Identifying planets around O-type and B-type stars is inherently difficult ; the most massive known planet host has a mass of only about 3 M _ { \odot } .
However , planetary systems which survive the transformation of their host stars into white dwarfs can be detected via photospheric trace metals , circumstellar dusty and gaseous discs , and transits of planetary debris crossing our line-of-sight .
These signatures offer the potential to explore the efficiency of planet formation for host stars with masses up to the core-collapse boundary at \approx 8 M _ { \odot } , a mass regime rarely investigated in planet formation theory .
Here , we establish limits on where both major and minor planets must reside around \approx 6 M _ { \odot } -8 M _ { \odot } stars in order to survive into the white dwarf phase .
For this mass range , we find that intact terrestrial or giant planets need to leave the main sequence beyond approximate minimum star-planet separations of respectively about 3 and 6 au .
In these systems , rubble pile minor planets of radii 10 , 1.0 , and 0.1 km would have been shorn apart by giant branch radiative YORP spin-up if they formed and remained within , respectively , tens , hundreds and thousands of au .
These boundary values would help distinguish the nature of the progenitor of metal-pollution in white dwarf atmospheres .
We find that planet formation around the highest mass white dwarf progenitors may be feasible , and hence encourage both dedicated planet formation investigations for these systems and spectroscopic analyses of the highest mass white dwarfs .