Search Publications
Momentum transfer from solar wind to interplanetary field enhancements inferred from magnetic field draping signatures
Lai, H. R.; Russell, C. T.; Jia, Y. D. +2 more
Characterized by a cusp-shaped enhancement in the magnetic field strength, the magnetic structure in the solar wind, called an interplanetary field enhancement (IFE), has been investigated since its discovery. To understand its three-dimensional magnetic field geometry, we study an IFE detected by five spacecraft simultaneously. Field lines are se…
A New Sample of Obscured AGNs Selected from the XMM-Newton and AKARI Surveys
Oyabu, Shinki; Gandhi, Poshak; Awaki, Hisamitsu +4 more
We report a new sample of obscured active galactic nuclei (AGNs) selected from the XMM-Newton serendipitous source and AKARI point-source catalogs. We match X-ray sources with infrared (18 and 90 µm) sources located at | b| \gt 10^\circ to create a sample consisting of 173 objects. Their optical classifications and absorption column densitie…
Probing Magnetic Fields at the Base of the Solar Convection Zone with Meridional Flows
Liang, Zhi-Chao; Chou, Dean-Yi
Solar magnetic fields are responsible for most of the activities on the Sun. Many theories predict that it is generated by a dynamo near the base of the convection zone (BCZ), located at 0.71{R}⊙ . In this study, we use the solar-cycle variations of the meridional flow to probe magnetic field variations near the BCZ. A helioseismic time…
New Mn II energy levels from the STIS-HST spectrum of the HgMn star HD 175640
Castelli, F.; Kurucz, R. L.; Cowley, C. R.
Aims: The NIST database lists several Mn ii lines that were observed in the laboratory but not classified. They cannot be used in spectrum synthesis because their atomic line data are unknown. These lines are concentrated in the 2380-2700 Å interval. We aimed to assign energy levels and log gf values to these lines.
Methods: Semi-empiric…
Candidates source regions of martian meteorites as identified by OMEGA/MEx
Bibring, J. -P.; Poulet, F.; Quantin, C. +3 more
The objective of this study is to identify and map spectral analogues of some key martian meteorites (basaltic shergottites Los Angeles, Shergotty, QUE 94201, lherzolitic shergottite ALH A77005, Nakhla, Chassigny and the orthopyroxenite ALH 84001) in order to localize terrain candidates for their source regions. We develop a best fit procedure to …
Metallicity Distribution Functions of Four Local Group Dwarf Galaxies
Holtzman, Jon; Anthony-Twarog, Barbara J.; Saha, Abhijit +1 more
We present stellar metallicities in Leo I, Leo II, IC 1613, and Phoenix dwarf galaxies derived from medium (F390M) and broad (F555W, F814W) band photometry using the Wide Field Camera 3 instrument on board the Hubble Space Telescope. We measured metallicity distribution functions (MDFs) in two ways, (1) matching stars to isochrones in color-color …
An Emerging Wolf-Rayet Massive Star Cluster in NGC 4449
Johnson, Kelsey E.; Indebetouw, Rémy; Reines, Amy E. +1 more
We present a panchromatic investigation of the partially embedded, emerging massive cluster Source 26 (=S26) in NGC 4449 with optical spectra obtained at Apache Point Observatory and archival Hubble, Spitzer, and Herschel 5 Space Telescope images. First identified as a radio continuum source with a thermal component due to ionized mater…
The Optical Wind Line Variability of η Carinae During the 2009.0 Event
Gull, T. R.; Gies, D. R.; Richardson, N. D. +2 more
We report on high-resolution spectroscopy of the 2009.0 spectroscopic event of η Carinae collected via SMARTS observations using the CTIO 1.5 m telescope and echelle spectrograph. Our observations were made almost every night over a two-month interval around the photometric minimum of η Car associated with the periastron passage of a hot companion…
Distant ionospheric photoelectron energy peak observations at Venus
Coates, A. J.; Fedorov, A.; Barabash, S. +4 more
The dayside of the Venus ionosphere at the top of the planet's thick atmosphere is sustained by photoionization. The consequent photoelectrons may be identified by specific peaks in the energy spectrum at 20-30 eV which are mainly due to atomic oxygen photoionization. The ASPERA-4 electron spectrometer has an energy resolution designed to identify…
Seed Population in Large Solar Energetic Particle Events and the Twin-CME Scenario
Li, Gang; Ding, Liu-Guan; Le, Gui-Ming +2 more
It has recently been suggested that large solar energetic particle (SEP) events are often caused by twin coronal mass ejections (CMEs). In the twin-CME scenario, the preceding CME provides both an enhanced turbulence level and enhanced seed population at the main CME-driven shock. In this work, we study the effect of the preceding CMEs on the seed…