Search Publications
The Star Formation History of LGS 3
Dolphin, Andrew E.; Miller, Bryan W.; Lee, Myung Gyoon +2 more
We have determined the distance and star formation history of the Local Group dwarf galaxy LGS 3 from deep Hubble Space Telescope WFPC2 observations. LGS 3 is intriguing because ground-based observations showed that, while its stellar population is dominated by old, metal-poor stars, there is a handful of young, blue stars. Also, the presence of H…
Far-Infrared Detection of H3O+ in Sagittarius B2
Cernicharo, José; Goicoechea, Javier R.
We report the first far-infrared detection of the hydronium ion (H3O+) toward the Sagittarius B2 molecular cloud, near the Galactic center. Using the Infrared Space Observatory Long-Wavelength Spectrometer, we have detected three lines arising from the ν2 ground-state inversion mode (0+-->0-
Hα Proxies for EIT Crinkles: Further Evidence for Preflare ``Breakout''-Type Activity in an Ejective Solar Eruption
Qiu, Jiong; Wang, Haimin; Moore, Ronald L. +1 more
We present Hα observations from Big Bear Solar Observatory of an eruptive flare in NOAA Active Region 8210, occurring near 22:30 UT on 1998 May 1. Previously, using the EUV Imaging Telescope (EIT) on the SOHO spacecraft, we found that a pattern of transient, localized brightenings, which we call ``EIT crinkles,'' appears in the neighborhood of the…
STIS Echelle Observations of the Intrinsic UV Absorption in the Seyfert 1 Galaxy NGC 3783
Kraemer, S. B.; Crenshaw, D. M.; Gabel, J. R.
We present observations of the UV absorption lines in the Seyfert 1 galaxy NGC 3783, obtained with the medium resolution (λ/Δλ~40,000) echelle gratings of the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST). The spectra reveal the presence of three kinematic components of absorption in Lyα, C IV, and N V, at radial …
The X-Ray Afterglow of GRB 000926 Observed by BeppoSAX and Chandra: A Mildly Collimated Fireball in a Dense Medium?
Piro, L.; Antonelli, L. A.; Frail, D. A. +8 more
We present X-ray observations of the afterglow of GRB 000926, performed around and after the break observed in the optical light curve 2 days after the burst. The steep X-ray light curve observed around the break confirms the presence of this feature in X-rays. However, the spectral and temporal properties are not consistent with a standard jet sc…
Boron Abundances in Early B Stars: Results from the B III Resonance Line in IUE Data
Proffitt, Charles R.; Quigley, Mark F.
We have used archival International Ultraviolet Explorer high-dispersion SWP spectra to study the B III resonance line at 2065.8 Å in 44 early B stars. We find a median boron abundance about half that of solar system meteoritic material, consistent with the values found from previous studies of boron in early B stars. About one-third of the stars …
Constraining the Black Hole Mass and Accretion Rate in the Narrow-Line Seyfert 1 Galaxy RE J1034+396
Fiore, F.; Comastri, A.; Siemiginowska, A. +4 more
We present a comprehensive study of the spectrum of the narrow-line Seyfert 1 (NLS1) galaxy RE J1034+396, summarizing the information obtained from the optical to X-rays with observations from the William Herschel 4.2 m Telescope, the Hubble Space Telescope, the Extreme Ultraviolet Explorer, ROSAT, ASCA, and BeppoSAX. The BeppoSAX spectra reveal a…
An Observational Manifestation of Magnetoatmospheric Waves in Internetwork Regions of the Chromosphere and Transition Region
Peter, H.; Judge, P. G.; Cally, P. S. +7 more
We discuss an observational signature of magnetoatmospheric waves in the chromosphere and transition region away from network magnetic fields. We demonstrate that when the observed quantity, line or continuum emission, is formed under high-β conditions, where β is the ratio of the plasma and magnetic pressures, we see fluctuations in intensity and…
New Constraints on Protostellar Jet Collimation from High-Density Gas UV Tracers
Gómez de Castro, Ana I.; Verdugo, Eva
The analysis of high-resolution profiles of the semiforbidden UV lines of C III]1908 and Si III]1892 in the spectra of T Tauri stars (TTSs) shows the following: (1) There is C III]1908 and Si III]1892 emission at velocities that are similar to those observed in the optical forbidden lines formed in the T…
High-Resolution Spectroscopic Observations of Hipparcos Red Clump Giants: Metallicity and Mass Determinations
Zhao, G.; Mao, Shude; Qiu, H. M.
We obtain high-resolution and high signal-to-noise ratio spectra of 39 red clump giants selected from the Hipparcos Catalogue. We determine their atmospheric parameters, iron abundances, α-element enhancements, and masses. We find that the sample can be divided into a metal-poor group and a metal-rich group. The majority of the stars are metal-ric…