Radio Detection of A Candidate Neutron Star Associated with Galactic Center Supernova Remnant Sagittarius A East

摘要

We report the VLA detection of the radio counterpart of the X-ray objectreferred to as the "Cannonball", which has been proposed to be the remnantneutron star resulting from the creation of the Galactic Center supernovaremnant, Sagittarius A East. The radio object was detected both in our new VLAimage from observations in 2012 at 5.5 GHz and in archival VLA images fromobservations in 1987 at 4.75 GHz and in the period from 1990 to 2002 at 8.31GHz. The radio morphology of this object is characterized as a compact,partially resolved point source located at the northern tip of a radio "tongue"similar to the X-ray structure observed by Chandra. Behind the Cannonball, aradio counterpart to the X-ray plume is observed. This object consists of abroad radio plume with a size of 30\arcsec$\times$15\arcsec, followed by alinear tail having a length of 30\arcsec. The compact head and broad plumesources appear to have relatively flat spectra ($\propto\nu^\alpha$) with meanvalues of $\alpha=-0.44\pm0.08$ and $-0.10\pm0.02$, respectively; and thelinear tail shows a steep spectrum with the mean value of $-1.94\pm0.05$. Thetotal radio luminosity integrated from these components is $\sim8\times10^{33}$erg s$^{-1}$, while the emission from the head and tongue amounts for only$\sim1.5\times10^{31}$ erg s$^{-1}$. Based on the images obtained from the twoepochs' observations at 5 GHz, we infer the proper motion of the object:$\mu_\alpha = 0.001 \pm0.003$ arcsec yr$^{-1}$ and $\mu_\delta = 0.013\pm0.003$ arcsec yr$^{-1}$. With an implied velocity of 500 km s$^{-1}$, aplausible model can be constructed in which a runaway neutron star surroundedby a pulsar wind nebula was created in the event that produced Sgr A East. Theinferred age of this object, assuming that its origin coincides with the centerof Sgr A East, is approximately 9000 years.