Radio detections of SAX J1808.4-3658
ATel #524; M. P. Rupen (NRAO/GSFC), V. Dhawan, A. J. Mioduszewski (NRAO)
on 17 Jun 2005; 20:16 UT
Credential Certification: Michael P. Rupen (mrupen@nrao.edu)
Subjects: Radio, Optical, X-ray, Binary, Neutron Star, Transient, Pulsar
Very Large Array (VLA) observations of the accreting millisecond pulsar
SAX J1808.4-3658 (see ATels #505, #506, #507, #511, #513, #515, #517)
have given results as follows (the 4 June measurement is taken from the
ATCA, as given in ATel #513, and is included here for comparison):
| Date |
4.86 GHz |
8.46 GHz |
| 2 June 2005 |
... |
[0.15 +/- 0.09 mJy/beam] |
| 4 June 2005* |
[ +/- 0.22 mJy/beam] |
[ +/- 0.30 mJy/beam] |
| 7 June 2005 |
0.35 +/- 0.09 mJy |
... |
| 11 June 2005 |
0.39 +/- 0.07 mJy |
... |
| 16 June 2005 |
[0.14 +/- 0.07 mJy/beam]
| 0.44 +/- 0.07 mJy
|
Here VLA non-detections are reported (within brackets) as the nominal flux
density at the location of the source, +/- the rms noise. Noise estimates
are based on measurements in source-free regions of the images.
The radio spectrum is only poorly constrained by these data, being
alpha= 2.0 +/- 1.0 (flux density going as nu^alpha) on June 16. Radio
detections from previous outbursts (e.g., Gaensler, Stappers, & Getts 1999,
ApJ 522, L117) suggest this is synchrotron emission, but we cannot yet
confirm that in this case. Further radio observations, covering a wider
range of frequencies, are planned.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc.
