COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                        Number 3332

                                          Konkoly Observatory
                                          Budapest
                                          29 May 1989

                                          HU ISSN 0374 - 0676


 PHOTOMETRIC DETECTION OF ECLIPSE IN THE SPECTROSCOPIC BINARY HD 116093


Quite recently Griffin (1988) pointed out the possibility of an eclipse in the
spectroscopic binary HD 116093. According to his prediction we carried out BV
photoelectric observations of the system during the night of March 19, 1989,
and successfully obtained an eclipsing light variation. These BV observation
were made independently at two different places in Japan, Tamashima in
Okayama Prefecture and Kakuda in Miyagi Prefecture.

Table I shows the individual instruments used. Throughout the observations
BD +24d 2570 (V=8.88m, B-V=0.97m, U-B=0.69m) was used as the comparison star,
and it was occasionally checked against HD 116234 (as a check star). Figure I
shows the finding chart. In the photometric reduction, extinction correction
and transformation to the standard BV system were made in a similar way as in
our previous reports (Ohshima 1988, Ito 1988).

The individual observations obtained are listed in Table II where the magnitude
differences are given in the sense m_var-m_comp. The Delta (B-V), Delta B and
Delta V values are all plotted in Figure 2, where filled circles represent
Ohshima's observations while open circles Ito's ones. Figure 2 clearly
indicates that the eclipse is partial. The characteristics of the eclipse is
shown in Table III where the minimum epoch was determined with Hertzsprung's
method (Henden and Kaitchuck 1982).


                               [FIGURE 1]

                Figure 1. Finding chart of HD116093


                Name                   R.A. (1950.0)    Dec.     Sp.
Var. star:  HD 116093 = BD +23d2562   13h18m39s       22d44.1  F3+F8
Comp. star: SAO 82795 = BD +24d2570   13h18m45s       23d45.4   K0
Check star: HD 116234 = BD +23d2564   13h19m33s       22d34.3   F8


                                [FIGURE 2]

 Figure 2. BV observations of the eclipse of HD 116093 on March 19, 1989


                  Table I. Instrumentation

Observer:       O. Ohshima                      Y. Ito
Telescope:      20-cm reflector                 15-cm refractor
PMT:            R 647-04 (Hamamatsu)            1P21 (Hamamatsu)
Filters:                      GG 495 (2-mm) for V
                       GG385 (2-mm) + BG12 (1-mm) for B
Data acquisition: Photon counter + PC           D.C. amplification + A/D
                                                converter + PC
Site:           Tamashima                       Kakuda Girls Senior H.S.

Table II. Individual observations

No.   Hel. J. D.   Delta V   Delta B   Delta (B-V)   Observer*
      2447600+
1     4.9986       0.347     -0.185    -0.532         I
2     5.0139       0.343     -0.191    -0.534         I
3     5.0259       0.328     -0.225    -0.553         I
4     5.0327       0.309     -0.215    -0.524         O
5     5.0429       0.336     -0.153    -0.489         O
6     5.0463       0.334     -0.148    -0.482         O
7     5.0538       0.299     -0.204    -0.503         I
8     5.0577       0.319     -0.211    -0.530         I
9     5.0595       0.273     -0.198    -0.471         O
10    5.0662       0.393     -0.158    -0.551         O
11    5.0694       0.404     -0.115    -0.520         O
12    5.0725       0.398     -0.094    -0.492         O
13    5.0759       0.419     -0.084    -0.503         O
14    5.0791       0.430     -0.064    -0.494         O
15    5.0798       0.410     -0.058    -0.463         I
16    5.0899       0.462     -0.017    -0.479         O
17    5.0931       0.500     -0.029    -0.529         O
18    5.0979       0.469     -0.029    -0.497         O
19    5.1012       0.448     -0.019    -0.467         O
20    5.1039       0.479     -0.012    -0.491         I
21    5.1076       0.517     -0.036    -0.481         I
22    5.1080       0.521     -0.022    -0.543         O
23    5.1143       0.525      0.033    -0.492         O
24    5.1160       0.546      0.016    -0.530         I
25    5.1172       0.530      0.022    -0.508         O
26    5.1198       0.499     -0.027    -0.526         I
27    5.1234       0.550      0.051    -0.499         O
28    5.1298       0.533      0.020    -0.513         O
29    5.1312       0.541      0.073    -0.468         I
30    5.1432       0.627      0.097    -0.530         O
31    5.1467       0.585      0.102    -0.483         O
32    5.1514       0.602      0.062    -0.539         O
33    5.1619       0.569      0.025    -0.544         O
34    5.1651       0.604      0.022    -0.513         I
35    5.1655       0.539      0.030    -0.509         O
36    5.1704       0.586      0.072    -0.513         I
37    5.1768       0.529     -0.038    -0.567         O
38    5.1795       0.526      0.037    -0.489         I
39    5.1917       0.491     -0.071    -0.562         O
40    5.2216       0.421     -0.082    -0.503         I
41    5.2283       0.405     -0.124    -0.529         I
42    5.2328       0.356     -0.111    -0.467         I
43    5.2371       0.361     -0.122    -0.482         O
44    5.2384       0.395     -0.106    -0.501         I
45    5.2407       0.376     -0.136    -0.511         O
46    5.2424       0.394     -0.115    -0.509         I
47    5.2469       0.384     -0.134    -0.518         I
48    5.2773       0.307     -0.145    -0.452         I
49    5.2827       0.284     -0.182    -0.466         I
50    5.2883       0.335     -0.228    -0.563         I

* O = Ohshima; I = Ito

Table III. Observational results

Minimum:          2447605.150 +- 0.001 (Hel. J.D.)
Depth:            0.265 mag in B, 0.297 mag in V
Duration:         0.210 days
Out of eclipse:   delta V = 0.314m+-0.010 (s.d.) for n=9
                  delta B-V = -0.484+-0.011 (s.d.) for n=9

Combining the observed epoch of minimum in Table III with Griffin's (1988) time
of conjunction J.D.2446328.619, we can obtain a new ephemeris as follows:

          Min.=Hel.J.D. 2447605.150+53.1887d*E

In the present observations we used BD +24d2570 as the comparison star.
However, HD 116234 (see Figure 1) may be a better comparison for future
observations because its position is nearer to the variable and its colour is
also similar.

According to Griffin (1989), the secondary eclipse is also expected to occur in
the following dates in 1990 and 1991:

Jan. 12.05, March 6.23, Apr. 28.42, 1990,
Jan. 19.36, March 13.54, 1991,

for which photometric observations are highly desirable, as well.

We would like to express our gratitude to Dr. R. F. Griffin (the
Observatories, University of Cambridge), for his suggestion of photometric
observation and to Prof. M. Kitamura (National Astronomical Observatory of
Japan) for his encouragement.


OSAMU OHSHIMA*      and         YOSHIHARU ITO*
Tamashima 3-10-15               Kakuda Girls Senior High School
Kurashiki, Okayama              Nakajima-kami 250
713 Japan                       Kakuda, Miyagi, 981-15 Japan

* Member of Japan Amateur Photoelectric Observers Association (JAPOA)

References:

Griffin, R.F. 1988, J. Astrophys. Astr., 9, 205. [BIBCODE 1988JApA....9..205G ]
Griffin, R.F. 1989, private communication.
Henden, A.A., and Kaitchuck, R.H. 1982, Astronomical Photometry, Van Nostrand
   Reinhold Co., p.266. [BIBCODE 1982asph.book.....H ]
Ito, Y. 1988, Inf. Bull. Var. Stars, No. 3212.
Ohshima, O. 1988, Inf. Bull. Var. Stars, No. 3135.