The hardest X-ray source in the ASCA large sky survey: Discovery of a new type 2 seyfert

Masaaki Sakano; Katsuji Koyama; Takeshi Tsuru; Hisamitsu Awaki; Yoshihiro Ueda; Tadayuki Takahashi; Masayuki Akiyama; Kouji Ohta; Toru Yamada

doi:10.1086/306158

The hardest X-ray source in the ASCA large sky survey: Discovery of a new type 2 seyfert

Masaaki Sakano, Katsuji Koyama, Takeshi Tsuru, Hisamitsu Awaki, Yoshihiro Ueda, Tadayuki Takahashi, Masayuki Akiyama, Kouji Ohta, Toru Yamada

SCI - Astronomy

Research output: Contribution to journal › Article

9 Citations (Scopus)

Abstract

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 N_H = 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.

Original language	English
Pages (from-to)	129-133
Number of pages	5
Journal	Astrophysical Journal
Volume	505
Issue number	1 PART I
DOIs	https://doi.org/10.1086/306158
Publication status	Published - 1998

Keywords

Diffuse radiation
Galaxies: active
Galaxies: seyfert
X-rays: galaxies

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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Sakano, M., Koyama, K., Tsuru, T., Awaki, H., Ueda, Y., Takahashi, T., Akiyama, M., Ohta, K., & Yamada, T. (1998). The hardest X-ray source in the ASCA large sky survey: Discovery of a new type 2 seyfert. Astrophysical Journal, 505(1 PART I), 129-133. https://doi.org/10.1086/306158

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abstract = "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.",

keywords = "Diffuse radiation, Galaxies: active, Galaxies: seyfert, X-rays: galaxies",

author = "Masaaki Sakano and Katsuji Koyama and Takeshi Tsuru and Hisamitsu Awaki and Yoshihiro Ueda and Tadayuki Takahashi and Masayuki Akiyama and Kouji Ohta and Toru Yamada",

year = "1998",

doi = "10.1086/306158",

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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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