Search Publications
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…
A Highly Magnified Supernova at z = 1.703 behind the Massive Galaxy Cluster A1689
Kneib, J. -P.; Dahle, H.; Lidman, C. +17 more
Our ability to study the most remote supernova explosions, crucial for the understanding of the evolution of the high-redshift universe and its expansion rate, is limited by the light collection capabilities of telescopes. However, nature offers unique opportunities to look beyond the range within reach of our unaided instruments thanks to the lig…
Hubble Space Telescope Studies of Nearby Type Ia Supernovae: The Mean Maximum Light Ultraviolet Spectrum and its Dispersion
Cenko, S. Bradley; Law, Nicholas M.; Ellis, Richard S. +11 more
We present the first results of an ongoing campaign using the STIS spectrograph on board the Hubble Space Telescope (HST), whose primary goal is the study of near-ultraviolet (UV) spectra of local Type Ia supernovae (SNe Ia). Using events identified by the Palomar Transient Factory and subsequently verified by ground-based spectroscopy, we demonst…
Arp 220: Extinction and Merger-induced Star Formation
Genzel, R.; Sturm, E.; Tacconi, L. J. +3 more
We analyze new spatially resolved integral field spectroscopic H- and K-band data at a resolution of 0farcs3 (100 pc) and reanalyze interferometric CO(2-1) line observations of the prototypical merging system Arp 220. We find that the majority of the K-band luminosity is due to a 10 Myr old starburst, with a significant contribution from an underl…
Eclipses during the 2010 Eruption of the Recurrent Nova U Scorpii
Maehara, Hiroyuki; Schaefer, Bradley E.; Worters, Hannah L. +34 more
The eruption of the recurrent nova U Scorpii on 2010 January 28 is now the all-time best observed nova event. We report 36,776 magnitudes throughout its 67 day eruption, for an average of one measure every 2.6 minutes. This unique and unprecedented coverage is the first time that a nova has had any substantial amount of fast photometry. With this,…
Nonlinear Color-Metallicity Relations of Globular Clusters. II. A Test on the Nonlinearity Scenario for Color Bimodality Using the u-band Colors: The Case of M87 (NGC 4486)
Blakeslee, John P.; Sohn, Sangmo T.; Kim, Hak-Sub +4 more
The optical color distributions of globular clusters (GCs) in most large elliptical galaxies are bimodal. Based on the assumed linear relationship between GC colors and their metallicities, the bimodality has been taken as evidence of two GC subsystems with different metallicities in each galaxy and has led to a number of theories in the context o…