TY - JOUR
T1 - The hardest X-ray source in the ASCA large sky survey
T2 - Discovery of a new type 2 seyfert
AU - Sakano, Masaaki
AU - Koyama, Katsuji
AU - Tsuru, Takeshi
AU - Awaki, Hisamitsu
AU - Ueda, Yoshihiro
AU - Takahashi, Tadayuki
AU - Akiyama, Masayuki
AU - Ohta, Kouji
AU - Yamada, Toru
PY - 1998
Y1 - 1998
N2 - We present results of the ASCA deep-exposure observations of the hardest X-ray source discovered in the ASCA Large Sky Survey (LSS) project, designated as AX J131501 + 3141. We extract its accurate X-ray spectrum, taking into account the contamination from a nearby soft source (AX J131502 + 3142) separated from it by only 1′. AX J131501 + 3141 exhibits a large absorption of NH = 6-2+4 × 1022 H cm-2, with a photon index Γ = 1.51-0.6+0.7. The 2-10 keV flux was about 5 × 10-13 ergs cm-2 s-1, and was time variable by a factor of 30% in 0.5 yr. From the highly absorbed X-ray spectrum and the time variability, as well as the results of the optical follow-up observations, 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 our understanding of the origin of the cosmic X-ray background.
AB - We present results of the ASCA deep-exposure observations of the hardest X-ray source discovered in the ASCA Large Sky Survey (LSS) project, designated as AX J131501 + 3141. We extract its accurate X-ray spectrum, taking into account the contamination from a nearby soft source (AX J131502 + 3142) separated from it by only 1′. AX J131501 + 3141 exhibits a large absorption of NH = 6-2+4 × 1022 H cm-2, with a photon index Γ = 1.51-0.6+0.7. The 2-10 keV flux was about 5 × 10-13 ergs cm-2 s-1, and was time variable by a factor of 30% in 0.5 yr. From the highly absorbed X-ray spectrum and the time variability, as well as the results of the optical follow-up observations, 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 our understanding of the origin of the cosmic X-ray background.
KW - Diffuse radiation
KW - Galaxies: active
KW - Galaxies: seyfert
KW - X-rays: galaxies
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U2 - 10.1086/306158
DO - 10.1086/306158
M3 - Article
AN - SCOPUS:22444453373
VL - 505
SP - 129
EP - 133
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 1 PART I
ER -