Search Publications
Reconciliation of the Surface Brightness Fluctuation and Type Ia Supernova Distance Scales
Riess, Adam G.; Ajhar, Edward A.; Schmidt, Brian P. +2 more
We present Hubble Space Telescope measurements of surface brightness fluctuation (SBF) distances to early-type galaxies that have hosted Type Ia supernovae (SNe Ia). The agreement in the relative SBF and SN Ia multicolor light-curve shape and delta-m15 distances is excellent. There is no systematic scale error with distance, and previou…
The Abundances of Solid N2 and Gaseous CO2 in Interstellar Dense Molecular Clouds
Allamandola, L. J.; Sandford, S. A.; Bernstein, M. P. +2 more
We present 2338-2322 cm-1 (4.277-4.307 µm) infrared spectra of a number of N2-containing mixed molecular ices and demonstrate that the strength of the infrared ``forbidden'' band due to the NN stretch near 2328 cm-1 (4.295 µm) is extremely sensitive to the composition of the ice. The strength of the 232…
Interferometric Astrometry with Hubble Space Telescope Fine Guidance Sensor 3: The Parallax of the Cataclysmic Variable TV Columbae
McArthur, B. E.; Benedict, G. F.; Franz, O. G. +14 more
TV Col is a 13th magnitude intermediate polar cataclysmic variable with multiple periods found in the light curves. Past estimates predicted a distance of 400 pc to greater than 500 pc. Recently completed Hubble Space Telescope fine guidance sensor interferometric observations allow us to determine the first trigonometric parallax to TV Col. This …
A Search for Early Optical Emission from Short- and Long-Duration Gamma-Ray Bursts
Hurley, Kevin; McKay, Tim; Kehoe, Robert +16 more
Gamma-ray bursts of short duration may harbor vital clues to the range of phenomena producing bursts. However, recent progress from the observation of optical counterparts has not benefited the study of short bursts. We have searched for early optical emission from six gamma-ray bursts using the telephoto array on the Robotic Optical Transient Sea…
The MACHO Project Hubble Space Telescope Follow-Up: Preliminary Results on the Location of the Large Magellanic Cloud Microlensing Source Stars
Alcock, C.; Allsman, R. A.; Alves, D. R. +21 more
We attempt to determine whether the MACHO microlensing source stars are drawn from the average population of the LMC or from a population behind the LMC by examining the Hubble Space Telescope (HST) color-magnitude diagram (CMD) of microlensing source stars. We present WFPC2 HST photometry of eight MACHO microlensing source stars and the surroundi…
1997 December 12 Helical Coronal Mass Ejection. II. Density, Energy Estimates, and Hydrodynamics
Raymond, J. C.; Ciaravella, A.; Peres, G. +2 more
We use Ultraviolet Coronagraph and Spectrometer (UVCS) spectra to investigate the density range of the plasma ejected during the coronal mass ejection (CME) on 1997 December 12. Time-dependent ionization states for several phenomenological models, with the boundary conditions derived from the EUV Imaging Telescope (EIT) and UVCS observations, were…
Plasmoid Formation and Acceleration in the Solar Streamer Belt
Velli, Marco; Einaudi, Giorgio; Chibbaro, Sergio +1 more
The dynamical behavior of a configuration consisting of a plane fluid wake flowing in a current sheet embedded in a plasma sheet that is denser than its surroundings is discussed. This configuration is a useful model for a number of structures of astrophysical interest, such as solar coronal streamers, cometary tails, the Earth's magnetotail and G…
Identification of the Low-Mass X-Ray Binary and Faint X-Ray Sources in NGC 6652
Heinke, C. O.; Grindlay, J. E.; Edmonds, P. D.
We have detected three new X-ray point sources, in addition to the known low-mass X-ray binary (LMXB) X1832-330, in the globular cluster NGC 6652 with a Chandra 1.6 ks HRC-I exposure. Star 49 (MV~4.7), suggested by Deutsch and coworkers as the optical candidate for the LMXB, is identified (<0.3") not with the LMXB, but with another, …
An Upper Mass Limit for the Progenitor of the Type II-P Supernova SN 1999gi
Smartt, Stephen J.; Gilmore, Gerard F.; Trentham, Neil +2 more
Masses and progenitor evolutionary states of Type II supernovae remain almost unconstrained by direct observations. Only one robust observation of a progenitor (SN 1987A) and one plausible observation (SN 1993J) are available. Neither matched theoretical predictions, and in this Letter we report limits on a third progenitor (SN 1999gi). The Hubble…
Observational Constraints on the Abundance and Evolution of ``XCN'' in Interstellar Grain Mantles
Whittet, D. C. B.; Boogert, A. C. A.; Pendleton, Y. J. +3 more
The 4.62 µm ``XCN'' absorption feature, attributed to CN-bearing molecules in solids, is potentially an important diagnostic of the evolution of organic matter in the interstellar medium and the envelopes of newly formed stars. We report quantitative limits on the strength of this feature in the diffuse interstellar medium toward the reddene…