TY - JOUR
T1 - The hardest X-ray source discovered in the ASCA Large Sky Survey
T2 - Implications to the cosmic X-ray background
AU - Sakano, M.
AU - Koyama, K.
AU - Tsuru, T.
AU - Awaki, H.
AU - Ueda, Y.
AU - Takahashi, T.
AU - Akiyama, M.
AU - Ohta, K.
AU - Yamada, T.
N1 - Funding Information:
We would like to thank the ASCA team and the MOSAIC CCD camera team of the KISO observatory. MA and MS acknowledge support from an Research Fellowships of the JSPS for Young Scientists. The optical follow-up program was supported by a grand-in-aid from the Ministry of Education, Science, Sports and Culture of Japan and from Sumitomo Foundation.
PY - 2000
Y1 - 2000
N2 - 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.
AB - 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.
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U2 - 10.1016/S0273-1177(99)00853-4
DO - 10.1016/S0273-1177(99)00853-4
M3 - Article
AN - SCOPUS:0040951663
SN - 0273-1177
VL - 25
SP - 849
EP - 852
JO - Advances in Space Research
JF - Advances in Space Research
IS - 3-4
ER -