maser emission, D-type symbiotic (wind-accreting) • Anomalous Li abundance • Probable distance ~2.7 kpc • Fast rise and decline of nova indicate massive WD (>1 Msun) . • Orbital period uncertain; binary separation ~4 dayγ-ray peak • RG wind & nova shell velocities inferred from optical spectral line-width measurements 2010 Dec 3 - Cheung

  9. V407 Cyg Binary System . Asymmetric distribution of material from Red Giant wind 2010 Dec 3 - Cheung

  10. Nova γ-ray and X-ray Evolution • Nova shell initially freely expands into asymmetric dense medium • Shell toward RG slows down quickly • Gamma rays peak early when efficiency for pion and inverse-Compton processes is favorable • Shell decelerates slowly away from RG • Later X-rays peak, flux increasing with volume of shock-heated gas White dwarf at center Credit: S. Razzaque 2010 Dec 3 - Cheung

  11. γ-ray Spectrum and Energetics 15-day average • Gamma-ray emission process could be: • pion: acceleratedp’s collide with ambient material producing0with prompt decay • inverse Compton: accelerated electrons up-scattering infrared photons from the red giant 2010 Dec 3 - Cheung

  12. Nova V407 Cygni Highlights & Thoughts • Some Fermi-LAT Galactic plane γ-ray transients still unidentified • V407 Cyg first γ-ray nova (white dwarf in binary system) • Fermi acceleration in nova shell; interaction with massive red giant wind plays important role • Shell evolution recapitulates SNR evolution in miniature, and scaled down in timescale • Gamma-ray nova V407 Cyg 2010 not necessarily unique; symbiotic binaries relatively common, novae are numerous • Related binary systems? GX 1+4 = red giant (M6 III) + neutron star. GRS 1915+105 K-giant + black black. 2010 Dec 3 - Cheung

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