DETECTION OF AN UNRESOLVED NUCLEAR RADIO-SOURCE IN M31 (VOL 390, PG L9,199 2)

An unresolved radio source with a flux density of 28 +/- 5 muJy has be en detected at the center of the galaxy M31. This source coincides wit h the optical stellar nucleus and with a variable Einstein X-ray sourc e but is only 1/300 as luminous as the Galactic center source Sgr A an d one-fifth as luminous as Sgr A. Consequently, this object is the we akest known nuclear radio source. No evidence is found for radio emiss ion from the remnant of supernova 1885A in M31. An upper limit of 15 m uJy (3 sigma) has been determined for the flux density of this source, which is 1/15 the value for Tycho's SNR if it were at the same distan ce.