Accreting neutron stars and black holes: a decade of discoveries

Psaltis, Dimitrios

doi:10.1017/cbo9780511536281.002

Cited by 30 publications

(20 citation statements)

References 119 publications

(169 reference statements)

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“…Matter is transferred from the companion star to the compact object and releases its gravitational potential energy mostly as high-energy radiation, making these systems the brightest sources in the X-ray sky [126, 92]. …”

Section: Probing Strong Gravitational Fields With Astrophysical Objectsmentioning

confidence: 99%

Probes and Tests of Strong-Field Gravity with Observations in the Electromagnetic Spectrum

Psaltis

2008

Living Rev. Relativ.

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Neutron stars and black holes are the astrophysical systems with the strongest gravitational fields in the universe. In this article, I review the prospect of using observations of such compact objects to probe some of the most intriguing general relativistic predictions in the strong-field regime: the absence of stable circular orbits near a compact object and the presence of event horizons around black-hole singularities. I discuss the need for a theoretical framework, within which future experiments will provide detailed, quantitative tests of gravity theories. Finally, I summarize the constraints imposed by current observations of neutron stars on potential deviations from general relativity.

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Section: Probing Strong Gravitational Fields With Astrophysical Objectsmentioning

confidence: 99%

Probes and Tests of Strong-Field Gravity with Observations in the Electromagnetic Spectrum

Psaltis

2008

Living Rev. Relativ.

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391

382

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“…In classical supergiant HMXB (SGXB), the persistent X-ray emission is explained by accretion of part of the stellar wind of the supergiant star onto the compact object situated in a close circular orbit (see reviews by White et al 1995;Psaltis 2006). The observed variability was explained in terms of wind instabilities generated by the interaction of the compact object with the strong stellar wind (Blondin et al 1990;Blondin 1994).…”

Section: Introductionmentioning

confidence: 99%

INTEGRAL andXMM-Newton observations of AX J1845.0-0433

Heras¹,

Walter²

2008

A&A

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Aims. AX J1845.0−0433 is a transient high-mass X-ray binary discovered by ASCA. The source displays bright and short flares observed by INTEGRAL. The transient behaviour and bright and short flares are studied to understand both the accretion mechanisms and nature of the source. Methods. Public INTEGRAL data and a pointed XMM-Newton observation are used to study in detail the flaring and quiescent phases. Results. AX J1845.0−0433 is a persistent X-ray binary with a O9.5I supergiant companion, emitting at a low 0.2−100 keV luminosity of ∼1035 erg s −1 with seldom flares and reaching luminosities of 10 36 erg s −1 . The most accurately measured X-ray position is RA (2000) = 18 h 45 m 01.4 s and Dec = −04• 33 57.7 (2 ). Variability factors of 50 are observed on timescales as short as hundreds of seconds. The broad-band spectrum is typical of wind-fed accreting pulsars with an intrinsic absorption of N H = (2.6±0.2)×10 22 cm −2 , a hard continuum of Γ = (0.7−0.9) ± 0.1, and a high-energy cutoff at E cut = 16 +5 −3 keV. An excess at low energies is also observed fitted with a black body with a temperature of kT = 0.18 ± 0.05 keV. Optically-thin and highly-ionised iron (Fe XVIII−XIX) located close to the supergiant star is detected during the quiescence phase. The spectral shape of the X-ray continuum remains unchanged. In contrast to the persistent quiescent emission, the flare characteristics suggest that clumps of mass M ∼ 10 22 g are formed within the stellar wind of the supergiant companion.

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“…In the case of a misalignment between the rotation and the magnetic axis, X-ray pulses are produced [16]. In such a slow rotating X-ray pulsar, the strong stellar magnetic field (≥ 10 12 G) is dynamically dominant.…”

Section: The Young Non-accreting Pulsar Modelmentioning

confidence: 99%

The Enigmatic Compact Object in the Stellar System LS I +61°303: Accreting or Not Accreting?

Massi¹

2007

AIP Conference Proceedings

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A new X-ray survey for accreting objects AIP Conf.Abstract. LS I +61 • 303 is up to now the only X-ray binary stellar system having variable TeV gamma-ray emission and periodic radio-outbursts that have been spatially resolved in ejecta with different position angles at the different epochs. We review here the data and discuss the two alternative models: a precessing microblazar or a young pulsar. THE SYSTEMLS I +61 303 is a high-mass X-ray binary (HMXB) at an estimated distance of 2 kpc [1]. The optical spectrum corresponds to a rapidly rotating B0 Ve star (V= 10.7 mag) that has a high velocity (1000 km s −1 ) low density wind at high latitudes and a dense and slow (100 km s −1 ) disk-like wind around the equator. A compact object travels through this dense equatorial wind, (Fig.1). Its nature is still unknown due to its large mass range, 1.4 < M < 3.8, that implies either a neutron star or a black hole. The main uncertainty for the mass comes from the orbital inclination, for which there is only a crude value of 30 • with an uncertainty of approximately 20 • [2, 3, 4]. One of the most unusual aspects of its radio emission is the fact that it exhibits two periodicities: 26.5 days periodic nonthermal outbursts [5, 6] and a ∼ 4.6 year modulation of both the outburst peak flux density and the orbital phase of the radio outbursts [7]. The 26.5 day periodicity, also detected in UBVRI photometric observations [8], corresponds to the orbital period of the binary system [2]. The second periodicity (the modulation of 4.6 years), has also been observed in the variations of the Hα emission line [9]. This fact implys that the long radio periodicity is related to variations that are present in the equatorial wind of the Be star and that are thought to occur in the form of a periodic outward moving density enhancement (i.e. shell ejection) [10]. During the peak of the ∼ 4.6-year cycle the strong outbursts occur in the orbital phase range Φ=0.5-0.8 [11] which does not include the periastron passages, i.e. Φ=0.23 (see Fig. 1). Two models have been proposed for this special HMXB. One assumes that the compact object is a non-accreting young pulsar whose relativistic wind strongly interacts with the wind of the Be star. The second one instead proposes a microquasar, that is an accreting object with ejection events associated to super-Eddington accretion.729

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Accreting neutron stars and black holes: a decade of discoveries

Cited by 30 publications

References 119 publications

Probes and Tests of Strong-Field Gravity with Observations in the Electromagnetic Spectrum

Probes and Tests of Strong-Field Gravity with Observations in the Electromagnetic Spectrum

INTEGRAL andXMM-Newton observations of AX J1845.0-0433

The Enigmatic Compact Object in the Stellar System LS I +61°303: Accreting or Not Accreting?

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