Models of hydrostatic magnetar atmospheres at high luminosities
| Autor: | Caroline D'Angelo, T. van Putten, Matthew G. Baring, Anna L. Watts, Chryssa Kouveliotou |
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| Přispěvatelé: | High Energy Astrophys. & Astropart. Phys (API, FNWI) |
| Jazyk: | angličtina |
| Rok vydání: | 2013 |
| Předmět: |
Astrophysics::High Energy Astrophysical Phenomena
FOS: Physical sciences Field strength Astrophysics Magnetar 01 natural sciences law.invention symbols.namesake law 0103 physical sciences Radiative transfer Astrophysics::Solar and Stellar Astrophysics 010306 general physics 010303 astronomy & astrophysics High Energy Astrophysical Phenomena (astro-ph.HE) Physics Photosphere Astronomy Astronomy and Astrophysics Radius Neutron star 13. Climate action Space and Planetary Science Eddington luminosity symbols Astrophysics::Earth and Planetary Astrophysics Hydrostatic equilibrium Astrophysics - High Energy Astrophysical Phenomena |
| Zdroj: | Monthly Notices of the Royal Astronomical Society, 434(2), 1398-1410. Oxford University Press |
| ISSN: | 1365-2966 0035-8711 |
| Popis: | We investigate the possibility of Photospheric Radius Expansion (PRE) during magnetar bursts. Identification of PRE would enable a determination of the magnetic Eddington limit (which depends on field strength and neutron star mass and radius), and shed light on the burst mechanism. To do this we model hydrostatic atmospheres in a strong radial magnetic field, determining both their maximum extent and photospheric temperatures. We find that spatially-extended atmospheres cannot exist in such a field configuration: typical maximum extent for magnetar-strength fields is ~10 m (as compared to 200 km in the non-magnetic case). Achieving balance of gravitational and radiative forces over a large range of radii, which is critical to the existence of extended atmospheres, is rendered impossible in strong fields due to the dependence of opacities on temperature and field strength. We conclude that high luminosity bursts in magnetars do not lead to expansion and cooling of the photosphere, as in the non-magnetic case. We also find the maximum luminosity that can propagate through a hydrostatic magnetar atmosphere to be lower than previous estimates. The proximity and small extent of the photospheres associated with the two different polarization modes also calls into question the interpretation of two blackbody fits to magnetar burst spectra as being due to extended photospheres. Accepted for publication in MNRAS. 14 pages, 6 figures, 2 tables |
| Databáze: | OpenAIRE |
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