Detection of low-luminosity X-ray pulsations from the accreting millisecond pulsar IGR J17511-3057: An ever-thinning thread between bright accretion and sub-luminous states
After nearly a decade in quiescence, the accreting millisecond pulsar IGR J17511$-$3057 displayed a new outburst on 2025 February 11, its third since discovery, following previous activity in 2009 and 2015. We report on an XMM-Newton Target of Opportunity observation performed on 2025 March 4, more...
| Autores: | , , , , , , , , , , , , , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2026 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/424856 |
| Acceso en línea: | http://hdl.handle.net/10261/424856 http://arxiv.org/abs/2507.13248v2 |
| Access Level: | acceso abierto |
| Palabra clave: | Accretion Accretion disks Pulsars: individual: IGR J17511-3057 Stars: low-mass Stars: neutron X-rays: binaries |
| Sumario: | After nearly a decade in quiescence, the accreting millisecond pulsar IGR J17511$-$3057 displayed a new outburst on 2025 February 11, its third since discovery, following previous activity in 2009 and 2015. We report on an XMM-Newton Target of Opportunity observation performed on 2025 March 4, more than twenty days after the outburst onset. From the X-ray spectrum - well described by an absorbed Comptonization model - we estimated an unabsorbed 0.5$-$10 keV luminosity of $L_X \sim 7 \times 10^{33} \, \mathrm{erg \, s^{-1}}$ (assuming a source distance equal to the upper limit of $6.9$ kpc). To place this in context, we analyzed an archival Chandra observation performed in 2019, which yielded a quiescent luminosity of $L_\mathrm{X,q} \sim 2 \times 10^{32} \, \mathrm{erg \, s^{-1}}$ in the same energy band. Although this comparison indicates that the source was still well above its quiescent level during the XMM-Newton observation, the estimated low luminosity during the late stage of the 2025 outburst would typically place the source in the propeller regime. Nevertheless, we unexpectedly detected coherent X-ray pulsations with an amplitude peaking at $\sim$42% in the 0.3$-$3 keV band. We also observed a spectral softening compared to the early stages of the outburst. Finally, we report a 3$σ$ upper limit of 60 $μ$Jy beam$^{-1}$ on the source flux density at 5.5 GHz from ATCA observations acquired on 2025 April 12, following a decline of the accretion activity, as indicated by our analysis of NICER data from 2025 March 15, which revealed no significant X-ray pulsations at a luminosity level of $L_X \sim 1 \times 10^{34} \, \mathrm{erg \, s^{-1}}$. We discuss our findings in the context of other accreting millisecond pulsars and draw comparisons with transitional systems in the sub-luminous disk state. |
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