Low-flux hard state of IE 1740.7-2942

Churazov, E.; Gilfanov, M.; Sunyaev, R.; Pavlinsky, M.; Гребенев, С. А.; Dyachkov, A.; Kovtunenko, V. M.; Kremnev, R. S.; Niel, M.; Mandrou, P.; Védrenne, G.; Roques, J. P.; Cordier, B.; Goldwurm, A.; Lebrun, F.; Paul, J.

doi:10.1086/172557

Cited by 46 publications

(28 citation statements)

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“…The considered effect of e + e − pair creation by the Coulomb barrier may be an additional observational signature of strange stars with nearly bare quark surfaces. In connection with this, it is interesting to note that the emission feature at ∼ 0.5 MeV was observed [19] in the spectrum of 1E 1740.7-2942 which answers the criteria formulated in Ref. [9] and may be, in fact, a strange star, not a black hole as it is usually assumed.…”

supporting

confidence: 76%

Bare Quark Matter Surfaces of Strange Stars ande+e−Emission

1998

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We show that the Coulomb barrier at the quark surface of a hot strange star may be a powerful source of e 1 e 2 pairs which are created in an extremely strong electric field of the barrier and flow away from the star. The luminosity in the outflowing pair plasma depends on the surface temperature T S and may be very high, up to ϳ3 3 10 51 ergs s 21 at T S ϳ 10 11 K. The effect of pair creation by the Coulomb barrier may be a good observational signature of strange stars which can give an answer to the question of whether a compact object is a neutron or strange star. [S0031-9007 (97)05046-1] PACS numbers: 97.60. -s, 12.38.MhWith the discovery of pulsars and their identification with the neutron stars, many people thought that neutron star matter is the ground state of matter at high density. Later, this belief was challenged by Witten [1]. He proposed that strange matter made of quarks is the ground state at ultrahigh density. If Witten's hypothesis is true, then neutron stars with a sufficiently high central density may transform themselves into strange stars [2]. In this case, at least some part of the compact objects known to astronomers as pulsars, powerful accreting x-ray sources, x-ray bursters, soft g-ray repeaters, etc. might be strange stars, not neutron stars as is usually assumed [2,3]. In principle, the question of whether compact objects are neutron or strange stars can be answered by comparing the core density of a neutron star to the strange matter transition density. Unfortunately, all the nuclear-physics calculations to date do not yield a definitive answer. As to available data on pulsars and other compact objects, they are not able to give us an answer either [4]. This is because the bulk properties of models of strange and neutron stars of masses that are typical for neutron stars, 1 & M͞M Ø & 1.8, are relatively similar. The situation changes, however, as regards the possibility that strange quark matter with the density of ϳ4 3 10 14 g cm 23 may be, by hypothesis, the absolute ground state of the strong interaction (i.e., absolutely stable with respect to 26 Fe) and can exist up to the surface of strange stars. This differs qualitatively from the case of the neutron star surface and opens a unique possibility to observe a superdense quark matter."Normal" matter (ions and electrons) may be at the quark surface of strange stars. The ions in the inner layer are supported against the gravitational attraction to the underlying strange star by a very strong electric field of the Coulomb barrier in the quark surface vicinity (see below). There is an upper limit to the amount of normal matter at the quark surface, DM & 10 25 M Ø [5]. Such a massive envelope of normal matter with DM ϳ 10 25 M Ø completely obscures the quark surface. However, it was pointed out [6] that a strange star at the moment of its formation is very hot. The temperature in the interior of such a star may be as high as a few 310 11 K. The rate of mass ejection from an envelope of such a hot strange star is very high [7], and if ...

