Search Publications
Absolute Dimensions of the M-Type Eclipsing Binary YY Geminorum (Castor C): A Challenge to Evolutionary Models in the Lower Main Sequence
Torres, Guillermo; Ribas, Ignasi
We present new spectroscopic observations of the detached late-type double-lined eclipsing binary YY Geminorum (P=0.814 day), a member of the Castor sextuple system and one of the benchmarks for the comparison between observations and stellar evolution theory in the lower main sequence. In addition, we have reanalyzed existing light curves in seve…
Massive Stars in the Arches Cluster
Gilmore, Diane; Teplitz, Harry I.; Graham, James R. +9 more
We present and use new spectra and narrowband images, along with previously published broadband images, of stars in the Arches cluster to extract photometry, astrometry, equivalent width, and velocity information. The data are interpreted with a wind/atmosphere code to determine stellar temperatures, luminosities, mass-loss rates, and abundances. …
Evidence of EIT and Moreton Waves in Numerical Simulations
Wu, S. T.; Chen, P. F.; Shibata, K. +1 more
Solar coronal mass ejections (CMEs) are associated with many dynamical phenomena, among which EIT waves have always been a puzzle. In this Letter MHD processes of CME-induced wave phenomena are numerically simulated. It is shown that as the flux rope rises, a piston-driven shock is formed along the envelope of the expanding CME, which sweeps the s…
The Chemical Composition and Age of the Metal-poor Halo Star BD +17°3248
Beers, Timothy C.; Truran, James W.; Burles, Scott +8 more
We have combined new high-resolution spectra obtained with the Hubble Space Telescope (HST) and ground-based facilities to make a comprehensive new abundance analysis of the metal-poor, halo star BD +17°3248. We have detected the third r-process peak elements osmium, platinum, and (for the first time in a metal-poor star) gold, elements whose abun…
Hubble Space Telescope/STIS Spectroscopy of the Optical Outflow from DG Tauri: Indications for Rotation in the Initial Jet Channel
Bacciotti, Francesca; Eislöffel, Jochen; Mundt, Reinhard +2 more
We have carried out a kinematical, high angular resolution (~0.1") study of the optical blueshifted flow from DG Tau within 0.5" from the source (i.e., 110 AU when deprojected along this flow). We analyzed optical emission line profiles extracted from a set of seven long-slit spectra taken with the Space Telescope Imaging Spectrograph (STIS) on bo…
A 20,000 Msolar Black Hole in the Stellar Cluster G1
Ho, Luis C.; Gebhardt, Karl; Rich, R. M.
We present the detection of a 2.0+1.4-0.8×104 Msolar black hole (BH) in the stellar cluster G1 (Mayall II), based on data taken with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. G1 is one of the most massive stellar clusters in M31. The central velocity dispersion (25 km …
The Internal Structure and Formation of Early-Type Galaxies: The Gravitational Lens System MG 2016+112 at z = 1.004
Treu, Tommaso; Koopmans, Léon V. E.
We combine our recent measurements of the velocity dispersion and the surface brightness profile of the lens galaxy D in the system MG 2016+112 (z=1.004) with constraints from gravitational lensing to study its internal mass distribution. We find the following: (1) dark matter accounts for more than 50% of the total mass within the Einstein radius…
Interacting Coronal Mass Ejections and Solar Energetic Particles
Kaiser, M. L.; Howard, R. A.; Gopalswamy, N. +5 more
We studied the association between solar energetic particle (SEP) events and coronal mass ejections (CMEs) and found that CME interaction is an important aspect of SEP production. Each SEP event was associated with a primary CME that is faster and wider than average CMEs and originated from west of E45°. For most of the SEP events, the primary CME…
Planetary Nebulae as Standard Candles. XII. Connecting the Population I and Population II Distance Scales
Ciardullo, Robin; Durrell, Patrick R.; Feldmeier, John J. +3 more
We report the results of [O III] λ5007 surveys for planetary nebulae (PNe) in six galaxies: NGC 2403, NGC 3115, NGC 3351, NGC 3627, NGC 4258, and NGC 5866. Using on-band/off-band [O III] λ5007 images, as well as images taken in Hα, we identify samples of PNe in these galaxies and derive their distances using the planetary nebula luminosity functio…
Hot Coronal Loop Oscillations Observed by SUMER: Slow Magnetosonic Wave Damping by Thermal Conduction
Ofman, L.; Wang, Tongjiang
Recently, strongly damped Doppler shift oscillations of hot (T>6 MK) coronal loops were observed with the Solar Ultraviolet Measurement of Emitted Radiation (SUMER) spectrometer on board the Solar and Heliospheric Observatory. The oscillations are interpreted as signatures of slow-mode magnetosonic waves excited impulsively in the loops. Using …