Engineering topics

Han, Inwoo

Publications and source records attributed to Han, Inwoo.

4 records

NASA NTRS2001

A Combined HIPPARCOS and Multichannel Astrometric Photometer Study of the Proposed Planetary System of Rho Coronae Borealis

Hipparcos and Multichannel Astrometric Photometer (MAP) observations of rho Coronae Borealis independently display astrometric motion at the period of the proposed extrasolar planetary companion to the star. Individual least-squares fits to each astrometric data set yield independent estimates of the semimajor axis, inclination, and node angle that are in excellent agreement. A combined solution of the Hipparcos and MAP data yields an inclination of 0.5 deg, a node at 30.5 +/- 12.4, and a semimajor axis of 1.66 +/- 0.35 mas, indicating a companion mass of 0.14 +/- 0.05 solar masses over two orders of magnitude greater than the minimum mass for the companion as determined by radial velocity studies. This mass is approximately that of an M dwarf star, the companion cannot be a planetary object.

Gatewood, George↗

NASA NTRS1990

Map-based trigonometric parallaxes of open clusters - The Pleiades

The multichannel astrometric photometer and Thaw refractor of the University of Pittsburgh's Allegheny Observatory have been used to determine the trigonometric parallax of the Pleiades star cluster. The distance determined, 150 with a standard error of 18 parsecs, places the cluster slightly farther away than generally accepted. This suggests that the basis of many estimations of the cosmic distance scale is approximately 20 percent short. The accuracy of the determination is limited by the number and choice of reference stars. With careful attention to the selection of reference stars in several Pleiades regions, it should be possible to examine differences in the photometric and trigonometric modulus at a precision of 0.1 magnitudes.

Gatewood, George↗

NASA NTRS1988

A study of Upgren 1

Upgren and Rubin (1965) have suggested that a small group of bright F stars, in the direction of the galactic north pole, may be the remnant of an old cluster. The multichannel astrometric photometer (MAP) has been used to determine the parallaxes of six of the candidate stars with an average precision of 1.1 thousandths of an arcsecond (1.1 mas). The derived distances are, as suggested, similar, and an unusual space density of F stars seems indicated. However, the derived space velocities indicate that the proposed cluster is composed of members of two dynamically different groups.

Gatewood, George↗

NASA NTRS1986

The astrometric search for IR dwarfs

The authors are unaware of any current astrometric search for Brown (IR) Dwarfs; the few results available have come from studies directed toward other goals. Nevertheless, the lack of confirmable results is somewhat unexpected. New electronic detectors now in use at two observatories, as well as that of planned systems, have sufficient accuracy to detect IR dwarf companions to any of hundreds, in the latter case millions, of stars. However, because of the limited size of the astrometric program that can be supported by each instrument, the number of existing and planned astrometric facilities are insufficient for extensive surveys.

Gatewood, George↗