Search Publications
The Hubble Constant: A Summary of the Hubble Space Telescope Program for the Luminosity Calibration of Type Ia Supernovae by Means of Cepheids
Panagia, N.; Saha, A.; Macchetto, F. D. +3 more
This is the final summary paper of our 15 yr program using the Hubble Space Telescope (HST) to determine the Hubble constant from the Cepheid-calibrated luminosity of Type Ia supernovae. Several recent developments have made it necessary to put the summary on H0 on a broader basis than we originally thought (see the four papers cited in…
Is the SMC Bound to the LMC? The Hubble Space Telescope Proper Motion of the SMC
van der Marel, Roeland P.; Kallivayalil, Nitya; Alcock, Charles
We present a measurement of the systemic proper motion of the Small Magellanic Cloud (SMC) made using the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST). We tracked the SMC's motion relative to four background QSOs over a baseline of approximately 2 yr. The measured proper motion is µW=-1.16+/-0.18 mas yr
A Statistical Study of Main and Residual Accelerations of Coronal Mass Ejections
Zhang, J.; Dere, K. P.
In this paper we present the results of a statistical study of the accelerations of coronal mass ejections (CMEs). A CME usually undergoes a multiphased kinematic evolution, with a main acceleration phase characterized by a rapid increase of CME velocity in the inner corona, followed by a relatively smooth propagation phase characterized by a cons…
The nature of SS433 and the ultraluminous X-ray sources
King, A. R.; Pringle, J. E.; Begelman, M. C.
The periodic precession (162-d) and nodding (6.3-d) motions of the jets in SS433 are driven in the outer regions of the disc, whereas the jets themselves, being relativistic, are launched near the black hole at the disc centre. Given that the nutation period is comparable to the dynamical time-scale in the outer regions of the disc, it seems unlik…
A Long, Hard Look at the Low/Hard State in Accreting Black Holes
Wijnands, R.; Fabian, A. C.; Miller, J. M. +5 more
We present the first results of coordinated multiwavelength observations of the Galactic black hole GX 339-4 in a canonical low/hard state, obtained during its 2004 outburst. XMM-Newton observed the source for two revolutions, or approximately 280 ks; RXTE monitored the source throughout this long stare. The resulting data offer the best view yet …
Pixie Dust: The Silicate Features in the Diffuse Interstellar Medium
Tielens, A. G. G. M.; Chiar, J. E.
We have analyzed the 9.7 and ``18'' µm interstellar silicate absorption features along the line of sight toward four heavily extincted galactic WC-type Wolf-Rayet (WR) stars. We construct two interstellar extinction curves from 1.25 to 25 µm using near-IR extinction measurements from the literature, along with the silicate profiles of …
Evidence for the strong effect of gas removal on the internal dynamics of young stellar clusters
Bastian, N.; Goodwin, S. P.
We present detailed luminosity profiles of the young massive clusters M82-F, NGC 1569-A and NGC 1705-1 which show significant departures from equilibrium (King and Elson, Fall & Freeman) profiles. We compare these profiles with those from N-body simulations of clusters that have undergone the rapid removal of a significant fraction of their ma…
The Sloan Lens ACS Survey. II. Stellar Populations and Internal Structure of Early-Type Lens Galaxies
Treu, Tommaso; Bolton, Adam S.; Burles, Scott +2 more
We use HST images to derive effective radii and effective surface brightnesses of 15 early-type (E+S0) lens galaxies identified by the SLACS Survey. Our measurements are combined with stellar velocity dispersions from the SDSS database to investigate for the first time the distribution of lens galaxies in the fundamental plane (FP) space. Accounti…
Solar Differential Rotation Influenced by Latitudinal Entropy Variations in the Tachocline
Toomre, Juri; Brun, Allan Sacha; Miesch, Mark S.
Three-dimensional simulations of solar convection in spherical shells are used to evaluate the differential rotation that results as thermal boundary conditions are varied. In some simulations a latitudinal entropy variation is imposed at the lower boundary in order to take into account the coupling between the convective envelope and the radiativ…
Magnetic field investigation of the Venus plasma environment: Expected new results from Venus Express
Barabash, S.; Russell, C. T.; Lammer, H. +24 more
The Venus Express mission is scheduled for launch in 2005. Among many other instruments, it carries a magnetometer to investigate the Venus plasma environment. Although Venus has no intrinsic magnetic moment, magnetic field measurements are essential in studying the solar wind interaction with Venus. Our current understanding of the solar wind int…