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IAUC 6157: 1995J; AL Com

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                                                  Circular No. 6157
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
Phone 617-495-7244/7440/7444     TWX 710-320-6842 ASTROGRAM CAM

     W. Johnson, Anza, CA, reports his discovery of an apparent
supernova located about 30" east and 30" north of the center of NGC
4512 (R.A. = 12h32m.6, Decl. = +63o54', equinox 2000.0); the
unfiltered CCD magnitude of SN 1995J on the two discovery frames,
taken on Apr. 4.45 and 4.46 UT, is about 16.5.  Nothing appears at
this position on the CCD Atlas of Deep Sky Objects (Buil and
Thouvenot 1991, Sky Publ.), though there is a foreground star of
mag about 16 located about 10" west and 25" south of the galaxy's
center.  P. Garnavich, P. Challis, and R. Kirshner, Center for
Astrophysics, report that an image taken by R. Jansen at the 1.2-m
telescope on Mt. Hopkins on Apr. 7.2 clearly shows a new star
(Johnson R magnitude 16.4 +/- 0.1) at the position reported by
Johnson; no object appears on the Palomar sky survey prints at that

     J. Patterson, Department of Astronomy, Columbia University,
communicates:  "Photometry of AL Com on Apr. 5/6 by D. Harvey,
Center for Basement Astrophysics-West, reveals periodic waves of
period 81.8 +/- 1.4 min, with substantial power also at the first
and second harmonics.  These are likely to be some version of
'superhumps'.  The amplitude was 0.1 mag, but may grow in the days
to come.  The waveform was highly variable and suggested the
possibility of multiple (noncommensurate) periods.  Finding the
correct periodic structure in these cases depends crucially on
amassing a dense data stream, and we eagerly seek collaboration
with observers who can contribute time-series photometry of this
star (V-band or unfiltered).  I can be reached at telephone
212-854-3276 (U.S.A.) or via e-mail at jop@carmen.phys.columbia.edu."
     J. A. DeYoung, U.S. Naval Observatory, reports:  "Time-resolved
Kron-Cousins I-band photometry of AL Com with the 0.61-m USNO
reflector in Washington, DC, on Apr. 6.010-6.094 and 7.016-7.158 UT
shows a modulation consistent with a period of 81.2 min.  A linear
least-squares fit to the five available minima gives the following
HJD ephemeris for minimum phase:  2449813.527 (+/-0.002) + 0.0564
(+/-0.0001)E.  The peak-to-peak amplitudes on Apr. 6 and 7 were
0.11 +/- 0.02 and 0.06 +/- 0.02 mag, respectively.  In addition,
there is phase-repeatable structure in the light curves."

1995 April 7                   (6157)            Daniel W. E. Green

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