The compactness of the isolated neutron star RX J0720.4−3125V. Hambaryan, V. Suleimanov, F. Haberl, A. D. Schwope, R. Neuhäuser, M. Hohle and K. WernerA&A, 601 (2017) A108DOI: https://doi.org/10.1051/0004-6361/201630368