Rear Lightbar for an Automobile

FIG. 1 is a left, front perspective view of a rear lightbar for an automobile showing our new design; FIG. 2 is a left, rear perspective view thereof; FIG. 3 is a left side view thereof; FIG. 4 is a right side view thereof; FIG. 5 is a front view thereof; FIG. 6 is a rear view thereof; and, FIG. 7 is a top view thereof. The deemphasized/reduced tone portions of the rear lightbar for an automobile depict portions that form no part of the claimed design.