Search Publications
Mixtures of clays and sulfates within deposits in western Melas Chasma, Mars
Wray, James J.; Weitz, Catherine M.; Noe Dobrea, Eldar
We have utilized several data sets from multiple spacecraft that have been acquired over a continuous observation campaign across the southwestern Melas Chasma region of Mars. The blocky deposit observed on the chasma floor and on portions of the southern wallrock consists of mixtures of light- and medium-toned materials that exhibit displacement …
THOR: The H i, OH, Recombination line survey of the Milky Way. The pilot study: H i observations of the giant molecular cloud W43
Menten, K. M.; Hill, T.; Henning, T. +30 more
To study the atomic, molecular, and ionized emission of giant molecular clouds (GMCs) in the Milky Way, we initiated a large program with the Karl G. Jansky Very Large Array (VLA): "THOR: The H i, OH, Recombination line survey of the Milky Way". We map the 21 cm H i line, 4 OH lines, up to 19 Hα recombination lines and thecontinuum from 1 to 2 GHz…
What Are Little Worlds Made Of? Stellar Abundances and the Building Blocks of Planets
Gaidos, Eric
If the photospheres of solar-type stars represent the composition of circumstellar disks from which any planets formed, spectroscopic determinations of stellar elemental abundances offer information on the composition of those planets, including smaller, rocky planets. In particular, the C/O ratio is proposed to be a key determinant of the composi…
MRK 1216 and NGC 1277 - an orbit-based dynamical analysis of compact, high-velocity dispersion galaxies
Gebhardt, Karl; van de Ven, Glenn; Husemann, Bernd +5 more
We present a dynamical analysis to infer the structural parameters and properties of the two nearby, compact, high-velocity dispersion galaxies MRK 1216 and NGC 1277. Combining deep Hubble Space Telescope imaging, wide-field integral field unit stellar kinematics, and complementary long-slit spectroscopic data out to three effective radii, we cons…
Excitation of Chirping Whistler Waves in a Laboratory Plasma
Bortnik, J.; Thorne, R. M.; Van Compernolle, B. +3 more
Whistler mode chorus emissions with a characteristic frequency chirp are important magnetospheric waves, responsible for the acceleration of outer radiation belt electrons to relativistic energies and also for the scattering loss of these electrons into the atmosphere. Here, we report on the first laboratory experiment where whistler waves exhibit…
New binaries among UV-selected, hot subdwarf stars and population properties
Buckley, D. A. H.; Vennes, S.; Németh, P. +4 more
We have measured the orbital parameters of seven close binaries, including six new objects, in a radial velocity survey of 38 objects comprising a hot subdwarf star with orbital periods ranging from ∼0.17 to 3 d. One new system, GALEX J2205-3141, shows reflection on an M dwarf companion. Three other objects show significant short-period variations…
Modelling the extreme X-ray spectrum of IRAS 13224-3809
Fabian, A. C.; Gallo, L. C.; Wilkins, D. R. +2 more
The extreme narrow-line Seyfert 1 galaxy IRAS 13224-3809 shows significant variability, frequency-dependent time lags, and strong Fe K line and Fe L features in the long 2011 XMM-Newton observation. In this work, we study the spectral properties of IRAS 13224-3809 in detail, and carry out a series of analyses to probe the nature of the source, foc…
High-resolution ALMA observations of SDP.81. I. The innermost mass profile of the lensing elliptical galaxy probed by 30 milli-arcsecond images
Tamura, Yoichi; Oguri, Masamune; Hayashi, Masao +3 more
We report the detailed modeling of the mass profile of a z = 0.2999 massive elliptical galaxy using 30 milli-arcsecond resolution 1 mm Atacama Large Millimeter/submillimeter Array (ALMA) images of the galaxy-galaxy lensing system SDP.81. The detailed morphology of the lensed multiple images of the z = 3.042 infrared-luminous galaxy, which is found…
Stirring in massive, young debris discs from spatially resolved Herschel images
Krivov, A. V.; Apai, D.; Ábrahám, P. +9 more
A significant fraction of main-sequence stars are encircled by dusty debris discs, where the short-lived dust particles are replenished through collisions between planetesimals. Most destructive collisions occur when the orbits of smaller bodies are dynamically stirred up, either by the gravitational effect of locally formed Pluto-sized planetesim…
Lower hybrid drift instability at a dipolarization front
André, M.; Vaivads, A.; Khotyaintsev, Yu. V. +1 more
We present observations of a reconnection jet front detected by the Cluster satellites in the magnetotail of Earth, which are commonly referred to as dipolarization fronts. We investigate in detail electric field structures observed at the front which have frequency in the lower hybrid range and amplitudes reaching 40 mV/m. We determine the freque…