arXiv subjects

B. D. Ball

Publications and source records attributed to B. D. Ball.

4 recordsLinked to original sources

arXiv2026

EMU discovery of Thunder: a bow-shock PWN powered by PSR J1631-4722 escaping Nimbus SNR (G336.7+0.5)

We report the discovery of a bow-shock pulsar wind nebula (PWN), dubbed Thunder, powered by the radio pulsar PSR J1631-4722 and projected within the Galactic supernova remnant (SNR) G336.7+0.5 (Nimbus). The system was first identified in observations from the Australian Square Kilometre Array Pathfinder (ASKAP) Evolutionary Map of the Universe (EMU) survey and further characterised using MeerKAT Galactic Plane Survey data together with follow-up observations at 5.5 and 9 GHz obtained with the Australia Telescope Compact Array (ATCA). Assuming a distance of 7 kpc, the radio images resolve an elongated ~80 arcsec (2.7 pc) cometary nebula, indicative of a high velocity pulsar. An X-ray counterpart extending ~50 arcsec (1.7 pc) is detected in archival XMM-Newton data. The flat radio spectrum ($\alpha$ = -0.27 $\pm$ 0.05) and hard X-ray photon index ($\Gamma$ = 1.6 $\pm$ 0.4) indicate synchrotron emission from relativistic particles injected in the pulsar wind. Polarisation analysis reveals a highly ordered magnetic field aligned with the nebular flow, with fractional polarisation reaching up to 30% in the tail. An equipartition estimate gives a PWN magnetic-field strength of Beq $\approx$ 54-140 $\mu$G. Pulsar timing over a ~2.2 yr baseline reveals strong timing noise and a small spin glitch with amplitude $\Delta{\nu}/{\nu}$ = 1.10$\times$10$^{-8}$. The SNR shows no clear diffuse X-ray counterpart. The morphology and multiwavelength properties of the Nimbus-Thunder system, along with evolutionary models, constrain the system's age to approximately 30-45 kyr, placing the remnant in the late Sedov phase, approaching the transition to the radiative stage.

astro-ph.HE↗

arXiv2026

A newly born spider system at the core of a radio shell: Evidence for a low-energy supernova

In a search for low surface brightness radio nebulae using the ASKAP-EMU survey, we discovered a faint radio shell, G289.6+5.8, and its central point radio source at the position of the soft gamma-ray source IGR J11187-5438. The central radio source is spatially coincident with a previously known low-mass X-ray binary (LMXB) with an M-type donor star. However, the newly determined Gaia DR3 distance of 267 pc and correspondingly low X-ray luminosity (3 x 10e31 erg/s) cast doubt on the LMXB classification. Neither radio nor X-ray pulsations are detected. Chance-alignments between radio shell, central radio source, optical star, gamma-ray, and X-ray sources appear unlikely. By combining all currently available evidence, we conclude that G289.6+5.8 is a remnant of a low-energy core-collapse explosion of an intermediate mass star (~8Msun) in a binary system with an M-type secondary, which remained bound after the explosion. In this scenario, G289.6+5.8 is a supernova remnant, while the central gamma- and X-ray source is associated with a young neutron star driving a pulsar wind interacting with its M-type stellar companion, making IGR J11187-5438 a nascent spider-type X-ray binary.

astro-ph.HE↗

arXiv2025

A Catalog of Galactic Supernova Remnants and Supernova Remnant Candidates from the EMU/POSSUM Radio Sky Surveys. I

We use data from the EMU (Evolutionary Map of the Universe) and POSSUM (Polarization Sky Survey of the Universe's Magnetism) radio southern sky surveys, conducted with the Australian Square Kilometre Array Pathfinder (ASKAP), to compile a catalogue of Galactic supernova remnants (SNRs) and candidate SNRs within the region of $277.5^\circ \leq \ell \leq 311.7^\circ$ Galactic longitude, $|b| \leq 5.4^\circ$ Galactic latitude, as well as an additional field along the Galactic plane, approximately $315.5^\circ \leq \ell \leq 323.0^\circ$ Galactic longitude, $-4.5^\circ \leq b \leq 1.5^\circ$ Galactic latitude. In the areas studied, there are 44 known SNRs and 46 SNR candidates that have been previously identified in the radio. We confirm eight of these candidates as SNRs based on evidence of linear polarization or through the calculation of nonthermal spectral indices. Additionally, we identify possible radio counterparts for seven SNR candidates that were previously only identified in X-rays (four) or optical (three). We also present six new SNRs and 37 new SNR candidates. The results of this study demonstrate the utility of ASKAP for discovering new and potential SNRs and refining the classification of previously identified candidates. In particular, we find that the EMU and POSSUM surveys are particularly well suited for observing high-latitude SNRs and confirming SNR candidates with polarization. The region studied in this work represents approximately one-quarter of the Galactic plane, by longitude, that will eventually be surveyed by EMU/POSSUM and we expect that the ongoing surveys will continue to uncover new SNRs and SNR candidates.

astro-ph.GA↗

arXiv2025

The Evolutionary Map of the Universe: A new radio atlas for the southern hemisphere sky

We present the Evolutionary Map of the Universe (EMU) survey conducted with the Australian Square Kilometre Array Pathfinder (ASKAP). EMU aims to deliver the touchstone radio atlas of the southern hemisphere. We introduce EMU and review its science drivers and key science goals, updated and tailored to the current ASKAP five-year survey plan. The development of the survey strategy and planned sky coverage is presented, along with the operational aspects of the survey and associated data analysis, together with a selection of diagnostics demonstrating the imaging quality and data characteristics. We give a general description of the value-added data pipeline and data products before concluding with a discussion of links to other surveys and projects and an outline of EMU's legacy value.

astro-ph.GA↗