Long-term coherent timing of the accreting millisecond pulsar IGR J17062-6143

Abstract

We report on a coherent timing analysis of the 163 Hz accreting millisecond X-ray pulsar IGR J17062-6143. Using data collected with the Neutron Star Interior Composition Explorer and XMM-Newton, we investigated the pulsar evolution over a timespan of four years. We obtained a unique phase-coherent timing solution for the stellar spin, finding the source to be spinning up at a rate of (3.77 ± 0.09) × 10 −15 Hz/s. We further find that the 0.4 − 6 keV pulse fraction varies gradually between 0.5% and 2.5% following a sinusoidal oscillation with a 1210 ± 40 day period. Finally, we supplemented this analysis with an archival Rossi X-ray Timing Explorer observation, and obtained a phase coherent model for the binary orbit spanning 12 years, yielding an orbital period derivative measurement of (8.4 ± 2.0) × 10 −12 s/s. This large orbital period derivative is inconsistent with a binary evolution that is dominated by gravitational wave emission, and is suggestive of highly non-conservative mass transfer in the binary system.

Spectral Evolution of Ultraluminous X-ray Pulsar NGC 300 ULX-1

“…Finally, we remark that in the spectrum for the "offeclipse" in NGC 300 X-1, we found a Gaussian emission line with centroid energy E = 0.949 +0.012 −0.013 keV and width σ = 0.089 +0.016 −0.014 keV, which could be associated with Fe-L emission or with the Ne X line (Degenaar et al 2013;Bult et al 2021). It could also be due to Fe XVIII from photoionized material originating in the outer edge of the accretion disk, as seen in Cyg X-2 (Vrtilek et al 1986;Chiappetti et al 1990), or the complex blending of Fe and O emission lines (Vrtilek et al 1988).…”