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Cyclotron Line Measurements with INTEGRALDue to its broadband energy coverage, INTEGRAL has made important contributions to observing and interpreting cyclotron lines, which are present in the 10-100 keV range of a sample of accreting pulsars. In these systems photons with energies fulfilling the resonance condition inelastically Compton scatter off electrons quantized in the accretion column above the neutron star's magnetic pole(s). This process gives rise to the broad, absorption-like lines or 'cyclotron resonant scattering features' (CRSF). The observed lines allow to directly measure the B-fields of these sources, resulting in values of a few times 1E12G. In this overview I will present recent highlights regarding CRSF observations as well as discuss current ideas and models for the physical conditions in the accretion column. Among the former are the stability of the spectrum of Vela X-1 during giant flares in 2003, the observation of three cyclotron lines during the 2004 outburst of V0332+53, the confirmation of the fundamental line at approximately 45 keV during a 2005 normal outburst of A0535-26, and the simultaneous detection of the two lines in the dipping source 4U 1907+09 (for which also a torque reversal was detected for the first time). Through these and other observations it has become increasingly apparent that two types of observations can potentially be used to constrain the accretion column geometry: the determination of energy ratios for multiple harmonic lines (only two sources with greater than 2 lines are known), was well as the evolution of the fundamental line centroid, which, for different sources, may or may not be correlated with flux. Furthermore, first steps have been taken away from the usual phenomenological description of the lines, towards a physical approach based on self-consistent CRSF modeling. Initial applications are presented.
Document ID
20080030241
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Authors
Pottschmidt, K.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Kreykenbohm, I.
(Erlangen-Nuernberg Univ. Germany)
Caballero, I.
(Institut fur Astronomie und Astrophysik Germany)
Fritz, S.
(Institut fur Astronomie und Astrophysik Germany)
Schoenherr, G.
(American Inst. of Physics New York, NY, United States)
Kretschmar, P.
(European Space Astronomy Centre Madrid, Spain)
Wilms, J.
(Erlangen-Nuernberg Univ. Germany)
McBride, V. A.
(Southampton Univ. United Kingdom)
Suchy, S.
(California Univ. San Diego, CA, United States)
Rothschild, R. E.
(California Univ. San Diego, CA, United States)
Date Acquired
August 24, 2013
Publication Date
March 31, 2008
Subject Category
Astrophysics
Meeting Information
Meeting: INTEGRAL Session of the 10th HEAD Meeting
Location: Los Angeles, CA
Country: United States
Start Date: March 31, 2008
End Date: April 3, 2008
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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