Search Publications
Evidence for Resonance Scattering in the X-Ray Grating Spectrum of the Supernova Remnant N49
Gu, Liyi; Uchida, Hiroyuki; Tsuru, Takeshi Go +2 more
Resonance scattering (RS) is an important process in astronomical objects, because it affects measurements of elemental abundances and distorts surface brightness of the object. It is predicted that RS can occur in plasmas of supernova remnants (SNRs). Although several authors reported hints of RS in SNRs, no strong observational evidence has been…
Probing Axial Symmetry Breaking in the Galaxy with Gaia Data Release 2
Yanny, Brian; Gardner, Susan; Hinkel, Austin
We study a set of solar neighborhood (d < 3 kpc) stars from Gaia Data Release 2 to determine azimuthal star count differences, I.e., left and right of the line from the Galactic Center (GC) through the Sun - and compare these differences north and south. In this companion paper to Gardner et al., we delineate our procedures to remove false asym…
Suzaku Measurements of Hot Halo Emission at Outskirts for Two Poor Galaxy Groups: NGC 3402 and NGC 5129
Sun, Ming; Dai, Xinyu; Nugent, Jenna M.
We present Suzaku off-center observations of two poor galaxy groups, NGC 3402 and NGC 5129, with temperatures below 1 keV. Through spectral decomposition, we measured their surface brightnesses and temperatures out to 530 and 1430 times the critical density of the universe for NGC 3402 and NGC 5129, respectively. These quantities are consistent wi…
Fluid Theory of Coherent Magnetic Vortices in High-β Space Plasmas
Alexandrova, Olga; Maksimović, Milan; Jovanović, Dušan +1 more
In situ observations in Earth's and Saturn's magnetosheaths and in the solar wind reveal the presence of Alfvén vortices as intermittent structures in the range of scales from fluid lengths down to a few ion lengths. The density and the magnetic field associated with them appear to be compressible for higher plasma betas. Until now, only incompres…
Spectroscopic Monitoring of Rapidly Rotating Early-type Stars in the Pleiades Cluster
Torres, Guillermo
Radial velocities for the early-type stars in the Pleiades cluster have always been challenging to measure because of the significant rotational broadening of the spectral lines. The large scatter in published velocities has led to claims that many are spectroscopic binaries, and in several cases, preliminary orbital solutions have been proposed. …
Distortion of Magnetic Fields in the Dense Core CB81 (L1774, Pipe 42) in the Pipe Nebula
Kwon, Jungmi; Nagata, Tetsuya; Tamura, Motohide +9 more
The detailed magnetic field structure of the starless dense core CB81 (L1774, Pipe 42) in the Pipe Nebula was determined based on near-infrared polarimetric observations of background stars to measure dichroically polarized light produced by magnetically aligned dust grains in the core. The magnetic fields pervading CB81 were mapped using 147 star…
Effects of Solar Activity on Taylor Scale and Correlation Scale in Solar Wind Magnetic Fluctuations
Zhou, G.; Wan, W.; He, H. -Q.
The correlation scale and the Taylor scale are evaluated for interplanetary magnetic field fluctuations from two-point, single time correlation function using the Advanced Composition Explorer (ACE), Wind, and Cluster spacecraft data during the time period from 2001 to 2017, which covers over an entire solar cycle. The correlation scale and the Ta…
Measuring Star Formation Histories, Distances, and Metallicities with Pixel Color-Magnitude Diagrams. II. Applications to Nearby Elliptical Galaxies
van Dokkum, Pieter; Conroy, Charlie; Cook, B. A.
We present spatially resolved measurements of star formation histories (SFHs), metallicities, and distances in three nearby elliptical galaxies and the bulge of M31 derived using the pixel color-magnitude diagram (pCMD) technique. We compute pCMDs from archival Hubble Space Telescope photometry of M87, M49, NGC 3377, and M31, and we fit the data u…
On the Origin of Metal-poor Stars in the Solar Neighborhood
Bilir, Selçuk; Şahin, Timur
We determined the ages, kinematic parameters, and Galactic orbital parameters of six metal-poor (-2.4 < [Fe/H] < -1.0 dex), F-type, high-proper-motion (HPM) stars to investigate their HPM nature and origin. For the kinematical procedure, the astrometric data from the Gaia DR2 were used. High-resolution ELODIE spectra of the six dwarfs were a…
Chromospheric Magnetic Field: A Comparison of He I 10830 Å Observations with Nonlinear Force-free Field Extrapolation
Shimizu, Toshifumi; Asensio Ramos, Andrés; Inoue, Satoshi +1 more
The nonlinear force-free field (NLFFF) modeling has been extensively used to infer the three-dimensional magnetic field in the solar corona. One of the assumptions in the NLFFF extrapolation is that the plasma beta is low, but this condition is considered to be incorrect in the photosphere. We examine direct measurements of the chromospheric magne…