Long term variability of Cygnus X-1 VII. Orbital variability of the focussed wind in Cyg X-1/HDE 226868 system

被引：36

作者：

Grinberg, V. ^{[1
]}

Leutenegger, M. A. ^{[2
,3
]}

Hell, N. ^{[4
,5
,6
]}

Pottschmidt, K. ^{[2
,3
]}

Boeck, M. ^{[4
,5
,7
]}

Garcia, J. A. ^{[8
]}

Hanke, M. ^{[4
,5
]}

Nowak, M. A. ^{[1
]}

Sundqvist, J. O. ^{[9
,10
]}

Townsend, R. H. D. ^{[11
]}

Wilms, J. ^{[4
,5
]}

机构：

[1] MIT, Kavli Inst Astrophys & Space Res, Cambridge, MA 02139 USA

[2] Univ Maryland Baltimore Cty, CRESST, Baltimore, MD 21250 USA

[3] NASA, Goddard Space Flight Ctr, Astrophys Sci Div, Greenbelt, MD 20771 USA

[4] FAU Erlangen Nrnberg, Dr Karl Remeis Sternwarte, D-96049 Bamberg, Germany

[5] FAU Erlangen Nrnberg, ECAP, D-96049 Bamberg, Germany

[6] Lawrence Livermore Natl Lab, Livermore, CA 94550 USA

[7] Max Planck Inst Radioastron, D-53121 Bonn, Germany

[8] Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA

[9] Univ Delaware, Bartol Res Inst, Newark, DE 19716 USA

[10] Univ Munich, Inst Astron & Astrophys, D-81679 Munich, Germany

[11] Univ Wisconsin, Dept Astron, Madison, WI 53706 USA

来源：

ASTRONOMY & ASTROPHYSICS | 2015年 / 576卷

关键词：

stars: individual: Cyg X-1; X-rays: binaries; binaries : close; stars:; winds; outflows; LINE-DRIVEN INSTABILITY; LUMINOUS OB STARS; X-RAY VARIABILITY; MASS-LOSS; STELLAR WIND; BLACK-HOLE; SUPERORBITAL VARIABILITY; OPTICAL-SPECTRUM; RADIO-EMISSION; H-ALPHA;

D O I：

10.1051/0004-6361/201425418

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

Binary systems with an accreting compact object off er a unique opportunity to investigate the strong, clumpy, line-driven winds of early-type supergiants by using the compact object's X-rays to probe the wind structure. We analyze the two-component wind of HDE 226868, the O9.7Iab giant companion of the black hole Cyg X-1, using 4.77 Ms Rossi X-ray Timing Explorer (RXTE) observations of the system taken over the course of 16 years. Absorption changes strongly over the 5.6 d binary orbit, but also shows a large scatter at a given orbital phase, especially at superior conjunction. The orbital variability is most prominent when the black hole is in the hard X-ray state. Our data are poorer for the intermediate and soft state, but show signs for orbital variability of the absorption column in the intermediate state. We quantitatively compare the data in the hard state to a toy model of a focussed Castor-Abbott-Klein wind: as it does not incorporate clumping, the model does not describe the observations well. A qualitative comparison to a simplified simulation of clumpy winds with spherical clumps shows good agreement in the distribution of the equivalent hydrogen column density for models with a porosity length on the order of the stellar radius at inferior conjunction; we conjecture that the deviations between data and model at superior conjunction could either be due to lack of a focussed wind component in the model or to a more complicated clump structure.

引用

页数：11