Integrate with REST API with session logins?

I am attempting to integrate with a web service via a REST API.  The web service authentication uses a login process.  There are no tokens.   Logins are valid for a single session.

I have been able to log into the service successfully.  However, when I attempt to issue any other request I receive a 401 (unauthorized access) error.

Is it possible that each REST API call is being made in a session of its own?  Any suggestions for how I might determine that?  If that is the case is it possible to establish integration with such a service remaining within OutSystems?

Hi David

Usually you get a token from the login process.

In all following requests to the API you need to send that token in an authorization header...

This service does not do that. They DO NOT return a token.  They only go by session.