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Register a new userX-ray Spectroscopy of the Highly Magnetized Pulsar PSR J1846-0258, its Wind Nebula and Hosting Supernova Remnant Kes 75
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E. V. Gotthelf
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We present broad-band X-ray spectroscopy of the energetic components that make up the supernova remnant (SNR) Kesteven 75 using concurrent 2017 Aug 17-20 XMM-Newton and NuSTAR observations, during which the pulsar PSR J1846-0258 is found to be in the quiescent state. The young remnant hosts a bright pulsar wind nebula powered by the highly-energetic (Edot = 8.1E36 erg/s) isolated, rotation-powered pulsar, with a spin-down age of only P/2Pdot ~ 728 yr. Its inferred magnetic field (Bs = 4.9E13 G) is the largest known for these objects, and is likely responsible for intervals of flare and burst activity, suggesting a transition between/to a magnetar state. The pulsed emission from PSR J1846-0258 is well-characterized in the 2-50 keV range by a power-law model with photon index Gamma_PSR = 1.24+/-0.09 and a 2-10 keV unabsorbed flux of (2.3+/-0.4)E-12 erg/s/cm^2). We find no evidence for an additional non-thermal component above 10 keV in the current state, as would be typical for a magnetar. Compared to the Chandra pulsar spectrum, the intrinsic pulsed fraction is 71+/-16% in 2-10 keV band. A power-law spectrum for the PWN yields Gamma_PWN = 2.03+/-0.03 in the 1-55 keV band, with no evidence of curvature in this range, and a 2-10 keV unabsorbed flux (2.13+/-0.02)E-11 erg/s/cm^2. The NuSTAR data reveal evidence for a hard X-ray component dominating the SNR spectrum above 10 keV which we attribute to a dust-scattered PWN component. We model the dynamical and radiative evolution of the Kes 75 system to estimate the birth properties of the neutron star, the energetics of its progenitor, and properties of the PWN. This suggests that the progenitor of Kes 75 was originally in a binary system which transferred most its mass to a companion before exploding.
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We present the results of detailed spatial and spectral analysis of the pulsar wind nebula (PWN) in supernova remnant Kes 75 (G29.7-0.3) using a deep exposure with Chandra X-ray observatory. The PWN shows a complex morphology with clear axisymmetric structure. We identified a one-sided jet and two bright clumps aligned with the overall nebular elongation, and an arc-like feature perpendicular to the jet direction. Further spatial modeling with a torus and jet model indicates a position angle $207arcdegpm8 arcdeg$ for the PWN symmetry axis. We interpret the arc as an equatorial torus or wisp and the clumps could be shock interaction between the jets and the surrounding medium. The lack of any observable counter jet implies a flow velocity larger than 0.4c. Comparing to an archival observation 6 years earlier, some small-scale features in the PWN demonstrate strong variability: the flux of the inner jet doubles and the peak of the northern clump broadens and shifts 2 outward. In addition, the pulsar flux increases by 6 times, showing substantial spectral softening from $Gamma$=1.1 to 1.9 and an emerging thermal component which was not observed in the first epoch. The changes in the pulsar spectrum are likely related to the magnetar-like bursts of the pulsar that occurred 7 days before the Chandra observation, as recently reported from RXTE observations.
PSR J1846-0258 is a radio-quiet rotation-powered pulsar at the center of Supernova remnant Kes 75. It is the youngest pulsar (~723 year) of all known pulsars and slows down very predictably since its discovery in 2000. Till June 7, 2006 very stable behavior has been displayed both in the temporal and spectral domains with pulsed emission detectable by INTEGRAL IBIS ISGRI and RXTE HEXTE up to ~150 keV. Then, a dramatic brightening was detected of the pulsar during June 7-12, 2006 Chandra observations of Kes 75. This radiative event, lasting for ~55 days, was accompanied by a huge timing glitch, reported on for the first in present work. Moreover, several short magnetar-like bursts were discovered. In this work not only the time-averaged pre-outburst X-ray/soft gamma-ray characteristics are discussed in detail, but also the spectral evolution during the outburst and its relaxation phase are addressed using RXTE PCA and HEXTE and INTEGRAL IBIS ISGRI data.
