2005IAUC.8477....2M

Further to IAUC 8473, S. Mattila, R. Greimel, C. Gerardy, and W. P. S. Meikle, together with D. L. Clements and K. Nandra (Imperial College, London), report the discovery on a K_s-band image obtained on Jan. 30.3 UT of a strong outburst in the B1 nucleus (Wynn-Williams et al. 1991, Ap.J. 377, 426) of the galaxy Arp 299. The nucleus was not in outburst in their previous such image taken on 2004 June 6.0, and the difference in brightness yields a magnitude for the new source of K_s = +12.6 ± 0.1; at a distance of 45 Mpc, this translates to M(K_s) about -20.7, which is about a magnitude brighter than would be expected for the brightest supernovae (cf. Mattila and Meikle 2001, MNRAS 324, 325). The new source is located at R.A. = 11h28m31s.02, Decl. = +58o33'40".7 (equinox 2000.0), which is < 0".1 from the K_s-band nucleus B1 and < 0".5 from the location of the x-ray-determined active galactic nucleus (AGN) in Arp 299 (Ballo et al. 2004, Ap.J. 600, 634). The source is therefore most likely associated with an AGN outburst in the nucleus B1.