Search Publications
RR Lyrae Variables in M33. I. Evidence for a Field Halo Population
Sarajedini, Ata; Schommer, Robert; Barker, M. K. +2 more
We present observations of RR Lyrae variables in the Local Group late-type spiral galaxy M33. Using the Advanced Camera for Surveys on the Hubble Space Telescope, we have identified 64 ab-type RR Lyrae stars in M33. We have estimated reddenings for these stars based on their minimum light V-I colors and metallicities based on their periods. From t…
Radiatively Inefficient Accretion Flow in the Nucleus of NGC 1097
Eracleous, Michael; Terashima, Yuichi; Storchi-Bergmann, Thaisa +3 more
We present a model for the accretion flow around the supermassive black hole in the LINER nucleus of NGC 1097 that fits the optical to X-ray spectral energy distribution (SED). The X-ray segment of the SED is based on observations with the Chandra X-Ray Observatory, which are reported here for the first time. The inner part of the flow is modeled …
Spectroscopic Metallicities for Fornax Ultracompact Dwarf Galaxies, Globular Clusters, and Nucleated Dwarf Elliptical Galaxies
Infante, L.; Hilker, M.; Jordán, A. +1 more
Various formation channels for the puzzling ultracompact dwarf galaxies (UCDs) have been proposed in the last few years. To better judge some of the competing scenarios, we present spectroscopic [Fe/H] estimates for a sample of 26 compact objects in the central region of the Fornax Cluster, covering the magnitude range of UCDs and bright globular …
Satellites of the Largest Kuiper Belt Objects
Brown, M. E.; Rabinowitz, D. L.; Trujillo, C. A. +12 more
We have searched the four brightest objects in the Kuiper Belt for the presence of satellites using the newly commissioned Keck Observatory Laser Guide Star Adaptive Optics system. Satellites are seen around three of the four objects: Pluto (whose satellite Charon is well-known and whose recently discovered smaller satellites are too faint to be d…
The interplay between star formation and the nuclear environment of our Galaxy: deep X-ray observations of the Galactic centre Arches and Quintuplet clusters
Wang, Q. Daniel; Dong, Hui; Lang, Cornelia
The Galactic centre (GC) provides a unique laboratory for a detailed examination of the interplay between massive star formation and the nuclear environment of our Galaxy. Here, we present a 100-ks Chandra Advanced CCD Imaging Spectrometer (ACIS) observation of the Arches and Quintuplet star clusters. We also report on a complementary mapping of t…
Newly discovered active binaries in the RasTyc sample of stellar X-ray sources. I. Orbital and physical parameters of six new binaries
Freire Ferrero, R.; Guillout, P.; Frasca, A. +3 more
We present the first results from follow-up optical observations, both photometric and spectroscopic, of stellar X-ray sources, selected from the RasTyc sample, resulting from the cross-correlation of ROSAT All-Sky Survey (RASS) and TYCHO catalogues. In particular, we report on the discovery of six late-type binaries, for which we obtained good ra…
Jupiter's atmospheric temperatures: From Voyager IRIS to Cassini CIRS
Achterberg, Richard K.; Flasar, F. Michael; Simon-Miller, Amy A. +4 more
Retrievals performed on Cassini Composite Infrared Spectrometer data obtained during the distant Jupiter flyby in 2000/2001 have been used to generate global temperature maps of the planet in the troposphere and stratosphere, but to higher latitudes than were shown previously by Flasar et al. [Flasar, F.M., 39 colleagues, 2004a. Nature 427, 132-13…
The X-Ray Synchrotron Emission of RCW 86 and the Implications for Its Age
Vink, Jacco; Bamba, Aya; Yamazaki, Ryo +3 more
We report X-ray imaging spectroscopy observations of the northeastern shell of the supernova remnant RCW 86 using Chandra and XMM-Newton. Along this part of the shell, the dominant X-ray radiation mechanism changes from thermal to synchrotron emission. We argue that both the presence of X-ray synchrotron radiation and the width of the synchrotron-…
The ACS Virgo Cluster Survey. XIV. Analysis of Color-Magnitude Relations in Globular Cluster Systems
Jordán, Andrés; Mieske, Steffen; Tonry, John L. +8 more
We examine the correlation between globular cluster (GC) color and magnitude using HST ACS imaging for a sample of 79 early-type galaxies (-21.7<MB<-15.2 mag) with accurate SBF distances from the ACS Virgo Cluster Survey. Using the KMM mixture modeling algorithm, we find a highly significant correlation, γz≡d(g-z)/dz=-0…
A regular period for Saturn's magnetic field that may track its internal rotation
Russell, C. T.; Dougherty, M. K.; Smith, E. J. +1 more
The rotation rate of a planet is one of its fundamental properties. Saturn's rotation, however, is difficult to determine because there is no solid surface from which to time it, and the alternative `clock'-the magnetic field-is nearly symmetrically aligned with the rotation axis. Radio emissions, thought to provide a proxy measure of the rotation…