The radio counterpart of IGR J00291+5934
ATel #361; Rob Fender (Southampton), Ger de Bruyn (ASTRON / Groningen),Guy Pooley (MRAO Cambridge), Ben Stappers (ASTRON)
on 7 Dec 2004; 15:18 UT
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Subjects: Radio, Optical, X-ray, Transient
We report further observations of the proposed radio counterpart to
the accreting millisecond X-ray pulsar IGR J00291+5934.
Following the report of a possible ~1.1 mJy radio counterpart at
15 GHz on 2004 Dec 4 (ATEL #355), further observations with the Ryle
Telescope (12 hr from 2004 Dec 05 13h41m UT) did not detect the source
with a 3-sigma upper limit of ~0.6 mJy.
A ~10hr observation with the Westerbork Synthesis Radio Telescope
(WSRT) (2004-12-06 14:45 UT --- 2004-12-07 00:58 UT) has detected a
radio source with a mean flux density of 250 +/- 35 microJy at 5 GHz,
with some possible evidence for fading during the run. The 5GHz WSRT
source lies within one arcsec of the proposed optical counterpart
(ATEL #354, ATEL #356).
The fading of the 15 GHz source combined with the positional
coincidence of the 5GHz radio source with the proposed optical
counterpart strongly suggests that this is the rapidly decaying radio
counterpart of IGR J00291+5934. The origin of the radio emission is
presumably the earlier transient production of a relativistic outflow.