The hardest X-ray source discovered in the ASCA Large Sky Survey: Implications to the cosmic X-ray background

M. Sakano, K. Koyama, T. Tsuru, H. Awaki, Y. Ueda, T. Takahashi, M. Akiyama, K. Ohta, Toru Yamada

Research output: Contribution to journalArticle

Abstract

We present results of ASCA deep exposure observations and optical identifications of the hardest X-ray source discovered in the ASCA Large Sky Survey project, designated as AX J131501+3141. AX J131501+3141 exhibits a large X-ray absorption of N H = (6 +4 -2 ) × 10 26 H m -2 . The observed X-ray flux was time variable by a factor of 30% in 0.5 year: F x (2-10 keV) =(4.8-6.2) ×10 -16 J m -2 s -1 . From optical photometric and spectroscopic observations, we found one galaxy with R = 15.6 mag in the X-ray error circle, whose emission line ratios are similar to those found in type 2 Seyfert galaxies. Its redshift is determined to be 0.07, hence the absorption-corrected X-ray luminosity is L x ∼ 2 × 10 36 J s -1 (2-10 keV). Accordingly, we conclude that AX J131501+3141 is a type 2 Seyfert galaxy. Discovery of such a low flux and highly absorbed X-ray source could have a significant impact on the origin of the cosmic X-ray background.

Original languageEnglish
Pages (from-to)849-852
Number of pages4
JournalAdvances in Space Research
Volume25
Issue number3-4
DOIs
Publication statusPublished - 2000 Jan 1

ASJC Scopus subject areas

  • Aerospace Engineering
  • Astronomy and Astrophysics
  • Geophysics
  • Atmospheric Science
  • Space and Planetary Science
  • Earth and Planetary Sciences(all)

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