Search Publications
Hubble Space Telescope STIS Observations of the Accreting White Dwarfs in BW Sculptoris, BC Ursae Majoris, and SW Ursae Majoris
Szkody, Paula; Howell, Steve B.; Sion, Edward M. +1 more
We have observed the short-period dwarf novae BW Scl, BC UMa, and SW UMa using the Hubble Space Telescope Space Telescope Imaging Spectrograph (STIS). In all three systems, the white dwarf is the dominant source of far-ultraviolet flux, even though in BC UMa and SW UMa an additional continuum component contributes ~10% and ~20% of the 1400 Å flux,…
Changes in the Subsurface Stratification of the Sun with the 11-Year Activity Cycle
Kosovichev, A. G.; Lefebvre, S.
We report on changes in the Sun's subsurface stratification inferred from helioseismology data. Using data from the Solar and Heliospheric Observatory (SOHO) Michelson Doppler Imager (MDI) for the last 9 years and, more precisely, the temporal variation of f-mode frequencies, we have computed the variation in the radius of subsurface layers of the…
New Geoeffective Parameters of Very Fast Halo Coronal Mass Ejections
Cho, K. -S.; Kim, Y. -H.; Moon, Y. -J. +4 more
We have examined the physical characteristics of very fast coronal mass ejections (CMEs) and their geoeffective parameters. For this we consider SOHO LASCO CMEs whose speeds are larger than 1300 km s-1. By examining all SOHO EIT and SOHO LASCO images of the CMEs, we selected 38 front-side very fast CMEs and then examined their associati…
The Optical Counterpart of M101 ULX-1
Chu, You-Hua; Kuntz, K. D.; Gruendl, Robert A. +4 more
We have identified the optical counterpart of the ultraluminous X-ray source M101 ULX-1 (CXOKM101 J140332.37+542102), by comparing Hubble Space Telescope Advanced Camera for Surveys images with Chandra ACIS-S images. The optical counterpart has V=23.75 and colors consistent with those for a mid-B supergiant. Archival Wide Field Planetary Camera 2 …
Detection of a Hot Binary Companion of η Carinae
Hillier, D. John; Gull, Theodore R.; Sonneborn, George +2 more
We report the detection of a hot companion of η Carinae using high-resolution spectra (905-1180 Å) obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. Observations were obtained at two epochs of the 2024 day orbit: 2003 June, during ingress to the 2003.5 X-ray eclipse, and 2004 April, several months after egress. These data …
X-Ray Cluster Associated with the z = 1.063 CSS Quasar 3C 186: The Jet is Not Frustrated
Elvis, Martin; Cheung, C. C.; Bechtold, Jill +5 more
We report the Chandra discovery of an X-ray cluster at redshift z=1.063 associated with the compact steep spectrum (CSS) radio-loud quasar 3C 186 (Q0740+380). Diffuse X-ray emission is detected out to ~120 kpc from the quasar and contains 741+/-40 net counts. The X-ray spectrum of the extended emission shows strong Fe-line emission (EW=412 eV) at …
The Lensed Arc Production Efficiency of Galaxy Clusters: A Comparison of Matched Observed and Simulated Samples
Maoz, Dan; Rix, Hans-Walter; Bartelmann, Matthias +3 more
We compare the statistical properties of giant gravitationally lensed arcs produced in matched simulated and observed cluster samples. The observed sample consists of 10 X-ray-selected clusters at redshifts zc~0.2 imaged with HST by Smith et al. The simulated data set is produced by lensing the Hubble Deep Field, which serves as a backg…
Boron Depletion in F and G Dwarf Stars and the Beryllium-Boron Correlation
Deliyannis, Constantine P.; Steinhauer, Aaron; Boesgaard, Ann Merchant
Boron provides a special probe below the stellar surface since it survives to greater depths than do Li and Be. To search for B depletions we have observed B in 13 F and G dwarfs with large Be depletions; for comparison we have also obtained spectra of five stars that are undepleted in Li and Be. We have used HST with STIS to obtain spectra of the…
Active Galactic Nucleus Feedback and Gas Mixing in the Core of NGC 4636
O'Sullivan, E.; Vrtilek, J. M.; Kempner, J. C.
Chandra observations of NGC 4636 show disturbances in the galaxy X-ray halo, including armlike high surface brightness features (tentatively identified as active galactic nucleus-driven shocks) and a possible cavity on the west side of the galaxy core. We present Chandra and XMM-Newton spectral maps of NGC 4636 that confirm the presence of the cav…
The Role of Magnetic Helicity in Coronal Mass Ejections
MacNeice, P. J.; Antiochos, S. K.; Phillips, A. D.
We investigate the factors responsible for initiating coronal mass ejections (CMEs), specifically, the role of magnetic helicity. Using numerical simulations of the breakout model for CMEs, we show that eruption occurs at a fixed magnitude of free energy in the corona, independent of the value of helicity. Almost identical eruptions are obtained f…