Hunting for Spiders with NTT/ULTRACAM

Spider binaries are systems with a bright pulsar ablating an orbiting low-mass companion. One half of the 'Transitional Millisecond Pulsar' population, they don't host an accretion disc - however, their polar jets still emit bursts of gamma rays as they sweep the sky hundreds of times a second.

These gamma rays are beacons, and can sometimes be the first sign of a new pulsar system. But such detections often have localisations several arc-minutes across. Not only that, but without prior knowledge of the system parameters, detecting and studying their gamma-ray pulsations - and thus, the jets that emit them - is nearly impossible. So how do we find these systems?

The answer is in the optical; as the companion star orbits, the bright, ablating pulsar illuminates its day side, causing characteristic sinusoidal-like optical variations of up to a magnitude in size. Not only is this easily detectable by current optical telescopes, but when modelled, these variations can reveal the temperatures, distances, masses, and heating mechanisms of these systems.
This talk showcases the results of an optical survey that follows up on several unidentified Fermi gamma-ray sources with NTT/ULTRACAM. Over the course of 22 nights, spread over six months, we hunted for the distinctive sinusoidal lightcurve of these as-yet undiscovered spider systems.

We will detail the methodology of our search, from the preparation to its execution. We will report on several new spider pulsar candidates, including preliminary reports on their characteristics. We will thus demonstrate the power of following up large-scale gamma ray surveys, and show off a few unexpected findings too.