ASCA observations of two ultraluminous IRAS galaxies: IRAS 15307+3252 and IRAS 20460+1925

Yasushi Ogasaka; Hajime Inoue; William N. Brandt; Andrew C. Fabian; Tsuneo Kii; Takao Nakagawa; Ryuichi Fujimoto; Chiko Otani

doi:10.1093/pasj/49.2.179

ASCA observations of two ultraluminous IRAS galaxies: IRAS 15307+3252 and IRAS 20460+1925

Yasushi Ogasaka, Hajime Inoue, William N. Brandt, Andrew C. Fabian, Tsuneo Kii, Takao Nakagawa, Ryuichi Fujimoto, Chiko Otani

Research output: Contribution to journal › Article › peer-review

33 Scopus citations

Abstract

We report on ASCA observations of two ultraluminous far-infrared galaxies, IRAS 15307+3252 and IRAS 20460+1925. An X-ray flux of 1.53 × 10^-12 erg cm^-2 s^-1 in the 2-10 keV band was detected from IRAS 20460+1925. The continuous spectrum is well represented by a power law with a photon index of 1.99^+0.18_-0.15 and excess photoelectric absorption by a column of (2.6^+0.29_-0.32) × 10²² cm^-2 in the rest frame. The spectrum also shows an iron K emission line with an equivalent width of 260⁺¹⁴⁵_-137 eV and a centroid energy of 6.36±0.08 keV in the rest frame. These spectral properties are consistent with those of Seyfert-2 galaxies, although the intrinsic 2-10 keV X-ray luminosity (corrected for absorption) of 1.20 × 10⁴⁴ erg s^-1 is high and close to that of quasars. No X-rays were detected from IRAS 15307+3252, and the upper limit to the X-ray flux is 7.2 × 10^-14 erg cm^-2 s^-1 in the 2-10 keV band. However, the upper limit on the ratio of the X-ray flux to the far-infrared flux is not inconsistent with a source containing a highly obscured quasar.

Original language	English (US)
Pages (from-to)	179-185
Number of pages	7
Journal	Publications of the Astronomical Society of Japan
Volume	49
Issue number	2
DOIs	https://doi.org/10.1093/pasj/49.2.179
State	Published - 1997

All Science Journal Classification (ASJC) codes

Astronomy and Astrophysics
Space and Planetary Science

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@article{806e6d704db1412390e39b7e34738685,

title = "ASCA observations of two ultraluminous IRAS galaxies: IRAS 15307+3252 and IRAS 20460+1925",

abstract = "We report on ASCA observations of two ultraluminous far-infrared galaxies, IRAS 15307+3252 and IRAS 20460+1925. An X-ray flux of 1.53 × 10-12 erg cm-2 s-1 in the 2-10 keV band was detected from IRAS 20460+1925. The continuous spectrum is well represented by a power law with a photon index of 1.99+0.18-0.15 and excess photoelectric absorption by a column of (2.6+0.29-0.32) × 1022 cm-2 in the rest frame. The spectrum also shows an iron K emission line with an equivalent width of 260+145-137 eV and a centroid energy of 6.36±0.08 keV in the rest frame. These spectral properties are consistent with those of Seyfert-2 galaxies, although the intrinsic 2-10 keV X-ray luminosity (corrected for absorption) of 1.20 × 1044 erg s-1 is high and close to that of quasars. No X-rays were detected from IRAS 15307+3252, and the upper limit to the X-ray flux is 7.2 × 10-14 erg cm-2 s-1 in the 2-10 keV band. However, the upper limit on the ratio of the X-ray flux to the far-infrared flux is not inconsistent with a source containing a highly obscured quasar.",

author = "Yasushi Ogasaka and Hajime Inoue and Brandt, {William N.} and Fabian, {Andrew C.} and Tsuneo Kii and Takao Nakagawa and Ryuichi Fujimoto and Chiko Otani",

year = "1997",

doi = "10.1093/pasj/49.2.179",

language = "English (US)",

volume = "49",

pages = "179--185",

journal = "Publication of the Astronomical Society of Japan",

issn = "0004-6264",

publisher = "Astronomical Society of Japan",

number = "2",

}

ASCA observations of two ultraluminous IRAS galaxies : IRAS 15307+3252 and IRAS 20460+1925. / Ogasaka, Yasushi; Inoue, Hajime; Brandt, William N.; Fabian, Andrew C.; Kii, Tsuneo; Nakagawa, Takao; Fujimoto, Ryuichi; Otani, Chiko.

In: Publications of the Astronomical Society of Japan, Vol. 49, No. 2, 1997, p. 179-185.

Research output: Contribution to journal › Article › peer-review

TY - JOUR

T1 - ASCA observations of two ultraluminous IRAS galaxies

T2 - IRAS 15307+3252 and IRAS 20460+1925

AU - Ogasaka, Yasushi

AU - Inoue, Hajime

AU - Brandt, William N.

AU - Fabian, Andrew C.

AU - Kii, Tsuneo

AU - Nakagawa, Takao

AU - Fujimoto, Ryuichi

AU - Otani, Chiko

PY - 1997

Y1 - 1997

N2 - We report on ASCA observations of two ultraluminous far-infrared galaxies, IRAS 15307+3252 and IRAS 20460+1925. An X-ray flux of 1.53 × 10-12 erg cm-2 s-1 in the 2-10 keV band was detected from IRAS 20460+1925. The continuous spectrum is well represented by a power law with a photon index of 1.99+0.18-0.15 and excess photoelectric absorption by a column of (2.6+0.29-0.32) × 1022 cm-2 in the rest frame. The spectrum also shows an iron K emission line with an equivalent width of 260+145-137 eV and a centroid energy of 6.36±0.08 keV in the rest frame. These spectral properties are consistent with those of Seyfert-2 galaxies, although the intrinsic 2-10 keV X-ray luminosity (corrected for absorption) of 1.20 × 1044 erg s-1 is high and close to that of quasars. No X-rays were detected from IRAS 15307+3252, and the upper limit to the X-ray flux is 7.2 × 10-14 erg cm-2 s-1 in the 2-10 keV band. However, the upper limit on the ratio of the X-ray flux to the far-infrared flux is not inconsistent with a source containing a highly obscured quasar.

AB - We report on ASCA observations of two ultraluminous far-infrared galaxies, IRAS 15307+3252 and IRAS 20460+1925. An X-ray flux of 1.53 × 10-12 erg cm-2 s-1 in the 2-10 keV band was detected from IRAS 20460+1925. The continuous spectrum is well represented by a power law with a photon index of 1.99+0.18-0.15 and excess photoelectric absorption by a column of (2.6+0.29-0.32) × 1022 cm-2 in the rest frame. The spectrum also shows an iron K emission line with an equivalent width of 260+145-137 eV and a centroid energy of 6.36±0.08 keV in the rest frame. These spectral properties are consistent with those of Seyfert-2 galaxies, although the intrinsic 2-10 keV X-ray luminosity (corrected for absorption) of 1.20 × 1044 erg s-1 is high and close to that of quasars. No X-rays were detected from IRAS 15307+3252, and the upper limit to the X-ray flux is 7.2 × 10-14 erg cm-2 s-1 in the 2-10 keV band. However, the upper limit on the ratio of the X-ray flux to the far-infrared flux is not inconsistent with a source containing a highly obscured quasar.

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