A dark cloud associated with an unidentified EGRET source

Tomoharu Oka, Nobuyuki Kawai, Tsuguya Naito, Takahiko Horiuchi, Masaaki Namiki, Yoshitaka Saito, Roger W. Romani, Tadashi Kifune

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)


CO J = 1-0 mapping observations of the dark nebula Lynds 227, which is possibly associated with the unidentified EGRET source 2EG J1811-2339, are presented. We detected a large amount of molecular gas along Lynds 227 with a total mass of (1-2) × 104 M surrounding an X-ray synchrotron nebula, which was detected by the ASCA within the error circle of 2EG J1811-2339. Molecular gas along Lynds 227 shows spatial anticorrelation with the X-ray synchrotron nebula, suggesting that the synchrotron nebula is interacting with the Lynds 227 cloud. We propose a γ-ray emission mechanism for 2EG J1811-2339: high-energy electrons are injected from a rotation-powered pulsar and further accelerated in shock waves generated by the interaction with ambient matter. The high-energy electrons move into the molecular cloud at the Lynds 227 and collide with dense interstellar matter to yield high-energy γ-ray photons, mainly through relativistic bremsstrahlung.

Original languageEnglish
Pages (from-to)764-771
Number of pages8
JournalAstrophysical Journal
Issue number2 PART 1
Publication statusPublished - 1999 Dec 1
Externally publishedYes


  • Gamma rays: theory
  • ISM: clouds
  • ISM: individual (Lynds 227)
  • ISM: molecules
  • Pulsars: individual (2EG J1811-2339)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


Dive into the research topics of 'A dark cloud associated with an unidentified EGRET source'. Together they form a unique fingerprint.

Cite this