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Title: A Chandra grating observation of the dusty Wolf-Rayet star WR 48a

We present results of a Chandra High-Energy Transmission Grating (HETG) observation of the carbon-rich Wolf-Rayet (WR) star WR 48a. These are the first high-resolution spectra of this object in X-ray. Blueshifted centroids of the spectral lines of ∼ – 360 km s{sup –1} and line widths of 1000-1500 km s{sup –1} (FWHM) were deduced from the analysis of the line profiles of strong emission lines. The forbidden line of Si XIII is strong and not suppressed, indicating that the rarified 10-30 MK plasma forms far from strong sources of far-ultraviolet emission, most likely in a wind collision zone. Global spectral modeling showed that the X-ray spectrum of WR 48a suffered higher absorption in the 2012 October Chandra observation compared with a previous 2008 January XMM-Newton observation. The emission measure of the hot plasma in WR 48a decreased by a factor ∼3 over the same period of time. The most likely physical picture that emerges from the analysis of the available X-ray data is that of colliding stellar winds in a wide binary system with an elliptical orbit. We propose that the unseen secondary star in the system is another WR star or perhaps a luminous blue variable.
Authors:
 [1] ;  [2] ;  [3]
  1. Space Research and Technology Institute, Akad. G. Bonchev Str., bl.1, Sofia 1113 (Bulgaria)
  2. Department of Geology and Astronomy, West Chester University, West Chester, PA 19383 (United States)
  3. CASA, University of Colorado, Boulder, CO 80309 (United States)
Publication Date:
OSTI Identifier:
22357206
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 785; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; CARBON; COLLISIONS; COMPARATIVE EVALUATIONS; EMISSION; FAR ULTRAVIOLET RADIATION; HOT PLASMA; LINE WIDTHS; ORBITS; POWER TRANSMISSION; RESOLUTION; SHOCK WAVES; STELLAR WINDS; WOLF-RAYET STARS; X RADIATION; X-RAY SPECTRA