Search Publications
X-ray and radio observations of the activation stages of an X-class solar flare
Hudson, H. S.; Karlický, M.; Fárník, F. +1 more
We report interesting developments prior to the impulsive phase of an X-class solar flare that occurred on September 24, 2001. Our multiwavelength study makes use of X-ray data from the Yohkoh satellite, the Ondřejov radio spectral observations in the decimetric band, and the new Hard X-Ray Spectrometer instrument (HXRS) on board the MTI satellite…
A Method for Black Hole Mass Determination in Accretion-powered X-Ray Sources
Titarchuk, Lev; Shrader, Chris R.
We describe a method for the determination of black hole masses based on information inferred from high-energy spectra. It is required that the spectral energy distribution consist of thermal and Comptonized components. One can then, in principle, infer the depth of the gravitational potential well for sources of known distance. The thermal compon…
Three-component Stäckel potentials satisfying recent estimates of Milky Way parameters
Famaey, B.; Dejonghe, H.
We present a set of three-component Stäckel potentials defined by five parameters and designed to model the Milky Way. We review the fundamental constraints that any model of the Milky Way must satisfy, including the most recent ones derived from Hipparcos data, and we study how the parameters of the presented potentials can vary in order to match…
Minor axis kinematics of 19 S0-Sbc bulges
Peletier, R. F.; Falcón-Barroso, J.; Vazdekis, A. +1 more
We present minor axis kinematic profiles for a well-studied sample of 19 early- to intermediate-type disk galaxies. We introduce, for the first time, the use of single-burst stellar population (SSP) models to obtain stellar velocities, velocity dispersions and higher order Gauss-Hermite moments (h3, h4) from galaxy spectra in…
Relative Flux Calibration of Keck HIRES Echelle Spectra
O'Meara, John M.; Tytler, David; Lubin, Dan +2 more
We describe a method to calibrate the relative flux levels in spectra from the High-Resolution Echelle Spectrograph (HIRES) on the Keck I telescope. Standard data reduction techniques that transfer the instrument response between HIRES integrations leave errors in the flux of 5%-10% because the effective response varies during the night. The flux …
Infrared Space Observatory and Ground-Based Infrared Observations of the Classical Nova V723 Cassiopeiae
Hayward, T. L.; Gehrz, R. D.; Eyres, S. P. S. +13 more
We present observations of the classical nova V723 Cassiopeiae (Nova Cas 1995), obtained both with the Infrared Space Observatory (ISO) and from the ground. The infrared spectrum was dominated in the first year by H and He recombination lines, and at later times by coronal lines. The H recombination lines imply a reddening of E(B-V)=0.78, an elect…
Star Formation and Asymmetry in the Spiral Arms of M51: Variable Star Formation Caused by More than One Spiral Density Wave
Gutermuth, Robert; Quillen, A. C.; Henry, Alaina L.
In the inner 3 kpc of M51, we find that logarithmic spirals provide good fits to the peak intensities in molecular gas observed by the Berkeley-Illinois-Maryland Association array in the CO (J=1-0) emission line along the spiral arms. However, we measure significant asymmetries between the location and density of the arms observed on one side of t…
The Phoenix Deep Survey: X-ray properties of faint radio sources
Georgakakis, A.; Sullivan, M.; Georgantopoulos, I. +4 more
In this paper, we use a 50-ks XMM-Newton pointing overlapping with the Phoenix Deep Survey, a homogeneous radio survey reaching µJy sensitivities, to explore the X-ray properties and the evolution of star-forming galaxies. Multiwavelength ultraviolet, optical and near-infrared photometric data are available for this field and are used to est…
Spectroscopy of Solar Prominences Simultaneously From Space and Ground
Dammasch, I. E.; Wiehr, E.; Stellmacher, G.
We present a comprehensive set of spectral data from two quiescent solar prominences observed in parallel from space and ground: with the VTT, simultaneous two-dimensional imaging of Hβ4862 Å and Caii 8542 Å yields a constant ratio, indicating small spatial pressure variations over the prominence. With the Gregory, simultaneous spectra of Caii 854…
GRB 010921: Strong Limits on an Underlying Supernova from the Hubble Space Telescope
Piro, L.; Axelrod, T. S.; Frontera, F. +24 more
GRB 010921 was the first HETE-2 gamma-ray burst (GRB) to be localized via its afterglow emission. The low redshift of the host galaxy, z=0.451, prompted us to undertake intensive multicolor observations with the Hubble Space Telescope with the goal of searching for an underlying supernova (SN) component. We do not detect any coincident SN to a lim…