  Convincing evidence for long-term variations in the emission properties of
the anomalous X-ray pulsar 1RXS J170849.0-400910 has been gathered in the last
few years. In particular, and following the pulsar glitches of 1999 and 2001,
XMM-Newton witnessed in 2003 a decline of the X-ray flux accompanied by a
definite spectral softening. This suggested the existence of a correlation
between the luminosity and the spectral hardness in this source, similar to
that seen in the soft gamma-repeater SGR 1806-20. Here we report on new Chandra
and Swift observations of 1RXS J170849.0-400910 performed in 2004 and 2005,
respectively. These observations confirm and strengthen the proposed
correlation. The trend appears to have now reversed: the flux increased and the
spectrum is now harder. The consequences of these observations for the twisted
magnetosphere scenario for anomalous X-ray pulsars are briefly discussed.
