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IAUC 4318: 1987A

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                                                  Circular No. 4318
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM    Telephone 617-495-7244/7440/7444

     M. Phillips, Cerro Tololo Interamerican Observatory, reports
that spectra from 320 to 1000 nm obtained on Feb. 25 with the 1.5-m
reflector and the CCD spectrograph show clear evidence of P-Cyg
lines at H alpha, beta, delta and possibly He I 587.6 nm.  The blueshift of
the absorption minimum of H alpha is 17 400 km/s.  The blueshifts of H beta
and delta are 16 100 and 15 500 km/s, respectively.  On this basis
the supernova might be classed as type II.  J. Matthews, observing
with the CTIO 0.40-m reflector measured preliminary photoelectric
magnitudes of V = 4.6, B-V = 0.0 on Feb. 25.17 UT.
     M. Shara and B. McLean, Space Telescope Science Insitute; and
N. Sanduleak, Warner and Swasey Observatory, have also remarked on
the very close positional coincidence of the supernova and the
blue supergiant Sanduleak -69 202 (see IAUC 4317).  Sanduleak notes
that the image of the supergiant appears to be elongated northwest-
southeast, suggesting a companion a magnitude or two fainter and
separated by 1" or less.  B. M. Lasker, Space Telescope Science
Institute, also remarks on this duplicity, a Cerro Tololo plate
on 1974 Nov. 6 (scale 18"/mm) showing a companion in p.a. 315 deg of
mag about 16 but apparently separated by as much as 3".
     C. Wheeler, University of Texas; and R. Kirshner, Center for
Astrophysics, have expressed the need to inform the astronomical
community of the types of observations that should be made of the
object.  If the supernova is of type I, as suggested on IAUC 4316,
it can be expected to brighten, over the course of the next two or
three weeks, to mag -1.  If, as seems to be coming more probable,
it is of type II, it should brighten to mag +1.  Kirshner notes:
"Suggested observations include accurate photometry and
spectrophotometry over a wide wavelength interval at low dispersion,
careful monitoring of line shapes at moderate dispersion, and
observation of interstellar and possible circumstellar features at
high dispersion.  Frequent sampling is highly desirable.  This
supernova offers unique opportunities for polarimetry across
scattering lines to determine atmospheric properties.  High angular
resolution methods of speckles and interferometry are especially
important, as this source is bright enough and will grow large
enough for present methods to be effective."
     Visual magnitude estimates by R. H. McNaught, Coonabarabran:
Feb. 25.401 UT, 4.3; 25.460, 4.2; 25.572, 4.5; 25.659, 4.4.

1987 February 25               (4318)              Brian G. Marsden

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