Search Publications
The Occurrence and Speed of CMEs Related to Two Characteristic Evolution Patterns of Helicity Injection in Their Solar Source Regions
Wang, Haimin; Chae, Jongchul; Liu, Rui +4 more
Long-term (a few days) variation of magnetic helicity injection was calculated for 28 solar active regions that produced 47 coronal mass ejections (CMEs) to find its relationship to the CME occurrence and speed using SOHO/MDI line-of-sight magnetograms. As a result, we found that the 47 CMEs can be categorized into two different groups by two char…
A Herschel Search for Cold Dust in Brown Dwarf Disks: First Results
Pascucci, Ilaria; Henning, Thomas; Ménard, François +7 more
We report initial results from a Herschel program to search for far-infrared emission from cold dust around a statistically significant sample of young brown dwarfs. The first three objects in our survey are all detected at 70 µm, and we report the first detection of a brown dwarf at 160 µm. The flux densities are consistent with the p…
Detecting the Warm-Hot Intergalactic Medium through X-Ray Absorption Lines
Shull, J. Michael; Wang, Q. Daniel; Yao, Yangsen +1 more
The warm-hot intergalactic medium (WHIM) at temperatures 105-107 K is believed to contain 30%-50% of the baryons in the local universe. However, all current X-ray detections of the WHIM at redshifts z > 0 are of low statistical significance (lsim 3σ) and/or controversial. In this work, we aim to establish the detection lim…
Far-ultraviolet Continuum Emission: Applying This Diagnostic to the Chromospheres of Solar-mass Stars
France, Kevin; Linsky, Jeffrey L.; Ayres, Tom +2 more
The far-ultraviolet (FUV) continuum flux is recognized as a very sensitive diagnostic of the temperature structure of the Sun's lower chromosphere. Until now analysis of the available stellar FUV data has shown that solar-type stars must also have chromospheres, but quantitative analyses of stellar FUV continua require far higher quality spectra a…
Investigation of Intermittency in Magnetohydrodynamics and Solar Wind Turbulence: Scale-dependent Kurtosis
Oughton, Sean; Matthaeus, William H.; Wan, Minping +1 more
The behavior of scale-dependent (or filtered) kurtosis is studied in the solar wind using magnetic field measurements from the ACE and Cluster spacecraft at 1 AU. It is also analyzed numerically with high-resolution magnetohydrodynamic spectral simulations. In each case the filtered kurtosis increases with wavenumber, implying the presence of cohe…
The Emission of Cygnus X-1: Observations with INTEGRAL SPI from 20 keV to 2 MeV
Malzac, J.; Jourdain, E.; Roques, J. P.
We report on Cyg X-1 observations performed by the SPI telescope on board the INTEGRAL mission and distributed over more than 6 years. We investigate the variability of the intensity and spectral shape of this peculiar source in the hard X-ray domain, and more particularly up to the MeV region. We first study the total averaged spectrum which pres…
Suzaku Observations of 4U 1957+11: Potentially the Most Rapidly Spinning Black Hole in (the Halo of) the Galaxy
Pottschmidt, Katja; Wilms, Jörn; Nowak, Michael A. +3 more
We present three Suzaku observations of the black hole candidate 4U 1957+11 (V1408 Aql)—a source that exhibits some of the simplest and cleanest examples of soft, disk-dominated spectra. 4U 1957+11 also presents among the highest peak temperatures found from disk-dominated spectra. Such temperatures may be associated with rapid black hole spin. Th…
Numerical Modeling of the Initiation of Coronal Mass Ejections in Active Region NOAA 9415
Poedts, S.; Zuccarello, F. P.; Meliani, Z.
Coronal mass ejections (CMEs) and solar flares are the main drivers of weather in space. Understanding how these events occur and what conditions might lead to eruptive events is of crucial importance for up to date and reliable space weather forecasting. The aim of this paper is to present a numerical magnetohydrodynamic (MHD) data-inspired model…
Study of Single-lobed Circular Polarization Profiles in the Quiet Sun
Sainz Dalda, A.; Martínez-Sykora, J.; Title, A. +1 more
The existence of asymmetries in the circular polarization (Stokes V) profiles emerging from the solar photosphere has been known since the 1970s. These profiles require the presence of a velocity gradient along the line of sight (LOS), possibly associated with gradients of magnetic field strength, inclination, and/or azimuth. We have focused our s…
Hydrogen Fluoride in High-mass Star-forming Regions
Ceccarelli, C.; Lis, D. C.; Phillips, T. G. +5 more
Hydrogen fluoride (HF) has been established to be an excellent tracer of molecular hydrogen in diffuse clouds. In denser environments, however, the HF abundance has been shown to be approximately two orders of magnitude lower. We present Herschel/HIFI observations of HF J = 1-0 toward two high-mass star formation sites, NGC 6334 I and AFGL 2591. I…