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IAUC 8112: 2003df; IGR J17464-3213 = XTE J17464-3213

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                                                  Circular No. 8112
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
URL http://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)

     Further to IAUC 8111, W. M. Wood-Vasey, G. Aldering, and P.
Nugent report the discovery of an apparent supernova (mag 20.3) on
unfiltered NEAT images taken during Mar. 9.47-9.49 UT.  The new
object is located at R.A. = 12h07m31s.36, Decl. = +26o57'36".2
(equinox 2000.0), which is 2" west and 8" north of the center of
the apparent host galaxy.  Additional magnitudes for SN 2003df from
NEAT images:  2002 May 4.15, [21.5; 2003 Mar. 21.45, 20.7; Apr.
8.15, 20.7.

IGR J17464-3213 = XTE J17464-3213
     D. Baba and T. Nagata, Nagoya University, on behalf of the
Infrared Survey Facility and Simultaneous Three-color Infrared
Imager for Unbiased Survey teams of Nagoya University and the
National Astronomical Observatory of Japan; I. Iwata and T. Kato,
Kyoto University; and H. Yamaoka, Kyushu University, report on
near-infrared (J, H, K_s) imaging of the field of the x-ray
transient IGR J17464-3213.  Two distinct infrared sources exist
within 2" of the radio counterpart (IAUC 8105); the northeast one
(with magnitudes K_s = 13.9 +/- 0.2 on Apr. 5.97 UT and K_s = 13.6
+/- 0.2 on Apr. 6.97) is not visible on public 2MASS images, and
the southwest one has similar brightness to the source on the 2MASS
image.  Given the proximity to the radio counterpart and the
apparent absence on the 2MASS images, the northeast source (at R.A.
= 17h46m15s.57, Decl. = -32o14'01".1, equinox 2000.0; from 34 2MASS
reference stars; rms error 0".1) is likely to be the infrared
counterpart of IGR J17464-3213.
     M. P. Rupen, A. J. Mioduszewski, and V. Dhawan, National Radio
Astronomy Observatory (NRAO), report a strong radio flare from this
x-ray transient and blackhole candidate (IAUC 8105).  Observations
with the Very Large Array (VLA) on Apr. 6 and 8 UT show that the
source increased in flux density by almost a factor 5 at 4.9 GHz,
from 20.1 +/- 0.3 to 96 +/- 2 mJy.  The radio spectrum also changed
significantly, from flattish (optically thick) on Apr. 6 to falling
with frequency (optically thin) on Apr. 8, with flux densities
varying from 19.5 +/- 0.3 to 68 +/- 2 mJy at 8.5 GHz, 20 +/- 1 to
54 +/- 2 mJy at 14.9 GHz, 22 +/- 2 to 51 +/- 2 mJy at 22.5 GHz, and
17 +/- 3 to 42 +/- 4 mJy at 43.4 GHz.  The Apr. 8 spectrum, in
particular, is not well fit by a single power law, in the sense
that the flux density is too high at the highest frequencies.  This
suggests the existence of several overlapping components (e.g., an
extended jet and a compact core) and may indicate that another
flare is on the way.

                      (C) Copyright 2003 CBAT
2003 April 8                   (8112)            Daniel W. E. Green

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