Search Publications
Temporal Evolution of Solar Wind Ion Composition and their Source Coronal Holes during the Declining Phase of Cycle 23. I. Low-latitude Extension of Polar Coronal Holes
Young, Peter R.; Wang, Yi-Ming; Ko, Yuan-Kuen +2 more
We analyzed 27 solar wind (SW) intervals during the declining phase of cycle 23, whose source coronal holes (CHs) can be unambiguously identified and are associated with one of the polar CHs. We found that the SW ions have a temporal trend of decreasing ionization state, and such a trend is different between the slow and fast SW. The photospheric …
Constraining the Dust Coma Properties of Comet C/Siding Spring (2013 a1) at Large Heliocentric Distances
Samarasinha, Nalin H.; A'Hearn, Michael F.; Li, Jian-Yang +5 more
The close encounter of comet C/2013 A1 (Siding Spring) with Mars on 2014 October 19 presented an extremely rare opportunity to obtain the first flyby quality data of the nucleus and inner coma of a dynamically new comet. However, the comet's dust tail potentially posed an impact hazard to those spacecraft orbiting Mars. To characterize the comet a…
Hubble Space Telescope Observations and Geometric Models of Compact Multipolar Planetary Nebulae
Zhang, Yong; Kwok, Sun; Hsia, Chih-Hao +1 more
We report high angular resolution Hubble Space Telescope observations of 10 compact planetary nebulae (PNs). Many interesting internal structures, including multipolar lobes, arcs, two-dimensional rings, tori, and halos, are revealed for the first time. These results suggest that multipolar structures are common among PNs, and these structures dev…
Helioseismology of Pre-emerging Active Regions. III. Statistical Analysis
Leka, K. D.; Barnes, G.; Birch, A. C. +1 more
The subsurface properties of active regions (ARs) prior to their appearance at the solar surface may shed light on the process of AR formation. Helioseismic holography has been applied to samples taken from two populations of regions on the Sun (pre-emergence and without emergence), each sample having over 100 members, that were selected to minimi…
On the Nature of the Deeply Embedded Protostar OMC-2 FIR 4
Manoj, P.; Megeath, S. T.; Osorio, M. +7 more
We use mid-infrared to submillimeter data from the Spitzer, Herschel, and Atacama Pathfinder Experiment telescopes to study the bright submillimeter source OMC-2 FIR 4. We find a point source at 8, 24, and 70 µm, and a compact, but extended source at 160, 350, and 870 µm. The peak of the emission from 8 to 70 µm, attributed to th…
Excitation of Kinetic Alfvén Waves by Fast Electron Beams
Chen, L.; Wu, D. J.; Zhao, G. Q. +2 more
Energetic electron beams, which are ubiquitous in a large variety of active phenomena in space and astrophysical plasmas, are one of the most important sources that drive plasma instabilities. In this paper, taking account of the return-current effect of fast electron beams, kinetic Alfvén wave (KAW) instability driven by a fast electron beam is i…
0.94-2.42 µm Ground-based Transmission Spectra of the Hot Jupiter HD-189733b
Waldmann, I. P.; Tinetti, G.; Swain, M. R. +3 more
We present here new transmission spectra of the hot Jupiter HD-189733b using the SpeX instrument on the NASA Infrared Telescope Facility. We obtained two nights of observations where we recorded the primary transit of the planet in the J, H, and K bands simultaneously, covering a spectral range from 0.94 to 2.42 µm. We used Fourier analysis …
High Resolution X-Ray Spectroscopy of the Local Hot Gas along the 3C 273 Sightline
Fang, Taotao; Jiang, Xiaochuan
X-ray observations of highly ionized metal absorption lines at z = 0 provide critical information on the hot gas distribution in and around the Milky Way. We present a study of more than 10 yr of Chandra and XMM-Newton observations of 3C 273, one of the brightest extragalactic X-ray sources. Compared with previous works, we obtain much tighter con…
Pre-flare Dynamics of Sunspot Groups
Korsós, M. B.; Ludmány, A.; Baranyi, T.
Several papers provide evidence that the most probable sites of flare onset are the regions of high horizontal magnetic field gradients in solar active regions. Besides the localization of flare-producing areas, this work intends to reveal the characteristic temporal variations in these regions prior to flares. This study uses sunspot data instead…
The Two-dimensional Spatial Distributions of the Globular Clusters and Low-mass X-Ray Binaries of NGC 4649
Zezas, A.; Luo, B.; Fabbiano, G. +5 more
We report significant anisotropies in the projected two-dimensional (2D) spatial distributions of globular clusters (GCs) of the giant Virgo elliptical galaxy NGC 4649 (M60). Similar features are found in the 2D distribution of low-mass X-ray binaries (LMXBs), both associated with GCs and in the stellar field. Deviations from azimuthal symmetry su…