The painting, ‘El sueño (La cama),’ will be auctioned in New York at Sotheby’s on Nov. 20. Frida Kahlo’s “El sueño (La cama)” — in English, “The Dream (The Bed)” — is causing a stir among art historians as its estimated $40 million to $60 million price tag would make it the most expensive work by any female or Latin American artist when it goes to auction later this month.Sotheby’s auction house will put the painting up for sale on Nov. 20 in New York after exhibiting it in London, Abu Dhabi, Hong Kong and Paris.“This is a moment of a lot of speculation,” said Mexican art historian Helena Chávez Mac Gregor, a researcher at UNAM’s Institute of Aesthetic Research and author of “El listón y la bomba. El arte de Frida Kahlo.” (The ribbon and the bomb. The art of Frida Kahlo).In Mexico, Kahlo’s work is protected by a declaration of artistic monument, meaning pieces within the country cannot be sold or destroyed. However, works from private collections abroad — like the painting in question, whose owner remains unrevealed — are legally eligible for international sale.“The system of declaring Mexican modern artistic heritage is very anomalous,” said Mexican curator Cuauhtémoc Medina, an art historian and specialist in contemporary art.