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13 results on '"Ohl, R. G."'

1. Photospheric Metals in the FUSE Spectrum of the Subdwarf B Star PG0749+658

Author

Ohl, R. G., Chayer, P., and Moos, H. W.

Subjects
Astrophysics
Abstract

We present an abundance analysis of the far-ultraviolet (905--1187 A) spectrum of the subdwarf B star PG0749+658, obtained by the Far Ultraviolet Spectroscopic Explorer (FUSE). The data have a resolution of about R = lambda / Delta lambda = 12000--15000 (20--25 km/s). We determine C, N, Si, P, S, Cr, Mn, Fe, Co, and Ni abundances, and upper limits on the abundance of Cl and V, using a grid of synthetic spectra based on a LTE stellar atmosphere model. He, C, N, Si, and Cl are depleted by a factor of >~10 with respect to solar, while P, S, and Fe are diminished by less than a factor of 10. We measure a solar abundance of Cr, Mn, and Co and a Ni enhancement of ~0.6 dex. We compare these values to predictions based on radiative levitation theory. The radial velocity of the foreground interstellar material has one dominant component, and coincides with that of the photospheric lines., Comment: 8 pages, 2 figures; This paper will appear in the FUSE special issue of ApJ Letters

Published
2000

2. Far-Ultraviolet Color Gradients in Early-Type Galaxies

Author

Ohl, R. G., O'Connell, R. W., Bohlin, R. C., Collins, N. R., Dorman, B., Fanelli, M. N., Neff, S. G., Roberts, M. S., Smith, A. M., and Stecher, T. P.

Subjects
Astrophysics
Abstract

We discuss far-UV (1500 A) surface photometry and FUV-B color profiles for 8 E/S0 galaxies from images taken with the Ultraviolet Imaging Telescope, primarily during the Astro-2 mission. In three cases, the FUV radial profiles are more consistent with an exponential than a de Vaucouleurs function, but there is no other evidence for the presence of a disk or of young, massive stars. In all cases except M32 the FUV-B color becomes redder at larger radii. There is a wide range of internal radial FUV-B color gradients. However, we find no correlation between the FUV-B color gradients and internal metallicity gradients based on Mg absorption features. We conclude that metallicity is not the sole parameter controlling the "UV upturn component" in old populations., Comment: 11 pages; tar.gz file includes LaTeX text file, 3 PostScript figures. Paper to be published in ApJ Letters

Published
1998
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3. Overview of the Far Ultraviolet Spectroscopic Explorer Mission

Author

Moos, H. W., Cash, W. C., Cowie, L. L., Davidsen, A. F., Dupree, A. K., Feldman, P. D., Friedman, S. D., Green, J. C., Green, R. F., Gry, C., Hutchings, J. B., Jenkins, E. B., Linsky, J. L., roger malina, Michalitsianos, A. G., Savage, B. D., Shull, J. M., Siegmund, O. H. W., Snow, T. P., Sonneborn, G., Vidal-Madjar, A., Willis, A. J., Woodgate, B. E., York, D. G., Ake, T. B., Andersson, B. -G, Andrews, J. P., Barkhouser, R. H., Bianchi, L., Blair, W. P., Brownsberger, K. R., Cha, A. N., Chayer, P., Conard, S. J., Fullerton, A. W., Gaines, G. A., Grange, R., Gummin, M. A., Hebrard, G., Kriss, G. A., Kruk, J. W., Mark, D., Mccarthy, D. K., Morbey, C. L., Murowinski, R., Murphy, E. M., Oegerle, W. R., Ohl, R. G., Oliveira, C., Osterman, S. N., Sahnow, D. J., Saisse, M., Sembach, K. R., Weaver, H. A., Welsh, B. Y., Wilkinson, E., Zheng, W., Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Institut d'Astrophysique de Paris (IAP), and Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Space Vehicles, Ultraviolet: General, [SDU]Sciences of the Universe [physics], Astrophysics (astro-ph), Instrumentation: Spectrographs, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Astrophysics::Galaxy Astrophysics, Telescopes
Abstract

