What is the fine-grained topic of the following text: "The spectral data provided by XMM-Newton, combined with a new way of analysing the data, allowed us to finally make the first detailed measurements of the magnetic field of a magnetar, confirming it as one of the largest values ever measured in the Universe," adds Norbert Schartel, ESA's XMM-Newton Project Scientist. Only return the topic.
Measurement of a magnetar's magnetic field using XMM-Newton spectral data