A 6.4-hr positive superhump period in TV Col

Abstract

Re-examination of photometric data of TV Col (Hellier, 1993) reveals positive superhumps in addition to the negative superhumps previously known. The superhump period is 0.265+/-0.005 day - about 16 percent longer than the orbital period - which obeys the relation between superhump-period excess and orbital period (Stolz and Schoembs 1984). As a confirmed permanent superhumper, the accretion disc of TV Col is naturally thermally stable. Therefore, our result supports the idea of Hellier and Buckley (1993) that the short-term outbursts seen in its light curve are mass transfer events rather than thermal instabilities in the disc. At 5.5-hr, TV Col has a longer orbital period than any known superhumper, and thus a mass ratio which is probably outside the range at which superhumps can occur according to current theory.