The following are examples of my research activities in cross-dispersion
Figure 1 (Top): Simulations of how the dispersed images of the binary
Cepheid + A star system AW Per are expected to appear on the FOC detector
when the separations of the components of the system perpendicular to the
dispersion are: 0 milli arc sec (mas), 28 mas, and 56 mas (a wavelength
scale is shown at the bottom). The two spectra lie on top of one another in
the uppermost image, are under resolved in the middle one and are just
resolved in the lower one. In the resolved image, it is clear that the
Cepheid is dominating the long wavelength portion of the spectrum and the
A star dominates the short wavelength portion.
(Bottom): The wavelength dependence of the cross-dispersion centroid
position derived from the simulated images and normalized to unity. This
quantity shows how the centroid shifts from the position of one star to the
other and also demonstrates how the presence of strong features in one star,
such as the Mg II 2800 Å doublet in the Cepheid, causes the centroid
to swing toward the position of the other star over a localized region.
- Cross-dispersion imaging
- Massa and Endal developed the
notion of cross-dispersion imaging to obtain "super-Rayleigh" spatial
resolution for certain applications. I am currently the PI on a Cycle
6 HST GO proposal to apply this technique to binary Cepheid + B
star binaries. If sucessful, it would be the first time that a binary
system with a Cepheid component has been spatially resolved, and would
open up the possibility of bypassing 2 rungs of the "Cosmic Distance
Ladder". A talk decussing the results of these observations delivered
in March 2001 can be found
- A further application of this
concept has been proposed for a balloon project entitled
ELFS -- Extremely Long Focal Length
- ``Optical concepts for the Binary Star Explorer'', W.A. Traub, D.
Massa, A. Endal, J.M. Beckers, D.W. Latham, H.A. McAlister, & S.B.
Parsons, 1987, SPIE, 751, 72
- ``An Instrument for Optimizing a Space borne Interferometer:
Applications to Calibrating the Cepheid Distance Scale'', D. Massa & A.S.
Endal 1987, AJ, 93, 760
- ``Expected Angular Separations of Late-Type Supergiant + B Star
Binaries in the Milky Way and LMC'', D. Massa & A.S. Endal 1987, AJ, 93,