logging out after a few minutes despite authentication in owin

Question

I use owin and although I have set the expired time defined in Startup.cs as 2 days, it exits itself after 15 minutes when the site is open in browser

public void ConfigureAuth(IAppBuilder app)
{
      app.UseCookieAuthentication(new CookieAuthenticationOptions
        {
       AuthenticationType = DefaultAuthenticationTypes.ApplicationCookie,
       LoginPath = new PathString("/Admin/Login"),
       ExpireTimeSpan = TimeSpan.FromDays(2.0)
         });
}