Heating of the real polar cap of radio pulsars

Sznajder, Maciej; Geppert, U.

doi:10.1093/mnras/staa492

Cited by 18 publications

(16 citation statements)

References 57 publications

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“…The obtained temperature is within the range of typical BB temperatures of hot polar caps of old pulsars, while the BB radius is a factor of 10 smaller than the "canonical" cap radius R pc = R NS (2πR NS /cP ) 1/2 ≈ 238 m for P = 0.808 s, assuming a plausible intrinsic NS radius R NS = 13 km. A similar discrepancy between R BB and R pc is observed in other old pulsars (see Sznajder & Geppert 2020;Posselt et al 2012, and references therein). Figure 6 shows the fit, for the absorbed and unabsorbed spectra, together with the PL fit to the optical-UV spectrum shown in Figure 5.…”

Section: Possible Power-law Spectrum Of the Tentative Pulsar Counterpartsupporting

confidence: 77%

Hubble Space Telescope observations of the old pulsar PSR J0108-1431

Abramkin,

Shibanov,

Mignani

et al. 2021

Preprint

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We present results of optical-UV observations of the 200 Myr old rotation-powered radio pulsar J0108−1431 with the Hubble Space Telescope. We found a putative candidate for the far-UV (FUV) pulsar counterpart, with the flux density f ν = 9.0±3.2 nJy at λ = 1528 Å. The pulsar was not detected, however, at longer wavelengths, with 3σ upper limits of 52, 37, and 87 nJy at λ = 4326, 3355, and 2366 Å, respectively. Assuming that the pulsar counterpart was indeed detected in FUV, and the previously reported marginal U and B detections with the Very Large Telescope were real, the optical-UV spectrum of the pulsar can be described by a power-law model with a nearly flat f ν spectrum. Similar to younger pulsars detected in the optical, the slope of the nonthermal spectrum steepens in the X-ray range. The pulsar's luminosity in the 1500-6000 Å wavelength range, L ∼ 1.2 × 10 27 (d/210 pc) 2 erg s −1 , corresponds to a high efficiency of conversion of pulsar rotation energy loss rate Ė to the optical-UV radiation, η = L/ Ė ∼ (1-6) × 10 −4 , depending on somewhat uncertain values of distance and spectral slope. The brightness temperature of the bulk neutron star surface does not exceed 59,000 K (3σ upper bound), as seen by a distant observer. If we assume that the FUV flux is dominated by a thermal component, then the surface temperature can be in the range of 27,000-55,000 K, requiring a heating mechanism to operate in old neutron stars.

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Section: Possible Power-law Spectrum Of the Tentative Pulsar Counterpartsupporting

confidence: 77%

Hubble Space Telescope observations of the old pulsar PSR J0108-1431

Abramkin,

Shibanov,

Mignani

et al. 2021

Preprint

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“…Recent observations with NICER [187] discovered that these thermal spots have complicated shapes in the case of millisecond radio pulsars. These complicated shapes suggest that the underlying magnetic field contains small-scale magnetic fields [189,210] or the presence of a quadrupole component [211].…”

Section: Thermal Maps Of Nss and Their Relation To Magnetic Fields And Evolutionmentioning

confidence: 99%

Evolution of Neutron Star Magnetic Fields

2021

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Neutron stars are natural physical laboratories allowing us to study a plethora of phenomena in extreme conditions. In particular, these compact objects can have very strong magnetic fields with non-trivial origin and evolution. In many respects, its magnetic field determines the appearance of a neutron star. Thus, understanding the field properties is important for the interpretation of observational data. Complementing this, observations of diverse kinds of neutron stars enable us to probe parameters of electro-dynamical processes at scales unavailable in terrestrial laboratories. In this review, we first briefly describe theoretical models of the formation and evolution of the magnetic field of neutron stars, paying special attention to field decay processes. Then, we present important observational results related to the field properties of different types of compact objects: magnetars, cooling neutron stars, radio pulsars, and sources in binary systems. After that, we discuss which observations can shed light on the obscure characteristics of neutron star magnetic fields and their behaviour. We end the review with a subjective list of open problems.

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“…Recent observations with NICER [180] discovered that these thermal spots have complicated shapes in the case of millisecond radio pulsars. These complicated shapes suggest that the underlying magnetic field contains small-scale magnetic fields [182,203] or presence of a quadrupole component [204].…”

Section: Thermal Maps Of Nss and Their Relation To Magnetic Fields An...mentioning

confidence: 99%