|Coronagraphic Imaging of Nearby Stars|
Coronagraphic Imaging of Nearby Stars
Comparison with Ground-based View
Two nearby stars GJ1245AC (red dwarf binary system, distance ~14.8 light years) and GL293 (white dwarf, distance ~18.8 light years) have been imaged with the FOS/RD detector in ACQIMAGE mode.
The two components of the GJ1245AC binary system have been resolved in the FOS ACQIMAGE. The HST observation yields a separation of ~0.5 arcseconds between the two components with a position angle of 144 degrees. Comparison with the predicted orbit (Harrington 1990) shows the companion to be closer to the primary then expected, indicating a mass lower than the 0.085 solar mass estimate. In the right image, the companion is the bright area below the bar, while the faint area above the bar is the scattered light from the primary star.
No faint companion was found about Gl293.
[Left] Photographs showing sky surrounding targets, extracted from digital scan archive data of the Guide Star Selection System. The cross on the GSSS image represents the position of the target star at the EPOCH of the HST observation demonstrating there is no other star in the vicinity at that time.
[Middle] Short exposure FOS ACQIMAGE of targets. The target stars were observed with the 3.7" square aperture. The obvious choppy smearing of targets in the vertical direction within each deconvolved ACQIMAGE, as well as the noisy appearance of the point sources, is due to ringing from the image edges in the Fourier transform used to remove the rectangular nature of the FOS diodes.
[Right] Long exposure FOS ACQIMAGE of targets while centered behind the 0.27" bar of the 2.0-BAR aperture. The 2.0-BAR aperture is1.71" square with the bar across the center of the aperture. APEAK-DOWN target acquisition with the mirror was used to centerthe targets behind the bar. The PSF of Gl 293 is split, whilefor the GJ 1245 AC image, the companion is the bright area below the bar. The deconvolved images demonstratethat the PSF has been split and it is possible to image as close as 0.16" to a star. The FOS ACQIMAGE scale is ~0.08 arcseconds/pixel.
HST FOS Imaging Team: A. Schultz, H. Hart, F. Hamilton, M. Kochte (Computer Sciences Corporation), F. Bruhweiler (Catholic U.), G.F. Benedict (U. Texas), J.J. Caldwell, C. Cunningham (York University, Canada), O.G. Franz (Lowell Obs.), C.D. Keyes (STScI), J.C. Brandt (U. Colo.)
|Students for the Exploration and Development of Space|
Created by R. Mark Elowitz
Maintained byGuy K. McArthur