Gamma-ray Nova V407 Gamma-ray Nova V407 Cyg and Fermi-LAT Cyg and Fermi-LAT

Galactic Plane TransientsGalactic 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 TransientsFermi-LAT Galactic Plane Transients

LAT Galactic plane (|b|<10o) transients from daily search*

Low Galactic latitude blazars in 1st LAT AGN Catalog

2010 Dec 3 - Cheung

*Excludes flaring from known sources like Cyg X-3 and Crab

Counterpart Search - Fermi J0910-5041Counterpart 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)

2010 Dec 3 - Cheung

- Background blazar? Blazar gamma-ray activity typically more ‘long lived’

- Galactic origin? More follow-up necessary

Counterpart Search - 3EG J0903-3531Counterpart Search - 3EG J0903-3531

68% 68%

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

Updated LAT 95% error circle (8 months) contains a flat-spectrum radio source that is detected with Swift/XRT

Preliminary2010 Dec 3 - Cheung

Other bright Galactic plane transients

- Fermi J1057-6027 (Yasuda et al. Atel #2081) – no ID

- Fermi J0109+6134 (Vandenbroucke et al. 2010) - blazar

Fermi-LAT Discovery of a NovaFermi-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 First ray detection of a novaray detection of a nova White dwarf in binary systemWhite dwarf in binary system

1FGL J2111.3+4607

Nova 2010V407 Cygni

PSR J2021+4026

LAT 0.2-100 GeV

2010 Dec 3 - Cheung

Abdo et al. 2010 Science, 329, 817

(arXiv:1008.3912)

Corresponding authors: Cheung, A.B. Hill, P. Jean, S. Razzaque, K.S. Wood

V407 Cygni: a variable starV407 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 LightcurvesPanchromatic 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 SystemV407 Cyg Binary System

.

2010 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 Msun)

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 SystemV407 Cyg Binary System

.

2010 Dec 3 - Cheung

Asymmetric distribution of material from Red Giant wind

Nova γ-ray and X-ray Evolution 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 Energeticsγ-ray Spectrum and Energetics

15-day average

Gamma-ray emission process could be:

pion:pion: accelerated accelerated pp’s ’s collide with ambient collide with ambient material producingmaterial producing 00 with with prompt decayprompt decay• inverse Compton:inverse Compton: accelerated electrons up-accelerated electrons up-scattering infrared photons scattering infrared photons from the red giantfrom the red giant

2010 Dec 3 - Cheung

Nova V407 Cygni Highlights & ThoughtsNova 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