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IAUC 6993: 1998dm; XTE J2123-058; C/1998 M2

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                                                 Circular No. 6993
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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SUPERNOVA 1998dm IN MCG -01-4-44
     M. Modjaz, T. Shefler, E. Halderson, J. Y. King, W. D. Li,
R. R. Treffers, and A. V. Filippenko, University of California at
Berkeley, report their discovery of an apparent supernova during
the course of the Lick Observatory Supernova Search (cf. IAUC 6627)
with the 0.8-m Katzman Automatic Imaging Telescope (KAIT).  SN
1998dm was found and confirmed on unfiltered images taken on Aug.
22.5 (mag about 16.8) and 23.4 UT (mag about 16.5).  The new object
is located at R.A. = 1h26m13s.97, Decl. = -6o06'14".0 (equinox
2000.0), which is  about 13".8 west and 37".0 south of the nucleus
of MCG -01-4-44 (= UGCA 17).  A KAIT image obtained on Aug. 17.5
shows no star at this position (limiting mag about 18.5).

XTE J2123-058
     C. Zurita and J. Casares, Instituto de Astrofisica de Canarias
(IAC); and R. I. Hynes, University of Sussex, communicate:  "New R-
band images of the x-ray transient XTE J2123-058 (IAUC 6955) have
been obtained on Aug. 2-16 with the 0.8-m IAC80 telescope at the
Observatorio del Teide.  Following the behavior of the XTE/ASM
lightcurve, the system declined optically from the beginning of
August at approximately 0.1 mag/day.  The average magnitude on Aug.
16 was R = 19.1.  As noted by Tomsick et al. (IAUC 6957), the
object is visible on a digitized U.K. Schmidt plate.  We estimate a
photographic magnitude fainter than 20 from this image, indicating
that the object is likely still several magnitudes above its
quiescent state.  Despite the drop in luminosity, we observe a
dramatic increase in orbital modulation, the current amplitude
being 1.4 mag.  Two full cycles were recorded on Aug. 15 and 16,
showing an almost sinusoidal modulation, consistent with x-ray
heating of the companion star.  We also note two narrow 0.2-mag
dips superposed at phases 0 and 0.5, which could be associated with
mutual eclipses between the companion star and accretion disc.  The
revised ephemeris is HJD 2451042.639(5) + 0.24821(3)E.  More
observations at other wavelengths are urgently required to follow
the evolution of the lightcurve of this unusual transient."

     Total visual magnitude estimates:  July 22.95 UT, 13.8 (R. J.
Bouma, Lattrop, The Netherlands, 0.40-m reflector); Aug. 10.87,
14.2 (M. Lehky, Hradec Kralove, Czech Republic, 0.42-m reflector);
19.99, 12.8 (J. Carvajal, Toledo, Spain, 0.32-m reflector); 22.93,
12.5 (Carvajal, Avila, Spain).

                      (C) Copyright 1998 CBAT
1998 August 23                 (6993)            Daniel W. E. Green

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