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IAUC 6934: 1998cl; XTE J1748-288; C/1998 J1

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                                                 Circular No. 6934
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)


SUPERNOVA 1998cl IN MARKARIAN 261
     Michael Schwartz, Cottage Grove, OR, reports the discovery of
an apparent supernova (mag about 17) located at R.A. = 13h29m59s.8,
Decl. = +75o34'09".0 (equinox 2000.0), which is about 5" west and
1" north of Markarian 261 (whose nucleus is ill-defined) on
unfiltered CCD frames taken with the 0.35-m Tenagra I automated
supernova patrol telescope on June 3.28 UT.  The object is also
present with unchanged brightness on a frame taken with the same
equipment on June 6.26.  The object does not appear on an
unfiltered CCD image taken with the same equipment on 1997 July
7.33, and the star is not present on second Palomar Sky Survey
plates.


XTE J1748-288
     T. Strohmayer and F. E. Marshall, Goddard Space Flight Center,
on behalf of the RXTE Science Operations Center, report an improved
position for this x-ray transient (IAUC 6932) of R.A. = 17h48m08s,
Decl. = -28o29'.2 (equinox 2000.0) with an estimated uncertainty of
1' based on scans across the source with the Proportional Counter
Array on the Rossi X-ray Timing Explorer on June 5.13 UT.  The
observed 2-10-keV flux of about 600 mCrab indicates a continued
brightening of the source.
     R. M. Hjellming and M. P. Rupen, National Radio Astronomy
Observatory (NRAO); and A. J. Mioduszewski, Joint Institute for
VLBI in Europe and NRAO, report:  "Very Large Array observations on
June 7.40 UT of the field of XTE J1748-288 show the presence of an
unresolved radio source with flux densities of 50 +/- 3 and 28 +/-
2 mJy at 1.46 and 4.86 GHz, respectively.  Its position is R.A. =
17h48m05s.06, Decl. = -28o28'25".8  (equinox 2000.0; uncertainty
0".6), which is 1' from the center of the 1' uncertainty region for
XTE J1748-288 (see above).  It is a candidate for the radio
counterpart of the x-ray transient because it is much stronger than
the usual background radio source, but variability still needs to
be established."


COMET C/1998 J1 (SOHO)
     J. Crovisier, D. Bockelee-Morvan, P. Colom, and E. Gerard,
Observatoire de Paris-Meudon; and N. Biver, Institute for Astronomy,
University of Hawaii, report observations of OH 18-cm lines with
the Nancay radio telescope around the time of the outburst of the
comet (cf. IAUC 6926).  The OH production rates were as follows, in
units of 10E29 molecules/s:  June 1.6 UT, 3; 2.6, 5; 3.6, 4; 4.6, 3.

                      (C) Copyright 1998 CBAT
1998 June 8                    (6934)            Daniel W. E. Green

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