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IAUC 5775: 1993J

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                                                  Circular No. 5775
Central Bureau for Astronomical Telegrams
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

     J. A. Phillips and S. R. Kulkarni, California Institute of
Technology, report:  "Using the four-element millimeter interferometer
at the Owens Valley Radio Observatory (OVRO), we have continued
monitoring the flux density of SN 1993J at a frequency of 99.4
GHz (+/- 3 mJy):  Apr. 11.24-11.52 UT, 18 mJy; 14.23-14.53, 17;
21.22-21.52, 20.  The fluxes listed for Apr. 11 and 14 supersede
the values we reported on IAUC 5763; the previous fluxes were
based on continuum synthesis maps with an effective bandwidth of
250 MHz.  The new values cited here were obtained from a wideband
digital correlator with an effective bandwidth of 1 GHz, and the
resulting uncertainties are a factor of two smaller.  Our flux
scale was established by observations of Uranus and Neptune.  The
respective fluxes we measured during the supernova observations for
three other compact radio sources are as follows:  3C 273, 22.1,
25.4, 27.3 Jy; 0954+658, 1.9, 1.9, 2.2 Jy; 3C 345, -, 5.1, 5.9 Jy.
This will facilitate comparisons of our flux scale with that of
other millimeter telescopes currently engaged in monitoring the
supernova.  The continuum source 0954+658 is only 24' from the
position of the supernova and was used as a phase calibrator for the
interferometric observations.  We have also used the OVRO millimeter
array to observe the supernova at 221.9 GHz.  Our first attempt
was on Apr. 20, and we did not detect any source at the location of
the radio supernova above a 3-sigma threshold of 48 mJy."
     B. Skiff, Lowell Observatory, provides the following Johnson V
magnitudes and Stromgren b-y colors (+/- 0.02) obtained on Apr.
26.1 UT for several additional GSC stars 4383.n near the supernova
(cf. IAUC 5742):  0150, V = 10.45, b-y = +0.79; 0384, 11.01, +0.33
(see note below); 0565, 11.42, +0.36; 0698, 10.82, +0.66.  The GSC
V magnitudes of these stars are 9.87, 10.85, 12.33, and 10.37,
respectively. On Apr. 26.15, the supernova was at V = 11.35, b-y =
     D. Hanzl, N. Copernicus Planetarium, Brno, communicates that
GSC 4383.0384 appears to be variable, first noted visually on Apr.
16 by K. Hornoch at Lelekovice and J. Kysely at Vlasim, and confirmed
photoelectrically by Hanzl as having a maximum at V = 10.98
+/- 0.05, amplitude about 0.35 mag, and period of probably < 1 day.
Hanzl also provides the following additional Johnson photometry for
SN 1993J:  Apr. 20.89 UT, V = 10.88 +/- 0.02, B-V = +0.74 +/- 0.02;
23.92, 11.09 +/- 0.05, +1.00 +/- 0.06; 25.02, 11.22 +/- 0.04, +1.05
+/- 0.04.

1993 April 26                  (5775)            Daniel W. E. Green

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