The Far Ultraviolet Spectroscopic Explorer satellite observes light in the far-ultraviolet spectral region, 905 - 1187 A with high spectral resolution. The instrument consists of four coaligned prime-focus telescopes and Rowland spectrographs with microchannel plate detectors. Two of the telescope channels use Al:LiF coatings for optimum reflectivity from approximately 1000 to 1187 A and the other two use SiC coatings for optimized throughput between 905 and 1105 A. The gratings are holographically ruled to largely correct for astigmatism and to minimize scattered light. The microchannel plate detectors have KBr photocathodes and use photon counting to achieve good quantum efficiency with low background signal. The sensitivity is sufficient to examine reddened lines of sight within the Milky Way as well as active galactic nuclei and QSOs for absorption line studies of both Milky Way and extra-galactic gas clouds. This spectral region contains a number of key scientific diagnostics, including O VI, H I, D I and the strong electronic transitions of H2 and HD., To appear in FUSE special issue of the Astrophysical Journal Letters. 6 pages + 4 figures

Published
2000
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6. On-Orbit Performance of the [ITAL]Far Ultraviolet Spectroscopic Explorer[/ITAL] Satellite

Author

Sahnow, D. J., primary, Moos, H. W., additional, Ake, T. B., additional, Andersen, J., additional, Andersson, B-G, additional, Andre, M., additional, Artis, D., additional, Berman, A. F., additional, Blair, W. P., additional, Brownsberger, K. R., additional, Calvani, H. M., additional, Chayer, P., additional, Conard, S. J., additional, Feldman, P. D., additional, Friedman, S. D., additional, Fullerton, A. W., additional, Gaines, G. A., additional, Gawne, W. C., additional, Green, J. C., additional, Gummin, M. A., additional, Jennings, T. B., additional, Joyce, J. B., additional, Kaiser, M. E., additional, Kruk, J. W., additional, Lindler, D. J., additional, Massa, D., additional, Murphy, E. M., additional, Oegerle, W. R., additional, Ohl, R. G., additional, Roberts, B. A., additional, Romelfanger, M. L., additional, Roth, K. C., additional, Sankrit, R., additional, Sembach, K. R., additional, Shelton, R. L., additional, Siegmund, O. H. W., additional, Silva, C. J., additional, Sonneborn, G., additional, Vaclavik, S. R., additional, Weaver, H. A., additional, and Wilkinson, E., additional

Published
2000
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7. Overview of the [ITAL]Far Ultraviolet Spectroscopic Explorer[/ITAL] Mission

Author

Moos, H. W., primary, Cash, W. C., additional, Cowie, L. L., additional, Davidsen, A. F., additional, Dupree, A. K., additional, Feldman, P. D., additional, Friedman, S. D., additional, Green, J. C., additional, Green, R. F., additional, Gry, C., additional, Hutchings, J. B., additional, Jenkins, E. B., additional, Linsky, J. L., additional, Malina, R. F., additional, Michalitsianos, A. G., additional, Savage, B. D., additional, Shull, J. M., additional, Siegmund, O. H. W., additional, Snow, T. P., additional, Sonneborn, G., additional, Vidal-Madjar, A., additional, Willis, A. J., additional, Woodgate, B. E., additional, York, D. G., additional, Ake, T. B., additional, Andersson, B-G, additional, Andrews, J. P., additional, Barkhouser, R. H., additional, Bianchi, L., additional, Blair, W. P., additional, Brownsberger, K. R., additional, Cha, A. N., additional, Chayer, P., additional, Conard, S. J., additional, Fullerton, A. W., additional, Gaines, G. A., additional, Grange, R., additional, Gummin, M. A., additional, Hebrard, G., additional, Kriss, G. A., additional, Kruk, J. W., additional, Mark, D., additional, McCarthy, D. K., additional, Morbey, C. L., additional, Murowinski, R., additional, Murphy, E. M., additional, Oegerle, W. R., additional, Ohl, R. G., additional, Oliveira, C., additional, Osterman, S. N., additional, Sahnow, D. J., additional, Saisse, M., additional, Sembach, K. R., additional, Weaver, H. A., additional, Welsh, B. Y., additional, Wilkinson, E., additional, and Zheng, W., additional

