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Abundance studies of sdB stars using UV echelle HST/STIS spectroscopy
Heber, U.; O'Toole, S. J.
Aims.We test the hypothesis that the pulsations in sdB stars are correlated with the surface abundances of iron-group elements. Any correlation might explain why, when given two spectroscopically similar stars, one will pulsate while the other will not.
Methods: .We have obtained high-resolution ultraviolet spectra two pulsating and three non-…
Latitudinal variations of HCN, HC 3N, and C 2N 2 in Titan's stratosphere derived from Cassini CIRS data
Fletcher, L.; Irwin, P. G. J.; Teanby, N. A. +9 more
Mid- and far-infrared spectra from the Composite InfraRed Spectrometer (CIRS) have been used to determine volume mixing ratios of nitriles in Titan's atmosphere. HCN, HC 3N, C 2H 2, and temperature were derived from 2.5 cm -1 spectral resolution mid-IR mapping sequences taken during three flybys, which p…
The Eclipsing Binary V1061 Cygni: Confronting Stellar Evolution Models for Active and Inactive Solar-Type Stars
Torres, Guillermo; Lacy, Claud H.; Marschall, Laurence A. +2 more
We present spectroscopic and photometric observations of the eclipsing system V1061 Cyg (P=2.35 days). A third star is visible in the spectrum, and the system is a hierarchical triple. We combine the radial velocities for the three stars, times of eclipse, and intermediate astrometric data from the Hipparcos mission (abscissa residuals) to establi…
Hierarchical Star Formation in the Spiral Galaxy NGC 628
Chandar, Rupali; Elmegreen, Bruce G.; Whitmore, Brad +2 more
The distributions of size and luminosity for star-forming regions in the nearby spiral galaxy NGC 628 are studied over a wide range of scales using progressively blurred versions of an image from the Hubble Space Telescope Advanced Camera for Surveys. Four optical filters are considered for the central region, including Hα. Two filters are used fo…
Alfvén vortex filaments observed in magnetosheath downstream of a quasi-perpendicular bow shock
André, M.; Maksimovic, M.; Alexandrova, O. +3 more
Magnetic field fluctuations in the frequency range [0.02-12.5] Hz are studied with the four Cluster satellites in the Earth magnetosheath downstream of a quasi-perpendicular bow shock. The turbulent spectrum presents a spectral break accompanied by a broad maximum usually interpreted as due to Alfvén ion cyclotron waves. In this paper we establish…
A 70 Kiloparsec X-Ray Tail in the Cluster A3627
Forman, W.; Sun, M.; Nulsen, P. E. J. +3 more
We present the discovery of a 70 kpc X-ray tail behind the small late-type galaxy ESO 137-001, in the nearby, hot (T=6.5 keV) merging cluster A3627, from both Chandra and XMM-Newton observations. The tail has a length-to-width ratio of ~10. It is luminous (L0.5-2keV~1041 ergs s-1), with a temperature of ~0.7 keV an…
Evolution of magnetic fields in stars across the upper main sequence: I. Catalogue of magnetic field measurements with FORS 1 at the VLT
Hubrig, S.; North, P.; Schöller, M. +1 more
To properly understand the physics of Ap and Bp stars it is particularly important to identify the origin of their magnetic fields. For that, an accurate knowledge of the evolutionary state of stars that have a measured magnetic field is an important diagnostic. Previous results based on a small and possibly biased sample suggest that the distribu…
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 …