Portal:Radiation astronomy/Resource/47

Clouds
"The Southern Galactic Plane Survey (SGPS; see the 2002 Annual Report), which combines 21-cm HI observations from Parkes and the Compact Array, is now complete. The SGPS provides a wonderful resource for understanding populations such as magnetars in the context of their environment. Examination of SGPS data around the position of the well-known magnetar 1E 1048.1­5937 reveals a striking cavity in HI, designated as GSH 288.3-0.5-28, that is almost centred on the position of the neutron star. The SGPS data imply that GSH 288.3-0.5-28 is at a distance of approximately 2.7 kpc, and is expanding at a velocity of approximately 7.5 kilometres per second into gas of density ~17 atoms cm-3."

"Shells like GSH 288.3-0.5-28 are common, and represent wind-blown bubbles powered by massive stars expanding into the interstellar medium. The size and expansion speed of GSH 288.3-0.5-28 then imply that the bubble is several million years old, and has been blown by a wind of mechanical luminosity ~4 x 1034 ergs per second, corresponding to a single star of initial mass 30 to 40 solar masses."

"Usually in such cases, the central star is obvious, in the form of a bright O star, supergiant or WR star at the shell's centre. However, even though this field lies in the rich Carina OB1 region, there are no known stars of the appropriate position, distance or luminosity to argue for an association with GSH 288.3-0.5-28. This raises the intriguing possibility that GSH 288.3-0.5-28 was blown by the massive star whose collapse formed 1E 1048.1-5937. The central location of the magnetar within the HI shell suggests that the supernova occurred quite recently. The corresponding blast waves would impact the walls of the HI shell approximately 3000 years after core collapse, producing significant X-ray and radio emission. The lack of such emission requires the neutron star to be very young, consistent with the small ages expected for active magnetars. A common distance of around three kpc is suggested by the properties of both objects."