Search Publications
Impact of Major Coronal Mass Ejections on Geospace during 2005 September 7-13
Wang, Yuming; Shen, Chenglong; Wang, S. +3 more
We have analyzed five major CMEs originating from NOAA active region (AR) 808 during the period of 2005 September 7-13, when the AR 808 rotated from the east limb to near solar meridian. Several factors that affect the probability of the CMEs' encounter with the Earth are demonstrated. The solar and interplanetary observations suggest that the sec…
The Polar Regions of Cassiopeia A: The Aftermath of a Gamma-Ray Burst?
Hwang, Una; Laming, J. Martin; Radics, Balint +2 more
Are the polar regions of Cas A the aftermath of a gamma-ray burst? Probably not, but it is interesting nevertheless to investigate just how close Cas A might have come to generating such an event. Focusing on the northeast jet filaments, we analyze the polar regions of the recently acquired very deep 1 Ms Chandra X-ray observation. We infer that t…
p-Mode Propagation through the Transition Region into the Solar Corona. I. Observations
Marsh, M. S.; Walsh, R. W.
Oscillations have long been observed in the sunspot umbral chromosphere and transition region, connected to global p-mode oscillations. These p-modes are thought to undergo mode conversion to slow magnetoacoustic waves in regions of strong magnetic field. More recently, propagating oscillations have also been observed in solar coronal loops. Using…
The Jet-Disk Connection in AGNs: Chandra and XMM-Newton Observations of Three Powerful Radio-Loud Quasars
Maraschi, L.; Tavecchio, F.; Gliozzi, Mario +2 more
The connection between the accretion process that powers AGNs and the formation of jets is still poorly understood. Here we tackle this issue using new, deep Chandra and XMM-Newton observations of the cores of three powerful radio-loud quasars, 1136-135, 1150+497 (Chandra), and 0723+679 (XMM-Newton), in the redshift range z=0.3-0.8. These sources …
A Method for Deriving Accurate Gas-Phase Abundances for the Multiphase Interstellar Galactic Halo
Sembach, Kenneth R.; Savage, Blair D.; Howk, J. Christopher
We describe a new method for accurately determining total gas-phase abundances for the Galactic halo interstellar medium with minimal ionization uncertainties. For sight lines toward globular clusters containing both ultraviolet-bright stars and radio pulsars, it is possible to measure column densities of H I and several ionization states of selec…
Infrared Observations of the Helix Planetary Nebula
Smith, Howard A.; Marengo, Massimo; Hora, Joseph L. +1 more
We have mapped the Helix (NGC 7293) planetary nebula (PN) with the IRAC instrument on the Spitzer Space Telescope. The Helix is one of the closest bright PNs and therefore provides an opportunity to resolve the small-scale structure in the nebula. The emission from this PN in the 5.8 and 8 µm IRAC bands is dominated by the pure rotational li…
Star Formation History of the Hubble Ultra Deep Field: Comparison with the Hubble Deep Field-North
Dickinson, Mark; Fan, Xiaohui; Thompson, Rodger I. +3 more
We use the NICMOS Treasury and ACS HUDF images to measure the extinction-corrected star formation history for 4681 galaxies in the region common to both images using the star formation rate distribution function and other techniques similar to those employed with the NICMOS and WFPC2 images in the HDFN. Unlike the HDFN, the NICMOS region of the HU…
Multiwavelength Study of Flow Fields in Flaring Super Active Region NOAA 10486
Xu, Yan; Cao, Wenda; Liu, Chang +5 more
We present high-resolution observations of horizontal flow fields measured by local correlation tracking from intensity images in three wavelengths, i.e., G band (GB), white light (WL), and near-infrared (NIR). The observations were obtained on 2003 October 29 within the flaring super active region NOAA 10486, which was the source of several X-cla…
HST NICMOS Imaging of the Planetary-mass Companion to the Young Brown Dwarf 2MASSW J1207334-393254
Zuckerman, B.; Song, Inseok; Schneider, G. +5 more
Multiband (0.9-1.6 µm) images of the TW Hydrae association (TWA) brown dwarf 2MASSW J1207334-393254 (also known as 2M 1207) and its candidate planetary-mass companion (2M 1207b) were obtained on 2004 August 28 and 2005 April 26 with HST NICMOS. The images from these two epochs unequivocally confirm the two objects as a common proper motion p…
From Radio to X-Ray: The Quiescent Atmosphere of the dMe Flare Star EV Lacertae
Hawley, Suzanne L.; Harper, Graham M.; Brown, Alexander +3 more
We report on multiwavelength observations spanning radio to X-ray wavelengths of the M dwarf flare star EV Lacertae and probing the characteristics of the outer atmospheric plasma from the upper chromosphere to the corona. We detect the star at a wavelength of 2 cm (15 GHz) for the first time. UV and FUV line profiles show evidence of nonthermal b…