Search Publications
A Sample of Clusters of Extragalactic Ultracompact H II Regions
Kobulnicky, Henry A.; Massey, Philip; Johnson, Kelsey E. +1 more
We report on the detection of optically thick free-free radio sources in the galaxies M33, NGC 253, and NGC 6946 using data in the literature. We interpret these sources as being young embedded star birth regions that are likely to be clusters of ultracompact H II regions. All 35 of the sources presented in this article have positive radio spectra…
Excitation of the Ganymede Ultraviolet Aurora
Wolven, Brian C.; Feldman, Paul D.; Strobel, Darrell F. +3 more
We analyze the ultraviolet aurorae observed on Ganymede by means of the Hubble Space Telescope and compare them to similar phenomena on Earth. We find that the tenuous nature of Ganymede's atmosphere precludes excitation of the aurora by high-energy electrons and requires a local acceleration mechanism. We propose the following as plausible mechan…
Detection of an X-Ray Jet in 3C 371 with Chandra
Maraschi, L.; Cheung, C. C.; Tavecchio, F. +4 more
We report the detection at X-rays of the radio/optical jet of 3C 371 from a short (10 ks) Chandra exposure in 2000 March. We also present a new MERLIN observation at 1.4 GHz together with a reanalysis of the archival Hubble Space Telescope Wide Field Planetary Camera 2 F555W image. Despite the limited signal-to-noise ratio of the Chandra data, the…
Searching for Ammonia in Grain Mantles toward Massive Young Stellar Objects
Whittet, D. C. B.; Gibb, E. L.; Chiar, J. E.
We present a study of the mid-infrared spectral regions of 17 objects observed with the Short-Wavelength Spectrometer on the Infrared Space Observatory (ISO SWS) in a search for the presence of the elusive NH3 solid-state absorption features at 2.96 and 9.0 µm. We compare the 3 µm profile with laboratory spectra of pure wate…
Early Chandra X-Ray Observations of η Carinae
Karovska, M.; Butt, Y. M.; Schlegel, E. M. +3 more
Subarcsecond-resolution Chandra observations of η Carinae reveal a 40''×70'' ring or partial shell of X-ray emission surrounding an unresolved bright central source. The spectrum of the central source is strongly absorbed and can be fitted with a high-temperature thermal continuum and emission lines. The surrounding shell is …
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…