Atmospheres and Spectra of Strongly Magnetized Neutron Stars. III. Partially Ionized Hydrogen Models

By W. Ho, D. Lai, A. Potekhin, G. Chabrier. 2001

166 citations recorded by the source corpus.

We construct partially ionized hydrogen atmosphere models for magnetized neutron stars in radiative equilibrium with surface fields B = 1012-5 × 1014 G and effective temperatures Teff ~ a few × 105-106 K. These models are based on the latest equation of state and opacity results for magnetized, partially ionized hydrogen plasmas that take into account various magnetic and dense medium effects. The atmospheres directly determine the characteristics of thermal emission from isolated neutron stars. For the models with B = 1012-1013 G, the spectral features due to neutral atoms lie at extreme UV and very soft X-ray energy bands and therefore are difficult to observe. However, the continuum flux is also different from the fully ionized case, especially at lower energies. For the superstrong field models (B ≳ 1014 G), we show that the vacuum polarization effect not only suppresses the proton cyclotron line as shown previously, but also suppresses spectral features due to bound species; therefore, spectral lines or features in thermal radiation are more difficult to observe when the neutron star magnetic field is ≳1014 G.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/063fe04897bdb7276085c7a102eeb3b4719995ac

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. J. Lattimer
2. A. Watts
3. A. Harding
4. T. Strohmayer
5. S. Guillot
6. W. Ho
7. D. Lai
8. José A. Pons

Citations in the corpus

• The Radius of the High-mass Pulsar PSR J0740+6620 with 3.6 yr of NICER Data (2024, methodology): “As before, we use the mass, inclination, and distance priors from Fonseca et al. (2021), interstellar attenuation model TBabs (Wilms et al. 2000, updated in 2016), and a fully ionized hydrogen atmosphere model NSX (Ho & Lai 2001).”
• A NICER View of PSR J0030+0451: Millisecond Pulsar Parameter Estimation (2019, methodology): “For all models a geometrically-thin (and thus plane-parallel) fully-ionized hydrogen NSX atmosphere is invoked for the radiating material (Ho & Lai 2001; Ho & Heinke 2009).”
• Cyclotron lines in highly magnetized neutron stars (2018, background): “1 in Ho et al. (2003) the atomic fraction of hydrogen at temperatures of kT = 50−100 eV typical for the M7 is rather low (<=0.3 %).”
• An Updated Mass–Radius Analysis of the 2017–2018 NICER Data Set of PSR J0030+0451 (2023, background): “Throughout this work we assume that the hot spots of PSR J0030 + 0451 have a fully ionized and nonmagnetic NSX hydrogen atmosphere ( Ho & Lai 2001; Ho & Heinke 2009 ) .”
• Toward a Mass and Radius Determination of the Nearby Isolated Neutron Star RX J185635–3754 (2001, background): “More recent models with higher magnetic fields, appropriate for magnetars, seem to require hard power-law tails (Ho & Lai 2001; Özel 2001), and even a deficit of low energy photons, relative to the best blackbody fit, neither of which are observed in this case (although their models are for hotter…”
• Physics of strongly magnetized neutron stars (2006, methodology): “Fitting formulae for Em0 are given in Potekhin (1998) and in Ho et al (2003).”
• PSR J0030+0451 Mass and Radius from NICER Data and Implications for the Properties of Neutron Star Matter (2019, methodology): “Our model atmospheres were constructed assuming that the gas in the atmosphere is fully ionized, and hence that the dominant opacity is free–free absorption (Ho & Lai 2001).”