Search Publications
Vector Magnetic Fields and Doppler Velocity Structures Around a Cancellation Site in the Quiet Sun
Ichimoto, K.; Iida, Y.; Yokoyama, T.
A cancellation is thought to be a basic process of the photospheric magnetic field and plays an important role in magnetic flux budget and in various solar activities. There are two major theoretical scenarios for this phenomena, the "U-loop emergence" and the "Ω-loop submergence" models. It is important to clarify which is the dominant process du…
Effects of α-Element Enhancement and the Thermally Pulsing-Asymptotic Giant Branch on Surface Brightness Fluctuation Magnitudes and Broadband Colors
Blakeslee, John P.; Worthey, Guy; Lee, Hyun-chul
We investigate the effects of α-element enhancement and the thermally pulsing-asymptotic giant branch (TP-AGB) stars on the surface brightness fluctuation (SBF) magnitudes and broadband colors of simple stellar populations and compare to the empirical calibrations. We consider a broad range of ages and metallicities using the recently updated Tera…
The Asymptotic Giant Branch and the Tip of the Red Giant Branch as Probes of Star Formation History: The Nearby Dwarf Irregular Galaxy KKH 98
Koo, D. C.; Melbourne, J.; Williams, B. +5 more
We investigate the utility of the asymptotic giant branch (AGB) and the red giant branch (RGB) as probes of the star formation history (SFH) of the nearby (D = 2.5 Mpc) dwarf irregular galaxy, KKH 98. Near-infrared (near-IR) Keck Laser Guide Star Adaptive Optics (AO) images resolve 592 IR-bright stars reaching over 1 mag below the tip of the RGB. …
X-ray Emission from the Sombrero Galaxy: Discrete Sources
Spitler, Lee R.; Jones, Christine; Gilfanov, Marat +7 more
We present a study of discrete X-ray sources in and around the bulge-dominated, massive Sa galaxy, Sombrero (M104), based on new and archival Chandra observations with a total exposure of ~200 ks. With a detection limit of L X ≈ 1037 erg s-1 and a field of view covering a galactocentric radius of ~30 kpc (11farcm5)…
Inertial-range spectrum of whistler turbulence
Narita, Y.; Gary, S. P.
We develop a theoretical model of an inertial-range energy spectrum for homogeneous whistler turbulence. The theory is a generalization of the Iroshnikov-Kraichnan concept of the inertial-range magnetohydrodynamic turbulence. In the model the dispersion relation is used to derive scaling laws for whistler waves at highly oblique propagation with r…
Direct measurements of the Poynting flux associated with convection electric fields in the magnetosphere
Tanaka, T.; Wygant, J.; Nishimura, Y. +6 more
Observations of Poynting fluxes associated with onset of convection electric fields are essential for understanding of electromagnetic energy transport from the solar wind toward the magnetosphere leading to changes in the convection electric field, which is one of the most fundamental parameters in the magnetosphere-ionosphere coupled system. We …
Chandra Detects the Rare Oxygen-type Wolf-Rayet Star WR 142 and OB Stars in Berkeley 87
Skinner, Stephen L.; Zhekov, Svetozar A.; Güdel, Manuel +2 more
We present first results of a Chandra X-ray observation of the rare oxygen-type Wolf-Rayet (WR) star WR 142 (= Sand 5 = St 3) harbored in the young, heavily obscured cluster Berkeley 87. Oxygen-type WO stars are thought to be the most evolved of the WRs and progenitors of supernovae or gamma-ray bursts. As part of an X-ray survey of supposedly sin…
The Dependence of the EIT Wave Velocity on the Magnetic Field Strength
Chen, P. F.; Yang, H. Q.
"EIT waves" are a wavelike phenomenon propagating in the corona, which was initially observed in the extreme ultraviolet (EUV) wavelength by the EUV Imaging Telescope (EIT). Their nature is still elusive, with the debate on-going between fast-mode wave model and non-wave model. In order to distinguish between these models, we investigate the relat…
Temporal variation of the tropospheric cloud and haze in the jovian equatorial zone
de Pater, Imke; Wong, Michael H.; Lii, Patrick S.
We analyze the temporal variation of the tropospheric cloud and haze in the jovian equatorial zone. In order to investigate the time evolution of the haze, we utilize a comprehensive set of archival WFPC2 images in the 953 and 893-nm wavelengths spanning over a decade of HST observations of Jupiter. We find that the latitude of the peak haze refle…
A blue tilt in the globular cluster system of the Milky Way-like galaxy NGC 5170
Bailin, Jeremy; Spitler, Lee R.; Forbes, Duncan A. +4 more
Here, we present Hubble Space Telescope/Advanced Camera for Surveys (ACS) imaging, in the B and I bands, of the edge-on Sb/Sc galaxy NGC 5170. Excluding the central disc region, we detect 142 objects with colours and sizes typical of globular clusters (GCs). Our main result is the discovery of a `blue tilt' (a mass-metallicity relation), at the 3σ…