COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3517 Konkoly Observatory Budapest 12 September 1990 HU ISSN 0374 - 0676 ON THE AMPLITUDE OF THE RECURRENT NOVA V 3890 SAGITTARII The recent discovery of a new outburst (Jones 1990) of this object, which was originally called "Nova Sgr 1962" (for the description of the first maximum see Dinerstein 1973), caused me to check the available plates of the Sonneberg Sky Patrol at the location of the star. On 7 of 679 suitable exposures taken at Sonneberg and in Namibia mainly by P. Ahnert, C. Hoffmeister, and H. Huth in the years 1926 to 1983 the variable is visible during the 1962 eruption and shows the following pg. magnitudes: 2437818.52 10m5 .54 10.6 7820.52 10.9: 7821.49 10.8 7824.45 11.1: .47 11.0 .49 11.2 The first two plates of this list were taken at the date of the Nantucket discovery plate (1962 June 2). With certainty the maximal brightness determined by us is much fainter than the value of 8.4m from the Nantucket exposure: The nova is only slightly brighter (by 0.4 mag at the most) than the nearby CoD -24d 14410 (star A of Dinerstein l.c.). The magnitude of A has been determined concurrently as 10.9m by linking it to the Henry Draper Catalogue pg. brightness data of 5 neighbouring stars and independently to Selected Area 134 (the systematic correction of Seares et al. (1924) end the difference in atmospheric extinction taken into account). Also the other magnitudes, on the subsequent part of the descending branch, are systematically 1.5 to 2 mag fainter then the corresponding trend of the lightcurve of Dinerstein. - At the remaining plates the star is invisible, fainter than 11.4m. We did not reach our goal to find some further eruption, and there is at present no possibility of correcting statistically the observed cycle length of 28 years. The 1990 eruption of V 3890 Sgr should have reached visually 8.0m at the most (Liller 1990; Jones 1990). The light-curve of this outburst very closely resembles that of 1962, if we assume photovisual magnitudes for the upper part of Dinerstein's curve. This assumption would be in accordance with our own magnitude determination on non-sensitized photographic plates if we pay regard to the positive colour index normally present in this phase of an eruption. An analogous example is V 745 Sco - pg. light-curve of 1937 see Duerbeck (1984), pv. maximum of 1989 see Liller (1989) et al. From all these facts we conclude that the outburst amplitude might have been not much larger than 7 mag pg., and not > 9 mag as assumed possible by Duerbeck (1987) e.g. This newly determined outburst range is well fitting the amplitude-cycle length relationship: For the three recurrent novae RS Oph, T Pyx, and V 1017 Sgr with an amplitude of about 7 mag an average cycle length of 26 years was observed, and the values for the second group V 394 CrA, T CrB, U Sco, and V 745 Sco are approximately 10 mag and 50 years (see e.g. Hoffmeister et al. 1990). W. WENZEL Sternwarte Sonneberg Zentralinstitut fur Astrophysik der Akademie der Wissenschaften der DDR References: Dinerstein, H., 1973, Inf. Bull. Variable Stars 845 Duerbeck, H.W., 1984, Inf. Bull. Variable Stars 2490 Duerbeck, H.W., 1987, Space Sci. Rev. 45, no. 1-2, p.123 [BIBCODE 1987SSRv...45....1D ] Hoffmeister, C., Richter, G., Wenzel, W., 1990, Veranderliche Sterne 3. Aufl., Verlag Barth, Leipzig, p.88 Jones, A.F., 1990, IAU Circ. 5002 [BIBCODE 1990IAUC.5002....1K ] Liller, W., 1989, IAU Circ. 4820; see also subsequent nrs. of the Circ. [BIBCODE 1989IAUC.4820....1L ] Liller, W., 1990, IAU Circ. 5010 Seares, F.H., et al., 1924, Contr. Mt. Wilson Obs. 13, p.145