C.D.S. - SIMBAD4 rel 1.7 - 2019.12.05CET16:26:28

2014A&A...562A..62K - Astronomy and Astrophysics, volume 562A, 62-62 (2014/2-1)

Spectral formation in a radiative shock: application to anomalous X-ray pulsars and soft gamma-ray repeaters.


Abstract (from CDS):

In the fallback disk model for the persistent emission of anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs), the hard X-ray emission arises from bulk- and thermal Comptonization of bremsstrahlung photons, which are generated in the accretion column. The relatively low X-ray luminosity of these sources implies a moderate transverse optical depth to electron scattering, with photons executing a small number of shock crossings before escaping sideways. We explore the range of spectral shapes that can be obtained with this model and characterize the most important parameter dependencies. We use a Monte Carlo code to study the crisscrossing of photons in a radiative shock in an accretion column and compute the resulting spectrum. As expected, high-energy power-law X-ray spectra are produced in radiative shocks with photon-number spectral index Γ>0.5. We find that the required transverse optical depth is 1≲τ{perpendicular}≲7. Such spectra are observed in low-luminosity X-ray pulsars. We demonstrate here with a simple model that Compton upscattering in the radiative shock in the accretion column can produce hard X-ray spectra similar to those seen in the persistent and transient emission of AXPs and SGRs. In particular, one can obtain a high-energy power-law spectrum, with photon-number spectral-index Γ∼1 and a cutoff at 100-200keV, with a transverse Thomson optical depth of ∼5, which is shown to be typical in AXPs/SGRs.

Abstract Copyright:

Journal keyword(s): accretion, accretion disks - stars: magnetars - X-rays: stars - pulsars: general

Simbad objects: 5

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Number of rows : 5

N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
1 PSR J0146+6145 Psr 01 46 22.21 +61 45 03.8   28.100 25.620     ~ 501 0
2 V* X Per HXB 03 55 23.0778791365 +31 02 45.045745259 6.090 6.840 6.720     O9.5III 898 0
3 NAME Sgr J0418+5729 gam 04 18 33.867 +57 32 22.91           ~ 178 0
4 BD+53 2790 HXB 22 07 56.2368407539 +54 31 06.405811141 9.4 10.11 9.84 9.64 9.43 O9.5Vep 171 0
5 2E 4673 HXB 23 01 08.14 +58 52 44.5           ~ 577 1

    Equat.    Gal    SGal    Ecl

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