Search Publications
An L Band Spectrum of the Coldest Brown Dwarf
Fortney, Jonathan J.; Freedman, Richard S.; Faherty, Jacqueline K. +10 more
The coldest brown dwarf, WISE 0855, is the closest known planetary-mass, free-floating object and has a temperature nearly as cold as the solar system gas giants. Like Jupiter, it is predicted to have an atmosphere rich in methane, water, and ammonia, with clouds of volatile ices. WISE 0855 is faint at near-infrared wavelengths and emits almost al…
Super-strong Magnetic Field in Sunspots
Okamoto, Takenori J.; Sakurai, Takashi
Sunspots are the most notable structure on the solar surface with strong magnetic fields. The field is generally strongest in a dark area (umbra), but sometimes stronger fields are found in non-dark regions, such as a penumbra and a light bridge. The formation mechanism of such strong fields outside umbrae is still puzzling. Here we report clear e…
Ages of the Bulge Globular Clusters NGC 6522 and NGC 6626 (M28) from HST Proper-motion-cleaned Color-Magnitude Diagrams
Vieira, R. G.; Bica, E.; Nardiello, D. +5 more
Bulge globular clusters (GCs) with metallicities [Fe/H] ≲ -1.0 and blue horizontal branches are candidates to harbor the oldest populations in the Galaxy. Based on the analysis of HST proper-motion-cleaned color-magnitude diagrams in filters F435W and F625W, we determine physical parameters for the old bulge GCs NGC 6522 and NGC 6626 (M28), both w…
The Anatomy of the Column Density Probability Distribution Function (N-PDF)
Goodman, Alyssa; Burkhart, Blakesley; Chen, Hope How-Huan +1 more
The column density probability distribution function (N-PDF) of Giant Molecular Clouds (GMCs) has been used as a diagnostic of star formation. Simulations and analytic predictions have suggested that the N-PDF is composed of a low-density lognormal component and a high-density power-law component tracing turbulence and gravitational collapse, resp…
A Large Moving Group within the Lower Centaurus Crux Association
Henning, Thomas; Goldman, Bertrand; Röser, Siegfried +2 more
Scorpius-Centaurus is the nearest OB association, and its hundreds of members are divided into subgroups, including the Lower Centaurus Crux (LCC). Here we study the dynamics of the LCC area. We report the revelation of a large moving group containing more than 1800 intermediate- and low-mass young stellar objects and brown dwarfs that escaped ide…
Magnetic Flux Cancelation as the Buildup and Trigger Mechanism for CME-producing Eruptions in Two Small Active Regions
Panesar, Navdeep K.; Moore, Ronald L.; Sterling, Alphonse C.
We follow two small, magnetically isolated coronal mass ejection (CME)-producing solar active regions (ARs) from the time of their emergence until several days later, when their core regions erupt to produce the CMEs. In both cases, magnetograms show: (a) following an initial period where the poles of the emerging regions separate from each other,…
A Very High Energy γ-Ray Survey toward the Cygnus Region of the Galaxy
Abeysekara, A. U.; Archer, A.; Aune, T. +67 more
We present results from deep observations toward the Cygnus region using 300 hr of very high energy (VHE) γ-ray data taken with the VERITAS Cerenkov telescope array and over 7 yr of high-energy γ-ray data taken with the Fermi satellite at an energy above 1 GeV. As the brightest region of diffuse γ-ray emission in the northern sky, the Cygnus regio…
Impact of Type II Spicules in the Corona: Simulations and Synthetic Observables
Martínez-Sykora, Juan; De Pontieu, Bart; Carlsson, Mats +2 more
The role of type II spicules in the corona has been a much debated topic in recent years. This paper aims to shed light on the impact of type II spicules in the corona using novel 2.5D radiative MHD simulations, including ion-neutral interaction effects with the Bifrost code. We find that the formation of simulated type II spicules, driven by the …
Pre-eruptive Magnetic Reconnection within a Multi-flux-rope System in the Solar Corona
Wang, Haimin; Wang, Yuming; Shen, Chenglong +2 more
The solar corona is frequently disrupted by coronal mass ejections (CMEs), whose core structure is believed to be a flux rope made of helical magnetic field. This has become a “standard” picture; though, it remains elusive how the flux rope forms and evolves toward eruption. While one-third of the ejecta passing through spacecraft demonstrate a fl…
A Subarcsecond ALMA Molecular Line Imaging Survey of the Circumbinary, Protoplanetary Disk Orbiting V4046 Sgr
Kastner, Joel H.; Forveille, T.; Hily-Blant, P. +6 more
We present a suite of Atacama Large Millimeter Array (ALMA) interferometric molecular line and continuum images that elucidate, on linear size scales of ∼30-40 au, the chemical structure of the nearby, evolved, protoplanetary disk orbiting the close binary system V4046 Sgr. The observations were undertaken in the 1.1-1.4 mm wavelength range (ALMA …