Periodic Reporting for period 3 - Spiders (Fundamental Physics Using Black Widow, Redback and Transitional Pulsar Binaries)
Reporting period: 2020-04-01 to 2021-09-30
Here are highlights related to each area:
1) Characterisation
- We have conducted over 100 hours of observations with world-class optical telescopes (>3 meters) in order to obtain photometric light curves for the largest sample of Spider binaries ever collected thus far. Nearly all of these data has been reduced, and there are currently 6 papers in preparation relating to these data.
- Three publications detailing observations and modelling of Spider binary systems have been published or are under journal review.
- Our group obtained and modelled the optical light curve of the second-fastest spinning MSP yet to be discovered, making it the most extreme black widow system to have been studied in this way.
- We have been involved with the first discovery of the long-term optical variability in Spider binary light curves, which indicates that the companion stars in these systems are likely undergoing physical change of time scales of a few years. The underlying reasons for these changes might be connected to the observed transitions seen in some other systems upon which states of active accretion onto the neutron stars are triggered.
2) Search
- We have developed a new method which utilises information from optical observations in order to constrain the range of parameters enabling searches for gamma ray and radio pulsations from Spider MSPs. This method has already led to two new discoveries.
- We have applied machine learning techniques to classify the optical light curves of sources observed with survey telescopes, with a specific focus on identifying light curves which resemble those of Spider systems. Initial results are promising, but progress has been hampered by a delay in the acquisition of new survey data.
3) Theoretical understanding
- We have been working on improving the modelling of Spider timing data by incorporating the various physical components contributing to tides as well as effects of general relativity. This has led to the prediction that these binary systems should not have a perfectly circular orbit, and the measurement of this effect can provide a proxy to understand the internal structure of the companion star in these systems. This result is not just limited to Spider binary systems, but has wide ranging implications for all binary star systems.
We expect to publish a full database of Spider binary physical parameters at this end of the project, along with a number of publications summarising the individual characteristic of these systems.