Further radio observations of XTE J1118+480
ATel #387; M. P. Rupen (NRAO/GSFC), V. Dhawan, A. J. Mioduszewski (NRAO)
on 13 Jan 2005; 21:50 UT
Credential Certification: Michael P. Rupen (mrupen@nrao.edu)
Subjects: Radio, Optical, X-ray, Binary, Black Hole, Transient
Very Large Array (VLA) observations of the black hole candidate binary
XTE J1118+480 (e.g., ATEL #383, ATEL #384, ATEL #386) confirm
Pooley's report of renewed radio activity (ATEL #385). All data were
observed on MJD 53383.32-.35, overlapping the end of Pooley's observations.
A preliminary reduction gives the following spectrum:
- 4.86 GHz: 5.8 +/- 0.1 mJy
- 8.46 GHz: 9.5 +/- 0.1 mJy
- 14.94 GHz: 8.5 +/- 0.5 mJy
- 22.46 GHz: 10.1 +/- 1.1 mJy
- 43.34 GHz: > 5.8 +/- 1.0 mJy
The uncertainties are 1sigma based on the rms noise in the map. The overall
spectrum is roughly flat above 8 GHz, consistent with Pooley's 15 GHz datum,
and as expected for a source in the low/hard state. The sharply rising
spectrum from 4.9 to 8.5 GHz (nu^0.89+/-0.04) is more surprising, and may
suggest an additional source of absorption, e.g., from ionized gas near
the source. Further radio observations are planned.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc.
