Search Publications
When Does the Onset of Multiple Stellar Populations in Star Clusters Occur? Detection of Enriched Stellar Populations in NGC 2121
de Grijs, Richard; Li, Chengyuan
Star-to-star light-element abundance variations, known as multiple stellar populations (MPs), are common in almost all Galactic globular clusters. Recently, MPs have also been detected in a number of massive clusters with ages in excess of 2 Gyr in the Large Magellanic Cloud (LMC), thus indicating that age is likely a control parameter for the pre…
Jensen-Shannon Complexity Measurements in Solar Wind Magnetic Field Fluctuations
Kivelson, Margaret G.; Weygand, James M.
Turbulent magnetic field fluctuations in the solar wind have been extensively investigated, but few studies have analyzed their complexity. Jensen-Shannon complexity maps of time series data provide a mathematical tool that can characterize fluctuations in laboratory experiments as stochastic, chaotic, or periodic phenomena. We apply this recently…
On the Source Position and Duration of a Solar Type III Radio Burst Observed by LOFAR
Kontar, Eduard P.; Zhang, PeiJin; Yu, SiJie +1 more
The flux of solar type III radio bursts have a time profile of rising and decay phases at a given frequency, which has been actively studied since the 1970s. Several factors that may influence the duration of a type III radio burst have been proposed. In this work, to study the dominant cause of the duration, we investigate the source positions of…
Polarimetric and Photometric Investigation of the Dark Globule LDN 1225: Distance, Extinction Law, and Magnetic Fields
Jose, Jessy; Wang, Jia-Wei; Lai, Shih-Ping +7 more
We present results based on the optical R-band observations of the polarization of 280 stars distributed toward the dark globule LDN 1225. Parallaxes from Gaia data release 2 along with the polarization data of ∼200 stars have been used to (a) constrain the distance of LDN 1225 as 830 ± 83 pc, (b) determine the contribution of interstellar polariz…
Observations of the Venus Dramatic Response to an Extremely Strong Interplanetary Coronal Mass Ejection
Xu, Qi; Zhang, Tielong; Rong, Zhaojin +4 more
On 2011 November 5, Venus Express observed the impact of an extremely strong interplanetary coronal mass ejection (ICME) on Venus. As a result, the Venusian induced magnetosphere dramatically fluctuated during the ICME passage: the bow shock was compressed and broadened by the sheath and the body of the ICME, respectively; an atypically strong mag…
Discovery of a White Dwarf Companion to HD 159062
Fulton, Benjamin J.; Hirsch, Lea A.; Howard, Andrew W. +11 more
We report on the discovery of a white dwarf companion to the nearby late G dwarf star, HD 159062. The companion is detected in 14 years of precise radial velocity (RV) data, and in high-resolution imaging observations. RVs of HD 159062 from 2003 to 2018 reveal an acceleration of -13.3 ± 0.12 {{m}} {{{s}}}-1 {yr}}-1, indicatin…
Statistical Study of Chromospheric Evaporation in Impulsive Phase of Solar Flares
Kerr, Graham S.; Kosovichev, Alexander G.; Sadykov, Viacheslav M. +1 more
We present a statistical study of chromospheric evaporation in solar flares using simultaneous observations by the RHESSI X-ray telescope and the Interface Region Imaging Spectrograph UV spectrograph. The results are compared with radiation hydrodynamic flare models from the F-CHROMA RADYN database. For each event, we study spatially resolved Dopp…
The Origin of [C II] 158 µm Emission toward the H II Region Complex S235
Schneider, N.; Tremblin, P.; Zavagno, A. +9 more
Although the {}2{{{P}}}3/2-{}2{{{P}}}1/2 transition of [C II] at λ ≃ 158 µ {{m}} is known to be an excellent tracer of active star formation, we still do not have a complete understanding of where within star formation regions the emission originates. Here, we use SOFIA upGREAT observations of [C I…
Coordinated UV and X-Ray Spectroscopic Observations of the O-type Giant ξ Per: The Connection between X-Rays and Large-scale Wind Structure
Ignace, Richard; Massa, Derck; Oskinova, Lida +1 more
We present new, contemporaneous Hubble Space Telescope STIS and XMM-Newton observations of the O7 III(n)((f)) star ξ Per. We supplement the new data with archival IUE spectra, to analyze the variability of the wind lines and X-ray flux of ξ Per. The variable wind of this star is known to have a 2.086-day periodicity. We use a simple, heuristic spo…
Spectral Magnetic Helicity of Solar Active Regions between 2006 and 2017
Gosain, Sanjay; Brandenburg, Axel
We compute magnetic helicity and energy spectra from about 2485 patches of about 100 Mm side length on the solar surface using data from Hinode during 2006-2017. An extensive database is assembled where we list the magnetic energy and helicity, large- and small-scale magnetic helicity, mean current helicity density, fractional magnetic helicity, a…