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Discovery of a radio emitting neutron star with an ultra-long spin period of 76 seconds (2206.01346v1)

Published 3 Jun 2022 in astro-ph.HE

Abstract: The radio-emitting neutron star population encompasses objects with spin periods ranging from milliseconds to tens of seconds. As they age and spin more slowly, their radio emission is expected to cease. We present the discovery of an ultra-long period radio-emitting neutron star, J0901-4046, with spin properties distinct from the known spin and magnetic-decay powered neutron stars. With a spin-period of 75.88 s, a characteristic age of 5.3 Myr, and a narrow pulse duty-cycle, it is uncertain how radio emission is generated and challenges our current understanding of how these systems evolve. The radio emission has unique spectro-temporal properties such as quasi-periodicity and partial nulling that provide important clues to the emission mechanism. Detecting similar sources is observationally challenging, which implies a larger undetected population. Our discovery establishes the existence of ultra-long period neutron stars, suggesting a possible connection to the evolution of highly magnetized neutron stars, ultra-long period magnetars, and fast radio bursts

Citations (62)

Summary

Discovery of an Ultra-Long Spin Period Neutron Star

The paper "Discovery of a radio emitting neutron star with an ultra-long spin period of 76 seconds" documents a significant finding in astrophysics surrounding the observation of PSR, a radio-emitting neutron star with a spin period notably longer than the typical range known for these objects. This discovery challenges existing models of pulsar evolution and the mechanics behind radio emission.

The spin period of 75.88 seconds for PSR indicates an ultra-long period previously undocumented in known radio-emitting neutron stars. This neutron star exhibits unusual radio emission properties, including quasi-periodicity and partial nulling, suggesting complex mechanisms potentially involving magnetar-like processes. Such characteristics are atypical and diverge from traditional pulsar behavior, which generally sees emission from stars with much shorter spin periods.

Key Findings

  • Unique Spin and Emission: PSR has a spin period of 75.88 s, which is markedly longer than the millisecond to tens of seconds range observed in other pulsars. Its characteristic age is estimated at 5.3 Myr, inferring that this neutron star is relatively old, yet still actively emitting radio waves.
  • Potential Supernova Remnant Association: Imaging data revealed a diffuse, shell-like structure around PSR, potentially indicative of a supernova remnant. Establishing this connection could provide insights into the star's formation and the longevity of radio emission.
  • Spectro-temporal Properties: The radio emission exhibits quasi-periodicity and partial nulling, traits that raise questions about the mechanisms of emission, offering parallels to fast radio bursts (FRBs) and magnetar behavior.
  • Theoretical Implications: PSR's position in the spin period-spin down rate space challenges existing models. The radio emission capabilities point to the potential existence of a larger population of ultra-long period neutron stars, perhaps connecting these entities to the evolution of ultra-long period magnetars or FRBs.

Implications and Speculations

The existence of ultra-long period neutron stars like PSR suggests the need to revisit models of pulsar death lines and spin evolution. The current understanding is that older pulsars with large magnetic fields should cease radio emissions as they slow down. However, PSR defies these expectations, indicating a potential mechanism that maintains or sporadically enables radio emissions even beyond what is considered the radio emission threshold.

Connections are drawn between PSR and phenomena observed in magnetars and X-ray isolated neutron stars (XINS), although PSR differs significantly in radio activity and pulsar population positioning. Despite a close comparison, PSR does not exhibit significant X-ray activity, a characteristic consistent with pulsar behavior but deviating from magnetar characteristics.

Future Directions

The discovery suggests there may be either many more undiscovered neutron stars in the galaxy, or that traditional models of pulsar life cycles are incomplete. Thus, deeper sky surveys and enhanced detection algorithms could reveal a population of similar ultra-long spin period objects.

Further studies leveraging multi-wavelength observations could help elucidate the underlying mechanisms prompting radio emissions in such exotic stars and might bridge understanding to FRB origins. This underscores the importance of continuing observational efforts with both traditional and novel methods to uncover the true variety and evolutionary patterns of neutron stars.

In summary, this paper presents findings that have critical implications for astrophysical theories on neutron star evolution, magnetospheric dynamics, and the characteristics of radio emissions.

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