ASCA observation of ultra-luminous X-ray sources in the nearby spiral galaxy NGC 2403

Jun'ichi Kotoku, Tsunefumi Mizuno, Aya Kubota, Kazuo Makishima

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The spiral galaxy NGC 2403 was observed with ASCA, and three previously known X-ray sources (sources 3, 4, and 5) were detected. Among them, the observed 0.5-10 keV flux of source 3 is 1.4 × 10-12 erg s-1 cm-2, implying a bolometric luminosity of 3.0 × 1039 erg s-1. Its spectrum can be explained by emission from an optically thick accretion disk with an inner-disk temperature of 1.1 keV. The spectrum and the high luminosity suggest that source 3 is a mass-accreting black hole binary. The observed properties of source 3 can be interpreted in terms of a black hole of mass ∼ 15 M⊙, accreting at near the Eddington rate.

Original languageEnglish
Pages (from-to)1081-1085
Number of pages5
JournalPublications of the Astronomical Society of Japan
Issue number6
Publication statusPublished - 2000 Jan 1



  • Black hole physics
  • Galaxies: individual (NGC 2403)
  • Galaxies: spiral
  • X-rays: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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