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Peer-reviewedCC BY 4.0The Astrophysical Journal Letters

A new , low braking index for the LMC PULSAR B0540-69

  • F E Marshall
  • Lucas Guillemot
  • A A Harding
  • D A Smith
  • Pierre Martin
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Abstract

We report the results of a 16-month monitoring campaign using the Swift satellite of PSR 0 ¯ 540, a young pulsar in the Large Magellanic Cloud. Phase connection was maintained throughout the campaign so that a reliable ephemeris could be determined, and the length of the campaign is adequate to accurately determine the spin frequency ν and its first and second derivatives. The braking index n is 0.031 ± 0.013 (90% confidence), a value much lower than previously reported for 0 ¯ 540 and almost all other young pulsars. We use data from the extensive monitoring campaign with RXTE to show that timing noise is unlikely to significantly affect the measurement. This is the first measurement of the braking index in the pulsar's recently discovered high spin-down state. We discuss possible mechanisms for producing the low braking index.

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Cite

BibTeXRIS
BibTeX
@article{marshall2026braking,
  title = {{A new , low braking index for the LMC PULSAR B0540-69}},
  author = {F E Marshall and Lucas Guillemot and A A Harding and D A Smith and Pierre Martin},
  journal = {The Astrophysical Journal Letters},
  year = {2026},
  month = oct,
  doi = {10.3847/2041-8205/827/2/l39},
  url = {https://insu.hal.science/insu-01400560v2},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - A new , low braking index for the LMC PULSAR B0540-69
AU  - F E Marshall
AU  - Lucas Guillemot
AU  - A A Harding
AU  - D A Smith
AU  - Pierre Martin
PY  - 2026
DA  - 2026/10/12
JO  - The Astrophysical Journal Letters
DO  - 10.3847/2041-8205/827/2/l39
UR  - https://insu.hal.science/insu-01400560v2
AB  - We report the results of a 16-month monitoring campaign using the Swift satellite of PSR 0 ¯ 540, a young pulsar in the Large Magellanic Cloud. Phase connection was maintained throughout the campaign so that a reliable ephemeris could be determined, and the length of the campaign is adequate to accurately determine the spin frequency ν and its first and second derivatives. The braking index n is 0.031 ± 0.013 (90% confidence), a value much lower than previously reported for 0 ¯ 540 and almost all other young pulsars. We use data from the extensive monitoring campaign with RXTE to show that timing noise is unlikely to significantly affect the measurement. This is the first measurement of the braking index in the pulsar's recently discovered high spin-down state. We discuss possible mechanisms for producing the low braking index.
SN  - 2041-8205
SN  - 2041-8213
ER  -