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http://hdl.handle.net/20.500.12386/27005
Title: | Discovery of a soft X-ray 8 mHz QPO from the accreting millisecond pulsar IGR J00291+5934 | Authors: | Ferrigno, C. Bozzo, E. Sanna, A. Pintore, Fabio PAPITTO, ALESSANDRO Riggio, A. Burderi, L. Di Salvo, T. Iaria, R. D'AI', ANTONINO |
Issue Date: | 2017 | Journal: | MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY | Number: | 466 | Issue: | 3 | First Page: | 3450 | Abstract: | We report on the analysis of the peculiar X-ray variability displayed by the accreting millisecond X-ray pulsar IGR J00291+5934 in a 80 ks-long joint NuSTAR and XMM-Newton observation performed during the source outburst in 2015. The light curve of the source is characterized by a flaring-like behaviour, with typical rise and decay time-scales of ∼120 s. The flares are accompanied by a remarkable spectral variability, with the X-ray emission being generally softer at the peak of the flares. A strong quasi-periodic oscillation (QPO) is detected at ∼8 mHz in the power spectrum of the source and clearly associated with the flaring-like behaviour. This feature has the strongest power at soft X-rays ( ≲ 3 keV). We carried out a dedicated hardness-ratio-resolved spectral analysis and a QPO phase-resolved spectral analysis, together with an in-depth study of the source-timing properties, to investigate the origin of this behaviour. We suggest that the unusual variability of IGR J00291+5934 observed by XMM-Newton and NuSTAR could be produced by a heartbeat-like mechanism, similar to that observed in black hole X-ray binaries. The possibility that this variability, and the associated QPO, are triggered by phases of quasi-stable nuclear burning, as sustained in the literature for a number of other neutron star binaries displaying a similar behaviour, cannot be solidly tested in the case of IGR J00291+5934 due to the paucity of type I X-ray bursts detected from this source. | URI: | http://hdl.handle.net/20.500.12386/27005 | URL: | https://academic.oup.com/mnras/article/466/3/3450/2736300 | ISSN: | 0035-8711 | DOI: | 10.1093/mnras/stw3344 | Bibcode ADS: | 2017MNRAS.466.3450F | Fulltext: | open |
Appears in Collections: | 1.01 Articoli in rivista |
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stw3344.pdf | PDF editoriale | 1.49 MB | Adobe PDF | View/Open |
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