FR-I radio galaxies NGC 315 and NGC 4261 were observed in X-rays with ASCA for ∼ 37 ks and ∼ 54 ks, respectively. Hard X-ray emission from a point-like source at the nucleus was detected at a 2-10 keV luminosity of 3.1 × 1041 and 9.2 × 1040 erg s-1, respectively, for assumed distances of 66 Mpc and 29 Mpc (for H0 = 75 km s-1 Mpc-1). The 2-10 keV spectra of NGC 315 and NGC 4261 were both fitted successfully with a power-law of photon index 2.02 ± 0.34 and 1.45 ± 0.11, respectively, plus emission from hot gas. The NGC 315 nucleus is mildly absorbed. No X-ray variability was detected from either object, with typical upper limits of several tens per cent. These results imply the presence of a low-luminosity active galactic nucleus in both galaxies, and reconfirm the previous recognition that the FR-I nuclei are significantly less X-ray luminous than the FR-II ones.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science