Search Publications
Polytropic Index of the Solar Wind Ions Near the Earth Calculated Using a Homogeneous Magnetohydrodynamic Bernoulli Integral
Wang, Xin; Pang, Xuexia; Wang, Feida +5 more
This paper, using the data of Cluster during 2001-2010, studies the polytropic processes of solar wind ions near the Earth. We calculate the polytropic index of ions for different outward electromagnetic energy ratios δE×B and entropy parameter changes δentropy based on the approach of the homogeneous magnetohydrodynamic Bern…
Pre-main-sequence Stars in Taurus: Comparison of Magnetic and Nonmagnetic Model Fits to the Low-mass Stars
Mullan, D. J.; MacDonald, J.
Stellar associations should be co-eval, but some associations exhibit apparently discrepant ages: M stars appear younger than FG stars. Among M stars in the Upper Sco association (age ≈ 11 Myr), magnetic effects have been shown to slow down evolution of the lowest mass stars, thereby alleviating the age discrepancy. A recent study of pre-main-sequ…
Faint Stars in a Faint Galaxy. I. Ultradeep Photometry of the Boötes I Ultrafaint Dwarf Galaxy
Wyse, Rosemary F. G.; Kozhurina-Platais, Vera; Platais, Imants +2 more
We present an analysis of new, extremely deep images of the resolved stellar population of the Boötes I ultrafaint dwarf spheroidal galaxy. These new data were taken with the Hubble Space Telescope, using the Advanced Camera for Surveys (Wide Field Camera) and Wide Field Camera 3 (UVIS), with filters F606W and F814W (essentially V and I), as part …
Dissecting the Global Cold Dust Properties and Possible Submillimeter Excess of 13 Nearby Spiral Galaxies from the NGLS
Wilson, Christine D.; Li, Dalei; Tang, Xindi +9 more
We select 13 nearby spiral galaxies from the Nearby Galaxies Legacy Survey (NGLS) project and perform spectral energy distribution fitting for each galaxy applying two-component modified blackbody models on a global scale aim to probe the potential submillimeter (submm) excess. We find that NGC 2976, NGC 3351, and NGC 4631 show excess emission at …
Magnetic Rayleigh-Taylor Instability in an Experiment Simulating a Solar Loop
Zhang, Yang; Wongwaitayakornkul, Pakorn; Bellan, Paul M.
A hoop force driven magnetic Rayleigh-Taylor instability (MRTI) is observed in a laboratory experiment that simulates a solar coronal loop. Increase of the axial wavelength λ is observed when the axial magnetic field increases. This scaling is consistent with the theoretical MRTI growth rate ${\gamma }^{2}={gk}-2{\left({\boldsymbol{k}}\cdot {{\bol…
A Simple Unified Spectroscopic Indicator of Stellar Luminosity: The Extended Flux-weighted Gravity-Luminosity Relationship
Rix, Hans-Walter; Kudritzki, Rolf-Peter; Urbaneja, Miguel A.
We show that for a wide range of stellar masses, from 0.3 to 20 M⊙, and for evolutionary phases from the main sequence to the beginning of the red giant stage, the stellar flux-weighted gravity, gF ≅ g/ ${T}_{\mathrm{eff}}^{4}$ , is tightly correlated with absolute bolometric magnitude ${M}_{\mathrm{bol}}$ . Such a correlatio…
Distribution of Water Vapor in Molecular Clouds. II
Bergin, Edwin A.; González-Alfonso, Eduardo; Tolls, Volker +8 more
The depth-dependent abundance of both gas-phase and solid-state water within dense, quiescent, molecular clouds is important to both the cloud chemistry and gas cooling. Where water is in the gas phase, it is free to participate in the network of ion-neutral reactions that lead to a host of oxygen-bearing molecules, and its many ortho- and para-en…
Hot Gas in Galaxy Halos Traced by Coronal Broad Lyα Absorbers
Richter, Philipp
We explore the possibility to systematically study the extended, hot gaseous halos of low-redshift galaxies with coronal broad Lyα absorbers (CBLAs). These are weak, thermally broadenend H I absorption lines arising from the tiny fraction of neutral hydrogen that resides in the collisionally ionized, million-degree halo gas in these galaxies. Usin…
A Catalog of 531 White Dwarf Candidates in the Local Galactic Halo from Gaia Data Release 2
Kim, Bokyoung; Lépine, Sebastien; Medan, Ilija
We present a catalog of 531 white dwarf candidates that have large apparent transverse motions relative to the Sun ( ${v}_{T}\gt 200$ km s-1), thus making them likely members of the local Galactic halo population. The candidates were selected from the Gaia Data Release 2 and are located in a great circle with 20° width running across bo…
KIC 12268220: A δ Scuti Pulsating Star and an Active Protohelium White Dwarf in an Eclipsing Binary System
Liu, Jifeng; Gao, Qing; Ren, Juanjuan +4 more
We present a photometric, spectroscopic, asteroseismic, and evolutionary analysis of the Algol-type eclipsing binary KIC 12268220. We find the O'Connell effect and anticorrelated eclipse timing variations in the Kepler light curve, revealing the presence of large starspots. Radial velocities and atmospheric parameters are obtained from ground-base…