To test alternative hypotheses for the behavior of KIC 8462852 , we obtained measurements of the star over a wide wavelength range from the UV to the mid-infrared from October 2015 through December 2016 , using Swift , Spitzer and at AstroLAB IRIS .
The star faded in a manner similar to the long-term fading seen in Kepler data about 1400 days previously .
The dimming rate for the entire period reported is 22.1 \pm 9.7 milli-mag yr ^ { -1 } in the Swift wavebands , with amounts of 21.0 \pm 4.5 mmag in the groundbased B measurements , 14.0 \pm 4.5 mmag in V , and 13.0 \pm 4.5 in R , and a rate of 5.0 \pm 1.2 mmag yr ^ { -1 } averaged over the two warm Spitzer bands .
Although the dimming is small , it is seen at \gtrsim 3 \sigma by three different observatories operating from the UV to the IR .
The presence of long-term secular dimming means that previous SED models of the star based on photometric measurements taken years apart may not be accurate .
We find that stellar models with T _ { eff } = 7000 - 7100 K and A _ { V } \sim 0.73 best fit the Swift data from UV to optical .
These models also show no excess in the near-simultaneous Spitzer photometry at 3.6 and 4.5 \mu m , although a longer wavelength excess from a substantial debris disk is still possible ( e.g. , as around Fomalhaut ) .
The wavelength dependence of the fading favors a relatively neutral color ( i.e. , R _ { V } \gtrsim 5 , but not flat across all the bands ) compared with the extinction law for the general ISM ( R _ { V } = 3.1 ) , suggesting that the dimming arises from circumstellar material .