Search Publications
Detection of Supersonic Downflows and Associated Heating Events in the Transition Region above Sunspots
Golub, L.; Tian, H.; De Pontieu, B. +18 more
Interface Region Imaging Spectrograph data allow us to study the solar transition region (TR) with an unprecedented spatial resolution of 0.''33. On 2013 August 30, we observed bursts of high Doppler shifts suggesting strong supersonic downflows of up to 200 km s-1 and weaker, slightly slower upflows in the spectral lines Mg II h and k,…
Physical Interpretation of the Angle-dependent Magnetic Helicity Spectrum in the Solar Wind: The Nature of Turbulent Fluctuations near the Proton Gyroradius Scale
Klein, Kristopher G.; TenBarge, Jason M.; Howes, Gregory G. +1 more
Motivated by recent observations of distinct parallel and perpendicular signatures in magnetic helicity measurements segregated by wave period and angle between the local magnetic field and the solar wind velocity, this paper undertakes a comparison of three intervals of Ulysses data with synthetic time series generated from a physically motivated…
Ground Level Enhancement in the 2014 January 6 Solar Energetic Particle Event
Gopalswamy, N.; Davila, J. M.; Yashiro, S. +4 more
We present a study of the 2014 January 6 solar energetic particle event which produced a small ground level enhancement (GLE), making it the second GLE of this unusual solar cycle 24. This event was primarily observed by the South Pole neutron monitors (increase of ~2.5%) while a few other neutron monitors recorded smaller increases. The associate…
Possible Detection of the Stellar Donor or Remnant for the Type Iax Supernova 2008ha
Foley, Ryan J.; Rest, Armin; Fong, Wen-fai +5 more
Type Iax supernovae (SNe Iax) are thermonuclear explosions that are related to SNe Ia, but are physically distinct. The most important differences are that SNe Iax have significantly lower luminosity (1%-50% that of typical SNe Ia), lower ejecta mass (~0.1-0.5 M ⊙), and may leave a bound remnant. The most extreme SN Iax is SN 2008ha, wh…
The Megasecond Chandra X-Ray Visionary Project Observation of NGC 3115: Witnessing the Flow of Hot Gas within the Bondi Radius
Bregman, Joel N.; Wong, Ka-Wah; Irwin, Jimmy A. +3 more
Observational confirmation of hot accretion model predictions has been hindered by the challenge to resolve spatially the Bondi radii of black holes with X-ray telescopes. Here, we use the Megasecond Chandra X-ray Visionary Project observation of the NGC 3115 supermassive black hole to place the first direct observational constraints on the spatia…
Hubble Space Telescope and Ground-based Observations of the Type Iax Supernovae SN 2005hk and SN 2008A
Filippenko, Alexei V.; Schneider, Donald P.; Foley, Ryan J. +24 more
We present Hubble Space Telescope (HST) and ground-based optical and near-infrared observations of SN 2005hk and SN 2008A, typical members of the Type Iax class of supernovae (SNe). Here we focus on late-time observations, where these objects deviate most dramatically from all other SN types. Instead of the dominant nebular emission lines that are…
Extended [C II] Emission in Local Luminous Infrared Galaxies
Elbaz, D.; Veilleux, S.; Sanders, D. B. +20 more
We present Herschel/PACS observations of extended [C II] 157.7 µm line emission detected on ~1-10 kpc scales in 60 local luminous infrared galaxies (LIRGs) from the Great Observatories All-sky LIRG Survey. We find that most of the extra-nuclear emission show [C II]/FIR ratios >=4 × 10-3, larger than the mean ratio seen in the n…
Predicted Space Motions for Hypervelocity and Runaway Stars: Proper Motions and Radial Velocities for the Gaia Era
Geller, Margaret J.; Brown, Warren R.; Kenyon, Scott J. +1 more
We predict the distinctive three-dimensional space motions of hypervelocity stars (HVSs) and runaway stars moving in a realistic Galactic potential. For nearby stars with distances less than 10 kpc, unbound stars are rare; proper motions alone rarely isolate bound HVSs and runaways from indigenous halo stars. At large distances of 20-100 kpc, unbo…
Investigating Nearby Star-forming Galaxies in the Ultraviolet with HST/COS Spectroscopy. I. Spectral Analysis and Interstellar Abundance Determinations
Aloisi, A.; James, B. L.; Wolfe, M. A. +2 more
This is the first in a series of three papers describing a project with the Cosmic Origins Spectrograph on the Hubble Space Telescope to measure abundances of the neutral interstellar medium (ISM) in a sample of nine nearby star-forming galaxies. The goal is to assess the (in)homogeneities of the multiphase ISM in galaxies where the bulk of metals…
Effects of Meridional Flow Variations on Solar Cycles 23 and 24
Hathaway, David H.; Upton, Lisa
The faster meridional flow that preceded the solar cycle 23/24 minimum is thought to have led to weaker polar field strengths, producing the extended solar minimum and the unusually weak cycle 24. To determine the impact of meridional flow variations on the sunspot cycle, we have simulated the Sun's surface magnetic field evolution with our newly …