Search Publications
Evidence for Black Hole Growth in Local Analogs to Lyman Break Galaxies
Heckman, Timothy M.; Hornschemeier, Ann; Overzier, Roderik A. +3 more
We have used XMM-Newton to observe six Lyman break analogs (LBAs): members of the rare population of local galaxies that have properties that are very similar to distant Lyman break galaxies. Our six targets were specifically selected because they have optical emission-line properties that are intermediate between starbursts and Type 2 (obscured) …
A Coherent Timing Solution for the Nearby, Thermally Emitting Isolated Neutron Star RX J0420.0-5022
van Kerkwijk, M. H.; Kaplan, D. L.
We present a phase-coherent timing solution for RX J0420.0-5022, the coolest (kT ~= 45 eV) and fastest-spinning (P = 3.45 s) of the seven so-called isolated neutron stars (INSs). Using 14 observations with the XMM-Newton spacecraft in 2010 and 2011, we were able to measure a spin-down rate \dot{\nu }=(-2.3+/- 0.2)\times 10^{-15}\,{\,Hz\,s}^{-1} (\…
Millimeter Imaging of the β Pictoris Debris Disk: Evidence for a Planetesimal Belt
Hughes, A. Meredith; Wilner, David J.; Andrews, Sean M.
We present observations at 1.3 mm wavelength of the β Pictoris debris disk with beam size 4farcs3 × 2farcs6 (83 × 50 AU) from the Submillimeter Array. The emission shows two peaks separated by ~7'' along the disk plane, which we interpret as a highly inclined dust ring or belt. A simple model constrains the belt center to 94 ± 8 AU, close to the p…
Spatially Resolving the HK Tau B Edge-on Disk from 1.2 to 4.7 µm: A Unique Scattered Light Disk
Pinte, C.; Ménard, F.; Duchêne, G. +3 more
We present spatially resolved scattered light images of the circumstellar disk around HK Tau B at 3.8 and 4.7 µm taken with the Keck Telescope Laser Guide Star Adaptive Optics (AO) system, and 1.6-2.12 µm images taken with the Very Large Telescope/NACO AO system. Combined with previously published optical Hubble Space Telescope data, w…
Resolving the Baryon-fraction Profile in Lensing Galaxies
Saha, Prasenjit; Ferreras, Ignacio; Falco, Emilio E. +1 more
The study of the distribution of baryonic matter within dark halos enriches our understanding of galaxy formation. We show the radial dependence of stellar baryon-fraction curves derived for 21 lensing galaxies from the CfA-Arizona Space Telescope LEns Survey (CASTLES) by means of stellar population synthesis and pixel-based mass reconstruction. T…
The Extreme Overabundance of Molybdenum in Two Metal-poor Stars
Peterson, Ruth C.
We report determinations of the molybdenum abundances in five mildly to extremely metal-poor turnoff stars using five Mo II lines near 2000 Å. In two of the stars, the abundance of molybdenum is found to be extremely enhanced, as high or higher than the neighboring even-Z elements ruthenium and zirconium. Of the several nucleosynthesis scenarios e…
Protostars and Stars in the Coronet Cluster: Age, Evolution, and Cluster Structure
Henning, Thomas; Kainulainen, Jouni; Sicilia-Aguilar, Aurora +1 more
We present new optical spectroscopy with the FLAMES spectrograph at the Very Large Telescope (VLT), near-IR imaging with VLT/HAWK-I, and 870 µm mapping with APEX/LABOCA of the Coronet cluster. The optical data allow us to estimate spectral types, extinction, and the presence of accretion in 6 more M-type members, in addition to the 12 that w…
The Relationship between Vertical and Horizontal Magnetic Fields in the Quiet Sun
Tsuneta, Saku; Ishikawa, Ryohko
Vertical magnetic fields have been known for decades to exist in the internetwork region of the Sun, while the properties of horizontal magnetic fields have only recently been extensively investigated with Hinode. Vertical and horizontal magnetic fields in the internetwork region are considered to be separate entities and have thus far not been in…
Taking Advantage of the COS Time-tag Capability: Observations of Pulsating Hot DQ White Dwarfs and Discovery of a New One
Chayer, P.; Fontaine, G.; Bergeron, P. +2 more
We present an analysis of the ultraviolet light curves of five Hot DQ white dwarfs recently observed with the Cosmic Origins Spectrograph (COS) on board the Hubble Space Telescope (HST). These light curves were constructed by extracting the time-tag information from the FUV and NUV spectroscopic data. Single-color light curves were thus produced i…
Achieving Self-consistent Nonlinear Force-free Modeling of Solar Active Regions
Leka, K. D.; Wheatland, M. S.
A nonlinear force-free solution is constructed for the coronal magnetic field in NOAA solar active region (AR) 10953 based on a photospheric vector magnetogram derived from Hinode satellite observations on 2007 April 30, taking into account uncertainties in the boundary data and using improved methods for merging multiple-instrument data. The solu…