Spectral variability of ultraluminous compact X-ray sources in nearby spiral galaxies

T. Mizuno, Aya Kubota, K. Makishima

Research output: Contribution to journalArticle

59 Citations (Scopus)

Abstract

Using the X-ray data taken with ASCA, a detailed analysis was made of intensity and spectral variations of three ultraluminous extragalactic compact X-ray sources (ULXs): IC 342 source 1, M81 X-6, and NGC 1313 source B, all exhibiting X-ray luminosity in the range from 2 × 1039 to 1.5 × 1040 ergs s-1. As already reported, IC 342 source 1 showed short-term X-ray intensity variability by a factor of 2.0 on a typical timescale of 10 ks. M81 X-6 varied by a factor of 1.6 across seven observations spanning 3 yr, while NGC 1313 source B varied by a factor of 2.5 between two observations conducted in 1993 July and 1995 November. The ASCA spectra of these sources acquired on these occasions were all described successfully as optically thick emission from standard accretion disks around black holes. This confirms previous ASCA works that explained ULXs as mass-accreting massive black hole binaries. In all three sources, the disk color temperature was uncomfortably high at Tin = 1.0-2.0 keV and was found to vary in proportion to the square root of the source flux. The apparent accretion disk radius is hence inferred to change as inversely proportional to Tin. This suggests a significant effect of advection in the accretion disk. However, even taking this effect fully into account, the too high values of Tin of ULXs cannot be explained. Further invoking the rapid black hole rotation may give a solution to this issue.

Original languageEnglish
Pages (from-to)1282-1289
Number of pages8
JournalAstrophysical Journal
Volume554
Issue number2 PART 1
DOIs
Publication statusPublished - 2001 Jun 20
Externally publishedYes

Fingerprint

spiral galaxies
tin
accretion
x rays
accretion disks
erg
advection
timescale
proportion
temperature
luminosity
color
radii
effect

Keywords

  • Accretion, accretion disks
  • Black hole physics
  • X-rays: galaxies

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Spectral variability of ultraluminous compact X-ray sources in nearby spiral galaxies. / Mizuno, T.; Kubota, Aya; Makishima, K.

In: Astrophysical Journal, Vol. 554, No. 2 PART 1, 20.06.2001, p. 1282-1289.

Research output: Contribution to journalArticle

Mizuno, T. ; Kubota, Aya ; Makishima, K. / Spectral variability of ultraluminous compact X-ray sources in nearby spiral galaxies. In: Astrophysical Journal. 2001 ; Vol. 554, No. 2 PART 1. pp. 1282-1289.
@article{c4be5094a36c4b84a390777e54b96e28,
title = "Spectral variability of ultraluminous compact X-ray sources in nearby spiral galaxies",
abstract = "Using the X-ray data taken with ASCA, a detailed analysis was made of intensity and spectral variations of three ultraluminous extragalactic compact X-ray sources (ULXs): IC 342 source 1, M81 X-6, and NGC 1313 source B, all exhibiting X-ray luminosity in the range from 2 × 1039 to 1.5 × 1040 ergs s-1. As already reported, IC 342 source 1 showed short-term X-ray intensity variability by a factor of 2.0 on a typical timescale of 10 ks. M81 X-6 varied by a factor of 1.6 across seven observations spanning 3 yr, while NGC 1313 source B varied by a factor of 2.5 between two observations conducted in 1993 July and 1995 November. The ASCA spectra of these sources acquired on these occasions were all described successfully as optically thick emission from standard accretion disks around black holes. This confirms previous ASCA works that explained ULXs as mass-accreting massive black hole binaries. In all three sources, the disk color temperature was uncomfortably high at Tin = 1.0-2.0 keV and was found to vary in proportion to the square root of the source flux. The apparent accretion disk radius is hence inferred to change as inversely proportional to Tin. This suggests a significant effect of advection in the accretion disk. However, even taking this effect fully into account, the too high values of Tin of ULXs cannot be explained. Further invoking the rapid black hole rotation may give a solution to this issue.",
keywords = "Accretion, accretion disks, Black hole physics, X-rays: galaxies",
author = "T. Mizuno and Aya Kubota and K. Makishima",
year = "2001",
month = "6",
day = "20",
doi = "10.1086/321418",
language = "English",
volume = "554",
pages = "1282--1289",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "2 PART 1",

}

TY - JOUR

T1 - Spectral variability of ultraluminous compact X-ray sources in nearby spiral galaxies

AU - Mizuno, T.

AU - Kubota, Aya

AU - Makishima, K.

PY - 2001/6/20

Y1 - 2001/6/20

N2 - Using the X-ray data taken with ASCA, a detailed analysis was made of intensity and spectral variations of three ultraluminous extragalactic compact X-ray sources (ULXs): IC 342 source 1, M81 X-6, and NGC 1313 source B, all exhibiting X-ray luminosity in the range from 2 × 1039 to 1.5 × 1040 ergs s-1. As already reported, IC 342 source 1 showed short-term X-ray intensity variability by a factor of 2.0 on a typical timescale of 10 ks. M81 X-6 varied by a factor of 1.6 across seven observations spanning 3 yr, while NGC 1313 source B varied by a factor of 2.5 between two observations conducted in 1993 July and 1995 November. The ASCA spectra of these sources acquired on these occasions were all described successfully as optically thick emission from standard accretion disks around black holes. This confirms previous ASCA works that explained ULXs as mass-accreting massive black hole binaries. In all three sources, the disk color temperature was uncomfortably high at Tin = 1.0-2.0 keV and was found to vary in proportion to the square root of the source flux. The apparent accretion disk radius is hence inferred to change as inversely proportional to Tin. This suggests a significant effect of advection in the accretion disk. However, even taking this effect fully into account, the too high values of Tin of ULXs cannot be explained. Further invoking the rapid black hole rotation may give a solution to this issue.

AB - Using the X-ray data taken with ASCA, a detailed analysis was made of intensity and spectral variations of three ultraluminous extragalactic compact X-ray sources (ULXs): IC 342 source 1, M81 X-6, and NGC 1313 source B, all exhibiting X-ray luminosity in the range from 2 × 1039 to 1.5 × 1040 ergs s-1. As already reported, IC 342 source 1 showed short-term X-ray intensity variability by a factor of 2.0 on a typical timescale of 10 ks. M81 X-6 varied by a factor of 1.6 across seven observations spanning 3 yr, while NGC 1313 source B varied by a factor of 2.5 between two observations conducted in 1993 July and 1995 November. The ASCA spectra of these sources acquired on these occasions were all described successfully as optically thick emission from standard accretion disks around black holes. This confirms previous ASCA works that explained ULXs as mass-accreting massive black hole binaries. In all three sources, the disk color temperature was uncomfortably high at Tin = 1.0-2.0 keV and was found to vary in proportion to the square root of the source flux. The apparent accretion disk radius is hence inferred to change as inversely proportional to Tin. This suggests a significant effect of advection in the accretion disk. However, even taking this effect fully into account, the too high values of Tin of ULXs cannot be explained. Further invoking the rapid black hole rotation may give a solution to this issue.

KW - Accretion, accretion disks

KW - Black hole physics

KW - X-rays: galaxies

UR - http://www.scopus.com/inward/record.url?scp=0035919371&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0035919371&partnerID=8YFLogxK

U2 - 10.1086/321418

DO - 10.1086/321418

M3 - Article

VL - 554

SP - 1282

EP - 1289

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 2 PART 1

ER -