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Free keywords:
XMM-NEWTON; SPIN-DOWN; MAGNETIC-FIELDS; PULSAR; EMISSION; PULSATIONS;
ASTROPY; NEARBYAstronomy & Astrophysics;
Abstract:
The X-ray thermal isolated neutron star (XTINS) RX J0806.4-4123 shows interesting multiwavelength properties that seemingly deviate from those of similar neutron stars. An accurate determination of the spin frequency change over time can assist in interpreting RX J0806.4-4123's properties in comparison to those of other XTINSs and the wider pulsar population. From 2019 to 2023 we carried out a tailored X-ray timing campaign of RX J0806.4-4123 with the NICER instrument. We used statistical properties of the Fourier coefficients and the Z K 2 test for phase connecting separate observations and finding a timing solution for the entire data set. We also developed a simple and universal method for estimating the uncertainties of the frequency nu and its derivative nu from the empirical dependencies of Z K 2 on trial values of these parameters, with account of all significant harmonics of the frequency. Applying this method, we determined a spin-down rate nu=-7.3(1.2)x10-17Hzs-1 . The resulting spin-down power E=2.6x1029 erg s-1 is the lowest among the XTINSs, and it is a factor of 60 lower than the X-ray luminosity of this neutron star. RX J0806.4-4123 is also among the pulsars with the lowest measured E in general.
