Detection of Strong Fe-K Lines from the Spiral Galaxies NGC 1365 and NGC 1386

Abstract

Two spiral galaxies, NGC 1365 and NGC 1386, were observed in X-rays with ASCA. Both galaxies exhibit hard X-ray emission from point-like sources at the nuclei. The continuous spectrum of NGC 1365 was fitted well with a power-law of photon index 0.8−0.2+0.7, whose 2–10 keV luminosity is (3.8±0.5) × 1040 erg s−1 for an assumed distance of 18.4 Mpc. NGC 1386 has an absorbed [NH = (2.8+2.7−2.6) × 1023) cm−2] power-law continuum, whose 2–10 keV luminosity (at 18.4 Mpc) is (2.6−2.0+3.2) × 1040 erg s−1 after removing the absorption. A broad (σ = 0.20+0.16−0.08 keV) Fe-K emission line centered at 6.61−0.06+0.08 keV was detected from the NGC 1365 nucleus at an equivalent width of 2.1+2.1−0.3 keV. The Fe-K line was also detected from NGC 1386 at an equivalent width of 1.6−1.2+7.9 keV and at a similar energy as the NGC 1365 line. These spectral features indicate that both galaxies host low-luminosity active galactic nuclei (LLAGNs).