Engineering topics

Benson, J. A.

Publications and source records attributed to Benson, J. A..

6 records

NASA NTRS1995

First 2.2 micrometer results from the iota interferometer

We present the first infrared fringe visibility measurements made with the Infrared Optical Telescope Array on Mt. Hopkins. Effective temperatures are derived for RX Boo, RS Cnc, and Beta Peg. RX Boo is the coolest small-amplitude variable giant star to have an effective temperature determination. We compare the size of its photosphere at infrared wavelengths with the sizes of its SiO and H20 radio emission regions. We also discuss initial performance parameters for the interferometer.

Dyck, H. M.↗

NASA NTRS1992

10 AU scale halo structure around DG Tauri

Lunar occultation observations of the active T Tauri star DG Tau show that in the infrared K band it has a core-halo structure: 20-25 percent of the flux comes from a region 10 AU in extent and the rest from an unresolved core smaller than an AU. These results are consistent with those reported by Leinert et al. from a separate observation. The results obtained here and those of Leinert et al., measuring the intensity distribution projected along directions spanning roughly 40 deg, indicate that the resolved structure is not highly elongated. The extended emission is interpreted as star light scattered by optically thin dust located in a halo surrounding the star.

Chen, Wen P.↗

NASA NTRS1992

Multiplicity among the young stars in Taurus

Twenty-eight young stars systems in the northern Taurus star-forming region are surveyed for multiplicity. These observations, made by infrared lunar occultation and imaging techniques, can identify binaries in the angular separation range 0.005-10 arcsec. Of the 28 systems, 11 are binaries and two are triples, giving an observed multiplicity of 1.5 stars per system. The binary frequency and distribution of separations are similar to those of the main-sequence F and G spectral-type stars. Stars that have detected companions and those without are indistinguishable in H-alpha equivalent width, indicating that stars with active inner disks are represented in both groups. The multiple systems are in general weaker 1.3 mm continuum emitters than the single stars, indicating that the large-scale disks in these systems are less massive. However, there are important exceptions so the evolution of disks in multiple systems is not clear.

Simon, M.↗

NASA NTRS1991

The light curve and changes in the circumstellar envelope around IRC + 10216

This paper presents results of NIR photometric observations of IRC + 10216 star during the time interval 1965-1990, which were combined with measurements of the circumstellar shell surrounding IRC + 10216 by IR speckle interferometry. Using these data together with published observations, a very precise light curve was constructed, demonstrating the occurrence of long-term changes in the circumstellar shell surrounding IRC + 10216. The observations are discussed in the framework of two alternatives: (1) the occurrence of dynamical changes in the shell and (2) blocking of the direct light from the star to a portion of the shell by intervening material.

Dyck, H. M.↗

NASA NTRS1990

Discovery of five pre-main-sequence binaries in Taurus

The progress of an infrared K band lunar occultation search for binaries among premain-sequence stars is reported. From the fall of 1986 to the fall of 1989, 13 objects have been observed, all in the Taurus star-forming region. Five new binaries have been discovered: DF Tau, DI Tau, FS Tau (Haro 6-5) A, FV Tau (Haro 6-8), and FW Tau, with projected separations ranging from 0.01 to 0.57 arcsec. Including results reported previously, a total of 31 objects, 21 in Taurus and 10 in Ophiuchus, have been surveyed and nine double systems have been found. The detected binary frequency (0.29) seems consistent with that of the solar-type main-sequence field stars.

Chen, W. P.↗

NASA NTRS1969

Hydraulic calipers

Hydraulic calipers determine area of annular openings in irregular or concealed passages. With modifications the device could be adapted to investigations of cross-sectional changes in heat flow passages, ducts, conduits, and heat exchanger elements.

Benson, J. A.↗