  Recently, Diaz Trigo et al. reported an XMM-Newton detection of
relativistically Doppler-shifted emission lines associated with steep-spectrum
radio emission in the stellar-mass black hole candidate 4U 1630-47 during its
2012 outburst. They interpreted these lines as indicative of a baryonic jet
launched by the accretion disk. Here we present a search for the same lines
earlier in the same outburst using high-resolution X-ray spectra from the
Chandra High-Energy Transmission Grating Spectrometer. While our observations
(eight months prior to the XMM-Newton campaign) also coincide with detections
of steep spectrum radio emission by the Australia Telescope Compact Array, we
find no evidence for any relativistic X-ray emission lines. Indeed, despite
$\sim5\times$ brighter radio emission, our Chandra spectra allow us to place an
upper limit on the flux in the blueshifted Fe XXVI line that is
$\gtrsim20\times$ weaker than the line observed by Diaz Trigo et al. We explore
several scenarios that could explain our differing results, including
variations in the geometry of the jet or a mass-loading process or jet baryon
content that evolves with the accretion state of the black hole. We also
consider the possibility that the radio emission arises in an interaction
between a jet and the nearby ISM, in which case the X-ray emission lines might
be unrelated to the radio emission.
