The Sensex at the Bombay Stock Exchange closed a modest 39 points, or 0.2 percent lower, at 19,545, on Tuesday, as investors booked profits ahead of the monthly settlement in the derivatives segment, and amid weak regional bourses. The Nifty at the National Stock Exchange shed 6 points, or 0.1 percent, to 5,868. Stock markets in Japan, China, Hong Kong, South Korea and Singapore lost between 0.5 percent and 1.2 percent.