Search Publications
Variability in Proto-planetary Nebulae. I. Light Curve Studies of 12 Carbon-rich Objects
Lu, Wenxian; Hrivnak, Bruce J.; Maupin, Richard E. +1 more
We have carried out long-term (14 years) V and R photometric monitoring of 12 carbon-rich proto-planetary nebulae. The light and color curves display variability in all of them. The light curves are complex and suggest multiple periods, changing periods, and/or changing amplitudes, which are attributed to pulsation. A dominant period has been dete…
Latitudinal variations in Saturn's ionosphere: Cassini measurements and model comparisons
Galand, Marina; Moore, Luke; Mendillo, Michael +2 more
We present a study of latitudinal variations in Saturn's ionosphere using Cassini Radio Science Subsystem (RSS) measurements and Saturn-Thermosphere-Ionosphere-Model (STIM) simulations. On the basis of Cassini RSS observations, the peak electron density (NMAX) and the total electron content (TEC) both exhibit a clear increase with latit…
New Abundance Determinations of Cadmium, Lutetium, and Osmium in the r-process Enriched Star BD +17 3248
Roederer, Ian U.; Sneden, Christopher; Cowan, John J. +1 more
We report the detection of Cd I (Z = 48), Lu II (Z = 71), and Os II (Z = 76) in the metal-poor star BD +17 3248. These abundances are derived from an ultraviolet spectrum obtained with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. This is the first detection of these neutron-capture species in a metal-poor star enriched b…
Discovery of Millihertz X-Ray Oscillations in a Transient Ultraluminous X-Ray Source in M82
Feng, Hua; Kaaret, Philip; Rao, Fengyun
We report on the discovery of X-ray quasi-periodic oscillations (QPOs) at frequencies of 3-4 mHz from a transient ultraluminous X-ray source X42.3+59 in M82. The QPOs are strong and broad and appear with weak or absent red noise, and are detected only in Chandra observations when the source is brighter than 1040 erg s-1. The …
Direct Imaging of Bridged Twin Protoplanetary Disks in a Young Multiple Star
Pyo, Tae-Soo; Tamura, Motohide; Hayashi, Masahiko +10 more
Studies of the structure and evolution of protoplanetary disks are important for understanding star and planet formation. Here we present the direct image of an interacting binary protoplanetary system. Both circumprimary and circumsecondary disks are resolved in the near-infrared. There is a bridge of infrared emission connecting the two disks an…
Evolution of the spectrum of solar wind velocity fluctuations from 0.3 to 5 AU
Roberts, D. Aaron
Recent work has shown that at 1 AU from the Sun, the power spectrum of the solar wind magnetic field has the -5/3 spectral slope expected for Kolmogorov turbulence but that the velocity has closer to a -3/2 spectrum. This paper traces the changes in solar wind velocity spectra from 0.3 to 5 AU using data from the Helios and Ulysses spacecraft to s…
Oxygen ion escape at Mars in a hybrid model: High energy and low energy ions
Jarvinen, Riku; Kallio, Esa; Janhunen, Pekka +2 more
We have studied the escape and energization of several O+ populations and an O2+ population at Mars by using a hybrid model. The quasi-neutral hybrid model, HYB-Mars model, included five oxygen ion populations making it possible to distinguish photoions from oxygen ions originating from charge exchange processes and from the ionosphere.…
The Herschel Virgo Cluster Survey. III. A constraint on dust grain lifetime in early-type galaxies
Bomans, D. J.; Bianchi, S.; Fritz, J. +28 more
Passive early-type galaxies (ETGs) provide an ideal laboratory for studying the interplay between dust formation around evolved stars and its subsequent destruction in a hot gas. Using Spitzer-IRS and Herschel data we compare the dust production rate in the envelopes of evolved AGB stars with a constraint on the total dust mass. Early-type galaxie…
The Vega debris disc: A view from Herschel
Heras, A. M.; Walker, H. J.; Ivison, R. J. +37 more
We present five band imaging of the Vega debris disc obtained using the Herschel Space Observatory. These data span a wavelength range of 70-500 µm with full-width half-maximum angular resolutions of 5.6-36.9”. The disc is well resolved in all bands, with the ring structure visible at 70 and 160 µm. Radial profiles of the disc surface …
High-resolution X-ray spectroscopy and imaging of Mrk 573
Guainazzi, Matteo; Bianchi, Stefano; Piconcelli, Enrico +4 more
We present a detailed analysis of the XMM-Newton Reflection Grating Spectrometer (RGS) high-resolution X-ray spectra of the Seyfert 2 galaxy, Mrk 573. This analysis is complemented by the study of the Chandra image and its comparison to optical (Hubble Space Telescope) and radio (Very Large Array) data. The soft X-ray emission is mainly due to gas…