Search Publications
Observations of Giant Outbursts from Cygnus X-1
Cline, T.; Hurley, K.; Golenetskii, S. +5 more
We present interplanetary network localization, spectral, and time history information for seven episodes of exceptionally intense gamma-ray emission from Cyg X-1. The outbursts occurred between 1995 and 2003, with durations up to ~28,000 s. The observed 15-300 keV peak fluxes and fluences reached 3×10-7 ergs cm-2 s-1
Properties of Solar Plasmas near Solar Maximum above Two Quiet Regions at Distances of 1.02-1.34 Rsolar
Landi, E.; Feldman, U.
In the present work we have analyzed the spectra emitted by two quiet solar regions observed off the solar disk by the SUMER instrument on board the SOHO satellite. The two complete spectra were recorded when the SOHO north-south axis was rotated relative to the Sun north-south axis by ~=150° clockwise. As a result, the SUMER slit could be placed …
Oxygen Abundance in the Template Halo Giant HD 122563
Damineli, Augusto; Hill, Vanessa; Meléndez, Jorge +7 more
HD 122563 is a well-known bright (V=6.2) halo giant of low metallicity ([Fe/H]~-2.7). We have observed HD 122563 for infrared OH lines at 1.5-1.7 µm in the H band with the NIRSPEC high-resolution spectrograph at the 10 m Keck Telescope. Optical spectra were obtained with the UVES spectrograph at the 8 m VLT UT2 telescope at ESO (Paranal) and…
A European Southern Observatory Very Large Telescope Survey of Near-Infrared (Z <= 25) Selected Galaxies at Redshifts 4.5 < z < 6: Constraining the Cosmic Star Formation Rate near the Reionization Epoch
Fontana, A.; Cristiani, S.; Giallongo, E. +4 more
We present the results of a Very Large Telescope (VLT) and Hubble Space Telescope imaging survey aimed at the identification of 4.5<z<6 galaxies. In the VLT data, a set of broadband and intermediate-band filters has been used to select 13 high-z candidates in a ZAB<=25 mag catalog, over an area of about 30 arcmin2. D…
Submillimeter Wave Astronomy Satellite Mapping Observations of Water Vapor around Sagittarius B2
Bergin, Edwin A.; Neufeld, David A.; Goldsmith, Paul F. +1 more
Observations of the 110-101 556.936 GHz transition of ortho-water with the Submillimeter Wave Astronomy Satellite have revealed the presence of widespread emission and absorption by water vapor around the strong submillimeter continuum source Sagittarius B2. An incompletely sampled spectral line map of a region of size 26
Composite Accretion Disk and White Dwarf Model Analyses of the Quiescence of Dwarf Novae: EM Cygni, CZ Orionis, and WW Ceti
Sion, Edward M.; Winter, Lisa
We explore the origin of the far-UV (FUV) spectra of three dwarf novae using combined high-gravity photosphere and accretion disk models. We have carried out an IUE archival comparative study of the three U Gem-type dwarf novae EM Cyg, CZ Ori, and WW Cet. For EM Cyg, the FUV spectrum during quiescence is dominated by an accretion disk with M=5×10<…
Hα Dimmings Associated with the X1.6 Flare and Halo Coronal Mass Ejection on 2001 October 19
Wang, Haimin; Ji, Haisheng; Chen, Huadong +1 more
As the optical counterpart of coronal dimmings, we present the first direct evidence of Hα dimmings associated with the X1.6 flare, filament eruption, and coronal mass ejection (CME) that occurred on 2001 October 19. As two main Hα flare ribbons parallel to the erupting filament slowly separated, two other ribbons first quickly expanded near the f…
X-Ray Spectroscopy of η Carinae with XMM-Newton
Ramsay, Gavin; Leutenegger, Maurice A.; Kahn, Steven M.
We present XMM-Newton observations of the luminous star η Carinae, including a high-resolution soft X-ray spectrum of the surrounding nebula obtained with the Reflection Grating Spectrometer (RGS). The European Photon Imaging Camera (EPIC) image of the field around η Car shows many early-type stars and diffuse emission from hot, shocked gas. The E…
Does the Sun Shrink with Increasing Magnetic Activity?
Antia, H. M.
It has been demonstrated that frequencies of f-modes can be used to estimate the solar radius to a good accuracy. These frequencies have been used to study temporal variations in the solar radius with conflicting results. The variation in f-mode frequencies is more complicated than what is assumed in these studies. If a careful analysis is perform…
An Icy, Bipolar Proto-Planetary Nebula with Knotty Jets: IRAS 22036+5306
Sahai, R.; Sánchez Contreras, C.; Zijlstra, A. +1 more
Using the Hubble Space Telescope's Wide Field Planetary Camera 2, we have discovered that the proto-planetary nebula (PPN) IRAS 22036+5306 (I22036) is an extended (5.7"×1.3") bipolar nebula. A dark, (partial) ringlike band defines the nebular waist region and probably results from a tilted, geometrically thick disk that obscures the central star. …