New expansion rate measurements of the Crab nebula in radio and optical

Abstract

We present new radio measurements of the expansion rate of the Crab nebula's synchrotron nebula over a ∼30-yr period. We find a convergence date for the radio synchrotron nebula of ce 1255 ± 27. We also re-evaluated the expansion rate of the optical line emitting filaments, and we show that the traditional estimates of their convergence dates are slightly biased. Using an un-biased Bayesian analysis, we find a convergence date for the filaments of ce 1091 ± 34 (∼ 40 yr earlier than previous estimates). Our results show that both the synchrotron nebula and the optical line-emitting filaments have been accelerated since the explosion in ce 1054, but that the synchrotron nebula has been relatively strongly accelerated, while the optical filaments have been only slightly accelerated. The finding that the synchrotron emission expands more rapidly than the filaments supports the picture that the latter are the result of the RayleighTaylor instability at the interface between the pulsar-wind nebula and the surrounding freely-expanding supernova ejecta, and rules out models where the pulsar wind bubble is interacting directly with the pre-supernova wind of the Crab's progenitor.

SN 1986J VLBI. IV. The Nature of the Central Component

“…We further found that the decrease of the absorption of the central component suggested a system that was decelerated perhaps slightly more than the shell, which is already significantly decelerated in SN 1986J (with r ∝ t 0.69 Paper II). One would expect a PWN, by contrast, to be somewhat accelerated, since the PWN is driven into the still freely expanding ejecta interior to the decelerated forward shock (e.g., Chevalier & Fransson 1992;Gelfand et al 2009;Bietenholz & Nugent 2015).…”

Dusty globules in the Crab Nebula

“…The velocity field over the expanding remnant has been mapped from proper motions of the optical filaments (Trimble 1968;Nugent 1998) and related radial velocities (Wykoff et al 1977). Bietenholz & Nugent (2015) also included radio measurements to conclude that the synchrotron nebula, fed by energy from a pulsar-wind nebula (see Bühler & Blandford 2014), has been strongly accelerated compared to the filaments.…”

3D mapping of the Crab Nebula with SITELLE. I. Deconvolution and kinematic reconstruction

“…The remarkable work of Trimble (1968) demonstrated that proper motion velocity vectors of filaments all share the same origin both in position and time, and that the expansion velocity is approximately proportional to the radius. Subsequent analyses have come to similar conclusions (Wyckoff & Murray 1977;Nugent 1998;Kaplan et al 2008;Bietenholz & Nugent 2015), though their results on the location of the explosion center or the mean expansion velocity differ by a few arcseconds (Kaplan et al 2008) (see Table 3.4). The expansion model we adopt is based on 3 parameters: the right ascension and declination (α c , δ c ) of the expansion center and the expansion factor e (e.g., Bietenholz & Nugent 2015): (1998) and Table 3 of Kaplan et al (2008).…”

“…Subsequent analyses have come to similar conclusions (Wyckoff & Murray 1977;Nugent 1998;Kaplan et al 2008;Bietenholz & Nugent 2015), though their results on the location of the explosion center or the mean expansion velocity differ by a few arcseconds (Kaplan et al 2008) (see Table 3.4). The expansion model we adopt is based on 3 parameters: the right ascension and declination (α c , δ c ) of the expansion center and the expansion factor e (e.g., Bietenholz & Nugent 2015): (1998) and Table 3 of Kaplan et al (2008). Following Kaplan et al (2008), ∆α and ∆δ are the offset in right ascension and declination between the center of the explosion and the star 5 to the northeast of the pulsar (which was first used by Trimble 1968 as a reference given its proximity to the center and its small proper motion).…”