Properties of M33 X-8, the nuclear source in the nearby spiral galaxy

Takano, Masatoshi; Mitsuda, K.; Fukazawa, Y.; Nagase, F.

doi:10.1086/187629

Cited by 39 publications

(53 citation statements)

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“…Today, the most favoured hypothesis is that M33-X8 is an intermediate (or even stellar) mass black hole, likely in a binary system. Recent studies with ASCA and BeppoSAX data (Takano et al 1994;Parmar et al 2001) agree in describing its X-ray energy spectrum with a power-law with a high energy exponential cutoff with ∼ 2 keV e-folding energy, or with a multicolor disk black-body (MCD), both consistent with the spectra of Galactic black-hole candidates and of ultra luminous sources (ULXs, see. e.g., Makishima et al 2000).…”

Section: Introductionmentioning

confidence: 62%

Spectral Variability of the Nucleus of M33 in aChandra/ACIS Observation

Parola

Damiani

Fabbiano

et al. 2003

ApJ

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We have analyzed a 90 ksec long observation of the bright nucleus of M33 made with Chandra /ACIS. We detected low-amplitude (∼ 10%) highly significant variability on timescales of ∼ 5000 sec. We also find associated spectral variability. The two main spectral components (a power-law with Γ ∼ 2 and a multicolor disk -MCD-with kT∼ 0.9 − 1.2 keV) vary in relative flux. The MCD temperature also increases with increasing MCD flux. The pattern of variability is reminiscent of (but not identical to) galactic black hole binaries. A ∼ 15 M ⊙ accreting black hole may explain this source.

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Section: Introductionmentioning

confidence: 62%

Spectral Variability of the Nucleus of M33 in aChandra/ACIS Observation

Parola

Damiani

Fabbiano

et al. 2003

ApJ

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“…Later on, ASCA (Takano et al 1994) observations extended up to 7 keV and strengthened the early results of Trinchieri et al (1988). The best-fit model was composed of a multicolour disc (MCD) plus a power law at high energies, Schulman & Bregman (1995), based on ROSAT observations, conclude that the probability of such an unusual X-ray binary close to the centre of M 33 is very small.…”

Section: To Increasementioning

confidence: 81%

“…On the other hand, Gottwald et al (1987) with EXOSAT, Trinchieri et al (1988) with Einstein, Takano et al (1994) with ASCA, Parmar et al (2001) with BeppoSAX, and La Parola et al (2003) with Chandra found that it was necessary to include an additional absorption component.…”

Section: Spectral Analysismentioning

confidence: 99%

XMM–Newtonobservations of the ultraluminous nuclear X-ray source in M 33

Foschini¹,

Rodríguez²,

Fuchs³

et al. 2004

A&A

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Abstract. We present observations with XMM-Newton of M 33 X-8, the ultraluminous X-ray source (L 0.5−10 keV ≈ 2×10 39 erg/s) closest to the centre of the galaxy. The best-fit model is similar to the typical model of Galactic black holes in very high state. Comparison with previous observations indicates that the source is still in a very high state after about 20 years of observations. No state transition has been observed even during the present set of XMM-Newton observations. We estimate the lower limit of the mass of the black hole >6 M , but with proper parameters taking into account different effects, the best estimate becomes 12 M . Our analysis favours the hypothesis that M 33 X-8 is a stellar mass black hole candidate, in agreement with the findings of other authors. In addition, we propose a different model where the high luminosity of the source is likely to be due to orientation effects of the accretion disc and anisotropies in the Comptonized emission.

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“…A great leap has been achieved with ASCA through the spectroscopy of a dozen ULXs (Takano et al 1994;Okada et al 1998;Colbert & Mushotzky 1999;Mizuno et al 1999;Kotoku et al 2000;Paper I); the spectra of a majority of them have been reproduced by the so-called multicolor disk (MCD) model (Mitsuda et al 1984) that describes emission from an optically thick standard accretion disk around a BH (Shakura & Sunyaev 1973). These results significantly reinforce the BH scenario of ULXs since the MCD model can explain the soft X-ray spectra of Galactic/Magellanic black hole binaries (BHBs) in the "soft (or high) state" (e.g., Makishima et al 1986;Ebisawa et al 1993;Dotani et al 1997;Kubota et al 1998;Feroci et al 1999;Paper I).…”

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confidence: 99%

Discovery of Spectral Transitions from Two Ultraluminous Compact X-Ray Sources in IC 342

Kubota

Mizuno

Makishima

et al. 2001

The Astrophysical Journal

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114

124

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Two ASCA observations were made of two ultraluminous compact X-ray sources (ULXs) in the spiral galaxy IC 342. In the 1993 observation, source 2 showed a 0.5-10 keV luminosity of ergs s (assuming a 39 Ϫ16 # 10 distance of 4.0 Mpc) and a hard power-law spectrum of photon index ∼1.4. As already reported, source 1 was ∼3 times brighter on that occasion and exhibited a soft spectrum represented by a multicolor disk model with an inner-disk temperature of ∼1.8 keV. The second observation, made in 2000 February, revealed that source 1 had made a transition into a hard spectral state, while source 2 made a transition into a soft spectral state. The ULXs are therefore inferred to exhibit two distinct spectral states, and they sometimes make transitions between them. These results significantly reinforce the scenario that describes ULXs as mass-accreting black holes.

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Properties of M33 X-8, the nuclear source in the nearby spiral galaxy

Cited by 39 publications

References 0 publications

Spectral Variability of the Nucleus of M33 in aChandra/ACIS Observation

Spectral Variability of the Nucleus of M33 in aChandra/ACIS Observation

XMM–Newtonobservations of the ultraluminous nuclear X-ray source in M 33

Discovery of Spectral Transitions from Two Ultraluminous Compact X-Ray Sources in IC 342

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