Yearly Accomplishments Report by Christian A. Hummel (1997)

In the past 6 months (since becoming an employee of the USNO), I have worked
on four distinct projects or accomplishments:

	1:	Reduction and final analysis of two spectroscopic binaries
		observed with NPOI, and completion of a publication draft
		describing these results.

	2:	Maintenance and development of software (CHAMELEON, AMOEBA)
		related to astrometry reduction and model fitting.

	3: 	Attendance of and presentation of posters at two conferences,
		the AAS meeting #191 in Washington and the SPIE meeting in Kona.
	
	4:	Continued scheduling of NPOI observations and reduction of data.
		A visit to Flagstaff for observations and discussion of data
		reduction items. Review of a paper for Astronomy and 
		Astrophysics.

ad 1:

I calibrated NPOI data of Mizar A (Zeta 1 Ursae Majoris) and Matar 
(Eta Pegasi), about 25 nights on the former and 15 nights on the latter.
I derived a new orbit for Mizar A (mean residual 80 micro arcseconds), and
determined stellar masses by combining the interferometry with spectroscopy
obtained from the literature. The fitting of orbital elements and masses to
the combined data was done using AMOEBA. In the case of Matar, I combined the
NPOI data with unpublished Mark III data, as well as spectroscopy of the
primary and a parallax measured for the system by Hipparcos in order to derive
orbital elements and component masses. (About 31 binary systems with Hipparcos 
orbit solutions are bright enough for us to observe. For these, masses can be
determined even if no spectroscopy is available.) I have written a draft of a 
paper on these results, which has been modified and improved several times 
using comments from the co-authors.

ad 2:

I added software to CHAMELEON in order to enable the computation of delay
corrections from the (x,y,z) catseye motions determined in INCHWORM. These
corrections are applied to the measured delay line positions. I also 
modified and improved code to determine dispersion corrections to the delays.
The corrections correlate very well with residual delay variations. The
improvement in the rms scatter of the 1s delay is several fold.

ad 3:

I presented the Mizar A and Matar results at the conferences in Washington
and Kona. The posters also explained the calibration and remaining problems,
as well as model fitting procedures. For the AAS meeting in Washington, I
prepared a press release showing images of Mizar A and the relative orbit,
as well as a poster display used at the USNO presentation booth.

ad 4:

I scheduled and reduced some 45 observations with NPOI. Calibration was often
preliminary since this is the PI's responsibility. A new binary was found
(Zeta Orionis), with a separation of 42 milliarcseconds. Orbital motion in
this system was detected in three observations spaced by approximately 15 days.