Central Bureau for Astronomical Telegrams
IAUC 6972: 1998cy, 1998cz, 1998da, 1998db, 1998dc; XTE J2123-058
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Circular No. 6972
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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SUPERNOVAE 1998cy, 1998cz, 1998da, 1998db, 1998dc
N. Regnault and O. Perdereau, Laboratoire de l'Accelerateur
Lineaire, Universite de Paris-Sud, on behalf of the EROS
collaboration (cf. IAUC 6762, 6904), report the discovery of five
apparent supernovae discovered in the course of their automated
supernova search with the 1-m Marly telescope (+ two 1-deg**2 CCD
cameras) at the European Southern Observatory:
SN Date UT R.A. (2000.0) Decl. V Offset
1998cy May 20 14h02m42.82 - 5 45'05.7 19.5: near center
1998cz May 21 12 03 06.50 -12 37 41.5 18.5: near center
1998da July 1 0 27 13.76 -39 25 25.6 20.5: 2".4 W, 1".2 S
1998db July 1 22 55 54.64 -39 26 29.8 19.4: near center
1998dc July 5 22 20 16.10 -44 33 56.1 19.5: 24".6 W, 3".9 N
SN 1998cz appeared in a frame constructed from the difference
between CCD frames taken on 1997 Feb. 9 and 1998 May 21, and it was
confirmed on frames taken on May 26. Likewise, SNe 1998cy, 1998da,
1998db, and 1998dc were not present on CCD frames taken on 1997 Feb.
3, 1997 Oct. 5, 1997 Oct. 22, and 1996 Oct. 8, respectively, and
they were confirmed on frames taken on 1998 May 26, July 2, July 2,
and July 6.
XTE J2123-058
J. A. Tomsick, J. Kemp, and J. P. Halpern, Columbia
University; and D. Hurley-Keller, University of Michigan, report on
the orbital period of this x-ray transient (IAUC 6955, 6958) from
photometry of its optical counterpart (IAUC 6957): "We obtained V-
band data at the MDM Observatory on June 30-July 4, and on the Kitt
Peak 0.9-m telescope on July 15 and 16. Quasi-sinusoidal
variations of amplitude 0.9 mag are seen. The best-fitting period
is 5.957 +/- 0.003 hr. Times of minimum light reported by Casares
et al. (IAUC 6971) are consistent with this period, and enable us
to eliminate all of the 1-day aliased candidates, including their
proposed values, from consideration. The mean light curve thus
obtained is not characterized by narrow eclipses, but is similar to
the smooth modulation seen in many low-mass x-ray binary systems,
with a flat top lasting 0.25 cycle and a broad triangular minimum
lasting 0.75 cycle. An ephemeris for the time of minimum light is
HJD 2451009.888(3) + 0.2482(1)E. At maximum light, V has remained
at about 16.8 since discovery. We also see evidence for three
optical bursts of amplitude 0.3 mag or greater on June 30 and July
1."
(C) Copyright 1998 CBAT
1998 July 20 (6972) Daniel W. E. Green
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