Search Publications
The Formation of Broad-Line Clouds in the Accretion Shocks of Active Galactic Nuclei
Fromerth, Michael J.; Melia, Fulvio
Recent work on the gas dynamics in the Galactic center has improved our understanding of the accretion processes in galactic nuclei, particularly with regard to properties such as the specific angular momentum distribution, density, and temperature of the inflowing plasma. With the appropriate extrapolation of the physical conditions, this informa…
Hubble Space Telescope STIS Observations of GRB 000301C: CCD Imaging and Near-Ultraviolet MAMA Spectroscopy
Fruchter, Andrew S.; Hogg, David W.; Livio, Mario +24 more
We present Space Telescope Imaging Spectrograph observations of the optical transient (OT) counterpart of the γ-ray burster GRB 000301C obtained 5 days after the burst, on 2000 March 6. CCD clear-aperture imaging reveals a R~=21.50+/-0.15 source with no apparent host galaxy. An 8000 s, 1150 Å<λ<3300 Å near-ultraviolet MAMA prism spectrum sho…
Far-Ultraviolet Intensities and Center-to-Limb Variations of Active Regions and Quiet Sun Using UARS SOLSTICE Irradiance Measurements and Ground-based Spectroheliograms
Woods, Thomas N.; Worden, John R.; Bowman, Kevin W.
The average intensity and center-to-limb variation of active regions, enhanced network (large-scale active region fragments), and quiet Sun are estimated by minimizing the variance between time series of the Solar-Stellar Irradiance Comparison Experiment (SOLSTICE) far-ultraviolet (FUV) irradiance measurements and a model of the solar irradiance t…
Rapid Temporal Variations of Interstellar Absorption Lines in the Carina Nebula
Walborn, Nolan R.; Danks, Anthony C.; Landsman, Wayne B. +3 more
Two observations of the complex interstellar absorption-line profiles in the UV spectrum of CPD -59°2603, obtained 22 months apart in the R~110,000 mode of the Space Telescope Imaging Spectrograph on the Hubble Space Telescope, reveal substantial variations in the intensities of several high-velocity components, including the virtual disappearance…
The Inner Nebula and Central Binary of the Symbiotic Star HM Sagittae
Davis, R. J.; Eyres, S. P. S.; Bode, M. F. +2 more
We present contemporaneous Hubble Space Telescope Wide Field Planetary Camera 2 and Very Large Array observations of the symbiotic nova HM Sge. We identify a number of discreet features at spatial scales smaller than ~0.1" embedded in the extended nebula, with radio and optical emission well correlated in the inner 1". For the first time we measur…
Observed and Predicted Ratios of the Horizontal and Vertical Components of the Solar p-Mode Velocity Eigenfunctions
Kosovichev, Alexander G.; Schou, Jesper; Rhodes, Edward J., Jr. +2 more
We present evidence that the observed ratios of the horizontal and vertical components of the solar intermediate-degree p-mode velocity eigenfunctions closely match theoretical predictions of these ratios. This evidence comes from estimates of the observed eigenfunction component ratios that were obtained from the fitting of the p-mode oscillation…
The Location of the Nucleus and the Morphology of Emission-Line Regions in NGC 1068
Chary, Ranga-Ram; Thompson, Rodger I.; Corbin, Michael R. +1 more
This Letter presents new Near-Infrared Camera and Multi-Object Spectrometer data on the location of the nucleus and the morphology of hydrogen and [Si VI] emission in NGC 1068. The peak of the emission at 2.2 µm is a strong point source that marks the location of the nucleus. The [Si VI] line emission region consists of two main components, …
Variable Ultraviolet Absorption in the Spectrum of MR 2251-178
Charlton, Jane C.; Eracleous, Michael; Ganguly, Rajib
We present an ultraviolet spectrum of MR 2251-178 taken with Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph (STIS) with the G230L grating. The observation is part of a snapshot program of quasars (QSOs) that systematically searches for intrinsic absorption lines through variability. The sample consists of all QSOs observed with …
Arp 220: A Circumnuclear Polar Ring as an Alternative to a Double Nucleus?
Eckart, A.; Downes, D.
Recent millimeter interferometer observations of Arp 220 have yielded ~0.5" resolution images showing two strong concentrations of millimeter radio continuum and CO line emission embedded in a larger molecular gas disk (r~1 kpc). The interferometer observations also revealed a complex velocity field with steep velocity gradients across each of the…
The Nuclear Stellar Cluster in the Seyfert 1 Galaxy NGC 3227: High Angular Resolution Near-Infrared Imaging and Spectroscopy
Tacconi, L. J.; Schinnerer, E.; Eckart, A.
Near-infrared (NIR) high angular resolution speckle imaging and imaging spectroscopy of the nuclear region (~10''~840 pc) of the Seyfert 1 galaxy NGC 3227 are presented. The images reveal an unresolved nuclear source in the K band in addition to a nuclear stellar cluster that is slightly resolved in the J and H bands. The contribution o…