Search Publications
Constraining Black Hole Spin via X-Ray Spectroscopy
Brenneman, Laura W.; Reynolds, Christopher S.
We present an analysis of the observed broad iron line feature and putative warm absorber in the long 2001 XMM-Newton observation of the Seyfert 1.2 galaxy MCG -06-30-15. The new kerrdisk model we have designed for simulating line emission from accretion disk systems allows black hole spin to be a free parameter in the fit, enabling the user to fo…
Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc-The Southern Sample
Gray, R. O.; Corbally, C. J.; Garrison, R. F. +5 more
We are obtaining spectra, spectral types, and basic physical parameters for the nearly 3600 dwarf and giant stars earlier than M0 in the Hipparcos catalog within 40 pc of the Sun. Here we report on results for 1676 stars in the southern hemisphere observed at Cerro Tololo Inter-American Observatory and Steward Observatory. These results include ne…
The cosmic infrared background resolved by Spitzer. Contributions of mid-infrared galaxies to the far-infrared background
Le Floc'h, E.; Dole, H.; Lagache, G. +7 more
Aims.We quantify the contributions of 24 µm galaxies to the Far-Infrared (FIR) Background at 70 and 160 µm. We provide new estimates of the Cosmic Infrared Background (CIB), and compare it with the Cosmic Optical Background (COB).
Methods: .Using Spitzer data at 24, 70 and 160 µm in three deep fields, we stacked more than 190…
Modeling of Flux Rope Coronal Mass Ejections
Howard, R. A.; Vourlidas, A.; Thernisien, A. F. R.
We present a forward-modeling technique for flux rope-like CMEs using an empirically defined model of a flux rope, the graduated cylindrical shell (GCS). To compare it with white-light coronagraph observations, we assume an electron distribution through the GCS and derive synthetic images in total and polarized brightness for various projections o…
The Sloan Lens ACS Survey. I. A Large Spectroscopically Selected Sample of Massive Early-Type Lens Galaxies
Treu, Tommaso; Koopmans, Léon V. E.; Bolton, Adam S. +2 more
The Sloan Lens ACS (SLACS) Survey is an efficient Hubble Space Telescope (HST) Snapshot imaging survey for new galaxy-scale strong gravitational lenses. The targeted lens candidates are selected spectroscopically from the Sloan Digital Sky Survey (SDSS) database of galaxy spectra for having multiple nebular emission lines at a redshift significant…
Calibration of Synthetic Photometry Using DA White Dwarfs
Holberg, J. B.; Bergeron, Pierre
We have calibrated four major ground-based photometric systems with respect to the Hubble Space Telescope (HST) absolute flux scale, which is defined by Vega and four fundamental DA white dwarfs. These photometric systems include the Johnson-Kron-Cousins UBVRI, the Strömgren uvby filters, the Two Micron All Sky Survey JHKs, and the Sloa…
Enceladus' Water Vapor Plume
West, R.; Pryor, W.; Stewart, A. I. F. +5 more
The Cassini spacecraft flew close to Saturn's small moon Enceladus three times in 2005. Cassini's UltraViolet Imaging Spectrograph observed stellar occultations on two flybys and confirmed the existence, composition, and regionally confined nature of a water vapor plume in the south polar region of Enceladus. This plume provides an adequate amount…
The surprising magnetic topology of τ Sco: fossil remnant or dynamo output?
Bouret, J. -C.; Donati, J. -F.; Howarth, I. D. +9 more
We report the discovery of a medium-strength (~0.5 kG) magnetic field on the young, massive star τ Sco (B0.2V), which becomes the third-hottest magnetic star known. Circularly polarized Zeeman signatures are clearly detected in observations collected mostly with the ESPaDOnS spectropolarimeter, recently installed on the 3.6-m Canada-France-Hawaii …
The X-Ray-to-Optical Properties of Optically Selected Active Galaxies over Wide Luminosity and Redshift Ranges
Lehmer, B. D.; Alexander, D. M.; Brandt, W. N. +5 more
We present partial-correlation analyses that examine the strengths of the relationships between l2500Å, l2keV, αOX, and redshift for optically selected active galactic nuclei (AGNs). We extend the work of Strateva and coworkers, which analyzed optically selected AGNs from the Sloan Digital Sky Survey (SDSS), by including 52 m…
An explanation for the soft X-ray excess in active galactic nuclei
Fabian, A. C.; Ross, R. R.; Gallo, L. +1 more
We present a large sample of type 1 active galactic nuclei (AGN) spectra taken with XMM-Newton, and fit them with both the conventional model (a power law and blackbody) and the relativistically blurred photoionized disc reflection model of Ross & Fabian. We find that the disc reflection model is a better fit. The disc reflection model success…