WD2 - Origin and physics of Soft Gamma-ray Repeaters and Anomalous X-ray Pulsars |
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Speaker |
Villanova Borges, Sarah |
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Coauthors |
Rodrigues, Cláudia .V., Coelho, Jaziel G., Malheiro, Manuel |
| Talk Title |
Can the anomalous X-ray pulsar 4U 0142+61 be described as an accreting white dwarf? |
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Abstract |
4U 0142+61 is an anomalous X-ray pulsar (AXP) and was reported for the first time in 1983 by the UHURU telescope. This object presents quiescent emission in a broad range of energy, from mid-infrared to hard X-rays, in addition to some outburst gamma-ray events. The object nature and the emission mechanism for the entire spectral range are still question for debate. The most accepted scenario is the magnetar model. However, that model presents some difficulties to explain the spectral energy distribution (SED) of 4U 0142+61. For that reason, some alternative models have already been proposed, such as neutron star accretion scenario and white-dwarf pulsar model, however, both of them also presents some difficulties to model the spectra. In this work, we present a new scenario that explains the quiescent emission of 4U 0142+61. We propose that this emission comes from an accreting isolated white dwarf surrounded by a debris disk, having gas and dusty regions. We obtained a good fit for the entire SED assuming that the optical and infrared emission are caused by the optically thick dusty disk and the white-dwarf photosphere, the hard X-rays are due to the post-shock region of the accretion column and the soft X-rays are formed by the heating of the white-dwarf surface. The fitted parameters points to a white dwarf that is a fast rotator, magnetic and near to the Chandrasekhar limit mass. All parameters are physically and geometrically consistent with the proposed scenario. Such a white dwarf is compatible with the expected product of the merger of two less massive CO white dwarfs. Those mergers are also suggested as a possible origin of the double-degenerated supernovae (SN) Ia. For that reason, 4U 0142+61 could be a SN Ia progenitor and hence can give hints of the origin of these important astrophysical events. |
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