A 50-year-old Lowell man was arrested and charged with murder on Saturday in connection with a slaying last week, prosecutors said. Robert Weidman is accused of attempting to rob a man and subsequently stabbing him to death on Woburn Street in Lowell at 10:15 p.m. Thursday, according to Middlesex District Attorney Marian T. Ryan’s office. Weidman is slated to be arraigned Monday in Lowell District Court and is currently being held at a local hospital. On Thursday, the victim was transported to Lahey Clinic in Burlington and died at 4 a.m. Friday, according to a statement issued by Ryan’s office. An autopsy will determine the exact cause of the man’s death.