Search Publications
The INTEGRAL/IBIS scientific data analysis
Foschini, L.; David, P.; Bird, A. J. +6 more
The gamma-ray astronomical observatory INTEGRAL, succesfully launched on 17th October 2002, carries two large gamma-ray telescopes. One of them is the coded-mask imaging gamma-ray telescope onboard the INTEGRAL satellite (IBIS) which provides high-resolution (~12') sky images of 29degx29deg in the energy range from 15 keV to …
X-Ray Fluctuation Power Spectral Densities of Seyfert 1 Galaxies
McHardy, I.; Nandra, K.; Vaughan, S. +11 more
By combining complementary monitoring observations spanning long, medium, and short timescales, we have constructed power spectral densities (PSDs) of six Seyfert 1 galaxies. These PSDs span >~4 orders of magnitude in temporal frequency, sampling variations on timescales ranging from tens of minutes to over a year. In at least four cases, the P…
A Planetary Companion to γ Cephei A
Cochran, William D.; Endl, Michael; Hatzes, Artie P. +5 more
We report on the detection of a planetary companion in orbit around the primary star of the binary system γ Cephei. High-precision radial velocity measurements using four independent data sets spanning the time interval 1981-2002 reveal long-lived residual radial velocity variations superposed on the binary orbit that are coherent in phase and amp…
The Relationship Between X-Ray Radiance and Magnetic Flux
Johns-Krull, Christopher M.; Pevtsov, Alexei A.; Longcope, Dana W. +4 more
We use soft X-ray and magnetic field observations of the Sun (quiet Sun, X-ray bright points, active regions, and integrated solar disk) and active stars (dwarf and pre-main-sequence) to study the relationship between total unsigned magnetic flux, Φ, and X-ray spectral radiance, LX. We find that Φ and LX exhibit a very nearly…
The Rest-Frame Optical Luminosity Density, Color, and Stellar Mass Density of the Universe from z = 0 to z = 3
van Dokkum, Pieter G.; Franx, Marijn; Labbé, Ivo +11 more
We present the evolution of the rest-frame optical luminosity density jrestλ, the integrated rest-frame optical color, and the stellar mass density, ρ*, for a sample of Ks band-selected galaxies in the Hubble Deep Field-South (HDF-S). We derived jrestλ in the rest-frame U, B, and V …
Reconstruction of solar irradiance variations in cycle 23: Is solar surface magnetism the cause?
Solanki, S. K.; Krivova, N. A.; Unruh, Y. C. +1 more
A model of solar irradiance variations is presented which is based on the assumption that solar surface magnetism is responsible for all total irradiance changes on time scales of days to years. A time series of daily magnetograms and empirical models of the thermal structure of magnetic features (sunspots, faculae) are combined to reconstruct tot…
Measuring Distances and Probing the Unresolved Stellar Populations of Galaxies Using Infrared Surface Brightness Fluctuations
Ajhar, Edward A.; Rieke, Marcia J.; Tonry, John L. +5 more
To empirically calibrate the IR surface brightness fluctuation (SBF) distance scale and probe the properties of unresolved stellar populations, we measured fluctuations in 65 galaxies using NICMOS on the Hubble Space Telescope. The early-type galaxies in this sample include elliptical and S0 galaxies and spiral bulges in a variety of environments.…
A class of compact dwarf galaxies from disruptive processes in galaxy clusters
Ferguson, H. C.; Hilker, M.; Drinkwater, M. J. +5 more
Dwarf galaxies have attracted increased attention in recent years, because of their susceptibility to galaxy transformation processes within rich galaxy clusters. Direct evidence for these processes, however, has been difficult to obtain, with a small number of diffuse light trails and intra-cluster stars being the only signs of galaxy disruption.…
Titan's atmosphere from ISO mid-infrared spectroscopy
Lellouch, E.; Feuchtgruber, H.; Coustenis, Athena +5 more
We have analyzed Titan observations performed by the Infrared Space Observatory (ISO) in the range 7-30 µm. The spectra obtained by three of the instruments on board the mission (the short wavelength spectrometer, the photometer, and the camera) were combined to provide new and more precise thermal and compositional knowledge of Titan's stra…
Ultradeep Near-Infrared ISAAC Observations of the Hubble Deep Field South: Observations, Reduction, Multicolor Catalog, and Photometric Redshifts
van Dokkum, Pieter G.; Franx, Marijn; Labbé, Ivo +10 more
We present deep near-infrared (NIR) Js-, H-, and Ks-band ISAAC imaging of the Wide Field Planetary Camera 2 (WFPC2) field of the Hubble Deep Field South (HDF-S). The 2.5‧×2.5‧ high Galactic latitude field was observed with the Very Large Telescope under the best seeing conditions, with integration times amounting to 33.6 hr i…