Search Publications
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…
Estimating Stellar Rotation from Starspot Detection during Planetary Transits
Silva-Valio, Adriana
A new method for determining the stellar rotation period is proposed here, based on the detection of starspots during transits of an extrasolar planet orbiting its host star. As the planet eclipses the star, it may pass in front of a starspot which will then make itself known through small flux variations in the transit light curve. If we are luck…
Morphologies and Color Gradients of Luminous Evolved Galaxies at z ~ 1.5
McGrath, Elizabeth J.; Stockton, Alan; Canalizo, Gabriela +2 more
We have examined in detail the morphologies of seven z ~ 1.5 passively evolving luminous red galaxies using high-resolution HST NICMOS and ACS imaging data. Almost all of these galaxies appear to be relaxed systems, with smooth morphologies at both rest-frame UV and visible wavelengths. Previous results from spectral synthesis modeling favor a sin…
Wavelet Analysis of AGN X-Ray Time Series: A QPO in 3C 273?
Bregman, J.; Espaillat, C.; Hughes, P. +1 more
Quasi-periodic signals have yielded important constraints on the masses of black holes in galactic X-ray binaries, and here we extend this to active galactic nuclei (AGNs). We employ a wavelet technique to analyze 19 observations of 10 AGNs obtained with the XMM-Newton EPIC pn camera. We report the detection of a candidate 3.3 ks quasi period in 3…
Coronal Mass Ejection-Associated Coronal Dimmings
Biesecker, D. A.; Reinard, A. A.
We report on a statistical analysis of 96 CME-associated EUV coronal dimmings between 1998 and 2000. We investigate the size and location of the events and characterize how these events evolve with time. The durations typically range from 3 to 12 hr. The dimmings appear most frequently within the belt of active regions (20°-50° latitude). Dimming …