If you search for java heap in the forum you get multiple questions and answers about this! 
Here’s a good answer: Editor crash: ‘java heap space’
You can control the alpha channel of a sprite. The sprite material has a tint constant. This allows you to change the tint (including alpha) using sprite.set_constant("#sprite", "tint.w", 0.5) or go.set("#sprite", "tint.w", 0.5) or go.animate("#sprite", "tint.w", go.PLAYBACK_ONCE_FORWARD, 0.5, go.EASING_LINEAR, 1).