Detection of pulsed X-ray emission from the isolated neutron star candidate eRASSU J131716.9-402647
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2024
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| _version_ | 1866909088283099136 |
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| author | Kurpas, J. Schwope, A. D. Pires, A. M. Haberl, F. |
| author_facet | Kurpas, J. Schwope, A. D. Pires, A. M. Haberl, F. |
| contents | The X-ray source eRASSU J131716.9-402647 was recently identified from observations with Spectrum Roentgen Gamma (SRG)/eROSITA as a promising X-ray dim isolated neutron star (XDINS) candidate on the premise of a soft energy distribution, absence of catalogued counterparts, and a high X-ray-to-optical flux ratio. Here, we report the results of a multi-wavelength observational campaign with XMM-Newton, NICER and the FORS2 instrument at the ESO-VLT. We found in both the XMM-Newton and NICER data that the X-ray emission is strongly pulsed at a period of $12.757$ s (pulsed fraction $p_\mathrm{f} = (29.1 \pm 2.6)$% in the 0.2-2 keV band). The pulse profile is double-humped, and the pulsed fraction increases with energy. The XMM-Newton and NICER epochs allow us to derive a 3$σ$ upper limit of $\dot{P}\leq 8\times 10^{-11}$ s s$^{-1}$ on the spin-down rate of the neutron star. The source spectrum is well described by a purely thermal continuum, either a blackbody with $kT\sim95$ eV or a magnetised neutron star atmosphere model with $kT \sim 35$ eV. Similarly to other thermally emitting isolated neutron stars, we found in either case strong deviations from the continuum, a broad absorption feature at energy $\sim260$ eV and a narrow one around $590$ eV. The FORS2 instrument at ESO-VLT has not detected the optical counterpart ($m_\mathrm{R}>27.5$ mag, $5σ$ detection limit), implying an X-ray-to-optical flux ratio of $10^4$ at least. The properties of eRASSU J131716.9-402647 strongly resemble those of a highly magnetised isolated neutron star and favour an XDINS or high-B pulsar nature. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2401_17290 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Detection of pulsed X-ray emission from the isolated neutron star candidate eRASSU J131716.9-402647 Kurpas, J. Schwope, A. D. Pires, A. M. Haberl, F. High Energy Astrophysical Phenomena The X-ray source eRASSU J131716.9-402647 was recently identified from observations with Spectrum Roentgen Gamma (SRG)/eROSITA as a promising X-ray dim isolated neutron star (XDINS) candidate on the premise of a soft energy distribution, absence of catalogued counterparts, and a high X-ray-to-optical flux ratio. Here, we report the results of a multi-wavelength observational campaign with XMM-Newton, NICER and the FORS2 instrument at the ESO-VLT. We found in both the XMM-Newton and NICER data that the X-ray emission is strongly pulsed at a period of $12.757$ s (pulsed fraction $p_\mathrm{f} = (29.1 \pm 2.6)$% in the 0.2-2 keV band). The pulse profile is double-humped, and the pulsed fraction increases with energy. The XMM-Newton and NICER epochs allow us to derive a 3$σ$ upper limit of $\dot{P}\leq 8\times 10^{-11}$ s s$^{-1}$ on the spin-down rate of the neutron star. The source spectrum is well described by a purely thermal continuum, either a blackbody with $kT\sim95$ eV or a magnetised neutron star atmosphere model with $kT \sim 35$ eV. Similarly to other thermally emitting isolated neutron stars, we found in either case strong deviations from the continuum, a broad absorption feature at energy $\sim260$ eV and a narrow one around $590$ eV. The FORS2 instrument at ESO-VLT has not detected the optical counterpart ($m_\mathrm{R}>27.5$ mag, $5σ$ detection limit), implying an X-ray-to-optical flux ratio of $10^4$ at least. The properties of eRASSU J131716.9-402647 strongly resemble those of a highly magnetised isolated neutron star and favour an XDINS or high-B pulsar nature. |
| title | Detection of pulsed X-ray emission from the isolated neutron star candidate eRASSU J131716.9-402647 |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2401.17290 |