COMMISSION 27 OF THE I. A. U.
            INFORMATION BULLETIN ON VARIABLE STARS
                       Number 2768

                                            Konkoly Observatory
                                            Budapest
                                            2 August 1985

                                            HU ISSN 0374 - 0676


           SPECTROPHOTOMETRY OF SUPERNOVA 1985H IN NGC 3359


    A spectrum of the supernova 1985H was obtained on April 13,1985 at McGraw-Hill
Observatory. This supernova was discovered in NGC 3359, an SBc spiral in Ursa Major,
by J. Nemec and S. Staples on April 3, 1985 (Kristian 1985). Our observation was made
with the Mark II intensified Reticon spectrometer attached to the 1.3 meter telescope.
A 300 line/mm grating was used, giving a dispersion of 2.3 angstrom/channel and a spectral
resolution of about 9 angstrom. The total exposure time on the supernova was 39.2 minutes, and
mid-exposure was at 4:23 UT. The spectral scans were reduced in the standard fashion, with
wavelength calibration being accomplished using scans of comparison lamps, and absolute
flux calibration being achieved using observations of two spectrophotometric standard stars
(EG 71 and Ross 640). Measurements indicate that our flux calibration is accurate to better
than +/-20% over the entire useful range of the spectrum. A fully reduced spectrum is shown
in Figure 1. It has been smoothed with a Gaussian profile whose width equals the FWHM
of the comparison lamp lines. No redshift corrections have been applied.


    The spectrum in Figure 1 is typical for a Type II supernova, showing strong P
Cygni lines of Halpha, Hbeta, Na I D, plus a number of unidentified features. The tick marks
indicating the various spectral features are located at the rest wavelengths of these lines in
the rest frame of the galaxy (Vr = 1013 km/s (Huchra et al. 1983)). It is interesting to
note the strong similarity between the spectrum presented here and the May 27 observation
of supernova 1985G in NGC 4451 reported in the preceding IBVS note. If these spectra
represent similar stages in the evolution of the two supernovae, then supernova 1985H must
be between one and two months "older" than 1985G, but escaped detection until it was
well past its maximum.

    The expansion velocity of the supernova, measured from the blue edge of the Halpha
absorption feature, is 6200 km/s. The V magnitude and B-V color have been determined
by convolving the appropriate filter functions with the observed spectrum. We find V =
17.0 and B-V = 1.5. Wheeler (1985) reported V =16.4 for this object from an observation
made on April 12. The difference of 0.6 magnitude cannot be accounted for by the +/-0.2
magnitude uncertainty in our value for V indicated by the accuracy of our flux 
calibration.



The very red color of 1985H indicates that a substantial amount of absorption occurs in
the vicinity of the supernova. Using the average light curves of Barbon et al. (1979), we


                              [FIGURE 1]


estimate that E(B-V) is between 0.5 and 0.6 magnitudes. The large amount of obscuration
implied by this value for the color excess helps to explain the faintness of the supernova,
and why it was not detected at an earlier stage.



                     JOHN J. SALZER and J. WARD MOODY

                     Department of Astronomy
                     University of Michigan
                     Ann Arbor, MI 48109 U.S.A.


References:

Barbon, R., Ciatti, F., and Rosino, L. 1979, Astron. Astrophys. 72, 287. [BIBCODE 1979A&A....72..287B ]
Huchra, J., Davis, M., Latham, D., and Tonry, J. 1983, Ap. J. Supp. 52, 89. [BIBCODE 1983ApJS...52...89H ]
Kristian, J. 1985, I. A. U. Circ. No. 4050. [BIBCODE 1985IAUC.4050....1K ]
Wheeler, J. C. 1985, I. A. U. Circ. No. 4053. [BIBCODE 1985IAUC.4053....2W ]