Search Publications
Hubble Space Telescope Snapshot Survey of Post-AGB Objects
Szczerba, R.; Meixner, M.; Ueta, T. +3 more
The results of a Hubble Space Telescope (HST) snapshot survey of post-AGB objects are shown. The aim of the survey is to complement existing HST images of protoplanetary nebulae and to connect various types of nebulosities with the physical and chemical properties of their central stars. Nebulosities are detected in 15 of 33 sources. Images and ph…
Thermal X-Rays from Millisecond Pulsars: Constraining the Fundamental Properties of Neutron Stars
Bogdanov, Slavko; Grindlay, Jonathan E.; Rybicki, George B.
We model the X-ray properties of millisecond pulsars (MSPs) by considering hot-spot emission from a weakly magnetized neutron star (NS) covered by a hydrogen atmosphere. We investigate the limitations of using the thermal X-ray pulse profiles of MSPs to constrain the mass-to-radius (M/R) ratio of the NS. The accuracy is strongly dependent on the v…
Magnetogram Measures of Total Nonpotentiality for Prediction of Solar Coronal Mass Ejections from Active Regions of Any Degree of Magnetic Complexity
Falconer, D. A.; Moore, R. L.; Gary, G. A.
For investigating the magnetic causes of coronal mass ejections (CMEs) and for forecasting the CME productivity of active regions, in previous work we have gauged the total nonpotentiality of a whole active region by either of two measures, LSSM and LSGM, two measures of the magnetic field along the main neutral line in a vec…
Solving the Discrepancy between the Seismic and Photospheric Solar Radius
Schmutz, W.; Haberreiter, M.; Kosovichev, A. G.
Two methods are used to observationally determine the solar radius: One is the observation of the intensity profile at the limb; the other one uses f-mode frequencies to derive a "seismic" solar radius which is then corrected to optical depth unity. The two methods are inconsistent and lead to a difference in the solar radius of ~0.3 Mm. Because o…
The Extended Star Formation History of the Andromeda Spheroid at 35 kpc on the Minor Axis
Ferguson, Henry C.; Brown, Thomas M.; Gilbert, Karoline M. +14 more
Using the HST ACS, we have obtained deep optical images reaching well below the oldest main-sequence turnoff in fields on the southeast minor axis of the Andromeda galaxy, 35 kpc from the nucleus. These data probe the star formation history in the extended halo of Andromeda—that region beyond 30 kpc that appears both chemically and morphologically…
The HD 163296 Circumstellar Disk in Scattered Light: Evidence of Time-Variable Self-Shadowing
Illingworth, Garth D.; Ardila, David R.; Krist, John E. +5 more
We present the first multicolor view of the scattered light disk of the Herbig Ae star HD 163296, based on coronagraphic observations from the Hubble Space Telescope Advanced Camera for Surveys (HST ACS). Radial profile fits of the surface brightness along the disk's semimajor axis indicate that the disk is not continuously flared, and extends to …
Modeling Ultraviolet Wind Line Variability in Massive Hot Stars
Blomme, R.; Lobel, A.
We model the detailed time-evolution of discrete absorption components (DACs) observed in P Cygni profiles of the Si IV λ1400 resonance doublet lines of the fast-rotating supergiant HD 64760 (B0.5 Ib). We adopt the common assumption that the DACs are caused by corotating interaction regions (CIRs) in the stellar wind. We perform 3D radiative trans…
Relationship between EIT Posteruption Arcades, Coronal Mass Ejections, the Coronal Neutral Line, and Magnetic Clouds
Yurchyshyn, Vasyl
There is observational evidence that the elongation of an Earth-directed coronal mass ejection (CME) may indicate the orientation of the underlying erupting flux rope. In this study, we compare orientations of CMEs, magnetic clouds (MCs), EIT (EUV Imaging Telescope) posteruption arcades, and the coronal neutral line (CNL). We report on good correl…
Exploring the Evolutionary Paths of the Most Massive Galaxies since z ~ 2
Barro, Guillermo; Pérez-González, Pablo G.; Conselice, Christopher J. +3 more
We use Spitzer MIPS data from the FIDEL Legacy Project in the extended Groth strip to analyze the stellar mass assembly of massive (M > 1011 M⊙) galaxies at z < 2 as a function of structural parameters. We find 24 µm emission for more than 85% of the massive galaxies morphologically classified as disks, and for mo…
2 Years of INTEGRAL Monitoring of GRS 1915+105. II. X-Ray Spectro-Temporal Analysis
Belloni, T.; Rodriguez, J.; Cadolle Bel, M. +14 more
This is the second paper presenting the results of 2 yr of monitoring of GRS 1915+105 with INTEGRAL, RXTE, and the Ryle Telescope. We present the X-ray spectral and temporal analysis of four observations showing strong radio to X-ray correlations. During one observation GRS 1915+105 was in a steady state, while during the three others it showed cy…