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(Referência obtida automaticamente do Web of Science, por meio da informação sobre o financiamento pela FAPESP e o número do processo correspondente, incluída na publicação pelos autores.)

Magnetic dipole moment of soft gamma-ray repeaters and anomalous X-ray pulsars described as massive and magnetic white dwarfs

Texto completo
Coelho, Jaziel G. [1] ; Malheiro, Manuel [1]
Número total de Autores: 2
Afiliação do(s) autor(es):
[1] CTA, Inst Tecnol Aeronaut, Dept Fis, BR-12228900 Sao Jose Dos Campos - Brazil
Número total de Afiliações: 1
Tipo de documento: Artigo Científico
Citações Web of Science: 19

Anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs) are some of the most interesting groups of pulsars that have been intensively studied in recent years. They are understood as neutron stars (NSs) with super-strong magnetic fields, namely B greater than or similar to 10(14) G. However, in the last two years two SGRs with low magnetic fields B similar to (10(12)-10(13)) G have been detected. Moreover, three fast and very magnetic white dwarfs (WDs) have also been observed in recent years. Based on these new pulsar discoveries, we compare and contrast the magnetic fields, magnetic dipole moment, characteristic ages, and X-ray steady luminosities of these two SGRs (in the WD model) with the three fast white dwarfs, to conclude that they show strong similarities corroborating an alternative description of several SGRs/AXPs as very massive and magnetic white dwarfs. We show that the values for m obtained for several SGRs and AXPs are in agreement with the observed range 10(34) emu <= m <= 10(36) emu of isolated and polar magnetic white dwarfs. This result, together with the fact that for magnetic white dwarfs B similar to (10(6)-10(8)) G their magnetic dipole moments are almost independent of the star rotation period (10(4) s less than or similar to P less than or similar to 10(6) s)-a phenomenology not shared by neutron star pulsars-suggests a possible magnetic white dwarf nature for some SGRs/AXPs that have much smaller periods (P similar to 10 s). Moreover, since for pulsars the dipole radiation power is proportional only to m and to the rotational star frequency, we can explain in the WD model-considering only the different scales of the magnetic dipole moment for WDs and NSs-why the steady luminosity L-X for several SGRs/AXPs (and in particular the low-B SGRs) compared to those of X-ray dim isolated neutron stars (XDINs) and high-B pulsars obeys the ratio L-X(SGRs/AXPs)/L-X(XDINs) similar to m(WD)/m(NS) similar to 10(3): all these X-ray sources have essentially the same rotational periods (P similar to 10 s) and the X-ray luminosity is correlated to the spin-down luminosity, which is equal to the dipole radiation power in the dipole model. (AU)

Processo FAPESP: 07/03633-3 - A matéria hadrônica e QCD em astrofísica: supernovas, GRBS e estrelas compactas
Beneficiário:Jorge Ernesto Horvath
Linha de fomento: Auxílio à Pesquisa - Temático