Search Publications
The magnetic field and wind confinement of θ1 Orionis C
Donati, J. -F.; Babel, J.; Harries, T. J. +3 more
We report the detection, through spectropolarimetric observations, of a strong dipolar magnetic field of presumably fossil origin at the surface of the very young O star θ1 Ori C. The Stokes V signatures we detect are variable with time, the variations being consistent with rotational modulation. A detailed modelling of our observations…
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. …
Exploring the Full Stellar Population of the Upper Scorpius OB Association
Brown, Anthony G. A.; Zinnecker, Hans; Guenther, Eike +2 more
We investigate the stellar population and star formation history of the Upper Scorpius OB association, the most nearby region of recent massive star formation, over the full stellar mass range from 0.1 to 20 Msolar. The first part of this paper describes an extension of our large spectroscopic survey (Preibisch et al., published in 2001…
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…
Post-T Tauri Stars in the Nearest OB Association
Meyer, Michael R.; Mamajek, Eric E.; Liebert, James
We present results of a spectroscopic survey of X-ray- and proper-motion-selected samples of late-type stars in the Lower Centaurus-Crux (LCC) and Upper Centaurus-Lupus (UCL) subgroups of the nearest OB association: Scorpius-Centaurus. The primary goals of the survey are to determine the star formation history of the OB subgroups and to assess the…
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…
Four-point Cluster application of magnetic field analysis tools: The Curlometer
Balogh, A.; Glassmeier, K. -H.; Dunlop, M. W. +1 more
For the first time, the Cluster spacecraft have collected 3-D information on magnetic field structures at small to medium scales in the Earth's dayside magnetosphere. We focus here on the first application of the Curlometer (direct estimation of the electric current density from curl(B), using measured spatial gradients of the magnetic field) anal…
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 …
Re-examining the X-ray versus spin-down luminosity correlation of rotation powered pulsars
Mereghetti, S.; Possenti, A.; Cerutti, R. +1 more
The empirical relation between the X-ray luminosity (in the 2-10 keV band) and the rate of spin-down energy loss Lsd of a sample of 39 pulsars is re-examined considering recent data from ASCA, RXTE, BeppoSAX, Chandra, and XMM-Newton and including statistical and systematic errors. The data show a significant scatter around an average co…