Published
2000
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8. Far-ultraviolet Color Gradients in Early-Type Galaxies

Author

Ohl, R. G., primary, O'Connell, R. W., additional, Bohlin, R. C., additional, Collins, N. R., additional, Dorman, B., additional, Fanelli, M. N., additional, Neff, S. G., additional, Roberts, M. S., additional, Smith, A. M., additional, and Stecher, T. P., additional

Published
1998
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9. Light-particle correlations with evaporation residues in theCa40+12C reaction atE(40Ca)=450 MeV

Author

Vineyard, M. F., primary, Atencio, S. E., additional, Crum, J. F., additional, Gilfoyle, G. P., additional, Glagola, B. G., additional, Henderson, D. J., additional, Kovar, D. G., additional, Maguire, C. F., additional, Mateja, J. F., additional, Ohl, R. G., additional, Prosser, F. W., additional, Rollinson, J. H., additional, and Trotter, R. S., additional

Published
1994
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10. Photospheric Metals in the FUSE Spectrum of the Subdwarf B Star PG0749+658

Author

Ohl, R. G., Pierre Chayer, and Moos, H. W.

Subjects
Astrophysics (astro-ph), FOS: Physical sciences, Astrophysics
Abstract

We present an abundance analysis of the far-ultraviolet (905--1187 A) spectrum of the subdwarf B star PG0749+658, obtained by the Far Ultraviolet Spectroscopic Explorer (FUSE). The data have a resolution of about R = lambda / Delta lambda = 12000--15000 (20--25 km/s). We determine C, N, Si, P, S, Cr, Mn, Fe, Co, and Ni abundances, and upper limits on the abundance of Cl and V, using a grid of synthetic spectra based on a LTE stellar atmosphere model. He, C, N, Si, and Cl are depleted by a factor of >~10 with respect to solar, while P, S, and Fe are diminished by less than a factor of 10. We measure a solar abundance of Cr, Mn, and Co and a Ni enhancement of ~0.6 dex. We compare these values to predictions based on radiative levitation theory. The radial velocity of the foreground interstellar material has one dominant component, and coincides with that of the photospheric lines., 8 pages, 2 figures; This paper will appear in the FUSE special issue of ApJ Letters

13. Imaging performance of telescope mirrors for far-ultraviolet astronomy.

Author

Ohl RG, Saha TT, Friedman SD, Barkhouser RH, and Moos HW

Abstract

We describe image testing, surface metrology, and modeling of telescope mirrors (0.5 m in diameter, f/4.3) for the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. Laboratory image testing of wavelengths in the visible, vacuum, and midultraviolet validated a theoretical analysis by use of the Optical Surface Analysis Code (OSAC). Our modeling is based on surface metrology, including measurements of figure, midfrequency error, and microroughness. This combination of metrology, out-of-band performance testing, and modeling verified that the mirrors would meet mission requirements. We use OSAC to predict the FUSE telescope's far-ultraviolet (90-120-nm) point-spread function and assess its effect on instrument efficiency. The mirrors have a 90% encircled energy diameter of 1.5 arc sec at lambda = 100 nm. Including the effects of spacecraft pointing error, the mirrors have a predicted average slit transmission at lambda = 100 nm of approximately 87% and 96% for the 1.25- and 4-arc sec-wide spectrograph slits, respectively, where the required transmissions are 50% and 95%.

Published
2000
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