We present the first maps of 4765-MHz OH masers in two star - forming regions Cepheus A and W75N , made with Multi-Element Radio Linked Interferometer Network .
In Cep A the emission has an arc - like structure of size 40 mas with a clear velocity gradient , and lies at the edge of H II region 3b .
Over a period of 8 weeks the maser diminished in intensity by a factor of 7 but its structure remained stable .
This structure coincides with a newly mapped 1720-MHz maser in Cep A within the positional error , and matches it in velocity .
No emission of any other ground state or 4.7-GHz excited OH transitions was detected in the 4765/1720-MHz region .
The 1720-MHz line exhibits Zeeman splitting that corresponds to a magnetic field strength of - 17.3 mG .
In W75N the excited 4765-MHz OH maser has a linear structure of size 45 mas with a well defined velocity gradient , and lies at the edge of H II region VLA 1 .
This structure coincides in position and velocity with the 1720-MHz masers .
We conclude that in both sources the 4765-MHz emission coexists with 1720-MHz emission in the same volume of gas .
In such a case the physical conditions in these regions are tightly constrained by the maser - pumping models .