De Grandis, D;
Rigoselli, M;
Mereghetti, S;
Younes, G;
Pizzocchero, P;
Taverna, R;
Tiengo, A;
... Zane, S; + view all
(2022)
Two decades of X-ray observations of the isolated neutron star RX J1856.5 − 3754: detection of thermal and non-thermal hard X-rays and refined spin-down measurement.
Monthly Notices of the Royal Astronomical Society
, 516
(4)
pp. 4932-4941.
10.1093/mnras/stac2587.
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Abstract
The soft X-ray pulsar RX J1856.5 − 3754 is the brightest member of a small class of thermally emitting, radio-silent, isolated neutron stars. Its X-ray spectrum is almost indistinguishable from a blackbody with kT∞≈60eV, but evidence of harder emission above ∼1keV has been recently found. We report on a spectral and timing analysis of RX J1856.5 − 3754 based on the large amount of data collected by XMM-Newton in 2002–2022, complemented by a dense monitoring campaign carried out by NICER in 2019. Through a phase-coherent timing analysis we obtained an improved value of the spin-down rate ν˙=−6.042(4)×10−16Hzs−1, reducing by more than one order magnitude the uncertainty of the previous measurement, and yielding a characteristic spin-down field of 1.47×1013G. We also detect two spectral components above ∼1keV: a blackbody-like one with kT∞=138±13eV and emitting radius 31+8−16m, and a power law with photon index Γ=1.4+0.5−0.4. The power-law 2–8 keV flux, (2.5+0.7−0.6)×10−15ergcm−2s−1, corresponds to an efficiency of 10−3, in line with that seen in other pulsars. We also reveal a small difference between the 0.1–0.3 keV and 0.3–1.2 keV pulse profiles, as well as some evidence for a modulation above 1.2 keV. These results show that, notwithstanding its simple spectrum, RX J1856.5 − 3754 still has a non-trivial thermal surface distribution and features non-thermal emission as seen in other pulsars with higher spin-down power.
| Type: | Article |
|---|---|
| Title: | Two decades of X-ray observations of the isolated neutron star RX J1856.5 − 3754: detection of thermal and non-thermal hard X-rays and refined spin-down measurement |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1093/mnras/stac2587 |
| Publisher version: | https://doi.org/10.1093/mnras/stac2587 |
| Language: | English |
| Additional information: | This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | X-rays: stars – stars: neutron – stars: individual RX J1856.5−3754– stars: individual RX J0420.0−5022 |
| UCL classification: | UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics UCL > Provost and Vice Provost Offices > UCL BEAMS UCL |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10155396 |
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