COMMISSION 27 OF THE I. A. U.
             INFORMATION BULLETIN ON VARIABLE STARS
                        Number 2767
                                            Konkoly Observatory
                                            Budapest
                                            2 August 1985

                                            HU ISSN 0374 - 0676


      SPECTROPHOTOMETRIC OBSERVATIONS OF SUPERNOVA 1985G IN NGC 4451

  We present observations of the Supernova 1985G in NGC 4451, a member of the Virgo
Cluster. The spectra shown in Figures 1 and 2 were obtained on 1985 April 13.2 and
May 27.2 with the Mark II intensified Reticon spectrometer attached to the 1.3m telescope
at McGraw-Hill Observatory. Both spectra were obtained within 30deg of the zenith, the
later one under photometric conditions. Standard stars were observed over a much larger
range of airmass and were combined to create mean adopted flux calibrations for each of the
two dates of observation. Relative to these means, the flux standards exhibit a scatter of
+/-0.11 mag and +/-0.02 mag at 5556angstrom for the respective April and May observations and
show no significant wavelength dependent residuals. These spectra have been smoothed for
illustration purposes using a Gaussian filter of FWHM equal to that of lines in the
wavelength calibration lamp spectra. No redshift correction has been made, but tick marks
have been added to the spectra to indicate the wavelengths of various spectral features in
the rest frame of NGC 4451.
  To facilitate comparison with models and other observations, we have determined the
monochromatic magnitude at 5556angstrom as well as broadband B and B-V by convolving the B
and V filter functions with the spectra. These data and various observational details are
presented in Table I. Compared with the April 13 observation, the May 27 spectrum shows
the development of many strong features in the 5300 - 6200angstrom spectral region and a
narrowing of the Halpha emission component. Expansion velocities have been determined by
measuring the wavelength of the blue absorption edge of Halpha; this gives 12,000 km/s with an
uncertainty of ~ +/- 300 km/s for both of our observations. This is smaller than the 13,000
km/s velocity measured by Chalabaev, et al. (IAU Circ. 4052) from a spectrum obtained on
April 10.
  In IAU Circular No. 4049, H. Kozai reported V~ 14.5 on March 21 followed by a
decrease to V~ 15.0 by March 25. Our observations give V=15.18 on April 13 and indicate
an essentially constant B magnitude and slight increase in B-V over the following 44 days.


                               [FIGURE 1]


                               [FIGURE 2]


                    TABLE I

               Details of the Observations.



                                    Fig.1          Fig.2

1985 Date (UT)                      April 13.2    May 27.2

Integration time on Object (sec)    1200           960
Instrumental Resolution (angstrom)   9              9
Monochromatic m_nu at 5556 angstrom 15.12          14.81
B mag                               16.05          16.03
B-V                                  0.87           0.96



This is consistent with the object being a Type II supernova with a plateau of somewhat
long duration in the light curve.





                      MICHAEL V. NEWBERRY
                      JOHN J. SALZER
                      J. WARD MOODY

                      Department of Astronomy
                      University of Michigan
                      Ann Arbor, MI 48109 USA