Friends and family of Abigail Hernandez, the teenager from North Conway, N.H., who disappeared on Oct. 9, held an online vigil Sunday evening to spread word of her disappearance through social media and to ask for the public’s help. Organizers asked participants to change their Facebook profile pictures to one of a set of images of Hernandez, including an FBI missing persons poster, and to post a short paragraph describing her case along with the hashtag #bringabbyhome. The vigil, which ran from 6 to 10 p.m., created a flurry of activity on Facebook and Twitter. Hernandez, 15, was last seen leaving Kennett High School in North Conway at around 2:30 p.m. on Oct. 9. The FBI is offering a $20,000 reward for information leading to the conviction of anyone who was involved in her disappearance.Matthew Higgins can be reached at email@example.com.