Search Publications
A Study of the Kinematic Evolution of Coronal Mass Ejections
Zhang, J.; Howard, R. A.; Dere, K. P. +1 more
We report the kinematic properties of a set of three coronal mass ejections (CMEs) observed with the LASCO (Large Angle and Spectrometric Coronagraph) on the Solar and Heliospheric Observatory (SOHO) spacecraft, which showed characteristics of impulsive, intermediate, and gradual acceleration, respectively. The first CME had a 30 minute long fast …
Galaxy Size Evolution at High Redshift and Surface Brightness Selection Effects: Constraints from the Hubble Ultra Deep Field
Bouwens, R. J.; Illingworth, G. D.; Blakeslee, J. P. +2 more
We use the exceptional depth of the Ultra Deep Field (UDF) and UDF-parallel Advanced Camera for Surveys fields to study the sizes of high-redshift (z~2-6) galaxies and address long-standing questions about possible biases in the cosmic star formation rate due to surface brightness dimming. Contrasting B-, V-, and i-dropout samples culled from the …
Constraining Solar Abundances Using Helioseismology
Basu, Sarbani; Antia, H. M.
Recent analyses of solar photospheric abundances suggest that the oxygen abundance in the solar atmosphere needs to be revised downward. In this study, we investigate the consequence of this revision on helioseismic analyses of the depth of the solar convection zone and the helium abundance in the solar envelope and find no significant effect. We …
High-Redshift Supernova Rates
Ferguson, Henry C.; Giavalisco, Mauro; Fruchter, Andrew S. +10 more
We use a sample of 42 supernovae detected with the Advanced Camera for Surveys on board the Hubble Space Telescope as part of the Great Observatories Origins Deep Survey to measure the rate of core-collapse supernovae to z~0.7 and Type Ia supernovae to z~1.6. This significantly increases the redshift range at which supernova rates have been estima…
Observations and Modeling of a Filament on the Sun
van Ballegooijen, A. A.
Hα observations of a filament were obtained at the Swedish Vacuum Solar Telescope in 1998 June. The U-shaped filament has a prominent barb that exhibits interesting fine structure and internal motions. A three-dimensional magnetic model of the filament is presented. The model is based on a National Solar Observatory (Kitt Peak) magnetogram and is …
Color-selected Galaxies at z ~ 6 in the Great Observatories Origins Deep Survey
Stern, D.; Dickinson, M.; Ferguson, H. C. +15 more
We report early results on galaxies at z~6 selected from Hubble Space Telescope imaging for the Great Observatories Origins Deep Survey. Spectroscopy of one object with the Advanced Camera for Surveys grism and from the Keck and Very Large Telescope observatories shows a strong continuum break and asymmetric line emission, identified as Lyα at z=5…
The Profiles of the 3-12 Micron Polycyclic Aromatic Hydrocarbon Features
Hony, S.; Tielens, A. G. G. M.; Allamandola, L. J. +4 more
We present spectra of the 3.3 µm and 11.2 µm polycyclic aromatic hydrocarbon (PAH) features of a large number of stellar sources, planetary nebulae, reflection nebulae, H II regions, and galaxies, obtained with Infrared Space Observatory Short Wavelength Spectrometer. Clear variations are present in the profiles of these features. Most…
XMM-Newton Observation of Solar Wind Charge Exchange Emission
Kuntz, K. D.; Snowden, S. L.; Collier, M. R.
We present an XMM-Newton spectrum of diffuse X-ray emission from within the solar system. The spectrum is dominated by probable C VI lines at 0.37 and 0.46 keV, an O VII line at 0.56 keV, O VIII lines at 0.65 and ~0.8 keV, Ne IX lines at ~0.92 keV, and Mg XI lines at ~1.35 keV. This spectrum is consistent with that expected from charge exchange em…
Bar Evolution over the Last 8 Billion Years: A Constant Fraction of Strong Bars in the GEMS Survey
Bell, Eric F.; Ravindranath, Swara; Somerville, Rachel S. +25 more
One-third of present-day spirals host optically visible strong bars that drive their dynamical evolution. However, the fundamental question of how bars evolve over cosmological times has yet to be resolved, and even the frequency of bars at intermediate redshifts remains controversial. We investigate the frequency of bars out to z ~ 1 drawing on a…
Discovery of a Transient Magnetar: XTE J1810-197
Safi-Harb, Samar; Hurley, Kevin; Kouveliotou, Chryssa +10 more
We report the discovery of a new X-ray pulsar, XTE J1810-197, that was serendipitously discovered on 2003 July 15 by the Rossi X- Ray Timing Explorer (RXTE) while observing the soft gamma repeater SGR 1806-20. The pulsar has a 5.54 s spin period, a soft X-ray spectrum (with a photon index of ~4), and is detectable in earlier RXTE observations back…