TY - JOUR
T1 - Heating in an extended accretion disk corona along the z-pattern in CYG X-2
AU - Schulz, N. S.
AU - Huenemoerder, D. P.
AU - Ji, L.
AU - Nowak, M.
AU - Yao, Y.
AU - Canizares, C. R.
PY - 2009
Y1 - 2009
N2 - We observed at very high spectral resolution the prototype Z-source Cyg X-2 twice along its entire X-ray spectral variation pattern. In this preliminary analysis, we find an extended accretion disk corona (ADC) exhibiting Lyα emissions from various H-like ions, as well as emissions from He-like ions of Fe and Al, and Be-like ions of Fe. The brightest lines show a range of line broadening: H-like lines are very broad with Doppler velocities between 1100 and 2700 km s-1, while some others are narrower with widths of a few hundred km s-1. Line diagnostics allow us for the first time to determine coronal parameters. The line properties are consistent with a stationary, extended up to 1010 cm, dense (1 × 1015 cm-3), and hot (log ξ ≳ 3; T ≳ 106 K) ADC. We find ongoing heating of the corona along the Z-track and determine that heating luminosities change from about 0.4×L Edd on the horizontal to about 1.4 × L Edd on the flaring branch.
AB - We observed at very high spectral resolution the prototype Z-source Cyg X-2 twice along its entire X-ray spectral variation pattern. In this preliminary analysis, we find an extended accretion disk corona (ADC) exhibiting Lyα emissions from various H-like ions, as well as emissions from He-like ions of Fe and Al, and Be-like ions of Fe. The brightest lines show a range of line broadening: H-like lines are very broad with Doppler velocities between 1100 and 2700 km s-1, while some others are narrower with widths of a few hundred km s-1. Line diagnostics allow us for the first time to determine coronal parameters. The line properties are consistent with a stationary, extended up to 1010 cm, dense (1 × 1015 cm-3), and hot (log ξ ≳ 3; T ≳ 106 K) ADC. We find ongoing heating of the corona along the Z-track and determine that heating luminosities change from about 0.4×L Edd on the horizontal to about 1.4 × L Edd on the flaring branch.
KW - Accretion, accretion disks
KW - Binaries: close
KW - Stars: individual (Cyg X-2)
KW - Stars: neutron
KW - Techniques: spectroscopic
KW - X-rays: stars
UR - https://www.scopus.com/pages/publications/64849099378
U2 - 10.1088/0004-637X/692/2/L80
DO - 10.1088/0004-637X/692/2/L80
M3 - Article
AN - SCOPUS:64849099378
SN - 0004-637X
VL - 692
SP - L80-L83
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
ER -