Do magnetars really exist?

• Published in: Astronomy reports 2012, Vol.56 (1), p.29-34
• Main Author: Malov, I. F.
• Format: Article
• Language: English
• Subjects: Astronomy; Astrophysics; Energy sources; Gamma rays; Magnetic fields; Nuclear reactions; Observations and Techniques; Physics; Physics and Astronomy; Radio astronomy; Stars & galaxies
• ISSN: 1063-7729; 1562-6881
• DOI: 10.1134/S1063772912010064

We perform a comparative analysis of the properties of isolated single neutron stars and show the absence of any single typical feature providing unambiguous evidence that they belong to the classes of AXPs or SGRs. Several objects with features intermediate between AXPs and radio transients (RRATs) have been discovered recently: radio pulsars with high magnetic fields, radio-emitting AXPs, etc. Assuming the existence of fields of 10 16 G in the stellar interiors cannot explain the giant gamma-ray outbursts of SGRs. It appears necessary to invoke other energy sources, such as nuclear reactions in the matter that breaks through the crust of the neutron star. For the recently discovered AXP PSR J1642-4950, we find that the angle β between its spin axis and magnetic moment is 15.6°. This agrees with earlier estimates for the AXPs J1810-197 and 1E 1547.0-5408, which have β < 10°. The similarity of these objects to aligned rotators enables a description using the drift model. This model yields a rotational period for PSR J1642-4950 of P = 0.32 s, amagnetic field in the radiation generation region of B = 950 G, and a surfacemagnetic field of B s = 3.39×10 12 G. It is shown that the cyclotron instability in the neighbourhood proximity of the light cylinder, associated with particles in the tail of the secondary-plasma distribution, can explain the generation of the radio emission of PSR J1642-4950, which should be observed predominantly at low frequencies (∼100 MHz).