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Discovery of the Hard Spectrum VHE γ-Ray Source HESS J1641-463

Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A.G.; Angüner, E.O.; Backes, M.; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker Tjus, J.; Berge, D.; Bernhard, S.; Bernlöhr, K.; Birsin, E.; Biteau, J.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Bregeon, J.; Brun, F.; Brun, P.; Bryan, M.; Bulik, T.; Carrigan, S.; Casanova, S.; Chadwick, P.M.; Chakraborty, N.; Chalme-Calvet, R.; Chaves, R.C.G.; Chrétien, M.; Colafrancesco, S.; Cologna, G.; Conrad, J.; Couturier, C.; Cui, Y.; Dalton, M.; Davids, I.D.; Degrange, B.; Deil, C.; deWilt, P.; Djannati-Ataï, A.; Domainko, W.; Donath, A.; Drury, L. O'C.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Edwards, T.; Egberts, K.; Eger, P.; Espigat, P.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M.V.; Fernandez, D.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gabici, S.; Gajdus, M.; Gallant, Y.A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J.F.; Gottschall, D.; Grondin, M.-H.; Grudzińska...

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A. Abramowski

F. Aharonian

F. Ait Benkhali

A.G. Akhperjanian

E.O. Angüner

M. Backes

S. Balenderan

A. Balzer

A. Barnacka

Y. Becherini

J. Becker Tjus

D. Berge

S. Bernhard

K. Bernlöhr

E. Birsin

J. Biteau

M. Böttcher

C. Boisson

J. Bolmont

P. Bordas

J. Bregeon

F. Brun

P. Brun

M. Bryan

T. Bulik

S. Carrigan

S. Casanova

N. Chakraborty

R. Chalme-Calvet

R.C.G. Chaves

M. Chrétien

S. Colafrancesco

G. Cologna

J. Conrad

C. Couturier

Y. Cui

M. Dalton

I.D. Davids

B. Degrange

C. Deil

P. deWilt

A. Djannati-Ataï

W. Domainko

A. Donath

L. O'C. Drury

G. Dubus

K. Dutson

J. Dyks

M. Dyrda

T. Edwards

K. Egberts

P. Eger

P. Espigat

C. Farnier

S. Fegan

F. Feinstein

M.V. Fernandes

D. Fernandez

A. Fiasson

G. Fontaine

A. Förster

M. Füßling

S. Gabici

M. Gajdus

Y.A. Gallant

T. Garrigoux

G. Giavitto

B. Giebels

J.F. Glicenstein

D. Gottschall

M.-H. Grondin

M. Grudzińska

D. Hadasch

S. Häffner

J. Hahn

J. Harris

G. Heinzelmann

G. Henri

G. Hermann

O. Hervet

A. Hillert

J.A. Hinton

W. Hofmann

P. Hofverberg

M. Holler

D. Horns

A. Ivascenko

A. Jacholkowska

C. Jahn

M. Jamrozy

M. Janiak

F. Jankowsky

I. Jung-Richardt

M.A. Kastendieck

K. Katarzyński

U. Katz

S. Kaufmann

B. Khélifi

M. Kieffer

S. Klepser

D. Klochkov

W. Kluźniak

D. Kolitzus

Nu Komin

K. Kosack

S. Krakau

F. Krayzel

P.P. Krüger

H. Laffon

G. Lamanna

J. Lau

J. Lefaucheur

V. Lefranc

A. Lemière

M. Lemoine-Goumard

J.-P. Lenain

T. Lohse

A. Lopatin

C.-C. Lu

V. Marandon

A. Marcowith

R. Marx

G. Maurin

N. Maxted

M. Mayer

T.J.L. McComb

J. Méhault

P.J. Meintjes

U. Menzler

M. Meyer

A.M.W. Mitchell

R. Moderski

M. Mohamed

K. Morå

E. Moulin

T. Murach

M. de Naurois

J. Niemiec

S.J. Nolan

L. Oakes

H. Odaka

S. Ohm

B. Opitz

M. Ostrowski

I. Oya

M. Panter

R.D. Parsons

M. Paz Arribas

N.W. Pekeur

G. Pelletier

P.-O. Petrucci

B. Peyaud

S. Pita

H. Poon

G. Pühlhofer

M. Punch

A. Quirrenbach

S. Raab

I. Reichardt

A. Reimer

O. Reimer

M. Renaud

R. de los Reyes

