-Cygni – before GLAST

Alberto Carramiñana

Instituto Nacional de Astrofísica, Óptica y Electrónica

Tonantzintla, México

The Multimessenger approach to HE -ray sources

Barcelona, 4- 7 july 2006

The -source 2CG 078+2

• One of 25 Cos-B sources• Located in the Cygnus region• Also 2EG J2020+4026, GeV J2020+4023, 3EG

J2020+4017:– F(>100 MeV)= 1.2310-6 cm-2s-1 → EF~210-10erg cm-2s-

1 the brightest unidentified EGRET source

– steady source, hard spectrum =–2.08– break at 4 GeV (photons up to 16 and 18 GeV)

Identifiyng 2EG J2020+4026

• Located at – 20:20:34 +40:26:24 -- 8’ radius (95% CL)– GeV photons 20:20:15 +40:21:00 -- 2014’ box

(95% CL)

• Inside SNR -Cygni (G78.2+2.1 @ 1.5 kpc)• No pulsations detectable in EGRET data• Unresolved with R<0.5• Multiwavelength ID approach, “Geminga-like”

Brazier et al. MNRAS 281, 1033 (1996)

Identifying 2EG J2020+4026

• ROSAT PSPC data on -Cygni SNR

• One X-ray point source: RX J2020.2+4026– Fx ~ 410-14 erg cm-2s-1→

F/Fx 5000

– no radio F400<600 mJy

• A 15-mag star in 5” error box (type K0V) - ruled out as RX J2020.2+4026 and 2EG J2020+4026 Brazier et al. (1996)

A deeper look• Now to 3EG J2020+4017

– at 20:21:01 +40:17:48 (displaced +.10,-.14º)

– RX J2020.2+4026 outside 95% (in 99%)

• Chandra observations of RX 2020.2+4026– coincident with K star– Fit to ROSAT-HRI points to

d<356 pc distance– Partial coverage of 3EG

error box– 38 cxo sources!

Becker et al. ApJ 615, 897 (2004)

RX J2020.2+4026

GBT on entire 99% 3EG boxS820<40Jy, S1400<20Jyradio quiet box

3EG J2020+4017 (II)

• Chandra observation of 3EG box– 30 point sources– Sx ~ 10-13 to 10-14 erg cm-2 s-1

Weisskopf et al. astro-ph/0606596

→ S/Sx > 2000 - 20000

1-30S(0.5-8 keV)

10-15 erg cm-2s-1

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Too many candidates left!!

The -source 2CG 078+2

• Uncertainty in error box location – 2EG = (305.14, 40.44) ±

0.15º– GeV = (305.07, 40.35) ±

(0.30,0.25) º– 3EG = (305.25, 40.29) ±

0.15º

• Coincidence with SNR call for PSR-ID– S/Sx > 2000 - 20000– Optical?– Radio below 40 Jy –

definitively radio quiet!

It will get it!