Renewed radio activity in H1743-322 = IGR J1746-3213 = XTE J17464-3213
ATel #314; M. P. Rupen, A. J. Mioduszewski, V. Dhawan (NRAO)
on 6 Aug 2004; 17:14 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Michael P. Rupen (mrupen@nrao.edu)
Subjects: Radio, Infra-Red, Optical, X-ray, Black Hole, Transient
Referred to by ATel #: 575
Very Large Array (VLA) observations of the black hole candidate binary
H1743-322 = IGR J1746-3213 = XTE J17464-3213 (e.g., ATEL #301, ATEL #304)
show renewed radio activity on 5 August 2004. Two sets of scans, from 01:18
to 01:34 and 03:34 to 03:46 UT, were consistent with a steady flux density
of 1.96 +/- 0.15 mJy at 4.86 GHz. Observations on 4 August 2004 from 05:21
to 05:29 UT gave no detection, with a nominal value at the source position of
0.14 +/- 0.17 mJy/beam at the same frequency. Based on past experience with
this and other sources, the radio rise probably corresponds to a state change
in the accretion disk, most directly reflected in a hardening of the on-going
X-ray flare.
During last year's outburst (e.g., ATEL #142) the source remained optically
thick in the radio for almost two weeks, then began a series of chaotic
radio flares. That slow, inverted-spectrum rise is very unusual among
X-ray binaries; assuming the source is currently beginning a similar outburst,
multi-wavelength observations would be extremely useful in understanding
this phase.
The best radio position for the core is:
17 46 15.5980 +/- 0.0050
-32 14 00.80 +/- 0.18
This is based primarily on data taken during the 2003 optically-thick rise,
with the positions of the phase calibrators corrected to those given in the
VLBA Calibrator Survey (VCS2 -- Fomalont et al. 2003). This position is
consistent with the core detected in November 2003, as well as the current
dectection. It represents an improved version of the radio position
reported in ATEL #
146, and is 0.36 arcsec east of the proposed infrared
counterpart (ATEL #
146; IAUC
8112 ). While this is nominally several times
the expected rms astrometric error, the radio source associated with the 2003
outburst was quite complex, with multiple components present on
most days, generally within half an arcsecond of the above core position.
These components probably correspond to short-lived ejecta flung out at
relativistic speeds from the core. The inverted radio spectrum during the
optically-thick rise suggests very strongly that the radio position is indeed
that of the core. This makes further infrared observations during the
current outburst especially important, since IR variability would provide the
most direct confirmation of the association.
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