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First detection of a VHE gamma-ray spectral maximum from a cosmicsource: HESS discovery of the Vela X nebula

Aharonian, F; Akhperjanian, AG; Bazer-Bachi, AR; Beilicke, M; Benbow, W; Berge, D; Bernlöhr, K; Boisson, C; Bolz, O; Borrel, V; Braun, I; Breitling, F; Brown, AM; Bühler, R; Busching, I; Carrigan, S; Chadwick, PM; Chounet, LM; Cornils, R; Costamante, L; Degrange, B; Dickinson, HJ; Djannati-Atai, A; Drury, LO; Dubus, G; Egberts, K; Emmanoulopoulos, D; Epinat, B; Espigat, P; Feinstein, F; Ferrero, E; Fontaine, G; Funk, S; Gallant, YA; Giebels, B; Glicenstein, JF; Goret, P; Hadjichristidis, C; Hauser, D; Hauser, M; Heinzelmann, G; Henri, G; Hermann, G; Hinton, JA; Hofmann, W; Holleran, M; Horns, D; Jacholkowska, A; de Jager, OC; Khelifi, B; Komin, N; Konopelko, A; Latham, IJ; Le Gallou, R; Lemiere, A; Lemoine-Goumard, M; Lohse, T; Martin, JM; Martineau-Huynh, O; Marcowith, A; Masterson, C; McComb, TJL; de Naurois, M; Nedbal, D; Nolan, SJ; Noutsos, A; Orford, KJ; Osborne, JL; Ouchrif, M; Panter, M; Pelletier, G; Pita, S; Puhlhofer, G; Punch, MP; Raubenheimer, BC; Raue, M; Rayner, SM; Reime...


F Aharonian

AG Akhperjanian

AR Bazer-Bachi

M Beilicke

W Benbow

D Berge

K Bernlöhr

C Boisson

O Bolz

V Borrel

I Braun

F Breitling

AM Brown

R Bühler

I Busching

S Carrigan

LM Chounet

R Cornils

L Costamante

B Degrange

HJ Dickinson

A Djannati-Atai

LO Drury

G Dubus

K Egberts

D Emmanoulopoulos

B Epinat

P Espigat

F Feinstein

E Ferrero

G Fontaine

S Funk

YA Gallant

B Giebels

JF Glicenstein

P Goret

C Hadjichristidis

D Hauser

M Hauser

G Heinzelmann

G Henri

G Hermann

JA Hinton

W Hofmann

M Holleran

D Horns

A Jacholkowska

OC de Jager

B Khelifi

N Komin

A Konopelko

IJ Latham

R Le Gallou

A Lemiere

M Lemoine-Goumard

T Lohse

JM Martin

O Martineau-Huynh

A Marcowith

C Masterson

TJL McComb

M de Naurois

D Nedbal

SJ Nolan

A Noutsos

KJ Orford

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Dr John
Emeritus Staff

M Ouchrif

M Panter

G Pelletier

S Pita

G Puhlhofer

MP Punch

BC Raubenheimer

M Raue

SM Rayner

A Reimer

O Reimer

J Ripken

L Rob

L Rolland

G Rowell

V Sahakian

L Sauge

S Schlenker

R Schlickeiser

U Schwanke

H Sol

D Spangler

F Spanier

R Steenkamp

C Stegmann

G Superina

JP Tavernet

R Terrier

CG Theoret

M Tluczykont

C van Eldik

G Vasileiadis

C Venter

P Vincent

HJ Volk

SJ Wagner


The Vela supernova remnant (SNR) is a complex region containing a number of sources of non-thermal radiation. The inner section of this SNR, within 2 degrees of the pulsar PSR B0833-45 , has been observed by the HESS $\gamma$-ray atmospheric Cherenkov detector in 2004 and 2005. A strong signal is seen from an extended region to the south of the pulsar, within an integration region of radius $0.8\ensuremath{^{\circ}} $ around the position ( $\rm\alpha = 08^{h} 35^{m} 00^{s}$, $\delta = -45\ensuremath{^{\circ}} 36\arcmin$ J2000.0). The excess coincides with a region of hard X-ray emission seen by the ROSAT and ASCA satellites. The observed energy spectrum of the source between 550 GeV and 65 TeV is well fit by a power law function with photon index $\Gamma = 1.45 \pm 0.09\ensuremath{_{{\rm stat}}}\ \pm 0.2\ensuremath{_{{\rm sys}}} $ and an exponential cutoff at an energy of $13.8 \pm 2.3\ensuremath{_{{\rm stat}}}\ \pm 4.1\ensuremath{_{{\rm sys}}} $ TeV. The integral flux above 1 TeV is $(1.28 \pm 0.17\ensuremath{_{{\rm stat}}}\ \pm 0.38\ensuremath{_{{\rm sys}}} ) \times 10^{-11}\ \ensuremath{{\rm cm}^{-2}\,{\rm s}^{-1}} $. This result is the first clear measurement of a peak in the spectral energy distribution from a VHE $\gamma$-ray source, likely related to inverse Compton emission. A fit of an Inverse Compton model to the HESS spectral energy distribution gives a total energy in non-thermal electrons of ~ $2 \times 10^{45}$ erg between 5 TeV and 100 TeV, assuming a distance of 290 parsec to the pulsar. The best fit electron power law index is 2.0, with a spectral break at 67 TeV.


Aharonian, F., Akhperjanian, A., Bazer-Bachi, A., Beilicke, M., Benbow, W., Berge, D., …Ward, M. (2006). First detection of a VHE gamma-ray spectral maximum from a cosmicsource: HESS discovery of the Vela X nebula. Astronomy & Astrophysics, 448(2), L43-L47.

Journal Article Type Article
Publication Date 2006-03
Journal Astronomy and astrophysics.
Print ISSN 0004-6361
Electronic ISSN 1432-0746
Publisher EDP Sciences
Peer Reviewed Peer Reviewed
Volume 448
Issue 2
Pages L43-L47
Keywords ISM : plerions, Gamma rays : observationsSYNCHROTRON NEBULA; SUPERNOVA REMNANT; PULSAR; RX-J0852.0-4622;EMISSION; PLERIONS; TEV; JET
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