We aim at characterising the structure of the gas and dust around the high mass X-ray binary GX 301–2 , a highly obscured X-ray binary hosting a hypergiant star and a neutron star , in order to better constrain its evolution .
We used Herschel PACS to observe GX 301–2 in the far infrared and completed the spectral energy distribution of the source using published data or catalogs , from the optical to the radio range ( 0.4 to 4 \times 10 ^ { 4 } \mathrm { \mu } m ) .
GX 301–2 is detected for the first time at 70 and 100 \mathrm { \mu } m. We fitted different models of circumstellar environments to the data .
All tested models are statistically acceptable , and consistent with a hypergiant star at \sim 3 kpc .
We found that the addition of a free-free emission component from the strong stellar wind is required and could dominate the far infrared flux .
Through comparisons with similar systems and discussion on the estimated model parameters , we favour a disk-like circumstellar environment of \sim 8 AU that would enshroud the binary system .
The temperature goes down to \sim 200 K at the edge of the disk , allowing for dust formation .
This disk is probably a rimmed viscous disk with an inner rim at the temperature of the dust sublimation temperature ( \sim 1 500 K ) .
The similarities between the hypergiant GX 301–2 , B [ e ] supergiants and the highly obscured X-ray binaries ( in particular IGR J16318–4848 ) are strengthened .
GX 301–2 might represent a transition stage in the evolution of massive stars in binary systems , connecting supergiant B [ e ] systems to luminous blue variables .