Web Authentication Authentication Api 2

I create a site using AngularJS and a pre-configured WebApi2 token authentication template (individual user accounts). I try to log into two sites at the same time, one at www.domain.com and the other at sub.domain.com

I am currently using the following code in angular to authenticate a user:

 $http({
            method: 'POST',
            url: '/Token',
            data: serializedData,
            headers: {
                'Content-Type': 'application/x-www-form-urlencoded'
            }
        }).success(function (data, status, headers, config) {
            $window.sessionStorage.token = data.access_token;
        });

and add an authorization header for each request after:

app.factory('authInterceptor', function ($rootScope, $q, $window) {
        return {
            request: function (config) {
                config.headers = config.headers || {};
                if ($window.sessionStorage.token) {
                    $window.sessionStorage.loggedIn = true;
                    config.headers.Authorization = 'Bearer ' + $window.sessionStorage.token;
                }
                return config;
            }
        };
    });

    app.config(function ($httpProvider) {
        $httpProvider.interceptors.push('authInterceptor');
    });

The above code allows each site to log in individually, however, sessionstorage is not saved on other windows / tabs, so it will not register the user in a subdomain.

( ): http://blog.auth0.com/2014/01/07/angularjs-authentication-with-cookies-vs-token/

( ). - , , cookie:

app.UseCookieAuthentication(new CookieAuthenticationOptions()
            {
                CookieDomain = ".domain.com"
            });

, ...