NGC-6438 - A TRIPLE SYSTEM

We provide photographic and photoelectric information as well as CCD i maging and medium resolution spectroscopy on this system located at a distance of similar to 32 Mpc. The SO galaxy has twisted isophotes whi ch also show changes in the ellipticity. Profiles toward the north of this galaxy are 0.1 and 0.2 mag brighter in the B and V bands, respect ively, than in any other direction, probably due to the presence of du st in the Irregular system. Several blue regions (B-V=0.26-0.40) are f ound in the Irregular object indicating ongoing star formation. One of these regions is located in an extreme of the northern arm, its lumin osity being similar to that of the nucleus which is very close to it. Analysis of the spectra shows typical absorption lines and a weak [N I I] emission in the SO galaxy, whereas H alpha, [N II], and [S II] emis sion lines are observed both in the nucleus and in the blue region men tioned above. We determine a high reddening E(B-V)=1.4 in the nuclear region of this system. Rotation curves show a different behavior for t he nucleus and the blue region, which have V(max)greater than or equal to 180 km/s and V-max=80 km/s, respectively. All this evidence could support the idea that NGC 6438 is an interacting tripler, one SO galax y and two disk galaxies undergoing a merger. (C) 1996 American Astrono mical Society.