A5059423955- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- History and Developments in Astronomy
- Galaxies: Formation, Evolution, Phenomena
- Astronomical and nuclear sciences
- Adaptive optics and wavefront sensing
- Astrophysical Phenomena and Observations
- Atmospheric Ozone and Climate
- Solar and Space Plasma Dynamics
- Pulsars and Gravitational Waves Research
- Geological and Geophysical Studies
- Methane Hydrates and Related Phenomena
- Space Science and Extraterrestrial Life
- Nuclear physics research studies
- Geochemistry and Geologic Mapping
- Chemical Thermodynamics and Molecular Structure
- Historical Astronomy and Related Studies
- Inertial Sensor and Navigation
- X-ray Diffraction in Crystallography
- Inorganic Fluorides and Related Compounds
- Geophysics and Gravity Measurements
University of California, Santa Cruz
2015-2024
University of Colorado Colorado Springs
2012-2014
Lickenbrock
1996-2010
Space Telescope Science Institute
1987-2008
Harvard University
1985-2008
University of Toronto
2000
Nia Association
1994
The University of Texas at Austin
1993-1994
University of Maryland, College Park
1994
Herzberg Institute of Astrophysics
1988-1994
AAT/IPCS spectra have been obtained from six H II regions at differing radial distances the centre of Sed galaxy NGC 300 (Sculptor Group) and three in giant barred spiral 1365 (Fornax which has an active nucleus. The analysed to determine abundances elements represented by observed emission lines for a combination electron temperatures based on various weak temperature-sensitive interpolation between photoionization models, using sum [O II] III] intensities relative Hβ select plausible model...
The globular cluster M15 is unique in its display of star-to-star variations the neutron-capture elements. Comprehensive abundance surveys have been previously conducted for handfuls red giant branch (RGB) and horizontal (RHB) stars. No attempt has made to perform a single, self-consistent analysis these stars, which exhibit wide range atmospheric parameters. In current effort, new comparative derivation presented three RGB six RHB members cluster. employs an updated version line transfer...
We present results from a survey of the central 700 arcmin2 region ρ Ophiuchi molecular cloud at 850 μm using Submillimeter Common-User Bolometer Array (SCUBA) on James Clerk Maxwell Telescope. Using clump-finding procedure developed by Williams et al., we identify 55 independent objects and compute size, flux, degree concentration. Comparison with isothermal, pressure-confined, self-gravitating Bonnor-Ebert spheres implies that clumps have internal temperatures 10-30 K surface pressures P/k...
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We derive the star formation histories of eight dwarf spheroidal (dSph) Milky Way satellite galaxies from their alpha element abundance patterns. Nearly 3000 stars our previously published catalog (Paper II) comprise data set. The average [alpha/Fe] ratios for all dSphs follow roughly same path with increasing [Fe/H]. do not observe predicted knees in vs. [Fe/H] diagram, corresponding to metallicity at which Type Ia supernovae begin explode. Instead, we find that supernova ejecta contribute...
We present a chemical composition analysis of 36 giant stars in the mildly metal-poor (⟨[Fe/H]⟩ = -1.21) globular cluster M5 (NGC 5904). The makes use high-resolution data acquired for 25 at Keck I telescope, as well reanalysis spectra 13 an earlier study Lick Observatory. employed two techniques: (1) adopting standard spectroscopic constraints, including setting surface gravity from ionization equilibrium iron, and (2) subsequent to investigating alternative approaches, consistent with...
Observations of 11 giants in the globular cluster Ml 3 fainter than M<SUB>v</SUB>=-1.7 have been obtained with High Resolution Echelle Spectrograph on Keck I Telescope. When combined similar data for brighter 3.0-m Shane Telescope's Hamilton spectrograph, these allow examination detailed abundances oxygen, sodium, magnesium, and aluminium over a wide range luminosity red giant branch. We find that oxygen depletions, correlated sodium enhancements, can be found luminosities down to nearly...
AAT/IPCS spectra have been obtained from seven outlying H II regions in the Local Group Im galaxy NGC 6822 and nucleus six at various radial distances isolated SBd 1313. Abundances are deduced emission-line intensities by a combination of direct electron-temperature determinations estimates based on excitation class inferred log (O + O III)/Hβ. Both galaxies quite uniform abundances all over, agreement with previous findings for arm barred spiral Magellanic Irregulars. The abundance ratio...
The Seyfert 1 galaxy Zw 229-015 is among the brightest active galaxies being monitored by Kepler mission. In order to determine black hole mass in from H-beta reverberation mapping, we have carried out nightly observations with Kast Spectrograph at Lick 3m telescope during dark runs June through December 2010, obtaining 54 spectroscopic total. We also obtained V-band imaging Katzman Automatic Imaging Telescope Observatory and 0.9m Brigham Young University West Mountain over same period....
view Abstract Citations (100) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS CNO Abundances of Bright Giants in the Globular Clusters M3 and M13 Smith, Graeme H. ; Shetrone, Matthew D. Bell, Roger A. Churchill, Christopher W. Briley, Michael M. Spectra ﾎｻ4300 CH ﾎｻ3883 CN bands have been obtained for a sample red giants Mi 3 which [0/Fe] abundances published literature. Measurements [C/Fe] [N/Fe] made by comparing observed spectra with...
