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IAUC 7300: XTE J1739-285; 1999ek; 1999em; C/1999 S4

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                                                  Circular No. 7300
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  ISSN 0081-0304
Phone 617-495-7244/7440/7444 (for emergency use only)


XTE J1739-285
     C. B. Markwardt, University of Maryland and Goddard Space
Flight Center (GSFC); F. E. Marshall and J. H. Swank, GSFC; and Wei
Cui, Massachusetts Institute of Technology, write:  "RXTE PCA scans
of the galactic-center region on Oct. 19.4 UT revealed a transient
x-ray source, designated XTE J1739-285.  The best-fitting position
for the source is R.A. = 17h39m.9, Decl. = -28o29' (equinox 2000.0;
estimated uncertainty about 5', due primarily to nearby
contaminating sources in the collimator field-of-view).
Approximate x-ray fluxes (with uncertainties of < 2 percent)
derived from PCA scans, in units of mCrab in the band 2-10 keV:
Oct. 19.4, 77; 21.2, 66; 24.4, 170; 27.1, 200; 30.2, 157.  The
source is distinct from known persistent x-ray sources SLX 1737-282
and GRS 1734-292.  A pointed PCA exposure of 1400 s on Oct. 29.6
revealed no detectable quasiperiodic oscillations or high-frequency
variability.  Follow-up observations by imaging instruments are
encouraged."


SUPERNOVA 1999ek IN UGC 3329
     S. Jha, P. Challis, P. Garnavich, and R. Kirshner, Harvard-
Smithsonian Center for Astrophysics, report that a spectrum,
obtained by M. Calkins with the F. L. Whipple Observatory 1.5-m
telescope (+ FAST spectrograph) on Oct. 30.46 UT, shows SN 1999ek
to be a type-Ia supernova near maximum light.  Adopting the NED
recession velocity for UGC 3329 of 5253 km/s yields an expansion
velocity for Si II (rest 635.5 nm) of 9800 km/s.  The estimated age
of the supernova from the spectral features as above is 1.2 +/- 3
days after maximum light.


SUPERNOVA 1999em IN NGC 1637
     CCD magnitude by D. Hanzl, Brno, Czech Republic:  Nov. 1.033
UT, V = 14.32 +/- 0.03.


COMET C/1999 S4 (LINEAR)
     Total visual magnitude estimates:  Oct. 31.79 UT, 14.6 (K.
Hornoch, Lelekovice, Czech Republic, 0.35-m reflector); Nov. 2.32,
14.1 (A. Hale, Cloudcroft, NM, 0.41-m reflector).

                      (C) Copyright 1999 CBAT
1999 November 3                (7300)            Daniel W. E. Green

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