Eta Carinae's Thermal X-ray Tail Measured with XMM-Newton and NuSTAR .

Autor: Hamaguchi K; CRESST and X-ray Astrophysics Laboratory NASA/GSFC, Greenbelt, MD 20771.; Department of Physics, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250., Corcoran MF; CRESST and X-ray Astrophysics Laboratory NASA/GSFC, Greenbelt, MD 20771.; Universities Space Research Association, 7178 Columbia Gateway Dr., Columbia, MD 21044., Gull TR; Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771., Takahashi H; Department of Physical Sciences, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526, Japan., Grefenstette B; Space Radiation Lab, California Institute of Technology, Pasadena, CA 91125., Yuasa T; Nishina Center, RIKEN, 2-1, Hirosawa, Wako, Saitama, Japan, 351-0198, Japan., Stuhlinger M; European Space Astronomy Centre (ESAC), P.O. Box 78, 28691 Villanueva de la Caada, Madrid, Spain., Russell C; Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771.; NASA Postdoctoral Program Fellow., Moffat AFJ; Département de physique and Centre de Recherche en Astrophysique du Québec (CRAQ), Université de Montréal, C.P. 6128., Madura T; CRESST and X-ray Astrophysics Laboratory NASA/GSFC, Greenbelt, MD 20771.; Universities Space Research Association, 7178 Columbia Gateway Dr., Columbia, MD 21044., Richardson ND; Département de physique and Centre de Recherche en Astrophysique du Québec (CRAQ), Université de Montréal, C.P. 6128., Groh J; Geneva Observatory, Geneva University, Chemin des Maillettes 51, CH-1290 Sauverny, Switzerland., Pittard J; School of Physics and Astronomy, The University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK., Owocki S; Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, Newark, DE 19716, USA.
Jazyk: angličtina
Zdroj: The Astrophysical journal [Astrophys J] 2016 Jan 19; Vol. Volume 817 (No 1).
DOI: 10.3847/0004-637x/817/1/23
Abstrakt: The evolved, massive highly eccentric binary system, η Car, underwent a periastron passage in the summer of 2014. We obtained two coordinated X-ray observations with XMM-Newton and NuSTAR during the elevated X-ray flux state and just before the X-ray minimum flux state around this passage. These NuSTAR observations clearly detected X-ray emission associated with η Car extending up to ~50 keV for the first time. The NuSTAR spectrum above 10 keV can be fit with the bremsstrahlung tail from a kT ~6 keV plasma. This temperature is Δ kT ~2 keV higher than those measured from the iron K emission line complex, if the shocked gas is in collisional ionization equilibrium. This result may suggest that the companion star's pre-shock wind velocity is underestimated. The NuSTAR observation near the X-ray minimum state showed a gradual decline in the X-ray emission by 40% at energies above 5 keV in a day, the largest rate of change of the X-ray flux yet observed in individual η Car observations. The column density to the hardest emission component, N H ~10 24 H cm -2 , marked one of the highest values ever observed for η Car, strongly suggesting the increased obscuration of the wind-wind colliding X-ray emission by the thick primary stellar wind prior to superior conjunction. Neither observation detected the power-law component in the extremely hard band that INTEGRAL and Suzaku observed prior to 2011. The power-law source might have faded before these observations.
Databáze: MEDLINE