This paper reviews many of the properties relating to chemical inhomogeneity globular clusters. Three main types anomalous stars are found within clusters: CH stars, weak-G-band and giants with enhanced CN bands. Of these, CN-enhanced most common, while rarest. A number characteristics these including relationship between carbon nitrogen abundances; correlations enhancements atomic line strengths; stellar luminosity dependence C N abundances, discussed. The cluster Omega Cen not only...
The double main sequence identified in the globular cluster Omega Centauri has been interpreted using isochrones to indicate a large variation abundance of helium. If true, helium enhancement carries strong implications for chemical and stellar evolutionary history this cluster. However, only indirect measures currently support conjecture. We report discovery line strength near-infrared He I 10830 A transition twelve similar red giants observed with PHOENIX on Gemini-S. Abundances these...
Abstract Reports of visual sightings bands on Neptune made by E. S. Holden and J. M. Schaeberle at Lick Observatory are described. Holden’s logbooks record that in 1888 September October were discerned the Neptunian disk noted seven nights. A summary logbook entries given this note, since they do not appear to have been previously published.
We report on a deep spectroscopic survey for star-to-star CN variations along the main sequence (MS) of globular cluster 47 Tuc with ESO's VLT. find significant bimodal distribution in S(3839) index main-sequence stars mass range ~0.85 to 0.65 M_sun, or from turn-off down ~2.5 mag below turn-off. An anti-correlation and CH is evident MS. The result discussed context ability faint MS alter their surface composition through internal evolutionary effects. argue against stellar evolution as only...
High-resolution, high signal-to-noise ratio, blue-violet spectra of three red giant branch tip stars in M15 have been obtained with the Keck I High-Resolution Echelle Spectrograph. These analyzed to determine abundances several neutron-capture elements, including radioactive chronometer element thorium. There are two principal results this study. First, heavier (Z>/=56) elements for each is well matched by a scaled solar system r-process abundance distribution. Second, weighted mean-observed...
High-resolution spectra have been obtained of six red giants in the globular cluster NGC 7006 using HIRES instrument on Keck I Telescope. The [iron-peak/Fe] and [α-nuclei/Fe] elemental ratios are similar to those found other halo clusters. Significant, but modest, star-to-star abundance differences for elements O, Na, Al, with [O/Fe] ratio being anticorrelated both [Na/Fe] [Al/Fe]. These anticorrelations indicate that O → N processed material, within which Ne has also converted Na Mg Al by...
Spectroscopy of the infrared He I (10830 Å) line with NIRSPEC on Keck and CSHELL at IRTF, ultraviolet C III (977 O VI (1032 emission FUSE, reveals that classical T Tauri star TW Hydrae exhibits P Cygni profiles, asymmetries, absorption indicative a continuous, fast (~400 km s-1), hot (~300,000 K) accelerating outflow mass-loss rate ~10-11 to 10-12 M☉ yr-1 or larger. Spectra Tau N appear consistent such wind. The source seems restricted stars themselves. Although mass accretion is an order...
We report the results of an analysis CN and CH band strengths among a large sample 47 Tucanae main-sequence turn-off stars presented earlier by Harbeck et al. The resulting C N abundances derived from synthetic spectra demonstrate: 1) A strongly anti-correlated relationship between [C/Fe] [N/Fe] with CN-strong exhibiting depleted carbon enhanced nitrogen. 2) both elements agree remarkably well those found evolved red giants cluster implying little change in surface at least Mv ~ +6.5 to tip...
By establishing that the length scale governing detachment of a shock wave from wedge is distance leading edge to sonic line, and by considering view observers with different scales, it predicted increases gradually angle for relaxing flow more rapidly in perfect gas. Both these features are confirmed experiments free-piston tunnel. The influence other scales discussed. phenomenon related relaxation effect which subsonic layer grows translational-rotational as inclination increased beyond...
It is now widely accepted that globular cluster red giant branch (RGB) stars owe their strange abundance patterns to a combination of pollution from progenitor and in situ extra mixing. In this hybrid theory first generation imprints into the gas which second forms. The suggests mixing operating both populations we use variation [C/Fe] with luminosity examine how efficient is. We investigate observed RGBs M3, M13, M92, M15, NGC 5466 as means test thermohaline parameter pair M3 M13 are...
view Abstract Citations (141) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Mass Functions for Globular Cluster Main Sequences Based on CCD Photometry and Stellar Models McClure, Robert D. ; Vandenberg, Don A. Smith, Graeme H. Fahlman, Gregory G. Richer, Harvey B. Hesser, James E. Harris, William Stetson, Peter Bell, R. Main-sequence luminosity functions constructed from observations of globular clusters reveal a strong trend in slope with...
The optical afterglow of long-duration GRB 071003 is among the brightest yet to be detected from any GRB, with R ≈ 12 mag in KAIT observations starting 42 s after trigger, including filtered detections during prompt emission. However, our high-S/N spectrum displays only extremely weak absorption lines at what we argue host redshift z = 1.60435, contrast three other, much stronger Mg II systems observed lower redshifts. Together Keck adaptive optics observations, which fail reveal a galaxy...
We review the observational evidence for extra mixing in stars on red giant branch (RGB) and discuss why thermohaline is a strong candidate mechanism. recall simple phenomenological description of aspects general. use observations M3 to constrain form diffusion coefficient any associated free parameters. This done by matching [C/Fe] [N/Fe] along RGB M3. After taking into account presumed initial primordial bimodality CN-weak CN-strong stars, our models can explain full spread [C/Fe]....