Open link in new browser window

I am just starting out with AS 3.0 (after having worked with Flash and AS 2.0 for a number of years).

I picked up this code from another source to open a new URL

button.addEventListener(MouseEvent.CLICK, buttonClickHandler);

function buttonClickHandler(event:MouseEvent):void {
navigateToURL(new URLRequest(“http://www.kirupa.com”);
}

This much all works fine. But my question is: how to open the new URL in its own browser window. In AS 2.0 it was just adding the “_blank” part after the URL address. But that does not work here.

If someone could enlighten me on how this works with AS 3 it would be appreciated. Thanks.