Search Publications
A ~ 40 Year Variability Cycle in the Luminous Blue Variable/Wolf-Rayet Binary System HD 5980?
Hillier, D. John; Morrell, Nidia; Gamen, Roberto +3 more
The massive Wolf-Rayet stellar system HD 5980 in the Small Magellanic Cloud entered a sudden and brief ~ 1-3 mag eruptive state in the mid-1990s. The cause of the instability is not yet understood, but mechanisms similar to those in luminous blue variables are suspected. Using a previously unreported set of spectroscopic data obtained in 1955-1967…
Radius-expansion Burst Spectra from 4U 1728-34: An Ultracompact Binary?
Marshall, Herman; Galloway, Duncan K.; Yao, Yangsen +2 more
Recent theoretical and observational studies have shown that ashes from thermonuclear burning may be ejected during radius-expansion bursts, giving rise to photoionization edges in the X-ray spectra. We report a search for such features in Chandra spectra observed from the low-mass X-ray binary 4U 1728-34. We analyzed the spectra from four radius-…
Seismic Constraints on Interior Solar Convection
DeRosa, Marc L.; Duvall, Thomas L., Jr.; Hanasoge, Shravan M.
We constrain the velocity spectral distribution of global-scale solar convective cells at depth using techniques of local helioseismology. We calibrate the sensitivity of helioseismic waves to large-scale convective cells in the interior by analyzing simulations of waves propagating through a velocity snapshot of global solar convection via method…
The analytic properties of the flapping current sheets in the earth magnetotail
Petrukovich, A. A.; Liu, Z. X.; Rong, Z. J. +2 more
The current sheet in Earth's magnetotail often flaps, and the flapping waves could be induced propagating towards the dawn and dusk flanks, which could make the current sheet dynamic. To explore the dynamic characteristics of current sheet associated with the flapping motion holistically and provide reasonable physical interpretations, detailed di…
Observations of X-ray and EUV fluxes during X-class solar flares and response of upper ionosphere
Mahajan, K. K.; Lodhi, Neelesh K.; Upadhayaya, Arun K.
Most studies dealing with solar flare effects in the upper ionosphere, where ionization is caused by EUV photons, have been based upon X-ray fluxes measured by the SOLRAD and GOES series of satellites. To check the validity of such studies, we compare simultaneous observations of GOES X-ray fluxes and SOHO EUV fluxes for 10 X-class solar flares wh…
Star Formation Histories in a Cluster Environment at z ~ 0.84
Ford, H. C.; Demarco, R.; Lidman, C. +8 more
We present a spectrophotometric analysis of galaxies belonging to the dynamically young, massive cluster RX J0152.7-1357 at z ~ 0.84, aimed at understanding the effects of the cluster environment on the star formation history (SFH) of cluster galaxies and the assembly of the red sequence (RS). We use VLT/FORS spectroscopy, ACS/WFC optical, and NTT…
Spatial identification of the overionized plasma in W49B
Ballet, J.; Miceli, M.; Bocchino, F. +2 more
Context. Recent Suzaku X-ray observations of the ejecta-dominated supernova remnant W49B have shown that there is a clear indication in the global spectrum for overionized plasma, whose physical origin is still under debate.
Aims: In order to ascertain the physical origin of this rapidly cooling plasma, we focus on its spatial localization wi…
The Chandra View of Nearby X-Shaped Radio Galaxies
Reynolds, Christopher S.; Cheung, Chi C.; Miller, M. Coleman +1 more
We present new and archival Chandra X-ray Observatory observations of X-shaped radio galaxies (XRGs) within z ~ 0.1 alongside a comparison sample of normal double-lobed FR I and II radio galaxies. By fitting elliptical distributions to the observed diffuse hot X-ray emitting atmospheres (either the interstellar or intragroup medium), we find that …
The effect of flares on total solar irradiance
Schmutz, Werner; de Wit, Thierry Dudok; Mekaoui, Sabri +3 more
Flares are powerful bursts of energy released by relatively poorly understood processes that take place in the atmospheres of stars. However, although solar flares, from our own Sun, are the most energetic events in the solar system, in comparison to the total output of the Sun they are barely noticeable. Consequently, the total amount of radiant …
Distribution of Satellite Galaxies in High-redshift Groups
Hwang, Ho Seong; Park, Changbom; Chen, Xuelei +1 more
We use galaxy groups at redshifts between 0.4 and 1.0 selected from the Great Observatories Origins Deep Survey to study the color-morphological properties of satellite galaxies and investigate possible alignment between the distribution of the satellites and the orientation of their central galaxy. We confirm the bimodal color and morphological-t…