Search Publications
Two-dimensional Structure of a Polar Coronal Hole at Solar Minimum: New Semiempirical Methodology for Deriving Plasma Parameters
Romoli, M.; Poletto, G.; Noci, G. +2 more
We develop a new technique to determine the plasma parameters in a polar coronal hole. This method makes use of the line intensities of the H I Lyα λ1215.6 line and of the O VI λλ1031.9, 1037.6 doublet, measured with the Ultraviolet Coronagraph Spectrometer (UVCS) on board the ESA-NASA solar spacecraft Solar and Heliospheric Observatory (SOHO) dur…
Far-Ultraviolet Spectroscopic Explorer Observations of the Magellanic Bridge Gas toward Two Early-Type Stars: Molecules, Physical Conditions, and Relative Abundances
Lehner, N.
We discuss Far Ultraviolet Spectroscopic Explorer (FUSE) observations of two early-type stars, DI 1388 (l=291.3d, b=-41.1d) and DGIK 975 (l=287.3d, b=-36.0d), in the low-density and low-metallicity (Z~0.08 Zsolar) gas of the Magellanic Bridge (MB). The data have a spectral resolution of about 15,000, and signal-to-noise ratios range bet…
QSO 2237+0305 VR Light Curves from Gravitational LensES International Time Project Optical Monitoring
Surdej, J.; Serra-Ricart, M.; Muñoz, J. A. +12 more
We present VR observations of QSO 2237+0305 conducted by the Gravitational Lensing International Time Project collaboration from 1999 October 1 to 2000 February 3. The observations were made with the 2.56 m Nordic Optical Telescope at Roque de los Muchachos Observatory, La Palma (Spain). The point-spread function (PSF) fitting method and an adapte…
The First Detections of the Extragalactic Background Light at 3000, 5500, and 8000 Å. II. Measurement of Foreground Zodiacal Light
Madore, Barry F.; Freedman, Wendy L.; Bernstein, Rebecca A.
We present a measurement of the absolute surface brightness of the zodiacal light (3900-5100 Å) toward a fixed extragalactic target at high ecliptic latitude based on moderate-resolution (~1.3 Å pixel-1) spectrophotometry obtained with the du Pont 2.5 m Telescope at the Las Campanas Observatory in Chile. This measurement and contemporan…
Are Coronal Loops Isothermal?
Schmelz, J. T.
A controversy over the temperature distribution of coronal loops has arisen recently because different investigators using different techniques have obtained very different answers. Analysis of Solar and Heliospheric Observatory (SOHO) Extreme ultraviolet Imaging Telescope (EIT) and Transition Region and Coronal Explorer (TRACE) data using narrowb…
The Relative Ages of the Globular Cluster Subpopulations in M87
Jordán, Andrés; Marzke, Ronald O.; Côté, Patrick +1 more
Relative ages for the globular cluster (GC) subpopulations in the Virgo giant elliptical galaxy M87 (NGC 4486) have been determined from Strömgren photometry obtained with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. Using a variety of population synthesis models, and assuming the GC mass at the turnover of the luminosity…
Ultraviolet Detection of Interstellar 12C17O and the CO Isotopomeric Ratios toward X Persei
Federman, S. R.; Lambert, David L.; Sheffer, Yaron
We report the detection of fully resolved absorption lines of A-X bands from interstellar 12C17O and 12C18O, through high-resolution spectroscopy of X Persei with the Space Telescope Imaging Spectrograph.3 The first ultraviolet measurement of an interstellar 12C17O column density sh…
Searching for the Physical Drivers of Eigenvector 1: From Quasars to Nanoquasars
Marziani, P.; Zamanov, R.
We point out an analogy between two accreting white dwarfs (CH Cyg and MWC 560) with jets and powerful quasars. In spite of the enormous difference in the mass of the central object (a factor ~107), the emission lines are strikingly similar to those of I Zw 1 (the prototype ``narrow-line Seyfert 1'' nucleus whose spectrum is widely used…
The Afterglow and Complex Environment of the Optically Dim Burst GRB 980613
McMahon, Richard G.; Halpern, Jules P.; Hjorth, Jens +15 more
We report the identification of the optical afterglow of GRB 980613 in R- and I-band images obtained between 16 and 48 hr after the gamma-ray burst. Early near-infrared (NIR) H and K' observations are also reported. The afterglow was optically faint (R~23) at discovery but did not exhibit an unusually rapid decay (power-law decay slope α<1.8 at…
Extreme-Ultraviolet Absorption Lines in Lyα Forest Absorbers and the Oxygen Abundance in the Intergalactic Medium
Kriss, Gerard A.; Zheng, Wei; Davidsen, Arthur F. +2 more
We create stacked composite absorption spectra from Hubble Space Telescope Faint Object Spectrograph data from four quasi-stellar objects to search for absorption lines in the extreme-ultraviolet wavelength region associated with Lyα forest absorbers in the redshift range 1.6<z<2.9. We successfully detect O V λ630 in Lyα absorbers throughout…