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supporting

confidence: 76%

Bare Quark Matter Surfaces of Strange Stars ande+e−Emission

1998

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“…During an 13 hour period on 1990 October 13 14, the SIGMA instrument observed a strong are from 1E 1740.7 2942 which exhibited an intense 10 ,2 cm ,2 s ,1 , broad line feature FWHM 240 keV with an energy of 470 keV Bouchet et al 1991. This feature has been interpreted as a broadened, red-shifted 511 keV line resulting from positron annihilation occurring in an accretion disk surrounding 1E 1740.7 2942 Sunyaev et al 1991;Ramaty et al 1992. Similar outbursts were observed by SIGMA in 1991 October and 1992 September Churazov et al 1993b;Cordier et al 1993, though a simultaneous observation of the Galactic center region by the OSSE instrument during the 1992 September outburst did not detect the reported excess Jung et al 1994. There is no direct evidence, however, that the transient line feature observed by SIGMA is related to the narrow 511 keV line which has been observed since the early 1970's.…”

Section: Number Of Pagessupporting

confidence: 52%

The distribution of galactic 511 keV positron annihilation radiation

Purcell¹,

Grabelsky²,

Ulmer³

et al. 1994

AIP Conference Proceedings

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The Oriented Scintillation Spectrometer Experiment OSSE on NASA's Compton Gamma-Ray Observatory has completed numerous observations of the Galactic plane and Galactic center region. A principle objective of these observations was to measure the distribution of the Galactic positron annihilation radiation. Most of these observations provided positive detections of the narrow 511 keV annihilation line. These data were tted using several di use distribution models representing various populations of progenitor objects. The only model investigated which i s n o t rejected is a two-component distribution consisting of spheroidal and disk components; all other models investigated can be rejected at the 4:5 con dence level. The size of the spheroidal component is found to be 500 pc; the disk component o f the distribution is not well constrained by the current observations. Adding a point source of emission at the location of the black hole candidate 1E 1740.7 2942 does not signi cantly improve the model ts. There is no evidence for signi cant time variability of the 511 keV line ux during observations of the Galactic center region. When compared to historical observations of the Galactic center region by other instruments, the two-component di use model suggests a limit to a time-variable component o f t h e 511 keV line ux of 4 10 ,4 cm ,2 s ,1 .

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“…The source of the incoming X-rays might be associated with a nearby X-ray source (e.g. Churazov et al 1993Churazov et al , 1E1740.7-2942 or with past activity of Sgr A , as suggested by Sunyaev, to explain the hard X-ray emission of the giant molecular cloud Sgr B2 in the GC region, leading to prediction of the bright 6.4 keV line later confirmed by the observations (Koyama et al 1996;Sunyaev & Churazov 1998;Murakami et al 2000;Revnivtsev et al 2004;Terrier et al 2010;Zhang et al 2015). A long outburst from Sgr A lasting more than 10 years and ending a few hundred years ago could explain the Sgr B2 emission (Koyama et al 1996;Terrier et al 2010).…”

Section: Introductionmentioning

confidence: 99%

NuSTAR and XMM–Newton observations of the Arches cluster in 2015: fading hard X-ray emission from the molecular cloud

Krivonos

Clavel

Hong

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present results of long NuSTAR (200 ks) and XMM-Newton (100 ks) observations of the Arches stellar cluster, a source of bright thermal (kT ∼2 keV) X-rays with prominent Fe XXV Kα 6.7 keV line emission and a nearby molecular cloud, characterized by an extended non-thermal hard X-ray continuum and fluorescent Fe Kα 6.4 keV line of a neutral or low ionization state material around the cluster. Our analysis demonstrates that the non-thermal emission of the Arches cloud underwent a dramatic change, with its homogeneous morphology, traced by fluorescent Fe Kα line emission, vanishing after 2012, revealing three bright clumps. The declining trend of the cloud emission, if linearly fitted, is consistent with half-life decay time of ∼ 8 years. Such strong variations have been observed in several other molecular clouds in the Galactic Centre, including the giant molecular cloud Sgr B2, and point toward a similar propagation of illuminating fronts, presumably induced by the past flaring activity of Sgr A .

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Low-flux hard state of IE 1740.7-2942

Cited by 46 publications

References 0 publications

Bare Quark Matter Surfaces of Strange Stars ande+e−Emission

Bare Quark Matter Surfaces of Strange Stars ande+e−Emission

The distribution of galactic 511 keV positron annihilation radiation

NuSTAR and XMM–Newton observations of the Arches cluster in 2015: fading hard X-ray emission from the molecular cloud

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