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IAUC 5758: 1993J; SU Tau

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                                                  Circular No. 5758
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM     EASYLINK 62794505
MARSDEN@CFA or GREEN@CFA (.SPAN, .BITNET or .HARVARD.EDU)


SUPERNOVA 1993J IN NGC 3031
     J. Blakeslee and J. Tonry, Massachusetts Institute of Technology,
communicate:  "We have measured the magnitudes of the progenitor
of SN 1993J in the V and Kron-Cousins I bands.  The images
were taken on the night of 1992 May 1 with the 2.4-m telescope (+
2048x2048 Loral CCD; scale 0".343/pixel) at MDM Observatory on Kitt
Peak.  The exposure times were 700 s in I and 300 s in V; the seeing
was 1".05 in the I image and 1".14 in the V image.  The night
was not photometric, but we were able to calibrate the photometry
to better than 3 percent by comparing the images to earlier ones,
which did not encompass the supernova progenitor, taken under
photometric conditions on the Kitt Peak 4-m telescope.  Using an
aperture of diameter 3".4 to minimize background contamination, we
find:  V = 20.88 +/- 0.13, I = 19.51 +/- 0.04.  Correcting by the
psf to an aperture of diameter 10", we find V = 20.79 +/- 0.13, I =
19.44 +/- 0.04; these are uncorrected for galactic extinction.  The
progenitor appears extended north-south as compared to nearby point
sources.  At least ten stars are visible within 10", with I-band
magnitudes ranging from 1 to 3 mag fainter than the progenitor.
Most of these are quite red.  The nearest is an object with I =
20.4 situated 3".8 to the northwest."
     Further photoelectric photometry (cf. IAUC 5750) by H. Smith,
E. Lansing, MI (S; forwarded by J. A. Mattei, AAVSO); R. Mutel and
P. Sauerbrei, University of Iowa (MS; comparison stars from Corwin,
IAUC 5742); and P. Prugniel, Observatoire de Haute Provence (P):
Mar. 31.05 UT, V = 10.8 (S); Apr. 3.2, B = 11.98 +/- 0.06, V =
11.69 +/- 0.07, R = 11.23 +/- 0.03, I = 10.96 +/- 0.09 (MS); 4.2, B
= 12.19 +/- 0.04, V = 11.86 +/- 0.06, R = 11.37 +/- 0.05, I = 11.13
+/- 0.06 (MS); 5.1, V = 11.86 +/- 0.10, R = 11.34 +/- 0.02, I =
11.03 +/- 0.07 (MS); 6.5, B = 12.21 +/- 0.07, V = 11.85 +/- 0.04, R
= 11.28 +/- 0.08, I = 11.11 +/- 0.04 (MS); 7.00, Bc = 12.36, Bc-Rc
= +0.78 (P); 7.052, V = 11.8 (S); 8.00, Bc = 12.25, Bc-Rc = +0.79
(P); 9.00, Bc = 12.15, Bc-Rc = +0.79 (P).  Mutel and Sauerbrei note
that there is no evidence for variability in the reference stars.


SU TAURI
     Further visual magnitude estimates (cf. IAUC 5732):  Mar.
31.14 UT, 11.3 (J. Bortle, Stormville, NY); Apr. 1.15, 11.8 (D.
York, Abiquiu, NM); 4.11, 12.6 (York); 5.03, 13.3 (Bortle); 8.08,
[13.5 (Bortle).


1993 April 10                  (5758)            Daniel W. E. Green

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