We report on the detection of X-ray emission from the unusual Galactic radio source G357.7–0.1 ( the “ Tornado ” ) .
Observations made with the Chandra X-ray Observatory demonstrate the presence of up to three sources of X-ray emission from the Tornado : a relatively bright region of dimensions 2 ^ { \prime } \times 1 ^ { \prime } coincident with and interior to the brightest radio emission at the “ head ” of the Tornado , plus two fainter extended regions possibly associated with the Tornado ’ s “ tail ” .
No X-ray point sources associated with the Tornado are seen down to a 3 \sigma luminosity ( 0.5–10 keV ) of 1 \times 10 ^ { 33 } erg s ^ { -1 } , for a distance to the system of 12 kpc .
The spectrum of the brightest region of X-rays is consistent with a heavily absorbed ( N _ { H } \approx 10 ^ { 23 } cm ^ { -2 } ) thermal plasma of temperature kT \sim 0.6 keV ; an absorbed power law can also fit the data , but implies an extremely steep photon index .
From these data we tentatively conclude that the Tornado is a supernova remnant ( SNR ) , although we are unable to rule out the possibility that the Tornado is powered either by outflows from an X-ray binary or by the relativistic wind of an unseen pulsar .
Within the SNR interpretation , the head of the Tornado is a limb-brightened radio shell containing centrally-filled thermal X-rays and which is interacting with a molecular cloud .
We therefore propose that the Tornado is a “ mixed morphology ” supernova remnant .
The unusual tail component of the Tornado remains unexplained in this interpretation , but might result from expansion of the SNR into an elongated progenitor wind bubble .