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 in the low-LAtitude NEighborhood (COBIPLANE), which led to discovery of five 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. COBIPLANE selection criteria, improved compared to its predecessor survey COBIPULSE, allowed us to find two candidates close to the Galactic plane: 4FGL J1517.9−5233 at b=4.18° and 4FGL J1639.3−5146 at b=−3.32°. These findings will not only facilitate future radio observations of these five candidates, but will also allow us to measure their neutron star masses via optical light curve modelling.
LOVE-NEST
Looking for Super-Massive Neutron Stars
