Search Publications
UBVR and Hubble Space Telescope Mid-Ultraviolet and Near-Infrared Surface Photometry and Radial Color Gradients of Late-Type, Irregular, and Peculiar Galaxies
Windhorst, Rogier A.; Jansen, Rolf A.; Hibbard, John E. +2 more
We introduce a data set of 142 mostly late-type spiral, irregular, and peculiar (interacting or merging) nearby galaxies observed in UBVR at the Vatican Advanced Technology Telescope (VATT), and we present an analysis of their radial color gradients. We confirm that nearby elliptical and early- to mid-type spiral galaxies show either no or only sm…
X-Ray Observations of the Boundary Layer in Dwarf Novae at Low Accretion Rates
Pandel, Dirk; Mason, Keith O.; Córdova, France A. +1 more
We present a spectral analysis of XMM-Newton data of 10 dwarf novae, 9 of which were observed during a quiescent state. The X-ray spectra indicate the presence of a hot, optically thin plasma with a temperature distribution consistent with a simple, isobaric cooling flow. The likely origin of the X-ray emission is cooling plasma in the boundary la…
A Large X-Ray Outburst in Mira A
Wood, Brian E.; Schlegel, Eric; Raymond, John C. +2 more
We report the Chandra ACIS-S detection of a bright soft X-ray transient in the Mira AB interacting symbiotic-like binary. We have resolved the system for the first time in X-rays. Using Chandra and Hubble Space Telescope images, we determine that the unprecedented outburst is likely associated with the cool asymptotic giant branch (AGB) star, Mira…
Nonlinear Alfvén waves, discontinuities, proton perpendicular acceleration, and magnetic holes/decreases in interplanetary space and the magnetosphere: intermediate shocks?
Lakhina, G. S.; Tsurutani, B. T.; Pickett, J. S. +3 more
Alfvén waves, discontinuities, proton perpendicular acceleration and magnetic decreases (MDs) in interplanetary space are shown to be interrelated. Discontinuities are the phase-steepened edges of Alfvén waves. Magnetic decreases are caused by a diamagnetic effect from perpendicularly accelerated (to the magnetic field) protons. The ion accelerati…
A photoionization-modelling study of 30 Doradus: the case for small-scale chemical inhomogeneity
Tsamis, Yiannis G.; Péquignot, Daniel
Photoionization models of the giant HII region (GHIIR) 30 Doradus are built and confronted to available ultraviolet (UV), optical, infrared (IR) [Infrared Space Observatory (ISO)] and radio spectra, under blackbody or CoStar spectral energy distributions for the primary source and various density distributions for the nebular gas. Chemically homog…
A possible association of the new VHE γ-ray source HESS J1825-137 with the pulsar wind nebula G18.0-0.7
Raux, J.; Ripken, J.; Funk, S. +96 more
We report on a possible association of the recently discovered very high-energy γ-ray source HESS J1825-137 with the pulsar wind nebula (commonly referred to as G 18.0 0.7) of the 2.1× 104 year old Vela-like pulsar PSR B1823 13. HESS J1825-137 was detected with a significance of 8.1σ in the Galactic Plane survey conducted with the HESS …
XMM-Newton observations of the Lockman Hole IV: spectra of the brightest AGN
Streblyanska, A.; Barcons, X.; Fabian, A. C. +5 more
This paper presents the results of a detailed X-ray spectral analysis of a sample of 123 X-ray sources detected with XMM-Newton in the Lockman Hole field. This is the deepest observation carried out with XMM-Newton with more that 600 ks of good EPIC-pn data. We have spectra with good signal to noise (>500 source counts) for all objects down to …
Dynamical Masses for Low-Mass Pre-Main-Sequence Stars: A Preliminary Physical Orbit for HD 98800 B
Torres, Guillermo; Latham, David W.; Wasserman, Lawrence H. +7 more
We report on Keck Interferometer observations of the double-lined binary (B) component of the quadruple pre-main-sequence (PMS) system HD 98800. With these interferometric observations, combined with astrometric measurements made by the Hubble Space Telescope (HST) Fine Guidance Sensors (FGS) and published radial velocity observations, we have est…
Chemical abundances in 43 metal-poor stars
Magain, P.; Gustafsson, B.; Asplund, M. +3 more
We have derived abundances of O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Fe, Ni, and Ba for 43 metal-poor field stars in the solar neighbourhood, most of them subgiants or turn-off-point stars with iron abundances [Fe/H] ranging from -0.4 to -3.0. About half of this sample has not been spectroscopically analysed in detail before. Effective temperatures…
Open flux estimates in Saturn's magnetosphere during the January 2004 Cassini-HST campaign, and implications for reconnection rates
Milan, S. E.; Badman, S. V.; Clarke, J. T. +4 more
During 8-30 January 2004, a sequence of 68 UV images of Saturn's southern aurora was obtained by the Hubble Space Telescope (HST), coordinated for the first time with measurements of the upstream interplanetary conditions made by the Cassini spacecraft. Using the poleward edge of the observed aurora as a proxy for the open-closed field line bounda…