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IAUC 6375: 1996N; GRO J1744-28

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                                                  Circular No. 6375
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
Phone 617-495-7244/7440/7444 (for emergency use only)

     S. D. Van Dyk, University of California at Berkeley; R. A.
Sramek, National Radio Astronomy Observatory (NRAO); K. W. Weiler
and M. J. Montes, Naval Research Laboratory; and N. Panagia, Space
Telescope Science Institute and European Space Agency, report:
"Observations of SN 1996N made on Apr. 1.96 UT with the NRAO's Very
Large Array telescope show a probable detection at wavelength 3.6
cm (8.4 GHz) of a source with a flux density of 0.15 +/- 0.03 mJy
at R.A. = 3h38m55s.374, Decl. = -26o20'03".96 (equinox J2000.0; +/-
0".2 in each coordinate).  This is coincident to within 1" with an
optical position for the supernova of R.A. = 3h38m55s.31, Decl. =
-26o20'04".1, measured by Van Dyk from a B-band image made on Apr.
2.02 by P. Ugarte and N. Suntzeff at Cerro Tololo.  Since SN 1996N
was reported to be apparently two weeks past optical maximum on
Mar. 23 (IAUC 6351), we are very likely detecting optically thin
radio emission (see Weiler et al. 1986, Ap.J. 301, 790).  Radio
monitoring is underway at this and other wavelengths."

GRO J1744-28
     J. E. Morrison and S. Roser, Astronomisches-Rechen-Institut,
Heidelberg, write:  "Cole et al. (IAUC 6356) report on positions of
possible optical counterparts for the radio source GRO J1744-28
based on HST-GSC reference positions.  They find an offset of 0".9
between the radio coordinates of GRO J1744-28 and their star 'a' or
'C'.  They discuss the possibility of a GSC-PPM systematic offset,
but find only -0".333 in R.A. and -0".024 in Decl., insufficient to
account for the 0".9 radio-optical offset.  We have completed GSC
1.2, a new astrometric reduction of GSC 1.1 onto the PPM system
removing plate and magnitude dependent systematics.  In a small
field around the position of the radio source, we find 13 GSC stars
between 17h44m and 17h45m, and -28o50' and -28o40', for which we
have R.A.(GSC1.2-GSC1.1) = -0".038 and Decl.(GSC1.2-GSC1.1) =
+0".45.  With these corrections, the offset between the radio
position and the infrared position of 'C' reduces to 0".5,
(radio-'C' = +0".18 in R.A., +0".45 in Decl.), which may possibly
be caused by the offset between the PPM and the radio system.
This strengthens the hypothesis that 'C' in the infrared and 'a' in
the optical are the counterparts of GRO J1744-28."

                      (C) Copyright 1996 CBAT
1996 April 9                   (6375)            Daniel W. E. Green

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