Pulsars, transients and relativistic astrophysics

Abstract:

Most stripped envelope supernova progenitors are formed through binary interaction, losing hydrogen and/or helium from their outer layers. An emerging class of supernovae with the highest degree of envelope-stripping are thought to be the product of stripping by a NS companion. However, relatively few examples are known and the outcomes of such systems can be diverse and are poorly understood at present. Here, we present spectroscopic observations and high cadence multi-band photometry of SN 2023zaw, a low ejecta mass and rapidly evolving supernova. SN 2023zaw was discovered in a nearby spiral galaxy at D = 39.7 Mpc, with significant Milky Way extinction, $E(B-V) = 0.21$, and significant (but uncertain) host extinction. Bayesian evidence comparison reveals that nickel is not the only power source and an additional energy source is required to explain our observations. Our models suggest an ejecta mass of $M_{\rm ej} \sim 0.07\,\rm M_\odot$ and a synthesised nickel mass of $M_{\rm ej} \sim 0.007\,\rm M_\odot$ is required to explain the explosion. However an additional heating from a magnetar or interaction with circumstellar material is required to power the early light curve

Abstract:

In MeerKAT observations pointed at a Galactic X-ray binary located on the Galactic plane, we serendipitously discovered a radio nebula with cometary-like morphology. The feature, which we named 'the Mini Mouse' based on its similarity with the previously discovered 'Mouse' nebula, points back towards the previously unidentified candidate supernova remnant G45.24+0.18. We observed the location of the Mini Mouse with MeerKAT in two different observations, and we localized with arcsecond precision the 138-ms radio pulsar PSR J1914+1054g, recently discovered by the FAST telescope, to a position consistent with the head of the nebula. We confirm a dispersion measure of about 418 pc cm-3 corresponding to a distance between 7.8 and 8.8 kpc based on models of the electron distribution. Using our accurate localization and two period measurements spaced 90 d apart, we calculate a period derivative of (2.7 ± 0.3) × 10 -14 s s-1. We derive a characteristic age of approximately 82 kyr and a spin-down luminosity of 4 × 1035 erg s-1. For a pulsar age comparable with the characteristic age, we find that the projected velocity of the neutron star is between 320 and 360 km s-1 if it was born at the location of the supernova remnant. The size of the proposed remnant appears small if compared with the pulsar characteristic age; however, the relatively high density of the environment near the Galactic plane could explain a suppressed expansion rate and thus a smaller remnant.