Search Publications
Advanced Camera for Surveys Observations of Young Star Clusters in the Interacting Galaxy UGC 10214
Ford, H. C.; Infante, L.; Feldman, P. D. +31 more
We present the first Advanced Camera for Surveys (ACS) observations of young star clusters in the colliding/merging galaxy UGC 10214. The observations were made as part of the Early Release Observation (ERO) program for the newly installed ACS during service mission SM3B for the Hubble Space Telescope (HST). Many young star clusters can be identif…
Highly Ionized Gas in the Galactic Halo: A FUSE Survey of O VI Absorption toward 22 Halo Stars
Savage, B. D.; Sembach, K. R.; Howk, J. C. +1 more
Far Ultraviolet Spectroscopic Explorer (FUSE) spectra of 22 Galactic halo stars are studied to determine the amount of O VI in the Galactic halo between ~0.3 and ~10 kpc from the Galactic midplane. Strong O VI λ1031.93 absorption was detected toward 21 stars, and a reliable 3 σ upper limit was obtained toward HD 97991. The weaker member of the O V…
Kink and Longitudinal Oscillations in the Magnetic Network on the Sun: Nonlinear Effects and Mode Transformation
van Ballegooijen, A. A.; Hasan, S. S.; Kalkofen, W. +1 more
We examine the propagation of kink and longitudinal waves in the solar magnetic network. Previously, we investigated the excitation of network oscillations in vertical magnetic flux tubes through buffeting by granules and found that footpoint motions of the tubes can generate sufficient wave energy for chromospheric heating. We assumed that the ki…
The First Detailed Look at a Brown Dwarf Disk
Apai, D.; Pascucci, I.; Henning, Th. +1 more
The combination of mid-infrared and recent submillimeter/millimeter measurements allows us to set up the first comprehensive spectral energy distribution (SED) of the circumstellar material around a young brown dwarf. Simple arguments suggest that the dust is distributed in the form of a disk. We compare basic models to explore the disk parameters…
High-Resolution STIS/Hubble Space Telescope and HIRES/Keck Spectra of Three Weak Mg II Absorbers toward PG 1634+706
Charlton, Jane C.; Churchill, Christopher W.; Rigby, Jane R. +3 more
High-resolution optical (HIRES/Keck) and UV (STIS/Hubble Space Telescope) spectra, covering a large range of chemical transitions, are analyzed for three single-cloud weak Mg II absorption systems along the line of sight toward the quasar PG 1634+706. Weak Mg II absorption lines in quasar spectra trace metal-enriched environments that are rarely c…
The Lack of Observational Evidence for the Quantum Structure of Spacetime at Planck Scales
Turatto, Massimo; Ragazzoni, Roberto; Gaessler, Wolfgang
It has been noted (Lieu & Hillmann) that the cumulative effect of Planck-scale phenomenology, or the structure of spacetime at extremely small scales, can be lead to the loss of the phase of radiation emitted at large distances from the observer. We elaborate on such an approach and demonstrate that such an effect would lead to an apparent blu…
Perpendicular Transport of Solar Energetic Particles in Heliospheric Magnetic Fields
McKibben, R. B.; Zhang, Ming; Jokipii, J. R.
This paper presents direct observational evidence for large perpendicular diffusive flows of solar energetic particles in heliospheric magnetic fields. Using anisotropy measurements of 40-92 MeV protons obtained by the High-Energy Telescope of the COSPIN consortium on Ulysses at high heliographic latitudes, we find that during several gradual sola…
Hot Gas in the Circumstellar Bubble S308
Guerrero, Martín A.; Chu, You-Hua; Gruendl, Robert A. +2 more
S308 is a circumstellar bubble blown by the WN4 star HD 50896. It is one of the only two single-star bubbles that show detectable diffuse X-ray emission. We have obtained XMM-Newton EPIC observations of the northwest quadrant of S308. The diffuse X-ray emission shows a limb-brightened morphology, with a clear gap extending from the outer edge of t…
Evidence for an Intermediate-Age, Metal-rich Population of Globular Clusters in NGC 4365
Forbes, Duncan A.; Brodie, Jean P.; Beasley, Michael A. +4 more
We present spectroscopy for globular clusters (GCs) in the elliptical galaxy NGC 4365, obtained with the Low-Resolution Imaging Spectrograph on the Keck I telescope. Previous studies have shown that the optical color distribution of GCs in NGC 4365 lacks the bimodal structure that is common in globular cluster systems, showing only a single broad …
Chandra Observation of the Edge-on Galaxy NGC 3556 (M108): Violent Galactic Disk-Halo Interaction Revealed
Wang, Q. Daniel; Irwin, Judith A.; Chaves, Tara
We present a 60 ks Chandra ACIS-S observation of the isolated edge-on spiral galaxy NGC 3556, together with a multiwavelength analysis of various discrete X-ray sources and diffuse X-ray features. Among 33 discrete X-ray sources detected within the IB=25 mag arcsec-2 isophote ellipse of the galaxy, we identify a candidate for…