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Peer-reviewedCC BY 4.0The Astrophysical Journal

Discovery of a 62 minute Long-period Transient with Near-orthogonal Rotator Geometry

  • Scott D. Hyman1
  • Natasha Hurley-Walker2
  • Dale A. Frail3
  • Emil Polisensky4
  • W. D. Cotton3
4 affiliations
  1. 1Sweet Briar College
  2. 2Curtin University
  3. 3National Radio Astronomy Observatory
  4. 4U.S. Naval Research Laboratory
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Abstract

We report the serendipitous discovery of the radio long-period transient (LPT) J155543.7−563102 (hereafter LPT J1555−5631) with a period of 62.2 minutes in MeerKAT and ASKAP survey data. The source emitted bright (10–30 mJy), steep-spectrum ( α ∼ −1.5), highly polarized radio pulses during a 15 hr active window in 2022 May, with no other quiescent or pulsed emission detected before or after over ∼5 yr. The mean light curve exhibits two alternating pulses per cycle. A main pulse (MP) and an interpulse (IP) separated by Δ ϕ = 165 . ° 4, with similar amplitudes but different polarization properties: the wider MP (3.9%) is partially linearly and circularly polarized and shows a constant polarization position angle, while the narrow IP (1.1%) is ∼100% circularly polarized. We classify LPT J1555−5631 as a near-orthogonal rotator, for which emission from both magnetic poles is visible during one rotation and the magnetic and rotation axes are almost perpendicular. The 14 . ° 6 deviation from an antipodal separation and the nearly constant polarization position angle suggest that the emission does not arise from the standard dipolar polar-cap geometry of ordinary pulsars, but instead originates within a broader, more complex magnetosphere. The observed properties of LPT J1555−5631 can be accommodated by extended emission regions, and favor coherent emission mechanisms such as the electron cyclotron maser instability, although they do not uniquely determine the progenitor or emission physics. If these inferences apply more broadly to the LPT population, they could account for why their beam widths are decoupled from rotation periods, the prevalence of flat polarization position angles, and may favor an elevated incidence of orthogonal rotators.

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Cite

BibTeXRIS
BibTeX
@article{hyman2026discovery,
  title = {{Discovery of a 62 minute Long-period Transient with Near-orthogonal Rotator Geometry}},
  author = {Scott D. Hyman and Natasha Hurley-Walker and Dale A. Frail and Emil Polisensky and W. D. Cotton},
  journal = {The Astrophysical Journal},
  year = {2026},
  month = nov,
  doi = {10.3847/1538-4357/aeb002},
  url = {https://iopscience.iop.org/article/10.3847/1538-4357/aeb002},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - Discovery of a 62 minute Long-period Transient with Near-orthogonal Rotator Geometry
AU  - Scott D. Hyman
AU  - Natasha Hurley-Walker
AU  - Dale A. Frail
AU  - Emil Polisensky
AU  - W. D. Cotton
PY  - 2026
DA  - 2026/11/06
JO  - The Astrophysical Journal
DO  - 10.3847/1538-4357/aeb002
UR  - https://iopscience.iop.org/article/10.3847/1538-4357/aeb002
AB  - We report the serendipitous discovery of the radio long-period transient (LPT) J155543.7−563102 (hereafter LPT J1555−5631) with a period of 62.2 minutes in MeerKAT and ASKAP survey data. The source emitted bright (10–30 mJy), steep-spectrum ( α ∼ −1.5), highly polarized radio pulses during a 15 hr active window in 2022 May, with no other quiescent or pulsed emission detected before or after over ∼5 yr. The mean light curve exhibits two alternating pulses per cycle. A main pulse (MP) and an interpulse (IP) separated by Δ ϕ = 165 . ° 4, with similar amplitudes but different polarization properties: the wider MP (3.9%) is partially linearly and circularly polarized and shows a constant polarization position angle, while the narrow IP (1.1%) is ∼100% circularly polarized. We classify LPT J1555−5631 as a near-orthogonal rotator, for which emission from both magnetic poles is visible during one rotation and the magnetic and rotation axes are almost perpendicular. The 14 . ° 6 deviation from an antipodal separation and the nearly constant polarization position angle suggest that the emission does not arise from the standard dipolar polar-cap geometry of ordinary pulsars, but instead originates within a broader, more complex magnetosphere. The observed properties of LPT J1555−5631 can be accommodated by extended emission regions, and favor coherent emission mechanisms such as the electron cyclotron maser instability, although they do not uniquely determine the progenitor or emission physics. If these inferences apply more broadly to the LPT population, they could account for why their beam widths are decoupled from rotation periods, the prevalence of flat polarization position angles, and may favor an elevated incidence of orthogonal rotators.
SN  - 1538-4357
SN  - 0004-637X
ER  -