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

Counterpart Search - Fermi J Fermi J (Cheung et al. ATel #1788) - Gal. latitude, b = -1.2 o - October 15, 2008 (10σ), 2 day gamma-ray flare - Gamma-ray flare 10x larger than average flux - Swift TOO within 1 day 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) 2010 Dec 3 - Cheung -Background blazar? Blazar gamma-ray activity typically more ‘long lived’ -Galactic origin? More follow-up necessary

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

Fermi-LAT Discovery of a Nova Fermi J (6-8σ) March (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  ray detection of a nova  White dwarf in binary system 1FGL J Nova 2010 V407 Cygni PSR J LAT GeV 2010 Dec 3 - Cheung Abdo et al Science, 329, 817 (arXiv: ) Corresponding authors: Cheung, A.B. Hill, P. Jean, S. Razzaque, K.S. Wood

V407 Cygni: a variable star 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 Symbiotic binary: small white dwarf (WD) star and large red giant (RG) star orbiting each other closely 2010 Dec 3 - Cheung Nova discovery by Nishiyama & Kabashima IAUC 2199 (2010); H. Maehara (Kyoto)

Panchromatic Lightcurves Asymmetric distribution of Red giant and wind radiation as seen by nova shell 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 ★ 2010 Dec 3 - Cheung

V407 Cyg Binary System Dec 3 - Cheung 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 M sun ) Orbital period uncertain; binary separation ~4 day γ-ray peak RG wind & nova shell velocities inferred from optical spectral line- width measurements

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

Nova γ-ray and X-ray Evolution White dwarf at center Credit: S. Razzaque 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 2010 Dec 3 - Cheung

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

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 K-giant + black black Dec 3 - Cheung