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The Role of Large Amplitude Upstream Low-frequency Waves in the Generation of Superthermal Ions at a Quasi-parallel Collisionless Shock: Cluster Observations
Wang, Shui; Huang, Can; Guo, Fan +3 more
The superthermal ions at a quasi-parallel collisionless shock are considered to be generated during the reformation of the shock. Recently, hybrid simulations of a quasi-parallel shock have shown that during the reformation of a quasi-parallel shock the large-amplitude upstream low-frequency waves can trap the reflected ions at the shock front whe…
Eta Carinae’s 2014.6 Spectroscopic Event: The Extraordinary He II and N II Features
Humphreys, Roberta M.; Davidson, Kris; Mehner, Andrea +2 more
Eta Carinae’s spectroscopic events (periastron passages) in 2003, 2009, and 2014 differed progressively. He ii λ4687 and nearby N ii multiplet 5 have special significance because they respond to very soft X-rays and the ionizing UV radiation field (EUV). Hubble Space Telescope (HST)/STIS observations in 2014 show dramatic increases in both feature…
End-of-life disposal of high elliptical orbit missions: The case of INTEGRAL
Armellin, Roberto; San-Juan, Juan F.; Lara, Martin
Nowadays there is international consensus that space activities must be managed to minimize debris generation and risk. The paper presents a method for the end-of-life (EoL) disposal of spacecraft in high elliptical orbits (HEO). The time evolution of HEO is strongly affected by Earth's oblateness and luni-solar perturbation, and this can cause in…
Energy-dependent orbital phases in NGC 300 X-1
Williams, B. F.; Binder, B.; Gross, J. +1 more
NGC 300 X-1 is a Wolf-Rayet (WR)+black hole binary that exhibits periodic decreases in X-ray flux. We present two new observations of NGC 300 X-1 from the Chandra X-ray Observatory (totalling ∼130 ks) along with Advanced Camera for Surveys imaging data from the Hubble Space Telescope (HST). We observe significant short-term variability in the X-ra…
Hot Plasma from Solar Active Region Cores: a Test of AC and DC Coronal Heating Models?
Schmelz, J. T.; Pathak, S.; Christian, G. M. +2 more
Direct current (DC) models of solar coronal heating invoke magnetic reconnection to convert magnetic free energy into heat, whereas alternating current (AC) models invoke wave dissipation. In both cases the energy is supplied by photospheric footpoint motions. For a given footpoint velocity amplitude, DC models predict lower average heating rates …
Mineralogical and spectral analysis of Vesta's Gegania and Lucaria quadrangles and comparative analysis of their key features
Longobardo, Andrea; Palomba, Ernesto; Zinzi, Angelo +9 more
This work is aimed at developing and interpreting infrared albedo, pyroxene and OH band depths, and pyroxene band center maps of Vesta's Gegania and Lucaria quadrangles, obtained from data provided by the Visible and InfraRed (VIR) mapper spectrometer on board NASA's Dawn spacecraft.
The Gegania and Lucaria quadrangles span latitudes from 22°…Collisionally Excited Filaments in Hubble Space Telescope Hα and Hβ Images of HH 1/2
Bally, J.; Raga, A. C.; Reipurth, B. +2 more
We present new Hα and Hβ images of the HH 1/2 system, and we find that the Hα/Hβ ratio has high values in ridges along the leading edges of the HH 1 bow shock and of the brighter condensations of HH 2. These ridges have Hα/Hβ = 4 → 6, which is consistent with collisional excitation from the n = 1 to the n = 3 and 4 levels of hydrogen in a gas of t…
Planck trispectrum constraints on primordial non-Gaussianity at cubic order
Cooray, Asantha; Smidt, Joseph; Feng, Chang +3 more
Non-Gaussianity of the primordial density perturbations provides an important measure to constrain models of inflation. At cubic order the non-Gaussianity is captured by two parameters τNL and gNL that determine the amplitude of the density perturbation trispectrum. Here we report measurements of the kurtosis power spectra of…
A Statistical Study of Distant Consequences of Large Solar Energetic Events
Schrijver, Carolus J.; Higgins, Paul A.
Large solar flares and eruptions may influence remote regions through perturbations in the outer-atmospheric magnetic field, leading to causally related events outside of the primary or triggering eruptions that are referred to as "sympathetic events". We quantify the occurrence of sympathetic events using the full-disk observations by the Atmosph…
Suzaku Observation of the Classical Nova V2491 Cyg in Quiescence.
Mukai, K.; Orio, M.; Zemko, P.
We present the Suzaku XIS observation of V2491 Cyg (Nova Cyg 2008 No. 2) obtained in quiescence, more than two years after the outburst. The nova was detected as a very luminous source in a wide spectral range from soft to hard X-rays. A very soft blackbody-like component peaking at 0.5 keV indicates that we observe either remaining, localized hyd…