Publication Date:
2020-09-01
Description:
PSR J1813–1749 is one of the most energetic rotation-powered pulsars known, producing a pulsar wind nebula (PWN) and gamma-ray and TeV emission, but whose spin period is only measurable in X-ray. We present analysis of two Chandra data sets that are separated by more than 10 yr and recent NICER data. The long baseline of the Chandra data allows us to derive a pulsar proper motion $mu _{
m RA}=(-0.067pm 0.010), mathrm{ arcsec},mathrm{yr^{-1}}$ and $mu _{
m Dec.}=(-0.014pm 0.007), mathrm{ arcsec},mathrm{yr^{-1}}$ and velocity $v_perp approx 900!-!1600, mathrm{km, s^{-1}}$ (assuming a distance d = 3–5 kpc), although we cannot exclude a contribution to the change in measured pulsar position due to a change in brightness structure of the PWN very near the pulsar. We model the PWN and pulsar spectra using an absorbed power law and obtain best-fitting absorption $N_{
m H}=(13.1pm 0.9)imes 10^{22}, mathrm{cm^{-2}}$, photon index Γ = 1.5 ± 0.1, and 0.3–10 keV luminosity $L_{
m X}approx 5.4imes 10^{34}, mathrm{erg, s^{-1}}(d/mbox{ 5 kpc})^2$ for the PWN and Γ = 1.2 ± 0.1 and $L_{
m X}approx 9.3imes 10^{33}, mathrm{erg, s^{-1}}(d/mbox{ 5 kpc})^2$ for PSR J1813–1749. These values do not change between the 2006 and 2016 observations. We use NICER observations from 2019 to obtain a timing model of PSR J1813–1749, with spin frequency ν = 22.35 Hz and spin frequency time derivative $dot{
u }=(-6.428pm 0.003)imes 10^{-11}, mathrm{Hz, s^{-1}}$. We also fit ν measurements from 2009 to 2012 and our 2019 value and find a long-term spin-down rate $dot{
u }=(-6.3445pm 0.0004)imes 10^{-11}, mathrm{Hz, s^{-1}}$. We speculate that the difference in spin-down rates is due to glitch activity or emission mode switching.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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