COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1955 Konkoly Observatory Budapest 1981 April 16 HU ISSN 0374-0676 TU Men, A NEW MEMBER OF THE SU UMa SUBGROUP OF DWARF NOVAE * TU Men = S 6732 was first discovered by Hoffmeister (1961 and 1963), who also classified it as an U-Geminorum star with a brightness range of 11- 17 p. During 1963 and 1978 TU Men has been observed in 2193 nights by several members of the VSSRASNZ (Bateson 1979). On these observations Bateson based his assumption that one could distinguish two groups of outbursts: Faint eruptions (m_v ~= 13.5m),which last approximately 1 day and recur every 37 d, and bright eruptions (m_v >= 12.5m), which last 4 - 20 days recuring every 194 days. TU Men therefore seemed to possess two characteristics of SU UMa stars, recently defined by Vogt (1980). A third, and probably the most important property of SU UMa stars - periodic superhumps during a superoutburst -, has been detected during an observation run at the European Southern Observatory at La Silla, where photometry and spectroscopy of TU Men was performed. (For more details see Table I.) The light curve, recorded during a time interval of 16 days, is shown in Fig. 1. It should be mentioned that Bateson (1980) reports a visual brightness of 11.6m for TU Men at JD 2444557 so that the duration of the supermaximum exceeds 22 days, as can be seen from Fig. 1. Figure 1 also demonstrates the periodic superhump phenomenon. The amplitude of the variations decreases from Delta m = 0.36m during the first two nights to Delta m = 0.13m at the end of the observations. * Based on observations collected at the European Southern Observatory, La Silla, Chile. Table I HJD Date Start End Telescope Filter Integr. 2444500+ time 1980-11-20/21 64.543 64.854 62cm Bochum white 1 sec 1980-11-20/21 64.73 64.85 50cm Danish u,b,v,y 10 sec 1980-11-21/22 65.520 65.770 62cm Bochum white 1 sec 1980-11-22/23 66.520 66.631 62cm Bochum white ~ 5 min 1980-11-23/24 67.527 67.653 62cm Bochum white 1 sec 1980-11-27/28 71.536 71.780 62cm Bochum white 1 sec 1980-11-30/01 74.670 74.837 1.5m Danish white 1 sec * 1980-12-01/02 75.635 75.840 1.5m Danish white 1 sec * 1980-12-02/03 76.561 76.687 1.5m Danish white 1 sec * 1980-12-03/04 77.587 77.684 1.5m Danish white 1 sec * 1980-12-04/05 78.564 78.704 1.5m Danish B 1 sec 1980-12-04/05 78.535 78.710 1m ESO I 1 sec 1980-12-05/06 79.545 79.667 1m ESO B/R 5 sec Table I: Journal of observations: Photometry During the nights 1980-11-24/25/26/27 and 1980-11-28/29 the brightness of TU Men was determined at a time between the superhumps during the nearly constant phase in order to record the progress of decline from supermaximum. * high speed photometry and simultaneously spectroscopic observations at the 1.5m ESO telescope The superhump-timings cannot be described by a constant period: With a period P determined from the first two nights, one gets a phase shift of maximal 1.4. P for the last recorded superhump. So, as in the case of VW Hyi (Hafner et al., 1979) and YZ Cnc (Patterson, 1979), a linear decreasing period has been adopted for the superhumps. A least square fit to the observed timings of maximal brightness yields the following ephemerides: HJD = 2444564.584 + .12625E - 6.1 x 10^-6 * E^2 +-3 +-15 +-1 [FIGURE 1] Fig.1. Light curve of TU Men over the whole observing run (1980, Nov. 20 - Dec. 6). For the reduction of measurements, star "E" from Bateson et al. (1977) was used as comparison star for TU Men. Note: For the last two nights the B-measurements are displayed. The most striking fact is the long superhump period P_s, which is the longest known until now. If one accepts that the orbital period P0 of TU Men is slightly different (+- 3-4%) from P_s, as for other SU UMa stars (Vogt, 1980), then the value of P0 lies in the range of 3h. As in the case of YZ Cnc (Patterson, 1979) this indicates that the SU UMa stars are not restricted to the ultrashort dwarf novae with P_0 <= 2h. A more detailed analysis of the photometry of TU Men together with an analysis of the spectroscopic observations will be published elsewhere. B. STOLZ R. SCHOEMBS Universitats-Sternwarte Scheinerstr. 1 D-8000 Munchen 80 Germany References Bateson, F.M., Morel, M., Winnett, R., 1977, Charts for Southern Variables, Series 9 [BIBCODE 1977csvs.book.....B ] Bateson, F.M., 1979, Publ. Var. Star Sect., Roy. Astron. Soc. New Zealand 7, 5 Bateson, F.M., 1979, Monthly Circ., Var. Star Sect., Roy. Astron. Soc. New Zealand M 80/11 Hafner, R., Schoembs, R., Vogt, N., 1979, Astron. Astrophys. 77, 7 [BIBCODE 1979A&A....77....7H ] Hoffmeister, C., 1961, Die Sterne 37, 205 [BIBCODE 1961Stern..37..204H ] Hoffmeister, C., 1963, Veroff. Sternw. Sonneberg 6, No. 1, 42 Patterson, J., 1979, Astron. J. 84, 804 [BIBCODE 1979AJ.....84..804P ] Vogt, N., 1980, Astron. Astrophys. 88, 66 [BIBCODE 1980A&A....88...66V ]