We report on our Spitzer observations of the anomalous X-ray pulsar 4U 0142 + 61 , made following a large X-ray burst that occurred on 2007 February 7 .
To search for mid-infrared flux variations , four imaging observations were carried out at 4.5 and 8.0 \mu m with the Infrared Array Camera from February 14 to 21 .
No significant flux variations were detected , and the average fluxes were 32.1 \pm 2.0 \mu Jy at 4.5 \mu m and 59.8 \pm 8.5 \mu Jy at 8.0 \mu m , consistent with those obtained in 2005 .
The non-detection of variability is interesting in light of reported rapid variability from this source in the near-infrared , but consistent with the fact that the source already went back to its quiescent state before our observations began , as indicated by contemporaneous X-ray observations .
In order to understand the origin of the near-infrared variability , frequent , simultaneous multi-wavelength observations are needed .