Search Publications
Chandra Observations of QSO 2237+0305
Agol, E.; Garmire, G. P.; Bautz, M. W. +2 more
We present the observations of the gravitationally lensed system QSO 2237+0305 (Einstein Cross) performed with the Advanced CCD Imaging Spectrometer on board the Chandra X-Ray Observatory on 2000 September 6 and on 2001 December 8 for 30.3 and 9.5 ks, respectively. Imaging analysis resolves the four X-ray images of the Einstein Cross. A possible f…
The Baldwin Effect and Black Hole Accretion: A Spectral Principal Component Analysis of a Complete Quasar Sample
Laor, Ari; Wills, D.; Shang, Zhaohui +4 more
We have performed a spectral principal component analysis (SPCA) for an essentially complete sample of 22 low-redshift QSOs with spectral data from Lyα to Hα. SPCA yields a set of independent principal component spectra, each of which represents a set of relationships among QSO continuum and line properties. We find three significant principal com…
Shaping Proto-Planetary and Young Planetary Nebulae with Collimated Fast Winds
Lee, Chin-Fei; Sahai, Raghvendra
Using two-dimensional hydrodynamical simulations, we investigate the interaction of a collimated fast wind (CFW) interacting with a spherical asymptotic giant branch (AGB) wind as the mechanism for shaping proto-planetary nebulae (PPNs) and young planetary nebulae. In particular, we compare our simulations with the observations of an evolved PPN w…
Hubble Space Telescope WFPC2 Imaging of the Disk and Jet of HV Tauri C
Ménard, François; Krist, John E.; Brandner, Wolfgang +4 more
We have obtained Hubble Space Telescope (HST) WFPC2 images of the HV Tauri young triple system. The tertiary star appears as a compact bipolar nebula at visual wavelengths as already known in the near-infrared. New, deeper adaptive optics observations made at the Canada-France-Hawaii Telescope show no point source in the nebula to a limiting magni…
Guilt by Association: The 13 Micron Dust Emission Feature and Its Correlation to Other Gas and Dust Features
Sloan, G. C.; Kraemer, Kathleen E.; Price, Stephan D. +1 more
A study of all full-scan spectra of optically thin oxygen-rich circumstellar dust shells in the database produced by the Short Wavelength Spectrometer on ISO reveals that the strength of several infrared spectral features correlates with the strength of the 13 µm dust feature. These correlated features include dust features at 19.8 and 28.1 …
The Observation of Sunspot Light-Bridge Structure and Dynamics
Berger, T. E.; Berdyugina, S. V.
We present very high resolution multiwavelength images of a sunspot light bridge in NOAA Active Region 10132 taken at the Swedish 1 m Solar Telescope on La Palma on 2002 September 25. The adaptive optics-corrected images resolve 100 km scale bright grains on either side of an approximately 380 km dark lane in the center of the bridge. Movies of th…
Imaging and Spectroscopic Investigations of a Solar Coronal Wave: Properties of the Wave Front and Associated Erupting Material
Harra, Louise K.; Sterling, Alphonse C.
Using spectral data from the Coronal Diagnostic Spectrometer (CDS) instrument on the Solar and Heliospheric Observatory spacecraft, we observe a coronal wave feature (often referred to as an EIT wave) that occurred in association with a solar eruption and flare on 1998 June 13. EUV images from the Transition Region and Coronal Explorer (TRACE) sat…
An Extensive Census of Hubble Space Telescope Counterparts to Chandra X-Ray Sources in the Globular Cluster 47 Tucanae. II. Time Series and Analysis
Heinke, Craig O.; Gilliland, Ronald L.; Edmonds, Peter D. +1 more
We report time series and variability information for the optical identifications of X-ray sources in 47 Tucanae reported in Paper I (at least 22 cataclysmic variables [CVs] and 29 active binaries). The radial distribution of the CVs is indistinguishable from that of the millisecond pulsars (MSPs) detected by Freire et al. A study of the eight CVs…
Oxygen Gas-Phase Abundance Revisited
Moos, H. W.; André, M. K.; Ferlet, R. +7 more
We present new measurements of the interstellar gas-phase oxygen abundance along the sight lines toward 19 early-type Galactic stars at an average distance of 2.6 kpc. We derive O I column densities from Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) observations of the weak 1355 Å intersystem transition. We derive total hy…
Constraints on Active Region Coronal Heating
Golub, L.; Antiochos, S. K.; DeLuca, E. E. +2 more
We derive constraints on the time variability of coronal heating from observations of the so-called active region moss by the Transition Region and Coronal Explorer (TRACE). The moss is believed to be due to million-degree emission from the transition regions at the footpoints of coronal loops whose maximum temperatures are several million degrees…