Subject
2 free books about astrophysics, free to read online. Chapter 1 of any book is free, no account needed.
Stellar atmospheres: A contribution to the observational study of high temperature in the reversing layers of stars
Cecilia Payne-Gaposchkin
On the distribution of intensity in stellar absorption lines
Payne-Gaposchkin, Cecilia; Shapley, Harlow
