X-Ray Doppler Imaging of 44i Bootis with Chandra
Abstract
Chandra High-Energy Transmission Grating observations of the bright eclipsing contact binary 44i Bootis show X-ray line profiles that are Doppler-shifted by orbital motions. The X-ray emission spectrum contains a multitude of lines superposed on a weak continuum, with strong lines of O VIII, Ne X, Fe XVII, and Mg XII. The profiles of these lines from the total observed spectrum show Doppler-broadened widths of ~550 km s-1. Line centroids vary with orbital phase, indicating velocity changes of greater than 180 km s-1. The first-order light curve shows significant variability but no clear evidence for either primary or secondary eclipses. Flares are observed for all spectral ranges; additionally, the light curve constructed near the peak of the emission measure distribution [Te=(5-8)×106 K] shows quiescent variability as well as flares. The phase dependences of line profiles and light curves together imply that at least half of the emission is localized at high latitude. A simple model with two regions on the primary star at relatively high latitude reproduces the observed line profile shifts and quiescent light curve. These first clear X-ray Doppler shifts of stellar coronal material illustrate the power of Chandra.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 2001
- DOI:
- 10.1086/338121
- arXiv:
- arXiv:astro-ph/0110560
- Bibcode:
- 2001ApJ...562L..75B
- Keywords:
-
- Atomic Processes;
- Stars: Binaries: Close;
- Stars: Activity;
- Stars: Individual: Constellation Name: 44i Bootis;
- Stars: Late-Type;
- X-Rays: Stars;
- Astrophysics
- E-Print:
- 15 pages, 6 figures to be published in Astrophysical Journal Letters