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IAUC 6926: 1998bu; 1998cf; XTE J2012+381; C/1998 J1

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                                                 Circular No. 6926
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html
Phone 617-495-7244/7440/7444 (for emergency use only)


SUPERNOVA 1998bu IN NGC 3368
     B. E. Schaefer, Yale University, reports the following
magnitudes obtained with the 3.5-m WIYN telescope and based on ten
Landolt comparison stars:  May 23.18 UT, B = 12.34 +/- 0.04, V =
11.92 +/- 0.03; 26.14, 12.44 +/- 0.04, 11.94 +/- 0.03.  Schaefer
remarks:  "Using these and other reported magnitudes (IAUC 6899,
6902, 6905, 6921), standard-template fits to the light curves of
type-Ia supernovae (Schaefer 1996, Ap.J. 460, L19) suggest that
peak magnitudes occurred on May 21.0 +/- 0.3, with B = 12.36 +/-
0.05, V = 11.93 +/- 0.04, and a decline rate in B from peak to 15
days later of 0.95 +/- 0.05."


SUPERNOVA 1998cf IN NGC 3504
     S. Ryder, Joint Astronomy Centre, reports that he obtained
images in J, H, and K of the nucleus of NGC 3504 on Apr. 23.3 UT
with the U.K. Infrared Telescope (+ IRCAM3).  These show SN 1998cf
(cf. IAUC 6914) at J = 14.9, H = 14.4, and K = 14.2, indicating
that it was already fading in the near-infrared.


XTE J2012+381
     G. G. Pooley, Mullard Radio Astronomy Observatory, Cambridge,
reports:  "Ryle Telescope observations at 15 GHz show that the
radio source reported by Hjellming et al. IAUC 6924) is variable at
15 GHz.  No detection was made on May 28.2 (rms 2 mJy) or 29.2 UT
(rms 0.3 mJy).  On May 30.3 and June 2.18, the flux was 1.6 +/- 0.5
and 3.2 +/- 0.6 mJy (means over 2.5 and 5.6 hr), respectively."


COMET C/1998 J1 (SOHO)
     W. Liller, Vina del Mar, Chile, provides the following V
magnitudes (estimated +/- 0.04) of the inner coma (square 75" x 75"
aperture):  May 28.962 UT, 6.87; 29.957, 6.96; 31.967, 5.87
(saturated image).  Nearly all of the brightness increase took
place in the inner 20" of the coma.
     This outburst has also been noted by visual observers.
Selected visual m_1 estimates:  May 26.37 UT, 5.1 (R. McNaught,
Bugaldie, N.S.W., Australia, naked eye); 29.34, 5.0 (D. A. J.
Seargent, The Entrance, N.S.W., naked eye); 30.70, 5.3 (T. Cooper,
Bredell, Kempton Park, S. Africa, 10x50 binoculars); June 1.35, 3.7
(G. J. Garradd, Loomberah, N.S.W., naked eye); 1.40, 3.4 (M.
Mattiazzo, Wallaroo, S. Australia, 7x50 binoculars).

                      (C) Copyright 1998 CBAT
1998 June 2                    (6926)            Daniel W. E. Green

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