code: @Override
    public void handleNotification(Notification notification, Object handback) {
      LocalGossipMember deadMember = (LocalGossipMember) notification.getUserData();
      GossipService.LOGGER.debug("Dead member detected: " + deadMember);
      members.put(deadMember, GossipState.DOWN);
      if (listener != null) {
        listener.gossipEvent(deadMember, GossipState.DOWN);
      }
    }
docs: All timers associated with a member will trigger this method when it goes off. The timer will
  go off if we have not heard from this member in <code> _settings.T_CLEANUP </code> time.