The curator and director of the Georgia O’Keeffe Museum is stepping down after 13 years with the Santa Fe, N.M., institution, the Associated Press and arts magazine Adobe Airstream report.

Barbara Buhler Lynes was the first curator of the museum, joining the O’Keeffe two years after its founding, and is considered one of the world’s leading authority on the 20th-century American artist. In a statement issued by the museum, she did not give a reason for her departure, which was announced Friday and took effect immediately, and museum officials declined to elaborate.