F. Rieger

C. Romoli

S. Rosier-Lees

G. Rowell

B. Rudak

C.B. Rulten

V. Sahakian

D. Salek

D.A. Sanchez

A. Santangelo

R. Schlickeiser

F. Schüssler

A. Schulz

U. Schwanke

S. Schwarzburg

S. Schwemmer

H. Sol

F. Spanier

G. Spengler

F. Spies

Ł Stawarz

R. Steenkamp

C. Stegmann

F. Stinzing

K. Stycz

I. Sushch

J.-P. Tavernet

T. Tavernier

A.M. Taylor

R. Terrier

M. Tluczykont

C. Trichard

K. Valerius

C. van Eldik

B. van Soelen

G. Vasileiadis

J. Veh

C. Venter

A. Viana

P. Vincent

J. Vink

H.J. Völk

F. Volpe

M. Vorster

T. Vuillaume

S.J. Wagner

P. Wagner

R.M. Wagner

M. Ward

M. Weidinger

Q. Weitzel

R. White

A. Wierzcholska

P. Willmann

A. Wörnlein

D. Wouters

R. Yang

V. Zabalza

D. Zaborov

M. Zacharias

A.A. Zdziarski

A. Zech

H.-S. Zechlin

Y. Fukui

H. Sano

T. Fukuda

S. Yoshiike

H.E.S.S. Collaboration


This Letter reports the discovery of a remarkably hard spectrum source, HESS J1641−463, by the High Energy Stereoscopic System (H.E.S.S.) in the very high energy (VHE) domain. HESS J1641−463 remained unnoticed by the usual analysis techniques due to confusion with the bright nearby source HESS J1640−465. It emerged at a significance level of 8.5 standard deviations after restricting the analysis to events with energies above 4 TeV. It shows a moderate flux level of phgr(E>1 TeV) = (3.64 ± 0.44stat ± 0.73sys) × 10−13 cm−2 s−1, corresponding to 1.8% of the Crab Nebula flux above the same energy, and a hard spectrum with a photon index of Γ = 2.07 ± 0.11stat ± 0.20sys. It is a point-like source, although an extension up to a Gaussian width of σ = 3 arcmin cannot be discounted due to uncertainties in the H.E.S.S. point-spread function. The VHE γ-ray flux of HESS J1641−463 is found to be constant over the observed period when checking time binnings from the year-by-year to the 28 minute exposure timescales. HESS J1641−463 is positionally coincident with the radio supernova remnant SNR G338.5+0.1. No X-ray candidate stands out as a clear association; however, Chandra and XMM-Newton data reveal some potential weak counterparts. Various VHE γ-ray production scenarios are discussed. If the emission from HESS J1641−463 is produced by cosmic ray protons colliding with the ambient gas, then their spectrum must extend close to 1 PeV. This object may represent a source population contributing significantly to the galactic cosmic ray flux around the knee.


Abramowski, A., Aharonian, F., Ait Benkhali, F., Akhperjanian, A., Angüner, E., Backes, M., …Collaboration, H. (2014). Discovery of the Hard Spectrum VHE γ-Ray Source HESS J1641-463. Astrophysical Journal Letters, 794(1),

Journal Article Type Article
Acceptance Date Sep 6, 2014
Publication Date Oct 10, 2014
Deposit Date Apr 15, 2015
Publicly Available Date Apr 21, 2015
Journal Astrophysical Journal Letters
Print ISSN 2041-8205
Electronic ISSN 2041-8213
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 794
Issue 1
Public URL
Related Public URLs


Published Journal Article (624 Kb)

Copyright Statement
© 2014. The American Astronomical Society. All rights reserved. Printed in the U.S.A.

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