GSH 90-28-17: a possible old supernova remnant

GSH 90-28-17 is a high-latitude Galactic H I supershell, identified in the H I supershell catalogues with a velocity v lsr -17 km s -1 . We used the new Galactic Arecibo L-band Feed Array (GALFA) H I survey data, which have much higher resolution and sensitivity than was previously available, to re-examine the properties of the supershell. We derived a new distance of 400 pc for GSH 90-28-17 and suggested that it is related to the Lac OB1 association. The radius of GSH 90-28-17 is 66.0 3.5 pc. The H I mass of the shell is (3.1 0.1) 10 4 M . It has an age of 4.5 Myr and a total kinetic energy of (8.2 0.3) 10 48 erg. We extracted radio continuum data for the GSH 90-28-17 region from the 408-MHz All-Sky Survey and Bonn 1420-MHz survey and filtered the diffuse background Galactic emission. A radio loop-like ridge is found to be associated with the H I shell at both frequencies and shows a non-thermal origin, with a temperature-temperature (TT)-plot index of = -1.35 0.69. In addition, the pulsar J2307+2225, with a similar distance, is found in the shell region. We conclude that GSH 90-28-17 is probably an old, type II supernova remnant in the solar neighbourhood.