Samuel C. Barden

EVALUATION OF SOME FIBER OPTICAL WAVEGUIDES FOR ASTRONOMICAL INSTRUMENTATION

Fused silica optical fibers were examined with a view toward use in fiber-coupled spectrographs. The emphasis of the investigation was on how well the input focal ratio was preserved during transmission down a long fiber. The best overall performance was given by the Galite 4000 series and the Maxlight 150 micron fibers. The Valtec products also yielded good results when cabled so that stress could not be easily induced. It was found that the smaller fibers yielded better performance with respect to focal ratio preservation.

Performance of the WIYN fiber-fed MOS system: Hydra

The KPNO fiber-fed, multi-object spectroscopic instrument, Hydra, has been moved from the Mayall to the WIYN telescope. Modifications to the instrument allow the fibers to align with the telescope exit pupil while lying along the curved focal surface. We also upgraded the manner in which the fibers are held in place around the focal plane in order to reduce neighboring fiber interactions beyond the pivot circle. In addition, the wavelength calibration assembly was modified to take advantage of extra room within the instrument. We developed guiding algorithms which utilize the field orientation probes (7-fiber coherent bundles). The bench spectrograph associated with Hydra was also moved over to the WIYN. Commissioning is currently underway at the time of this paper and is expected to be complete by mid-summer of 1995. We give a general description of the instrument, discuss initial efficiency and scattered light measurements, and comment on the performance of the guider.

Modifying Hydra for the WIYN telescope: an optimum telescope, fiber MOS combination

The KPNO fiber-fed, multi-object spectroscopic instrument, Hydra, is being moved from the Mayall to the WIYN telescope. The WIYN telescope has good concentricity between the focal surface radius and the exit pupil. The primary modification to the instrument will allow the fibers to align with the telescope exit pupil while lying along the curved focal surface. Maximum pupil alignment losses will be reduced from 15% at the Mayall to 5% at the WIYN. The new orientation of the instrument requires a different mechanism for accessing the fiber and focal plate for maintenance. We are also upgrading the manner in which the fibers are held in place around the focal plane in order to reduce neighboring fiber interactions beyond the pivot circle. The wavelength calibration assembly is being modified to take advantage of extra room in the instrument. For guiding, instead of using offset guide probes, we are developing an algorithm which will utilize the field orientation probes. The Bench Spectrograph associated with Hydra is also being moved over to the WIYN, however, we do not discuss the spectrograph in this paper.

BF Orionis - Evidence for an infalling circumstellar envelope

Analysis of the optical magnitudes and Balmer lines of the Herbig Ae/Be star BF Orionis confirm that the object is an early to mid A-type star, but appears to be below the zero-age main sequence. Enhanced metal line strengths (once thought to link BF Ori with the Am stars), line asymmetries, and radial velocities are shown to be signatures of an infalling circumstellar envelope. The possibility that BF Ori may have a late type companion is investigated, and it is concluded that it does not

Coordinated optical and ultraviolet observations of DH Leo

Results are reported from contemporaneous KPNO optical spectroscopy, IUE UV spectroscopy, and KPNO R photometry of the DH Leo triple system in spring 1987. The data are presented in tables, graphs, and spectral phase images and discussed in detail. The H-alpha, H-beta, H-gamma, H-delta, and Ca II H and IRT lines are found to have excess emission, and the phase modulation in H-alpha, H-beta, and Ca II is well correlated with the photometric modulation. This result is attributed to the combination of (1) a small amount of global chromospheric emission and (2) emission from plagelike regions associated with cool starspots. The (H-alpha)/(H-beta) ratio is found to be significantly lower than that in longer-period RS CVn systems. 22 refs.

Kitt Peak National Observatory fiber actuator device

A robot for positioning fiber optics in the focal plane of the Mayall 4-meter telescope has been constructed at Kin Peak National Observatory (KPNO). This fiber actuator device (FAD) will position up to 100 fibers for multi-object spectroscopy over a 45 arc-minute field. The positioner is based upon the AUTOFIB concept which uses magnets to hold the fibers in place. We have incorporated a unique gripping mechanism which allows a TV camera to view both the fiber and sky simultaneously.

Spectroscopic monitoring of RS CVN stars at Kitt Peak using the Penn State Fiber Optic Echelle

The Penn State Fiber Optic Echelle has been moved to Kitt Peak and works with either the coude feed telescope or 2.1 meter. It is about twice as efficient as the coude Camera No. 5 for similar bandpass at 600 nm and is comparable at 400 nm using the coude feed telescope. The high illumination stability afforded by the fiber is a decided advantage where spectrophotometric and radial velocity stability are at a premium, as in the study of active stars. We are using this instrument to intensively monitor about 10 regular RS CVn systems and about six short period and W UMa systems for a two week period each observing semester.

Search for Low-Amplitude Stellar Motions in NGC 752 1

We report preliminary results of a radial velocity study of the old open cluster NGC 752 using an ensemble mean approach with Hydra multi-fiber spectroscopy on the 3.5-m WIYN telescope. The goal is to detect the higher amplitude extra-solar planetary systems and brown dwarf binaries that might reside in the cluster. The oscillation modes of mid-F stars at the red ward edge of the instability strip can also be observed. The observation of NGC 752 is the first step in an ongoing study of a variety of clusters with different ages and metallicities.

Optical and UV spectroscopy of the peculiar RS CVN system, RT lacertae

Spectra in the H-alpha and H-beta regions of the peculiar double-lined RS CVn binary, RT Lacertae, were obtained in the fall of 1984. Limited International Ultraviolet Explorer (IUE) long wavelength low and high resolution spectra were obtained concurrently. The ground based spectra have shown an asymmetry with orbital phase in the H-alpha profile. The H-beta profiles were consistent with the same effect. One hemisphere showed excess emission and the other excess absorption, with a broad Gaussian emission component superposed upon the excess H-alpha line. An improved radial velocity curve, giving a better determined mass ratio and geometry was derived. This combined with the radii implied by the rotational broadening of the spectra, showed one component to be 80 to 90% filling the equilibrium Roche surface. The two-faced nature is, therfore, very likely due to mass transfer from the contact component impacting upon its companion. Low resolution ultraviolet data showed that the supposed cooler component is bluer than its companion. High resolution ultraviolet data taken during secondary eclipse showed Mg II emission strength which decreased more slowly than the area visible. The phase behavior of the low resolution data support the former situation, indicating traditional chromospheric activity.

SPECTRUM VARIABILITY IN HR 8752.

Observations in the region of H-alpha are presented for the luminous supergiant HR 8752. Two time scales for the variation of emission features are detected. Substantial changes in H-alpha appear to take months or years. More subtle changes can occur in a matter of days. The photospheric spectrum also shows evolution on both long and short time scales as has been noted by previous observers.