COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2367 Konkoly Observatory Budapest 11 July 1983 HU ISSN 0374-0676 LIGHT VARIABILITY OF NOVA DELPHINI 1967 IN 1981 AND 1982 Nova Delphini 1967 (=HR Del) has been monitored on three nights in 1981 (9.6 hours) and on three nights in 1982 (10.8 hours) at the Hamburg Observatory in Bergedorf, We used the 1.2 m (f/13) Ritchey -Chretien telescope equipped with the pulse counting photometer - polarimeter (RCA C 31034 photomultiplier; Schroder, 1978) and integrated for about 40 sec in an instrumental system close to the Johnson V-band (Schott 2 mm GG 495 + 1 mm VG 6 + 2 mm BG 38). Comparison star No. 6 (Barnes, Evans, 1970) was adopted as local standard and served also for determining the extinction. Similar to our observations made in 1977-1980 (Kohoutek, Pauls, 1980; Kohoutek et a1.,1981) the brightness variations were approximated by a one-cycle sinusoid, The times of five maxima were derived (Table I) from the light curves observed on five nights, whereas only a decrease in brightness was observed on 1981 Aug. 28/29. Table I Journal of observations and maxima of the light curve. ------------------------------------------------------------- Date Period Number T(MAX) 1981-1982 (UT) of obs. JDHel 2440000 + ------------------------------------------------------------- 1981 Aug. 28/29 21:39 - 00:48 16 -- Sep. 24/25 20:21 - 23:09 19 4872.342 Sep. 30/Oct.1 18:59 - 22:40 36 4878.371 1982 July 21/22 23:04 - 01:37 30 5172.489 July 27/28 21:38 - 01:38 46 5178.440 July 28/29 21:30 - 01:42 56 5179.502 ------------------------------------------------------------- Combining the maxima of the nights 1982 July 27/28 and July 28/29 the following periods were found in the range of 0.14d - 0.27d corresponding to E = 7,6,5,4 : 0.1524d, 0.1778d, 0.2134d, 0.2668d. We eliminated the shortest period by monitoring the nova for about 4 hours during some nights. Then we used the times of the three maxima observed in 1982 (Table I) and searched for elements of the light curve close to the remaining three possible periods given above. We derived the following periods: 0.17981d, 0.21231d, 0.26972d. +-29 +- 16 +- 43 Our best fit, 0.21231d, is close to the possible periods 0.2159d (found in 1977), 0.2167d (1979) and 0.2201d (1980) and it does not differ very much from the best solution 0.21417d found recently from the RV-data by Bruch (1982). [FIGURE 1] Figure 1 The light curve of N Del 1967 on three nights in 1981 and 1982; Delta v = v(Nova) - v(Comp. 6). As to the observations made in 1981 only two maxima are available (the time of the first maximum being uncertain), There exists a possible period 0.2149d close to our best 1982 fit. The decrease of the semi-amplitude of the light curve (see Kohoutek et al,, 1981) has continued, In 1981 and 1982 we measured A_v = 0.029 mag and 0.025 mag, respectively, With respect to the mean internal accuracy of one measurement of the nova (+-0.02 mag),the approximation of the light curve by a sinusoid of such small amplitude is not very reliable (see Fig. 1), The brightness of Nova Del 1967 still seems to drop very slightly: we observed Delta v = v(Nova) - v(Comp.6) to be +0.57 mag in 1981, and +0.63 mag in 1982. We wish to thank Dr. Maria-L. Roth for observing on one night. H.-M. STEINBACH L. KOHOUTEK Hamburger Sternwarte D-2050 Hamburg 80 Federal Republic of Germany References: Barnes, T.G., Evans, N.R., 1970, Publ.Astron.Soc.Pacific 82, 889 [BIBCODE 1970PASP...82..889B ] Bruch, A., 1982, Publ.Astron.Soc.Pacific 94, 916 [BIBCODE 1982PASP...94..916B ] Kohoutek, L., Pauls, R., 1980, Astron.Astrophys. 92, 200 [BIBCODE 1980A&A....92..200K ] Kohoutek, L., Pauls, R., Steinbach, H.-M., 1981, I.B.V.S. No. 1991 Schroder, R., 1978, Mitt.Astron.Ges. 43, 295 [BIBCODE 1978MitAG..43..295S ]