Anomalous surface brightness fluctuations in NGC 4489

Anomalously high K-band surface brightness fluctuations (SBF) have been rep orted in NGC 4489 by Pahre & Mould (1991), Jensen ct al. (1996) and Jensen et al. (1998). However, these conclusions were uncertain because of relativ ely low signal-to-noise data. New high signal-to-noise data for NGC 4489 ha ve been obtained at the NOAO/KPNO 2.1 m and the ESO/La Silla 3.5 m NTT tele scopes. Adopting the I-band SBF distance modulus determined by Tonry ct al. (2000b) and the (M) over bar (1) versus (V - I) calibration of Tonry ct al . (2000a), a value of (M) over bar (K) = -6.29 +/- 0.10 mag was derived. Re lative to the average empirical (M) over bar (K) derived for giant elliptic als by Jensen et al. (1908) ((M) over bar (K) = -5.61 +/- 0.12 mag). The de tection of an anomalous K-band SBF in NGC 4489 is confirmed at the two sigm a level. Such anomalous fluctuations could be caused by art extended giant branch, consisting of either intermediate-age AGE stars above the tip of th e first-ascent giant branch or high-metallicity first-ascent giants, or by lack of a full understanding of the K-band SBF calibration. This result rai ses questions about the accuracy of K band SBF distance measurements for el liptical galaxies with unknown stellar composition and underscores the need for (M) over bar (K) measurements over a larger range of color and luminos ity.