COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                       Number 3049

                                            Konkoly Observatory
                                            Budapest
                                            16 July 1987

                                            HU ISSN 0374-0676



        Request for VRI photometry of the RS CVn type binary
           HD 26337 during 15. through 30. December 1987


  Observers in the northern and southern hemisphere at all geographic longitudes are
begged to obtain VRI photometry of HD 26337, a relatively bright (Vmax = 6.9 mag)
spotted RS CVn type binary with a 1.94 day period. For more specific information on this
interesting star see Table 1 and Fekel et al. (1987), and Hall et al (1987); a V-light curve
can be found in the latter reference.

  We are going to apply the Doppler Imaging technique (Vogt and Penrod, 1983) to
this star during a 10-day run at Kitt Peak National Observatory from 18. - 23. and 26.-
29. December 1987 and we need simultaneous observed lightcurves in order to (i) obtain
an independent spot-model solution from the photometric data to prove and compare it
with the solution derived from Doppler Imaging, (ii) derive the spot temperature from the
V-I color curve and (iii) combine both solutions to a more accurate and unique spot map
of HD 26337. If successful, this would be the first time that a spot model is applied to
both light and color curves and high-resolution line profiles observed at the same time!
We hope this will also demonstrate more quantitatively to which extend older spot-model
solutions derived from photometry alone were affected by the non-uniqueness problem.

  What do we need? Several things should be considered by a photometrist who might
wish to observe HD 26337. The photometry should be done either in the Johnson VRI
or in the Kron-Cousins VRI standard system. Observers with a Solid-State Photometer
(e.g. the SSP-3 from Optec Inc.) are also encouraged to participate, their RI-filters are
designed to match the standard Johnson system. Please determine your own transformation 
coefficients, so that magnitudes on your instrumental system can be transformed to
one of the above mentioned standard systems; follow the outlinings in Hall (1983), Hall
and Genet (1982) or Sanders and Persha (1983). Another important. point is that the
observations should be carried out through the whole night (or so). HD 26337 has a 
photometric (and orbital) period of nearly 2.0 days, that makes it very difficult to obtain good

              Table 1
       Observational properties


    Var. star: HD 26337 = BD-8 801
    RA=04h07m15', D=-08d 01'27" (1950.0)
 mV(max)=6.9 mag, amplitude in V ~0.20 mag
        spectral type G5 IV
     photometric period 1.945 days
      orbital period 1.94722 days

Comp. star: 37 Eri = HD 26409 = BD-7 758
    RA=04h07m56', D=-07d 03'12" (1950.0)
     mV=5.6 mag, spectral type G5

       Check star: BD-9 843
    RA=04h09m32', D=-08d 57'55" (1950.0)
     mV=6.6 mag, spectral type G5

   Standard stars: Please chose from The
  Astronomical Almanac for standards on the
  Johnson system, or from Fernie (1983), and
   references therein, if you observe in the
        Kron-Cousins system.


                            [FIGURE 1]

         Fig.: 1  Finding chart for the stars in Table 1



phase coverage. Moreover, the spot behavior is changing so fast (see Hall et el. 1987) that
no more than ~ 5 - 10 rotation cycles should be combined. These requirements can be
only fullfilled if several observers at different geographic longitudes are observing 
simultaneousely. Therefore, our request goes especially to observers in Europe, Africa, Asia,
Australia and in the Pacific, but also to observers in the United States. Well equipped
amateur-astronomers are especially welcome and are also invited to 
participate in this
campaign. If you can use only V on your photometer, please go ahead, these observations
would be very valuable too. Finally, we plan to publish the photometric results in a 
separate I.B.V.S. and/or I.A.P.P.P. paper with all contributors as authors. If you decide to
help us and want to observe HD 26337, please use the comparison and check star listed in
Table 1 and identified in the accompaning finding chart.

  Please feel free to write for more information to me or Doug Hall at Dyer Observatory.



                 KLAUS G. STRASSMEIER
                  Dyer Observatory
                 Vanderbilt University
                 Nashville, TN 37235
                        U.S.A.





References

Fekel, F. C. et al.: 1987, Astron. J. submitted. [BIBCODE 1987AJ.....94..726F ]
Fernie, J. D.: 1983, Publ. Astron. Soc. Pacific, 95, 782. [BIBCODE 1983PASP...95..782F ]
Hall, D. S.: 1983, in IR & Solid-State Photometry, I.A.P.P.P. Commun., 14, p.14. [BIBCODE 1983IAPPP..14...14H ]
Hall, D. S., and Genet, R. M.: 1982, Photoelectric Photometry of Variable Stars - A
   practical Guide For The Smaller Observatory, ed. D.S. Hall and R.M. Genet
   (Dayton: Minuteman Press). [BIBCODE 1982ppvs.book.....H ]
Hall, D. S. et al.: 1987, Astron,. J. submitted. [BIBCODE 1987AJ.....94..723H ]
Sanders, W. H., and Persha, G.: 1983, in IR & Solid-State Photometry, I.A.P.P.P.
   Commun., 14, p.19. [BIBCODE 1983IAPPP..14...19S ]
Vogt, S. S., and Penrod, G. D.: 1983, Publ. Astron. Soc. Pacific, 95, 565. [BIBCODE 1983PASP...95..565V ]