Observations of the neutral hydrogen surrounding the radio-quiet neutron star RX J0822-4300 in Puppis A

We have observed the HI distribution in an area 40 x 40 arcmin(2) around the neutron star candidate RX J0822- 4300, which is located in the supernova remnant Puppis A. The observations of the lambda 21- cm line were obtained with the Australia Telescope Compact Array and were combined with single- dish data from the Southern Galactic Plane Survey. The spatial resolution is 90 arcsec, and the velocity resolution is 1 km s(-1). A sensitivity of similar to0.7 K was achieved. The results revealed a double- lobed feature of reduced emission at + 16 km s(-1), centred on the central compact object (CCO), and aligned with an HI hole blueshifted by 13 km s(-1). The HI depressions have probably been created by the sweeping up of 2 M. The alignment between the lobes and the optical expansion centre of Puppis A suggests that the CCO could be ejecting two opposite jets. The velocity at which the two lobes are best defined has allowed us to confirm that the distance to Puppis A is 2.2 kpc, based on a systemic velocity of + 16 km s(-1). The hydrogen column density computed using this systemic velocity is consistent with estimates from models for X- ray spectra, thus reinforcing our conclusion that the kinematic distance is 2.2 kpc.