Circular No. 6855
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)


XTE J0421+560
     D. Smith and R. Remillard, Massachusetts Institute of
Technology; and J. Swank, T. Takeshima, and E. Smith, Goddard Space
Flight Center, NASA, report: "The RXTE All-Sky Monitor has detected
a bright and rapidly rising x-ray transient, which we designate XTE
J0421+560.  The best-fit position is R.A. = 4h21m.01, Decl. =
+56o03'.5 (equinox 2000.0), with an error radius (90-percent
confidence) of 4'.  The ASM countrate (2-12 keV) was below 40 mCrab
(at 3 sigma) on Mar. 31.36 UT, rising rapidly thereafter to 139
(Mar. 31.64), 504 (31.77), and 1880 mCrab (Apr. 1.04).  An RXTE PCA
observation, which began on Apr. 1.08, confirms the presence of a
new source with a flux near 2 Crab.  The ASM spectrum appears very
hard, but the PCA light curve shows no obvious pulsations at
periods longer than 0.25 s.  Observations at other wavelengths are
urgently needed."


GRB 980329
      A. Guarnieri, Universita di Bologna; G. Clementini and G.
Valentini, Osservatorio Astronomico di Bologna; A. Castro-Tirado
and J. Gorosabel, Laboratorio de Astrofisica Espacial y Fisica
Fundamental, Madrid; and A. Pedrosa, Centro de Astrofisica da
Universidade do Porto, report on behalf of a large collaboration:
"R-band images containing the error box for 1SAX J0702.6+3850 (IAUC
6854) were obtained on Mar. 29.79 and 30.81 UT at the 1.52-m
telescope at Bologna Observatory, on Mar. 29.90, 30.91, and 31.95
at the 1.0-m Jacobus Kapteyn Telescope at La Palma, and on Mar.
31.02 and 31.92 at the OAN 1.52-m telescope at the German-Spanish
Calar Alto Observatory.  No variable object is found down to R =
22; any variation was smaller than 0.3 mag.  Observations at other
wavelengths, especially infrared, are encouraged."


NOVA SAGITTARII 1998
     Further visual magnitude estimates:  Mar. 27.33 UT, 8.4 (J. G.
de S. Aguiar, Campinas, Brazil); 30.138, 9.0 (K. Hornoch,
Lelekovice, Czech Republic); 30.177, 9.2 (P. Schmeer, Bischmisheim,
Germany); 30.213, 9.2 (A. Pereira, Cabo da Roca, Portugal); 31.124,
8.9 (Hornoch); 31.130, 9.0 (M. Plsek, Lelekovice, Czech Republic);
Apr. 1.194, 8.8 (Pereira).

                      (C) Copyright 1998 CBAT
1998 April 1                   (6855)            Daniel W. E. Green