We obtained high-resolution spectra and multicolor photometry of V1082 Sgr to study the donor star in this 20.8 hr orbital period binary , which is assumed to be a detached system .
We measured the rotational velocity ( v \sin i = 26.5 \pm 2.0 km s ^ { -1 } ) , which , coupled with the constraints on the white dwarf mass from the X-ray spectroscopy , leads to the conclusion that the donor star barely fills 70 % of its corresponding Roche lobe radius .
It appears to be a slightly evolved K2-type star .
This conclusion was further supported by a recently published distance to the binary system measured by the Gaia mission .
At the same time , it becomes difficult to explain a very high ( > 10 ^ { -9 } Â { M _ { \odot } ~ { } yr ^ { -1 } } ) mass transfer and mass accretion rate in a detached binary via stellar wind and magnetic coupling .