Search Publications
Fundamental Properties of the Highly Ionized Plasmas in the Milky Way
Savage, B. D.; Lehner, N.; Howk, J. C. +1 more
The cooling transition temperature gas in the interstellar medium (ISM), traced by the high ions, Si IV, C IV, N V, and O VI, helps to constrain the flow of energy from the hot ISM with T>106 K to the warm ISM with T < 2 × 104 K. We investigate the properties of this gas along the lines of sight to 38 stars in the Milky…
Widespread Nanoflare Variability Detected with Hinode/X-Ray Telescope in a Solar Active Region
Reale, Fabio; Tsuneta, Saku; Miceli, Marco +3 more
It is generally agreed that small impulsive energy bursts called nanoflares are responsible for at least some of the Sun's hot corona, but whether they are the explanation for most of the multimillion-degree plasma has been a matter of ongoing debate. We present here evidence that nanoflares are widespread in an active region observed by the X-Ray…
The ACS Survey of Galactic Globular Clusters. XI. The Three-dimensional Orientation of the Sagittarius Dwarf Spheroidal Galaxy and Its Globular Clusters
Anderson, Jay; Dotter, Aaron; Law, David R. +13 more
We use observations from the Hubble Space Telescope Advanced Camera for Surveys (HST/ACS) study of Galactic globular clusters to investigate the spatial distribution of the inner regions of the disrupting Sagittarius dwarf spheroidal galaxy (Sgr). We combine previously published analyses of four Sgr member clusters located near or in the Sgr core …
Discovery of a Super-Li-rich Turnoff Star in the Metal-poor Globular Cluster NGC 6397
Lind, Karin; Rich, R. Michael; Koch, Andreas
We report on the discovery of a super-Li-rich turnoff (TO) star in the old (12 Gyr), metal-poor ([Fe/H] = -2.1 dex) globular cluster (GC) NGC 6397, based on high-resolution MIKE/Magellan spectra. This star shows an unusually high lithium abundance of A(Li)NLTE = 4.03 ± 0.06 ± 0.14 dex (or, 4.21, accounting for possible contamination fro…
Coronal Seismology Using EIT Waves: Estimation of the Coronal Magnetic Field Strength in the Quiet Sun
Zhukov, A. N.; Dolla, L.; Rodriguez, L. +1 more
Coronal EIT waves have been observed for many years. The nature of EIT waves is still contentious, however, there is strong evidence that some of them might be fast magnetosonic waves, or at least have a fast magnetosonic wave component. The fast magnetosonic wave speed is formed from two components; the Alfvén speed (magnetic) and the sound speed…
Gas Kinematics in Lyα Nebulae
Kelson, Daniel D.; Davé, Romeel; Yang, Yujin +4 more
Exploring the origin of Lyα nebulae ("blobs") at high redshift requires measurements of their gas kinematics that are impossible with only the resonant, optically thick Lyα line. To define gas motions relative to the systemic velocity of the blob, the Lyα line must be compared with an optically thin line like Hα λ6563, which is not much altered by…
Concerning the Classical Cepheid VI C Wesenheit Function's Strong Metallicity Dependence
Gieren, W.; Turner, D.; Majaess, D.
Evidence is presented which supports findings that the classical Cepheid VI C period Wesenheit function is relatively insensitive to metallicity. The viability of a recently advocated strong metallicity dependence was evaluated by applying the proposed correction (γ = -0.8 mag dex-1) to distances established for the Magella…
A First Measurement of the Proper Motion of the Leo II Dwarf Spheroidal Galaxy
Lépine, Sébastien; Rich, R. Michael; Kuijken, Konrad +1 more
We use 14 year baseline images obtained with the Wide Field and Planetary Camera 2 on board the Hubble Space Telescope (HST) to derive a proper motion for one of the Milky Way's most distant dwarf spheroidal companions, Leo II, relative to an extragalactic background reference frame. Astrometric measurements are performed in the effective point-sp…
A Spitzer Infrared Spectrograph Detection of Crystalline Silicates in a Protostellar Envelope
Fischer, William J.; Hartmann, Lee; Calvet, Nuria +12 more
We present the Spitzer Space Telescope Infrared Spectrograph spectrum of the Orion A protostar HOPS-68. The mid-infrared spectrum reveals crystalline substructure at 11.1, 16.1, 18.8, 23.6, 27.9, and 33.6 µm superimposed on the broad 9.7 and 18 µm amorphous silicate features; the substructure is well matched by the presence of the oliv…
The Surface Composition of Large Kuiper Belt Object 2007 OR10
Brown, M. E.; Burgasser, A. J.; Fraser, W. C.
We present photometry and spectra of the large Kuiper belt object 2007 OR10. The data show significant near-infrared absorption features due to water ice. While most objects in the Kuiper belt with water ice absorption this prominent have the optically neutral colors of water ice, 2007 OR10 is among the reddest Kuiper belt objects known. One other…