Artigo Acesso aberto Revisado por pares

Discovery of a Third Harmonic Cyclotron Resonance Scattering Feature in the X-Ray Spectrum of 4U 0115+63

1999; IOP Publishing; Volume: 521; Issue: 1 Linguagem: Inglês

10.1086/312172

ISSN

1538-4357

Autores

W. A. Heindl, W. Coburn, D. E. Gruber, M. R. Pelling, R. E. Rothschild, J. Wilms, K. Pottschmidt, R. Staubert,

Tópico(s)

Astrophysical Phenomena and Observations

Resumo

We have discovered a third harmonic cyclotron resonance scattering feature (CRSF) in observations of the recent outburst of 4U 0115+63 with the Rossi X-Ray Timing Explorer (RXTE). The spectrum in a narrow pulse phase range shows CRSFs at 12.40, 21.45, and 33.56 keV. With centroid energy ratios to the fundamental of 1.73 ± 0.08 and 2.71 ± 0.13, the CRSFs are not harmonically spaced. Strong variability of the continuum and CRSFs with pulse phase indicate a complex emission geometry near the neutron star polar cap. In addition, one RXTE observation, which spanned periastron passage, revealed a strong 2 mHz quasi-periodic oscillation (QPO). This is slower by 2 orders of magnitude than the beat-frequency QPO expected in this system and slower by a factor of more than 5 compared with other QPOs seen in accreting X-ray pulsars.

Referência(s)