Detection of excess hard X-ray emission from the optical jet galaxy NGC 1097

Naoko Iyomoto, Kazuo Makishima, Yasushi Fukazawa, Makoto Tashiro, Yoshitaka Ishisaki, Naomasa Nakai, Yoshiaki Taniguchi

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Abstract

Using the ASCA observatory, X-ray observations were made of the spiral galaxy NGC 1097, which exhibits four optical jets. Hard X-ray emission from a point-like source at the nucleus was detected at a 2-10 keV luminosity of 1 × 1041 erg s-1 for an assumed distance of 24 Mpc. The 2-10 keV spectrum was well fitted with a power-law of photon index ∼ 1.8. Although no X-ray variability was detected during a ∼ 40 ks pointing, the observed X-ray to optical luminosity ratio of NGC 1097 is too high for the X-ray emission to be explained by an assembly of discrete X-ray sources. From our results and optical activity, the existence of a low-luminosity active galactic nucleus (LLAGN) is strongly suggested. In the soft X-ray band (0.5-2 keV) a thin thermal emission with a temperature kT ∼ 0.6 keV was also detected, which is understood to be emission from hot gas associated with starburst activity.

Original languageEnglish
Pages (from-to)231-236
Number of pages6
JournalPublications of the Astronomical Society of Japan
Volume48
Issue number2
DOIs
Publication statusPublished - Jan 1 1996
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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