Neutron stars, collapsed cores of massive stars, are the densest celestial objects ever observed after black holes. These systems rotate very rapidly (down to spin periods of a few milliseconds) and can be detected as pulsars through their extremely stable signal at the spin period. Some pulsars are found in close orbits with a companion star, so that the wind of high-energy particles ejected by the pulsar can strongly irradiate and ablate the companion. Such star-destroying behaviour has led to these pulsar systems being nicknamed as spiders. In our work we analyse the optical emission of a spider pulsar, PSR J1622-0315, using data taken last year with the Nordic Optical Telescope, during the first edition of the Observational Astrophysics course held at NTNU Physics Department. In this system the irradiation of the companion star by the pulsar wind is unexpectedly missing despite its very short orbital period (4 hours). We explain this surprising result by introducing a simple parameter which quantifies the effective amount of irradiation hitting the companion surface. This parameter turns out to be the most important factor in determining whether the companion is irradiated or not in spider pulsars.
LOVE-NEST
Looking for Super-Massive Neutron Stars
