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IAUC 6937: XTE J1748-288; 1998aq; 1998bu

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                                                 Circular No. 6937
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 J1748-288
     R. M. Hjellming, M. P. Rupen, and F. Ghigo, National Radio
Astronomy Observatory (NRAO); E. B. Waltman, Naval Research
Laboratory; and A. J. Mioduszewski, Joint Institute for VLBI in
Europe and NRAO, report:  "Very Large Array (VLA) and Green Bank
Interferometer (GBI) observations of the candidate for the radio
counterpart of XTE J1748-288 (IAUC 6934) show that the radio fluxes
on June 10 were factors of 3-4 above what was seen on June 7.  The
GBI showed preliminary fluxes at 2.25 and 8.3 GHz of about 110 and
about 50 mJy on June 10.19 UT.  At June 10.33, the VLA showed
preliminary fluxes of 160, 113, 90, 66, and 55 mJy at 1.46, 4.86,
8.46, 14.9, and 22.5 GHz, respectively.  This strong and
highly-variable radio behavior establishes that the source reported
on IAUC 6934 is the radio counterpart of the x-ray transient XTE
J1748-288."
     R. P. Fender and B. W. Stappers, Astronomical Institute 'Anton
Pannekoek', University of Amsterdam; and M. Wieringa and R. Wark,
Australia Telescope Compact Array (ATCA) Alert Team, report:  "We
have observed the proposed radio candidate to the x-ray transient
XTE J1748-288 (IAUC 6932, 6934) with ATCA between June 10.4 and
10.7 UT.  We measure peak flux densities of 115 +/- 10 and 100 +/-
10 mJy at 4.8 and 8.6 GHz, respectively.  The measurement at 4.8
GHz represents an increase in flux density at this frequency by a
factor of four in three days (IAUC 6934), thus strengthening the
association of the radio source with the x-ray transient.  If the
association is confirmed, this is the brightest new radio transient
since the superluminal jet source GRO J1655-40, and further
observations at all wavelengths are encouraged."


SUPERNOVA 1998aq IN NGC 3982
     CCD V magnitudes by D. Hanzl, Brno, Czech Republic (0.40-m
reflector; comparison stars from GSC): May 20.912 UT, 13.1; 28.915,
13.5; 29.940, 13.56; 31.947, 13.65; June 2.921, 13.67; 7.908, 14.0;
9.906, 13.90.


SUPERNOVA 1998bu IN NGC 3368
     Additional CCD photometry by Hanzl (cf. IAUC 6921): May 28.844
UT, V = 12.28 +/- 0.01, B-V = +0.64 +/- 0.02; 29.862, 12.38 +/-
0.01, +0.71 +/- 0.09; 31.873, 12.51 +/- 0.01, +0.75 +/- 0.02; June
2.872, 12.63 +/- 0.02, +0.73 +/- 0.03; 7.870, 12.84 +/- 0.02, -;
9.860, 12.94 +/- 0.01, +1.2 +/- 0.2.

                      (C) Copyright 1998 CBAT
1998 June 12                   (6937)            Daniel W. E. Green

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