~ 6.4 keV Fe line: changes over the 35 d cycle
Possible
reasons:
1)an array of Fe K fluorescence lines
for all charge states from Fe I-Fe XIII to
Fe XXIII;
2)Comptonization from a hot corona (t »1) for a narrower range of charge states
centered »FeXX
3)Keplerian broadening
At
F35= 0.17: V ~13000 km/s Æ R~4x108 cm for M=1.4 M* ~ magnetospheric radius for B ~1012 G.
Change in line width: the FWHM is a factor 5-10 larger when the source is ³on²
Probably
near neutral Fe (Fe XIV or colder) in
the low state and short-on.
Main-on
line energies correspond to Fe XX-Fe
XXI
(MOS:
6.52±0.03 keV; PN:6.50±0.02 keV)
(s~20-50 eV at F35=0.26,0.6 to s~300 at F35=0.17).
Change in line center:
Probably
near neutral Fe (Fe XIV or colder) in
the low state and short-on.Main-on
line energies correspond to Fe XX-Fe
XXI (MOS:
6.52±0.03 keV; PN:6.50±0.02 keV)ORŠ.