Context : Disks are expected to dissipate quickly in binary or multiple systems .
Investigating such systems can improve our knowledge of the disk dispersal .
The triple system GW Ori , still harboring a massive disk , is an excellent target .

Aims : We study the young stellar system GW Ori , concentrating on its accretion/wind activity and disk properties .

Methods : We use high-resolution optical spectra of GW Ori to do spectral classification and derive the radial velocities ( RV ) .
We analyze the wind and accretion activity using the emission lines in the spectra .
We also use U -band photometry , which has been collected from the literature , to study the accretion variability of GW Ori .
We characterize the disk properties of GW Ori by modeling its spectral energy distribution ( SED ) .

Results : By comparing our data to the synthetical spectra , we classify GW Ori as a G8 star .
Based on the RVs derived from the optical spectra , we confirm the previous result as a close companion in GW Ori with a period of \sim 242 days and an orbital semi-major axis of \sim 1 AU .
The RV residuals after the subtraction of the orbital solution with the equivalent widths ( EW ) of accretion-related emission lines vary with periods of 5–6.7 days during short time intervals , which are caused by the rotational modulation .
The H \alpha and H \beta line profiles of GW Ori can be decomposed in two central-peaked emission components and one blue-shifted absorption component .
The blue-shifted absorption components are due to a disk wind modulated by the orbital motion of the close companion .
Therefore , the systems like GW Ori can be used to study the extent of disk winds .
We find that the accretion rates of GW Ori are rather constant but can occasionally be enhanced by a factor of 2–3 .
We reproduce the SED of GW Ori by using disk models with gaps \sim 25–55 AU in size .
A small population of tiny dust particles within the gap produces the excess emission at near-infrared bands and the strong and sharp silicate feature at 10 \mu m. The SED of GW Ori exhibits dramatic changes on timescales of \sim 20 yr in the near-infrared bands , which can be explained as the change in the amount and distribution of small dust grains in the gap .
We collect a sample of binary/multiple systems with disks in the literature and find a strong positive correlation between their gap sizes and separations from the primaries to companions , which is generally consistent with the prediction from the theory .

Conclusions :