On the Integrated Spectrum of the X-Ray Binaries and the Origin of Soft X-Ray Emission from the Bulge of M31

Borozdin, K.; Priedhorsky, W. C.

doi:10.1086/312913

Cited by 9 publications

(9 citation statements)

References 18 publications

(25 reference statements)

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“…It also includes a significant contribution from a Raymond-Smith spectrum that most probably comes from hot ISM. Borozdin & Priedhorsky (2000) find a very similar spectrum (with the same ratio of 0.5 between the power law and the thermal component fluxes) when analyzing the ROSAT/PSPC spectrum of the unresolved emission in the central region (less than 8 0 ) of M31. Comparing this spectrum with that of the LMXBs in the same region, they conclude that the thermal spectrum is most probably produced by truly diffuse emission from interstellar gas.…”

Section: The Circumnuclear Emissionmentioning

confidence: 56%

Long‐Term X‐Ray Spectral Variability of the Nucleus of M81

Parola

Fabbiano

Elvis

et al. 2004

ApJ

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We have analyzed the soft X-ray emission from the nuclear source of the nearby spiral galaxy M81, using the available data collected with ROSAT, ASCA, BeppoSAX, and Chandra. The source flux is highly variable (sometimes dramatic: a factor of 4 in 20 days), showing variability at different timescales, from 2 days to 4 yr, and in particular a steady increase of the flux by a factor of k2 over 4 yr, broken by rapid flares. After accounting for the extended component resolved by Chandra, the nuclear soft X-ray spectrum (from ROSAT/PSPC, BeppoSAX/LECS, and Chandra data) cannot be fitted well with a single absorbed power-law model. Acceptable fits are obtained by adding an extra component, either a multicolor blackbody (MCBB) or an absorption feature. In the MCBB case, the inner accretion disk would be far smaller than the Schwartzchild radius for the 3 60 Â 10 6 M nucleus, requiring a strictly edge-on inclination of the disk, even if the nucleus is a rotating Kerr black hole. The temperature is 0.27 keV, larger than expected from the accretion disk of a Schwartzchild black hole but consistent with that expected from a Kerr black hole. In the power law+absorption feature model, we have either high-velocity (0.3c) infalling C v clouds or neutral C i absorption at rest. In both cases the C : O overabundance is a factor of 10.

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Section: The Circumnuclear Emissionmentioning

confidence: 56%

Long‐Term X‐Ray Spectral Variability of the Nucleus of M81

Parola

Fabbiano

Elvis

et al. 2004

ApJ

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“…They interpreted one of these sources (1 from the centre) as a possible central black hole, although it shows an unusual (soft) spectrum. In contrast, using ROSAT PSPC observations, Borozdin & Priedhorsky (2000) found all the resolved X-ray sources in the core of M 31 to be in accordance with LMXB spectra, this after subtracting a soft component (thought to be thermal emission from hot gas) derived from the area around the individual sources.…”

Section: Introductionmentioning

confidence: 84%

The second ROSAT PSPC survey of M 31 and the complete ROSAT PSPC source list

Supper

Hasinger

Lewin

et al. 2001

A&A

123

187

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Abstract. This paper reports the results of the analysis of the second ROSAT PSPC survey of M 31 performed in summer 1992. We compare our results with those of the first survey, already published in Supper et al. (1997). , distributed approximately equally between the bulge and disk. Within the bulge region, the luminosity of a possible diffuse component combined with faint sources below the detection threshold is (2.0 ± 0.5) × 10 38 erg s −1 . An explanation in terms of hot gaseous emission leads to a maximum total gas mass of (1.0 ± 0.3) × 10 6 M .

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“…From the extrapolation of the luminosity distribution, PFJ concluded that the detected population of X-ray sources could account for only ∼15-26% of the unresolved X-ray emission in M 31, suggesting that the remaining emission is truly diffuse or due to a new class of X-ray sources. Spectral analysis of ROSAT data performed by Borozdin & Priedhorsky (2000) and observations with XMM (Shirey et al 2001, hereafter Paper I) and Chandra (Garcia et al 2001) showed that the unresolved X-ray emission in the bulge of M 31 is significantly softer than most of the point sources and can be approximated with an optically-thin thermal plasma model (kT ∼ 0.3 keV) as expected from truly diffuse emission. The intensity of the color is proportional to the logarithm of the number of counts collected (with a maximum of 5000 counts).…”

Section: Introductionmentioning

confidence: 99%

The central region of M 31 observed with $\vec{XMM}$-$\vec{Newton}$

Osborne

Borozdin

Trudolyubov

et al. 2001

A&A

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Abstract. We present the results of a study of the variability of X-ray sources in the central 30 of the nearby Andromeda Galaxy (M 31) based on XMM-Newton Performance Verification observations. Two observations of this field, with a total exposure time of about 50 ks, were performed in June and December of 2000. We found 116 sources brighter than a limiting luminosity of 6×10 35 erg s −1 (0.3-12 keV, d = 760 kpc). For the ∼60 brightest sources, we searched for periodic and non-periodic variability; at least 15% of these sources appear to be variable on a time scale of several months. We discovered a new bright transient source ∼2.9 from the nucleus in the June observation; this source faded significantly and was no longer detected in December. The behaviour of the object is similar to a handful of Galactic LMXB transients, most of which are supposed to harbor black holes. We detected pulsations with a period of ∼865 s from a source with a supersoft spectrum. The flux of this source decreased significantly between the two XMM observations. The detected period is unusually short and points to a rapidly spinning magnetized white dwarf. The high luminosity and transient nature of the source suggest its possible identification with classical or symbiotic nova, some of which were observed earlier as supersoft sources.

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On the Integrated Spectrum of the X-Ray Binaries and the Origin of Soft X-Ray Emission from the Bulge of M31

Cited by 9 publications

References 18 publications

Long‐Term X‐Ray Spectral Variability of the Nucleus of M81

Long‐Term X‐Ray Spectral Variability of the Nucleus of M81

The second ROSAT PSPC survey of M 31 and the complete ROSAT PSPC source list

The central region of M 31 observed with $\vec{XMM}$-$\vec{Newton}$

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