New Chandra insights into the neutron star population of M28

We present a detailed spectral and temporal study of the neutron star population in the globular cluster M28, after analyzing the full ACIS dataset from the Chandra X-ray Observatory. We discover an orbital modulation in the X-ray flux of the redback and transitional millisecond pulsar PSR J1824-2452I during the pulsar state. Its orbital X-ray light curve shows a double-peaked maximum centered on the inferior conjunction of the pulsar, which suggests that the intrabinary shock is wrapped around the pulsar. We present improved mass and radius constraints from spectral fits of the quiescent LMXB in M28, using both hydrogen and helium neutron star atmosphere models. We also discover six new variable X-ray sources in the cluster.