COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                    Number 2626

                                   Konkoly Observatory
                                   Budapest
                                   14 November 1984

                                   HU ISSN 0374 - 0676




         A POSSIBLE DELTA SCUTI VARIABLE IN NGC 6405 *



  During the photometric search for CP2 stars in open clusters ( Maitzen,
and Schneider, 1984 ) star no. 31 (number from Rohlfs et al., 1959) was
found to be slightly variable. The observations were carried out during
May 1981 with the ESO 50 cm telescope at La Silla, Chile. The Stromgren
data, obtained during six nights, are as follows :


No  V        b-y     m1      c1       b        v        u        J.D.      phase
 1  11.581   0.252   0.108   0.900    11.833   12.193   13.453  4739.64679  .00
 2  11.625   0.252   0.165   1.011    11.877   12.294   13.722  4741.60126  .97
 3  11.580   0.284   0.113   1.043    11.864   12.261   13.701  4746.73163  .03
 4  11.631   0.263   0.161   1.021    11.894   12.318   13.763  4748.57666  .48
 5  11.671   0.229   0.198   1.025    11.900   12.327   13.779  4748.71271  .61
 6  11.679   0.213   0.187   1.020    11.892   12.292   13.712  4751.71008  .58
 7  11.658   0.242   0.182   0.906    11.900   12.324   13.654  4751.88367  .58
 8  11.574   0.263   0.165   0.958    11.837   12.265   13.651  4752.60559  .12
 9  11.621   0.256   0.140   1.115    11.877   12.273   13.784  4752.70569  .49
10  11.584   0.306   0.041   1.109    11.890   12.237   13.693  4752.76788  .92
11  11.514   0.277   0.141   0.983    11.791   12.209   13.610  4752.86444  .15
12  11.538   0.297   0.088   0.980    11.835   12.220   13.585  4752.90723  .13



A straightforward sine fit through the data yields a period of 1.043 hours.
This and the position inside the M_v -(b-y) diagram points to a possible delta Sct
nature of this star (Breger, 1979), while the Delta a photometry (Maitzen,
Schneider, 1984) does not show any CP2 character (both, delta Sct and radially
pulsating CP2 stars, occupy the same range inside the CM-diagram).
In Figure 1 the data for each Stromgren filter are plotted vs. the phase.
The phases are calculated by using

         J.D. = 2444739.64679 + 0.04346d E

The amplitudes obtained from the sine fit are:


     y : 0.09 b : 0.05 v : 0.07 u : 0.12 ( mag. )


*
  Based on observations collected at the European Southern Observatory
  ( ESO ), La Silla, Chile

                          [FIGURE 1]

Because of the small aperture of the telescope and the relatively small
brightness of the star the S/N ratio of the 120 second integrations is
fairly small. This and the small sample of data causes greater 
uncertainties in determining the period, phase lag and amplitude. To obtain
more accurate values of this object further observations are needed.



                         H. SCHNEIDER

                         Universitats-Sternwarte
                         Geismarlandstr. 11
                         D-3400 Gottingen
                         F.R.G.



 References:

 Breger, M. 1979, PASP, 91, 5. [BIBCODE 1979PASP...91....5B ]
 Maitzen, H.M., Schneider, H. 1984 Astron.Astrophys., 138, 189. [BIBCODE 1984A&A...138..189M ]
 Rohlfs, R., Schrick, K.-W., Stock, J. 1959, ZfA, 47, 15. [BIBCODE 1959ZA.....47...15R ]