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IAUC 7428: Poss. RADIO SN IN NGC 6240; 2000cj; AX J0051.6-7311

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                                                  Circular No. 7428
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)


POSSIBLE RADIO SUPERNOVA IN NGC 6240
     J. F. Gallimore, National Radio Astronomy Observatory, reports
the discovery of a possible radio supernova in the galaxy merger
NGC 6240 in 2.3-GHz (13-cm) Very Long Baseline Array observations
on 1999 Aug. 15 and 2000 Apr. 24.  The two parent galaxy nuclei
were detected at R.A. = 16h52m58s.9242, Decl. = +2 24'04".771 and
(end figures) 58s.8902, 03".334 (equinox 2000.0; absolute
astrometry accurate to 0".2; relative astrometry accurate to
0".001).  The radio flux densities of the parent nuclei did not
change between the two dates.  The possible radio supernova, which
dimmed from 1.3 to 0.5 mJy between the two dates, was detected at
position end figures 58s.8998, 03".591, which is 0".144 east and
0".257 north of the southern nucleus.  The radio luminosity of this
possible supernova is comparable to the very luminous radio
supernovae detected in Arp 220 by Smith et al. (1998, Ap.J. 493,
L17).  Gallimore adds that only two nuclear sources were present in
earlier MERLIN imagery, obtained by himself at 5 GHz on 1998 Jan.
12 (limit < 1 mJy, 3-sigma; 10-hr observation) and by R. Beswick,
NRAL, Jodrell Bank, at 1.4 GHz on 1996 Jan. 31 (confusion-limited;
flux density < 3 mJy).  SN 2000bg (cf. IAUC 7392) is also in NGC
6240.


SUPERNOVA 2000cj IN NGC 6753
     N. Suntzeff, Cerro Tololo Interamerican Observatory (CTIO),
reports that his reduction of a spectrum (range 450-670 nm,
resolution 1900), obtained by A. Kundu (University of Virginia) on
May 20.3 UT with the Las Campanas Swope 1-m telescope, shows that
SN 2000cj (cf. IAUC 7425) is a type-Ia supernova very close to
maximum light.


AX J0051.6-7311
     K. Torii, National Space Development Agency of Japan; and J.
Yokogawa, K. Imanishi, and K. Koyama, Kyoto University, report that
an ASCA observation made during Apr. 11-17 detected coherent
pulsations of period 172.40 +/- 0.03 s from a new source in the
Small Magellanic Cloud, designated AX J0051.6-7311 and located at
R.A. = 0h51m37s.8, Decl. = -73o11'01" (equinox 2000.0; error radius
1'.5).  The spectrum is characterized by a flat power-law function
with photon index 0.9 and x-ray flux 1.4 x 10**-12 erg cm**-2 s**-1
(0.7-10 keV).  Within the error region of AX J0051.6-7311 is a
ROSAT source known as RX J0051.9-7311 (Cowley et al. 1997, PASP
109, 21), having a Be star an an optical counterpart.

                      (C) Copyright 2000 CBAT
2000 May 24                    (7428)            Daniel W. E. Green

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