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Detection of continuum radio emission associated with Geminga




A deep Very Large Array observation of the Geminga pulsar field led to the discovery, at a higher than 10σ significance level, of radio emission trailing the neutron star proper motion. This ∼10 arcsec long radio feature, detected with a flux of ∼0.4 mJy at 4.8  GHz, is marginally displaced (2.7 ± 1.8 arcsec) from the pulsar (which, at any rate, is unlikely to contribute with magnetospheric pulsed emission more than 15 per cent to the total observed radio luminosity, ∼1026 erg s−1) and positionally coincident with the X-ray axial tail recently discovered by Chandra and ascribed to the pulsar wind nebula (PWN). Overall, the Geminga radio tail is compatible with the scenario of a synchrotron-emitting PWN, but the present data do not allow us to discriminate between different (and not always necessarily mutually exclusive) possible processes for producing that. If this radio feature results not from intrinsic peculiarities of Geminga, but from its proximity and radio-quiet nature (both helping in not hindering the faint diffuse radio emission), other relatively near and energetic radio-quiet pulsars could show similar structures in dedicated interferometric observations.