COBIPULSE: the discovery of three new spider pulsars

Compact binary millisecond pulsars, also known as “spiders”, host the most massive neutron stars ever observed to date. Expanding the currently known spider population holds the key to determining the maximum neutron star mass, which has crucial implications for astrophysics, nuclear physics and gravitational wave astronomy. Searching for the variable optical emission of their companions can reveal a radio-obscured population of spiders. In the linked article, we present the results of our COmpact BInary PULsar SEarch (COBIPULSE), which led to discovery of three variable optical sources identified as new spider candidates. Their optical light curves show flux modulation in the sub-day period range and effective temperatures of 5000−6000 K, consistently with spider pulsars. One of them, 3FGL J0737.2−3233, would be the closest known spider to Earth (D=659 pc). These results will not only facilitate future radio observations of these three candidates, but will also allow us to measure their neutron star masses via optical light curve modelling.