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West, D. K.

Publications and source records attributed to West, D. K..

11 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Hot wind from Gamma/2/ Velorum observed in the ultraviolet carbon lines

The close binary system Gamma(2) Vel, consisting of a WC8 and an O9 I star, has been observed in the ultraviolet at various phases. Preliminary analysis of selected data shows that the temperature of the stellar wind from this binary increases outward. This suggests that an additional source of energy other than radiation pressure may exist for the wind. The mass flow occurs in all directions from the binary. However, there is evidence of an increase in the mass flow through the third Lagrangian point, although from the extant data it is not possible to decide whether or not a similar increase in the mass outflow occurs through the second Lagrangian point. There is also evidence of mass surge, which probably is independent of orbital phase.

Kondo, Y.↗
NASA NTRS1978

In-flight performance of the IUE

A report on the initial performance of the IUE satellite, launched in January, 1978, is given. Attention is given to optical performance, camera performance, background corrections, photometric performance, and data reduction. Samples of high-dispersion and low-dispersion spectra are shown. A remaining problem of proper separation of high dispersion orders in data reduction is discussed.

Boggess, A.↗
NASA NTRS1977

A scientific operations plan for the large space telescope

The paper describes an LST ground system which is compatible with the operational requirements of the LST. The goal of the approach is to minimize the cost of post launch operations without seriously compromising the quality and total throughput of LST science. Attention is given to cost constraints and guidelines, the telemetry operations processing systems (TELOPS), the image processing facility, ground system planning and data flow, and scientific interfaces.

West, D. K.↗
NASA NTRS1976

Requirements and specifications of the space telescope for scientific operations

Requirements for the scientific operations of the Space Telescope and the Science Institute are used to develop operational interfaces between user scientists and the NASA ground system. General data systems are defined for observatory scheduling, daily science planning, and science data management. Hardware, software, manpower, and space are specified for several science institute locations and support options.

West, D. K.↗
NASA NTRS1975

A scientific operations plan for the NASA space telescope

A ground system is described which is compatible with the operational requirements of the space telescope. The goal of the ground system is to minimize the cost of post launch operations without seriously compromising the quality and total throughput of space telescope science, or jeopardizing the safety of the space telescope in orbit. The resulting system is able to accomplish this goal through optimum use of existing and planned resources and institutional facilities. Cost is also reduced and efficiency in operation increased by drawing on existing experience in interfacing guest astronomers with spacecraft as well as mission control experience obtained in the operation of present astronomical spacecraft.

West, D. K.↗
NASA NTRS1975

An upper limit on interstellar C IV in the spectrum of gamma-2 Velorum

An upper limit on the column density of C IV along the line of sight to gamma-2 Vel is derived from upper limits placed on the equivalent widths of the interstellar C IV doublet with rest wavelengths at 1548.20 A and 1550.77 A. A lower limit of 250,000 K is calculated for the electron temperature of O VI emitting regions by combining the C IV results with a measurement of the column density of interstellar O VI for the same star and using calculations for the relative ionization of some abundant elements as a function of electron temperature in a low-density plasma. Since gamma-2 Vel is in the central part of the Gum Nebula, the high temperature suggested by these results is shown to support the idea that a high-temperature phase of the interstellar medium, possibly maintained by supernova explosions, may exist.-

Lengyel-Frey, D.↗
NASA NTRS1972

An unusual absorption feature in the far ultraviolet spectrum of early type supergiants

The OAO-2 satellite has been used to obtain far ultraviolet scans of six early-type supergiants. The data reveal the presence of a distinct, broad absorption feature centered near 1720 A. This feature is unique in that it remains essentially constant in strength, breadth and central position over the spectral type range B0 I to A2 I. The feature also appears in the spectrum of the B-type shell star beta Tauri, with a strength comparable to that observed for the supergiants. It appears weakly, or not at all, in the B and A main sequence spectra we have examined. The hypothesis that the feature is due to a fortuitous blend of intrinsically strong lines arising primarily from the ground configurations of abundant metallic ions is discussed in detail.

Underhill, A. B.↗
NASA NTRS1972

OAO-2 observations of C III 1909 A line in gamma 2 Velorum

The C III 1909 A emission line in gamma 2 Velorum was observed over a period of 24 hours in an attempt to find short period time variability. Analysis of this data found no periods in the range of 0.5 to 200 minutes, and placed an upper limit of 3% on the amplitude of the stellar pulsations. Improved spectral resolution data for this line was obtained by offsetting the OAO-2 pointing in steps of 15 seconds of arc. The line profile derived by combining this offset data with the slit function shows a definite asymmetry. Although the improved resolution gives results which are barely sufficient for comparison with the prediction from model envelopes, some information concerning the abundance of carbon and the physical conditions of the envelope can be gained.

West, D. K.↗
NASA NTRS1972

An unusual absorption feature in the far-ultraviolet spectrum of early-type supergiants.

The OAO-II satellite has been used to obtain far-UV scans of six early-type supergiants. The data reveal the presence of a distinct, broad absorption feature centered near 1720 A. This feature is unique in that it remains essentially constant in strength, breadth, and central position over the spectral type range BO I to A2 I. The feature also appears in the spectrum of the B-type shell star zeta Tau, with a strength comparable to that observed for the supergiants. It appears weakly, or not at all, in the B and A main-sequence spectra examined. The presence of the feature in spectra of supergiants and a shell star supports the hypothesis that it is an extended-envelope phenomenon.

Underhill, A. B.↗