We examine the mid-infrared fluxes and spectral energy distributions for metal-poor stars with iron abundances [ Fe/H ] \lesssim - 5 , as well as two CEMP-no stars , to eliminate the possibility that their low metallicities are related to the depletion of elements onto dust grains in the formation of a debris disk .
Six out of seven stars examined here show no mid-IR excess .
These non-detections rule out many types of circumstellar disks , e.g .
a warm debris disk ( T \leq 290 K ) , or debris disks with inner radii \leq 1 AU , such as those associated with the chemically peculiar post-AGB spectroscopic binaries and RV Tau variables .
However , we can not rule out cooler debris disks , nor those with lower flux ratios to their host stars due to , e.g .
a smaller disk mass , a larger inner disk radius , an absence of small grains , or even a multicomponent structure , as often found with the chemically peculiar Lambda Bootis stars .
The only exception is HE0107-5240 , for which a small mid-IR excess near 10 microns is detected at the 2- \sigma level ; if the excess is real and associated with this star , it may indicate the presence of ( recent ) dust-gas winnowing or a binary system .