COMMISSION 27 OF THE I. A. U.
            INFORMATION BULLETIN ON VARIABLE STARS
                        Number 2713

                                       Konkoly Observatory
                                       Budapest
                                       25 April 1985

                                       HU ISSN 0374 - 0676


         DRAMATIC CHANGES IN THE POLARIZATION OF AR Pup


  AR Pup is supposed to be a carbon rich RV Tauri star of period around 75
days and it shows large infrared excess (Gehrz and Ney 1972). This star is
included in our programme of polarization observations of carbon variables
and has been observed on three different occasions with the PRL polarimeter
(Deshpande et al., 1985) attached to the 40-inch telescope at Kavalur 
Observatory. Although on these occasions the visual magnitudes were roughly the
same (~9.3 mag) there were dramatic changes in the wavelength dependence as
well as in the amount of polarization. The position angles also showed large
changes.

  The observations along with their probable errors are shown in Figure 1.
No recent photometric light curves seem to be available for this object for
accurately knowing the photometric phases corresponding to these epochs. But
from the old photometric data on the observed visual magnitudes, we guess
that the polarimetric observations might be outside the minima. The infrared
magnitudes of AR Pup are also variable. The JHKL magnitudes obtained with an
InSb photometer with the 40-inch reflector in February 1981 are: J=6.94,
H=5.27, K=3.61 and L=1.31. Gehrz and Ney (1972) give K=4.37 and L=1.98, quite
different from the values observed. But the K-L colours obtained on both these
occasions are essentially the same.



      A.V. RAVEENDRAN                           M.R. DESHPANDE
      N. KAMESWARA RAO                          U.C. JOSHI
      Indian Institute of Astrophysics          A.K. KULESHRESTHA
      Bangalore - 560034.                       Physical Research Laboratory
      India                                     Ahmedabad - 380009
                                                India



References:

Deshpande, M.R. et al., 1985, Bull.Astr.Soc. India, vol. 13, (in press)
Gehrz, R.D., and Ney, E.P., 1972, Publs.Astr.Soc.Pacif. 84, 768 [BIBCODE 1972PASP...84..768G ]


                             [FIGURE 1]