Search Publications
The Formation and Physical Origin of Highly Ionized Cooling Gas
Heckman, Timothy M.; Bordoloi, Rongmon; Wagner, Alexander Y. +1 more
We present a simple model that explains the origin of warm, diffuse gas seen primarily as highly ionized absorption-line systems in the spectra of background sources. We predict the observed column densities of several highly ionized transitions such as O VI, O vii, Ne viii, N v, and Mg x, and we present a unified comparison of the model predictio…
Hints for Small Disks around Very Low Mass Stars and Brown Dwarfs
Pascucci, Ilaria; Henning, Thomas; Ménard, François +6 more
The properties of disks around brown dwarfs and very low mass stars (hereafter VLMOs) provide important boundary conditions on the process of planet formation and inform us about the numbers and masses of planets than can form in this regime. We use the Herschel Space Observatory PACS spectrometer to measure the continuum and [O I] 63 µm lin…
Detection of Interstellar Ortho-D2H+ with SOFIA
Caselli, Paola; Menten, Karl M.; Okada, Yoko +9 more
We report on the detection of the ground-state rotational line of ortho-D2H+ at 1.477 THz (203 µm) using the German REceiver for Astronomy at Terahertz frequencies (GREAT) on board the Stratospheric Observatory For Infrared Astronomy (SOFIA). The line is seen in absorption against far-infrared continuum from the protost…
Non-local Thermodynamic Equilibrium Stellar Spectroscopy with 1D and >3D< Models. II. Chemical Properties of the Galactic Metal-poor Disk and the Halo
Kovalev, Mikhail; Hansen, Camilla Juul; Bergemann, Maria +5 more
From exploratory studies and theoretical expectations it is known that simplifying approximations in spectroscopic analysis (local thermodynamic equilibrium (LTE), 1D) lead to systematic biases of stellar parameters and abundances. These biases depend strongly on surface gravity, temperature and, in particular, for LTE versus non-LTE (NLTE), on me…
Theory and Transport of Nearly Incompressible Magnetohydrodynamics Turbulence. III. Evolution of Power Anistropy in Magnetic Field Fluctuations throughout the Heliosphere
Bruno, R.; Zank, G. P.; Shiota, D. +3 more
A theoretical model that describes the evolution of the power anisotropy in the energy-containing and inertial ranges throughout the heliosphere is developed for three possibilities: (i) no in situ sources of turbulence; (ii) stream-shear sources of 2D and slab turbulence; and (iii) a fully driven turbulence model that includes both stream-shear d…
The Origin of Solar Filament Plasma Inferred from In Situ Observations of Elemental Abundances
Chen, Y.; Li, B.; Song, H. Q. +6 more
Solar filaments/prominences are one of the most common features in the corona, which may lead to energetic coronal mass ejections (CMEs) and flares when they erupt. Filaments are about 100 times cooler and denser than the coronal material, and physical understanding of their material origin remains controversial. Two types of scenarios have been p…
Magnetar-like X-Ray Bursts Suppress Pulsar Radio Emission
Israel, G.; Kerr, M.; Rea, N. +9 more
Rotation-powered pulsars and magnetars are two different observational manifestations of neutron stars: rotation-powered pulsars are rapidly spinning objects that are mostly observed as pulsating radio sources, while magnetars, neutron stars with the highest known magnetic fields, often emit short-duration X-ray bursts. Here, we report simultaneou…
A Search for Spectral Hysteresis and Energy-dependent Time Lags from X-Ray and TeV Gamma-Ray Observations of Mrk 421
Maraschi, L.; Covino, S.; Antonelli, L. A. +222 more
Blazars are variable emitters across all wavelengths over a wide range of timescales, from months down to minutes. It is therefore essential to observe blazars simultaneously at different wavelengths, especially in the X-ray and gamma-ray bands, where the broadband spectral energy distributions usually peak. In this work, we report on three “targe…
A First Comparison of Millimeter Continuum and Mg II Ultraviolet Line Emission from the Solar Chromosphere
De Pontieu, B.; Schmit, D.; Leenaarts, J. +4 more
We present joint observations of the Sun by the Atacama Large Millimeter/submillimeter Array (ALMA) and the Interface Region Imaging Spectrograph (IRIS). Both millimeter/submillimeter-λ continuum emission and ultraviolet (UV) line emission originate from the solar chromosphere and both have the potential to serve as powerful and complementary diag…
Star Formation at z = 2.481 in the Lensed Galaxy SDSS J1110 = 6459. I. Lens Modeling and Source Reconstruction
Rigby, Jane R.; Florian, Michael; Whitaker, Katherine E. +6 more
Using the combined resolving power of the Hubble Space Telescope and gravitational lensing, we resolve star-forming structures in a z∼ 2.5 galaxy on scales much smaller than the usual kiloparsec diffraction limit of HST. SGAS J111020.0+645950.8 is a clumpy, star-forming galaxy lensed by the galaxy cluster SDSS J1110+6459 at z=0.659, with a total m…