Search Publications
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…
The radiative forcing variability caused by the changes of the upper cloud vertical structure in the Venus mesosphere
Pätzold, M.; Piccioni, G.; Ignatiev, N. I. +3 more
The upper cloud layer of Venus is a key factor affecting radiative energy balance of the mesosphere. Observations of the temperature and the cloud top structure by Venus Express revealed their strong variability with latitude. We used the 1-D radiative transfer model to study the dependence of the radiative forcing on the cloud top structure. The …
Warm gas in and around simulated galaxy clusters as probed by absorption lines
Putman, M. E.; Emerick, A.; Bryan, G.
Understanding gas flows into and out of the most massive dark matter structures in our Universe, galaxy clusters, is fundamental to understanding their evolution. Gas in clusters is well studied in the hot (> 106 K) and cold (< 104 K) regimes, but the warm gas component (104-106 K) is poorly constr…
Multiwavelength modelling the SED of supersoft X-ray sources I. The method and examples
Skopal, A.
Radiation of supersoft X-ray sources (SSS) dominates both the supersof X-ray and the far-UV domain. A fraction of their radiation can be reprocessed into the thermal nebular emission, seen in the spectrum from the near-UV to longer wavelengths. In the case of symbiotic X-ray binaries (SyXBs) a strong contribution from their cool giants is indicate…