2011A&A...532A..76F -
Astronomy and Astrophysics, volume 532A, 76-76 (2011/8-1)
4U 0115+63: phase lags and cyclotron resonant scattering.
FERRIGNO C., FALANGA M., BOZZO E., BECKER P.A., KLOCHKOV D. and SANTANGELO A.
Abstract (from CDS):
High-mass X-ray binaries are among the brightest objects of our Galaxy in the high-energy domain (0.1-100keV). Despite our relatively good knowledge of their basic emission mechanisms, the complex problem of understanding their time- and energy- dependent X-ray emission has not been completely solved. In this paper, we study the energy-dependent pulse profiles of the high-mass X-ray binary pulsar 4U 0115+63 to investigate how they are affected by cyclotron resonant scattering. We analyzed archival BeppoSAX and RXTE observations performed during the giant outburst of the source that occurred in 1999. We exploited a cross correlation technique to compare the pulse profiles in different energy ranges and developed a relativistic ray-tracing model to interpret our findings. We also studied the phase dependency of the cyclotron absorption features by performing phase-resolved spectroscopy. The pulse profiles of 4U 0115+63 displayed clear ``phase-lags'' at energies close to those of the cyclotron absorption features that characterize the X-ray emission of the source. We reproduce this phenomenon qualitatively by assuming an energy-dependent beaming of the emission from the column surface and verify that our model is also compatible with the results of phase-resolved spectral analysis. We show that cyclotron resonant scattering affects the pulse profile formation mechanisms in a complex way, which necessitates both improvements in the modeling and the study of other sources to be better understood.
Abstract Copyright:
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Journal keyword(s):
X-rays: binaries - pulsars: individual: 4U 0115+63
CDS comments:
Paragraph 1 EXO 2030+275 is a probable misprint for EXO 2030+375 and V 0332+65 for V 0332+53.
Simbad objects:
6
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