COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3375 Konkoly Observatory Budapest 21 September 1989 HU ISSN 0374 - 0676 The May-July 1989 crisis of V348 Sgr V348 Sgr is a unique variable star apparently related to the R CrB group (see the recent studies by Pollacco 1989 and Houziaux et al. 1987). The star happens to spend most of its time either near maximum (V ~12.5) or near minimum (V>18). It is imbedded in a faint emission nebula which may make measurement or even detection impossible in the minimum episodes. The stable phases usually last for several months (typically 8 to 9), but much faster events have been detected. In the absence of a daily monitoring the coverage of such fast episods is essentially a matter of luck. For instance in August 1981 a complete minimum (including decline and recovery) took about three weeks (Heck et el. 1982), but only part of the decline could be monitored photoelectrically. The descent was then clocked at about 2 mag/day in V. A few other short lived minima were recorded (in August 67 for instance, Duruy 1970), but the data are very scarce. Experienced visual observers noted that a similar event occured in 1989. It was first caught visually by McNaught (Marsden 1989a) who reported a fading from 12.5 in March and April to fainter than 13.9 on May 5. On May 17, the star was observed visually by Verdenet (Marsden 1989b) at V=15, while as of June 3 it was seen back at the maximum by A. Pearce (Marsden 1989). Remarkably enough this maximum did not last very long. In the beginning of July we were lucky to follow the first days of a new decline with the ESO 1m telescope on La Silla (Table 1). The ESO single channel photoelectric photometer was used in the Stromgren b band. The rate of variation was marginally slower than that observed in 1981. During the three hours period centered on JD 2,447,714.8 the decline rate Delta b/Delta T is estimated to be about 1.35 mag/day while, in 1981, between JD 2,444,837 and 2,444,838, a value of 1.6 mag/day was observed in b. This should have lead to fainter than magnitude 18 by July 9. Between June and August, several plates were taken with the Schmidt telescope at the Haute-Provence Observatory (Table 2). The second plate, obtained on July 14, and all subsequent ones, until August 31, show that V348 was effectively in its quiescent phase. Curiously enough, Marsden (1989b) reports a visual estimate of 14.0 by J. Bortle on July 9.13. If confirmed, this would imply an irregular descent with secondary maxima. On the other hand the field of V348 Sgr is very crowded, and closeby stars of magnitudes 14.4 and 14.8 have often be mistaken for V348 Sgr when at minimum. Table 1. Stromgren b photometry of V348 Sgr JD_hel Stromgren b +2,440,000.000 7711.811 12.9206 7711.813 12.9226 7712.799 13.0468 7712.800 13.0270 7714.742 14.1530 7714.743 14.1536 7714.750 14.1667 7714.751 14.1722 7714.767 14.1604 7714.769 14.1701 7714.787 14.2187 7714.789 14.2513 7714.812 14.2899 7714.813 14.2847 7714.832 14.2705 7714.833 14.2443 7714.854 14.2903 7714.856 14.2883 7714.866 14.3191 7714.867 14.3350 Table 2. V348 Sgr magnitudes on Schmidt photographs. The star was often too faint to be recorded. The magnitudes obtained with IIIaJ plates and TP2415 sheet films are not directly comparable to Stromgren b. This is not too important in view of the large variations we are dealing with. JD_hel Emulsion Magnitude +2,440,000.00 7685.06 IIIaJ 12.5 7722.96 IIIaJ > 18 7736.96 IIIaJ > 16 7765.84 IIIaJ > 18 7766.88 IIIaJ > 18 7767.84 IIIaJ > 16 7768.92 TP2415 > 14 7769.85 TP2415 > 18 The double event of May-July 1989 may be similar to what happened in August- October 1967. Unfortunately only a few visual observations were recorded. There is also some indications that an analogous behavior occured in September-November 1975. (See Fig. 1 of Heck et al.). It is quite probable that several other instances went unnoticed. Obviously a much more extensive coverage of the light-curve is needed before a clear understanding of the photometric variations is obtained. J. MANFROID, L. HOUZIAUX Institut d'Astrophysique Universite de Liege B-4200 Liege Belgium References Duruy, M.: 1970, Bull. Soc. Roy. Sci. Liege 39, 600 Heck, A., Houziaux, L., Manfroid, J.: 1982, Information Bull. on Variable Stars 2184 Houziaux, L., Bouchet, P., Heck, A., Manfroid, J.: 1987, Quart. J. Roy. astr. Soc. 28, 231 [BIBCODE 1987QJRAS..28..231H ] Marsden, B.: 1989a, IAU Circular 4780 [BIBCODE 1989IAUC.4780....3M ] Marsden, B.: 1989b, IAU Circular 4821 [BIBCODE 1989IAUC.4821....4V ] Pollacco, D.L.: 1989, Ph. D. Thesis, University of St. Andrews