We present new thermal IR photometry and spectral energy distributions ( SEDs ) of eight classical Cepheids ( type I ) and three type II Cepheids , using VISIR thermal IR photometric measurements , supplemented with literature data .
We used the BURST mode of the instrument to get diffraction-limited images at 8.59 , 11.25 and 11.85 \mu m. The SEDs show a IR excess at wavelengths longer than 10 \mu \mathrm { m } in ten of the eleven stars .
We tentatively attribute these excesses to circumstellar emission created by mass loss from the Cepheids .
With some hypotheses for the dust composition , we estimated a total mass of the envelope ranging from 10 ^ { -10 } to 10 ^ { -8 } M _ { \odot } .
We also detect a spatially extended emission around AX Cir , X Sgr , W Sgr , Y Oph and U Car while we do not resolve the circumstellar envelope ( CSE ) for the other stars .
The averaged circumstellar envelope brightnesses relative to the stellar photosphere are \alpha ( \mathrm { AX~ { } Cir } ) = 13.8 \pm 2.5 \%, \alpha ( \mathrm { X~ { } Sgr } ) = 7.9 \pm 1.4 % \%, \alpha ( \mathrm { W~ { } Sgr } ) = 3.8 \pm 0.6 \%, \alpha ( \mathrm { Y~ { } Oph } ) = 15.1 \pm 1 % .4 \% and \alpha ( \mathrm { U~ { } Car } ) = 16.3 \pm 1.4 \% at 8.59 \mu m. With this study , we extend the number of classical Cepheids with detected CSEs from 9 to 14 , confirming that at least a large fraction of all Cepheids are experiencing significant mass loss .
The presence of these CSEs may also impact the future use of Cepheids as standard candles at near and thermal infrared wavelengths .