Search Publications
Planetary Camera Observations of NGC 1275: Discovery of a Central Population of Compact Massive Blue Star Clusters
Holtzman, J. A.; Faber, S. M.; Ewald, S. P. +10 more
We have discovered a population of bright blue pointlike sources within 5 kpc of the nucleus of NGC 1275 using HST Planetary Camera observations. The typical object has M_v_ ~ - 12 to - 14 (H_0_ = 75 km s^-1^ Mpc^-1^ ); the brightest has M_v_ ~ - 16. They are all blue, with V - R <~ 0.3. The color distribution and lack of excess Hα emission are…
The Abundance of Boron in Three Halo Stars
Lambert, David L.; Lemke, Michael; Duncan, Douglas K.
B abundances for three halo stars: HD 140283, HD 19445, and HD 201891 are presented. Using recent determinations of the Be abundance in HD 140283, B/Be of 10 +5/-4 is found for this star, and similar ratios are inferred for HD 19445 and HD 201891. This ratio is equal to the minimum value of 10 expected from a synthesis of B and Be by high-energy c…
Ultraviolet Observations of the Gas Phase Abundances in the Diffuse Clouds toward zeta Ophiuchi at 3.5 Kilometers per Second Resolution
Savage, Blair D.; Sofia, Ulysses J.; Cardelli, Jason A.
Goddard High Resolution Spectrograph echelle mode measurements at 3.5 km/s resolution are presented for interstellar absorption produced by C II, O I, Mg I, Mg II, Al III, P II, Cr II, Mn II, Fe II, Ni II, Cu II, Zn II, Ga II, Ge II, and Kr I. The absorption line measurements are converted into representations of apparent column density per unit v…
Planetary Camera Observations of the M87 Stellar CUSP
Schneider, Donald P.; Lauer, Tod R.; Faber, S. M. +11 more
Analysis of V and I band HST Planetary Camera images of the giant elliptical galaxy M87 show that its central starlight distribution is consistent with the black hole M_black hole_ = 2.6 X 10^9^ M_sun_ cusp model proposed for M87 by Young et al, [ApJ, 221,721(1978)]. A combined approach of image deconvolution and modeling is used to investigate th…
Planetary Camera Observations of the Central Parsec of M32
Lauer, Tod R.; Faber, S. M.; Currie, Douglas G. +8 more
Analysis of V band HST Planetary Camera images of the elliptical galaxy M32 shows that its nucleus is extremely dense and remains unresolved at even the HST diffraction limit. A combined approach of image deconvolution and model fitting is used to investigate the starlight distribution into limiting radii of 0.04" (0.14 pc at 700 kpc). The logarit…
The Cepheid Distance to IC 4182: Calibration of M V(max) for SN IA 1937C and the Value of H 0
Saha, A.; Panagia, Nino; Sandage, Allan +2 more
Cepheid variables with periods from 2 to more than 50 days have been found in IC 4182 from observations with the Hubble Space Telescope over a time interval of 47 days, comprised of 20 epochs. The period-luminosity relation from photometry of 27 Cepheids in the F555W HST magnitude system gives an apparent V distance modulus of (m - M)_AV_ = 28.47 …
Hubble Space Telescope Planetary Camera Images of R136
Lauer, Tod R.; Faber, S. M.; Holtzman, Jon A. +9 more
The Planetary Camera of the Hubble Space Telescope has been used to obtain broad and narrowband images of R136, the core of the massive star cluster 30 Doradus in the Large Magellanic Cloud. R136a, the brightest component of R136, is shown to have at least 12 separate components, including the eight originally identified by speckle interferometry.…
Globular Cluster Photometry With the Hubble Space Telescope. I. Description of the Method and Analysis of the Core of 47 TUC
Schneider, Donald P.; Yanny, Brian; Bahcall, John N. +1 more
Accurate photometry for individual post-main-sequence stars in the core of the Galactic globular cluster 47 Tuc is presented and analyzed using an empirical point spread function model and Monte Carlo simulations. A V vs. V-I color-magnitude diagrams is constructed which shows several distinct stellar types, including RGB and HB stars. Twenty-four…
Possible cataclysmic variable in the core of the globular cluster 47 Tucanae
Ferraro, Francesco R.; Paresce, Francesco; de Marchi, Guido
SEVERAL globular clusters have low-luminosity X-ray sources at their cores1-3, of which X0021.8-7221 in 47 Tucanae (NGC104) is one of the brightest. The nature of these sources is a mystery, and attempts to detect optical counterparts have been frustrated by the overcrowding of stars in cluster cores. The resolution of ground-based obse…
Hubble Space Telescope Wide Field Camera Imaging of the Gravitational Lens 2237+0305
Schneider, Donald P.; Rix, Hans-Walter; Bahcall, John N.
Hubble Space Telescope Wide Field Camera images of the gravitational lens 2237+0305 in the F336W ("U") and F702W ("A") filters are used to construct models of the system. Positions for the four quasar images, accurate to +/-0.015", and relative magnitudes in U and R, accurate to +/-0.06 and 0.04 mag respectively, are determined. The upper limits o…