Search Publications
A 2000 Kilometer per Second ``Pristine'' Post-asymptotic Giant Branch Wind in the Proto-planetary Nebula He 3-1475
Sahai, R.; Sánchez Contreras, C.
We analyze (archival) Space Telescope Imaging Spectrograph long-slit Hα spectra of the proto-planetary nebula He 3-1475. We find two remarkable blueshifted absorption features arising from the inner ~5×1016 cm of the nebula, revealing the presence of two different winds outflowing at high velocity from the central star. The kinematic ag…
MACHO 96-LMC-2: Lensing of a Binary Source in the Large Magellanic Cloud and Constraints on the Lensing Object
Alcock, C.; Allsman, R. A.; Alves, D. R. +21 more
We present photometry and analysis of the microlensing alert MACHO 96-LMC-2 (event LMC-14 in an earlier paper). This event was initially detected by the MACHO Alert System and subsequently monitored by the Global Microlensing Alert Network (GMAN). The ~3% photometry provided by the GMAN follow-up effort reveals a periodic modulation in the light c…
Spatial Structure of Simple Spiky Bursts at Microwave/Millimeter Wavelengths
Kundu, M. R.; White, S. M.; Shibasaki, K. +2 more
We present the results of a study of spatial structure of sources of microwave and millimeter bursts with simple spiky time profiles at 17 and 34 GHz, similar to those found to be common at 3 mm wavelength. These bursts are of short duration, with fast 2-4 s rise time to peak, followed by a rapid exponential decay. When mapped at high spatial reso…
Molecular Gas in Optically Selected Mergers
Yun, Min S.; Hibbard, J. E.
We have mapped the 2.6 mm CO J=1-->0 emission in three optically selected ``Toomre sequence'' mergers (NGC 520, NGC 3921, NGC 4676). The molecular gas distribution is well resolved by the observations. For NGC 520 and NGC 4676A, the nuclear gas concentrations form a disklike or a ringlike structure, and the gas kinematics are regular and consis…
Supernova 1991T and the Value of the Hubble Constant
Gibson, Brad K.; Stetson, Peter B.
Based on multiepoch Hubble Space Telescope observations, we present the discovery of 16 high-quality Cepheid candidates in NGC 4527. Corrected for metallicity effects in the Cepheid period-luminosity relation, we derive a distance, including both random (r) and systematic (s) uncertainties, of 13.0+/-0.5(r)+/-1.2(s) Mpc. Our result is then used to…
Infrared Surface Brightness Fluctuations of the Coma Elliptical Galaxy NGC 4874 and the Value of the Hubble Constant
Graham, James R.; Liu, Michael C.
We have used the Keck I telescope to measure K-band surface brightness fluctuations (SBFs) of NGC 4874, the dominant elliptical galaxy in the Coma Cluster. We use deep Hubble Space Telescope (HST) WFPC2 optical imaging to account for the contamination due to faint globular clusters and improved analysis techniques to derive measurements of the SBF…
Circumstellar Carbonaceous Material Associated with Late-Type Dusty WC Wolf-Rayet Stars
Tielens, A. G. G. M.; Chiar, J. E.
We have studied the 5-8.5 µm infrared spectra of the late-type Wolf-Rayet stars WR 118, WR 112, and WR 104, the WN star WR 147, the B5 hypergiant Cygnus OB2 No. 12, and the Galactic center luminous blue variable Pistol Star using the Short Wavelength Spectrometer on the Infrared Space Observatory. We attribute an absorption feature at 6.2 &m…
A Far-Infrared Study of the CfA Seyfert Sample. I. The Data
Pérez García, A. M.; Rodríguez Espinosa, J. M.
We present mid- and far-IR Infrared Space Observatory data of the CfA Seyfert galaxy sample. These data allow a detailed study of the far-IR spectral energy distribution (SED) of these galaxies. A Bayesian inversion method has been used to invert the SED of these objects and to identify three characteristic temperature ranges of dust emission. The…
Two-dimensional Kinematical and Ionization Structure of the Warm Gas in the Nuclear Regions of Arp 220
Arribas, Santiago; Colina, Luis; Clements, David
Integral field optical spectroscopy using the INTEGRAL system has been used to characterize the kinematic and ionization properties of the warm gas within 2 kpc of the dust-enshrouded nucleus of Arp 220. Owing to the large internal extinction toward the nuclei, the brightest stellar and line-emitting regions observed at optical wavelengths do not …
Hydrodynamic Simulations of Proplyd Bow Shocks
Henney, W. J.; Arthur, S. J.; García-Arredondo, F.
We present two-dimensional hydrodynamic simulations of the interaction between an ionized photoevaporation flow from a proplyd and a stellar wind from a hot star. We consider both the case of a fully supersonic wind and the case of a wind that passes through a global shock to become subsonic before reaching the proplyd. We compare the results of o…