Search Publications
Multiwavelength Observations of Short-Timescale Variability in NGC 4151. IV. Analysis of Multiwavelength Continuum Variability
Shull, J. M.; Glass, I. S.; Malkan, M. A. +88 more
This paper combines data from the three preceding papers in order to analyze the multi-wave-band variability and spectral energy distribution of the Seyfert I galaxy NGC 4151 during the 1993 December monitoring campaign. The source, which was near its peak historical brightness, showed strong, correlated variability at X-ray, ultraviolet, and opti…
Projected Rotational Velocities of O-Type Stars
Penny, Laura R.
I present an homogeneous set of projected rotational velocities for 177 O stars based upon lUE high- dispersion spectra of the UV photo spheric lines. The line widths are estimated by cross-correlating each spectrum with the spectrum of a narrow-lined O star (HD 34078), and the widths of the cross-correlation functions are transformed to projected…
Adaptive Optics Near-Infrared Imaging of R136 in 30 Doradus: The Stellar Population of a Nearby Starburst
Genzel, R.; Quirrenbach, A.; Bertoldi, F. +6 more
We report 0".15 resolution near-infrared (NIR) imaging of R136, the central region of 30 Doradus in the large Magellanic Cloud. Our 12".8 x 12".8 images were recorded with the MPE camera SHARP II at the 3.6 m ESO telescope, using the adaptive optics system COME ON+. The high spatial resolution and sensitivity (20th magnitude in K) of our observati…
Helioseismic Constraints on the Gradient of Angular Velocity at the Base of the Solar Convection Zone
Kosovichev, A. G.
The layer of transition from the nearly rigid rotation of the radiative interior to the latitudinal differential rotation of the convection zone plays a significant role in the internal dynamics of the Sun. Using rotational splitting coefficients of the p-mode frequencies, obtained during 1986--1990 at the Big Bear Solar Observatory, we have found…
The White Dwarf Distance to the Globular Cluster NGC 6752 (and Its Age) with the Hubble Space Telescope
Ferraro, Francesco R.; Gilmozzi, Roberto; Wesemael, F. +6 more
Deep Hubble Space Telescope (HST) observations with WFPC2 of the nearby globular cluster NGC 6752 have allowed us to obtain accurate photometry for the cluster white dwarfs (WDs). A sample of local WDs of known trigonometric parallax and mass close to that of the cluster WDs have also been observed with WFPC2. Matching the cluster and the local WD…
Disk M Dwarf Luminosity Function from Hubble Space Telescope Star Counts
Gould, Andrew; Bahcall, John N.; Flynn, Chris
We study a sample of 257 Galactic disk M dwarfs (8 ≤ Mv ≤ 18.5) found in images obtained using the Hubble Space Telescope (HST). These include 192 stars in 22 fields imaged with the repaired Wide Field Camera (WFC2) with mean limiting mag I = 23.7 and 65 stars in 162 fields imaged with the prerepair Planetary Camera (PC 1) with mean lim…
HST Observations of Jets from Young Stars
Mundt, Reinhard; Ray, Thomas P.; Raga, Alejandro C. +2 more
We report on Hubble Space Telescope (HST) emission line ([S II] lambda lambda 6716,6731, H alpha , and [O I] lambda 6300) and nearby continuum imaging of the HL Tau and HH 30 jets from our own HST program as well as a study of HST Archive [S II] lambda lambda 6716,6731 images of the HH 1 and HH 34 jets. It is found in all cases that these jets are…
Hubble Deep Field Constraint on Baryonic Dark Matter
Gould, Andrew; Bahcall, John N.; Flynn, Chris
We use a new technique to search for faint red stars in the Hubble deep field. We distinguish unambiguously between stars and galaxies to I = 26.3. Our results place strong and general constraints on the I-band luminosity of the constituents of the Galactic dark halo.
The Dark Matter, Gas, and Galaxy Distributions in Abell 2218: A Weak Gravitational Lensing and X-Ray Analysis
Babul, A.; Kaiser, N.; Neumann, D. M. +4 more
We report on the detection of dark matter in the cluster Abell 2218 using the weak gravitational distortion of background galaxies. We find a highly significant, coherent detection of the distortion in the images of the background galaxies. We use Hubble Space Telescope (HST) images from the Medium Deep Survey to calibrate the suppression in the o…
WFPC2 Studies of the Crab Nebula. III. Magnetic Rayleigh-Taylor Instabilities and the Origin of the Filaments
Casertano, Stefano; Ballester, Gilda E.; Crisp, David +18 more
Recently obtained Hubble Space Telescope WFPC2 images of the Crab Nebula show that the emission-line filaments are dominated by structures that morphologically appear to be the result of magnetic Rayleigh- Taylor (R-T) instabilities at the interface between the pulsar-driven synchrotron nebula and a shell of swept- up ejecta. We replace this morph…