We report new Chandra X-ray observations of the shell supernova remnant (SNR) Kes 75 (G29.7-0.3) containing a pulsar and pulsar-wind nebula (PWN). Expansion of the PWN is apparent across the four epochs, 2000, 2006, 2009, and 2016. We find an expansion rate between 2000 and 2016 of the NW edge of the PWN of 0.249% +/- 0.023% yr^{-1}, for an expansion age R/(dR/dt) of 400 +/- 40 years and an expansion velocity of about 1000 km s^{-1}. We suggest that the PWN is expanding into an asymmetric nickel bubble in a conventional Type IIP supernova. Some acceleration of the PWN expansion is likely, giving a true age of 480 +/- 50 years. The pulsars birth luminosity was larger than the current value by a factor of 3 -- 8, while the initial period was within a factor of 2 of its current value. We confirm directly that Kes 75 contains the youngest known PWN, and hence youngest known pulsar. The pulsar PSR J1846-0258 has a spindown-inferred magnetic field of 5 x 10^{13} G; in 2006 it emitted five magnetar-like short X-ray bursts, but its spindown luminosity has not changed significantly. However, the flux of the PWN has decreased by about 10% between 2009 and 2016, almost entirely in the northern half. A bright knot has declined by 30% since 2006. During this time, the photon indices of the power-law models did not change. This flux change is too rapid to be due to normal PWN evolution in one-zone models.
The supernova remnant (SNR) Kes 75/PSR J1846-0258 association can be regarded as certain due to the accurate location of young PSR J1846-0258 at the center of Kes 75 and the detected bright radio/X-ray synchrotron nebula surrounding the pulsar. We provide a new distance estimate to the SNR/pulsar system by analyzing the HI and $^{13}$CO maps, the HI emission and absorption spectra, and the $^{13}$CO emission spectrum of Kes 75. No absorption features at negative velocities strongly argue against the widely-used large distance of 19 to 21 kpc for Kes 75, and show that Kes 75 is within the Solar circle, i.e. a distance $d<$13.2 kpc. Kes 75 is likely at distance of 5.1 to 7.5 kpc because the highest HI absorption velocity is at 95 km/s and no absorption is associated with a nearby HI emission peak at 102 km/s in the direction of Kes 75. This distance to Kes 75 gives a reasonable luminosity of PSR J1846-0258 and its PWN, and also leads to a much smaller radius for Kes 75. So the age of the SNR is consistent with the spin-down age of PSR J1846-0258, confirming this pulsar as the second-youngest in the Galaxy.
We report on the 2020 reactivation of the energetic high-magnetic field pulsar PSR J1846-0258 and its pulsar wind nebula (PWN) after 14 years of quiescence with new Chandra and Green Bank Telescope observations. The emission of short-duration bursts from J1846-0258 was accompanied by an enhancement of X-ray persistent flux and significant spectral softening, similar to those observed during its first bursting episode in 2006. The 2020 pulsar spectrum is described by a powerlaw model with a photon index Gamma=1.7pm0.3 in comparison to a Gamma=1.2pm0.1 before outburst and shows evidence of an emerging thermal component with blackbody temperature kT=0.7pm0.1 keV. The 0.5--10 keV unabsorbed flux increased from 5.4e-12 erg/cm^2/s in quiescence to 1.3e-11 erg/cm^2/s following the outburst. We did not detect any radio emission from the pulsar at 2 GHz and place an upper limit of 7.1 uJy and 55 mJy for the coherent pulsed emission and single-pulses, respectively. The 2020 PWN spectrum, characterized by a photon index of 1.92pm0.04 and X-ray luminosity of 1.2e-35 erg/s at a distance of 5.8~kpc, is consistent with those observed before the outburst. An analysis of regions closer to the pulsar shows small-scale time variabilities and brightness changes over the 20-yr period from 2000 to 2020, while the photon indices did not change. We conclude that the outburst in PSR J1846-0258 is a combination of crustal and magnetospheric effects, with no significant burst-induced variability in its PWN based on the current observations.
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