Yelena Bonner, an Armenian-born human rights activist and widow of Nobel Peace Prize winner Andrei Sakharov, has died, her daughter said early Sunday, June 19. She was 88.

The 88-year-old Bonner died of heart failure Saturday afternoon in Boston, according to her daughter, Tatiana Yankelevich. She had been hospitalized since Feb. 21, Yankelevich said.

Bonner grew famous through her marriage to Sakharov, the Soviet Union's leading dissident, but she carved out her own reputation as a tireless human rights campaigner in the face of relentless hostility from Soviet authorities.

After Sakharov died in 1989, and the Soviet Union collapsed two years later, Bonner continued to champion human rights. She edited her husband's memoirs, which were released in 1997.

Bonner's remains will be cremated and eventually buried in a Moscow cemetery alongside her husband, mother and brothers, AP reported.