Multiwavelength Pulsations and Surface Temperature Distribution in the Middle-Aged Pulsar B1055–52

Armin Vahdat, B. Posselt, G. G. Pavlov, Patrick Weltevrede, Andrea Santangelo, Simon J Johnston

Research output: Contribution to journalArticlepeer-review


We present a detailed study of the X-ray emission from PSR B1055–52 using XMM-Newton observations from 2019 and 2000. The phase-integrated X-ray emission from this pulsar is poorly described by existing neutron star atmosphere models. Instead, we confirm that, similar to other middle-aged pulsars, the best-fitting spectral model consists of two blackbody components, with substantially different temperatures and emitting areas, and a nonthermal component characterized by a power law. Our phase-resolved X-ray spectral analysis using this three-component model reveals variations in the thermal emission parameters with the pulsar’s rotational phase. These variations suggest a nonuniform temperature distribution across the neutron star’s surface, including the cold thermal component and probable hot spot(s). Such a temperature distribution can be caused by external and internal heating processes, likely a combination thereof. We observe very high pulse fractions, 60%–80% in the
0.7−1.5 keV range, dominated by the hot blackbody component. This could be related to temperature non-uniformity and potential beaming effects in an atmosphere. We find indication of a second hot spot that appears at lower energies (0.15 − 0.3 keV) than the first hot spot (0.5 − 1.5 keV) in the X-ray
light curves, and is offset by about half a rotation period. This finding aligns with the nearly orthogonal rotator geometry suggested by radio observations of this interpulse pulsar. If the hot spots are associated with polar caps, a possible explanation for their temperature asymmetry could be an offset magnetic dipole and/or an additional toroidal magnetic field component in the neutron star crust.
Original languageEnglish
JournalThe Astrophysical Journal
Publication statusAccepted/In press - 24 Jan 2024


  • Neutron stars(1108)
  • Pulsars(1306)
  • X-ray astronomy(1810)
  • High energy astro-physics(739)


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