Radial Velocities and Pulsation Ephemerides of 11 Field RR Lyrae Stars

We present new radial velocities, improved pulsation periods and reference epoch s of 11 field RR Lyrae ab-type variables: AS Vir, BS Aps, CD Vel, DT Hya, RV Oct, TY Gru, UV Oct, V1645 Sgr, WY Ant, XZ Aps and Z Mic. This study is based on high resolution spectra obtained with the echelle spectro graph of the 2.5-m du Pont telescope at Las Campanas Observatory. We obtained ~200 spectra per star (i.e, total of ~2300 spectra) distributed more or less uniformly throughout their pulsation cycles. Radial velocity curves and photometric lightcurves phased to our new ephemerides are presented for all program stars. In a subsequent paper, we will use these spectra to derive stellar atmospheric parameters and chemical compositions throughout the pulsational cycles, based purely on spectroscopic constraints.Comment: 28 pages, 14 figures, 5 tables. Accepted for publication in ApJ

The Chemical Compositions Of RR Lyrae Type C Variable Stars

We present a detailed chemical abundance study of eight RR Lyrae variable stars of subclass c (RRc). The target RRc stars chosen for study exhibit "Blazhko-effect" period and amplitude modulations to their pulsational cycles. Data for this study were gathered with the echelle spectrograph of the 100 inch du Pont telescope at Las Campanas Observatory. Spectra were obtained throughout each star's pulsation cycle. Atmospheric parameters-effective temperature, surface gravity, microturbulent velocity, and metallicity-were derived at multiple phase points. We found metallicities and element abundance ratios to be constant within observational uncertainties over the pulsational cycles of all stars. Moreover, the alpha-element and Fe-group abundance ratios with respect to iron are consistent with other horizontal-branch members (RRab, blue and red non-variables). Finally, we have used the [Fe/H] values of these eight RRc stars to anchor the metallicity estimates of a large-sample RRc snapshot spectroscopic study being conducted with the same telescope and instrument combination employed here.NSF AST-0908978, AST-1211585Baker Centennial Research EndowmentJohn W. Cox Endowment for the Advanced Studies in AstronomyMcDonald Observator

Bulletin No. 273 - Drainage and Irrigation, Soil, Economic, and Social Conditions, Delta Area, Utah, Division 3: Economic Conditions

Project 90-A Study of Factors Influencing the Financial Condition of Certain Utah Irrigation and Drainage Projects-was undertaken in 1928 as an intensified study of local areas. This study was divided among four departments, with a project leader for each particular phase of the study. These four project leaders, guided by the Station Director, have constituted a committee in immediate charge of this project. Subprojects and their respective leaders have been: A-Engineering and Engineering Economic Aspects, O. W. Israelsen; B-Soil Productivity Aspects, D. S. Jennings; C-Contributing Sociological Aspects, J. A. Geddes; and D-Economic Aspects, W. Preston Thomas

Neutron-Capture Nucleosynthesis in the First Stars

Recent studies suggest that metal-poor stars enhanced in carbon but containing low levels of neutron-capture elements may have been among the first to incorporate the nucleosynthesis products of the first generation of stars. We have observed 16 stars with enhanced carbon or nitrogen using the MIKE Spectrograph on the Magellan Telescopes at Las Campanas Observatory and the Tull Spectrograph on the Smith Telescope at McDonald Observatory. We present radial velocities, stellar parameters, and detailed abundance patterns for these stars. Strontium, yttrium, zirconium, barium, europium, ytterbium, and other heavy elements are detected. In four stars, these heavy elements appear to have originated in some form of r-process nucleosynthesis. In one star, a partial s-process origin is possible. The origin of the heavy elements in the rest of the sample cannot be determined unambiguously. The presence of elements heavier than the iron group offers further evidence that zero-metallicity rapidly-rotating massive stars and pair instability supernovae did not contribute substantial amounts of neutron-capture elements to the regions where the stars in our sample formed. If the carbon- or nitrogen-enhanced metal-poor stars with low levels of neutron-capture elements were enriched by products of zero-metallicity supernovae only, then the presence of these heavy elements indicates that at least one form of neutron-capture reaction operated in some of the first stars.Comment: Accepted for publication in the Astrophysical Journal (36 pages, 26 figures

Bulletin No. 325 - An Economic Study of Sheep Production in Southwestern Utah

Range sheep production has been one of the major agricultural enterprises in Utah, particularly in the southwestern part of the state, since these areas were first settled. Stock sheep numbers in Utah were about 2,100,000 by 1890, which is approximately the present number in the state. Since 1890 the numbers have fluctuated between 2,000,000 and 2,775,000. This important industry has, from the time of its introduction, been closely associated with the use of public range lands. The unrestricted grazing of public range lands resulted in damage to a considerable area and was one of the important factors that led to the establishment of federal agencies to administer these properties

Near-UV Observations of CS29497-030: New Constraints on Neutron-Capture Nucleosynthesis Processes

Employing spectra obtained with the new Keck I HIRES near-UV sensitive detector, we have performed a comprehensive chemical composition analysis of the binary blue metal-poor star CS29497-030. Abundances for 29 elements and upper limits for an additional seven have been derived, concentrating on elements largely produced via neutron-capture nucleosynthesis. Included in our analysis are the two elements that define the termination point of the slow neutron-capture process, lead and bismuth. We determine an extremely high value of [Pb/Fe] = +3.65 +/- 0.07 (sigma = 0.13) from three features, supporting the single-feature result obtained in previous studies. We also detect Bi for the first time in a metal-poor star. Our derived Bi/Pb ratio is in accord with those predicted from the most recent FRANEC calculations of the slow neutron-capture process in low-mass AGB stars. We find that the neutron-capture elemental abundances of CS29497-030 are best explained by an AGB model that also includes very significant amounts of pre-enrichment of rapid neutron-capture process material in the protostellar cloud out of which the CS29497-030 binary system formed. Thus, CS29497-030 is both an ``r+s'' and ``extrinsic AGB'' star. Furthermore, we find that the mass of the AGB model can be further constrained by the abundance of the light odd-element [Na/Fe] which is sensitive to the neutron excess.Comment: 7 pages = 4 + 2 colour encapsulated postscript figures + 1 table; to appear in ApJ Letters; additional jpeg figure available at ftp://www.astro.caltech.edu/users/iii/cs2949703

Metal-poor stars towards the Galactic bulge:a population potpourri

We present a comprehensive chemical abundance analysis of five red giants and two horizontal branch (HB) stars towards the southern edge of the Galactic bulge, at (l, b) ~ (0°,−11°). Based on high-resolution spectroscopy obtained with the Magellan/MIKE spectrograph, we derived up to 23 chemical element abundances and identify a mixed bag of stars, representing various populations in the central regions of the Galaxy. Although cosmological simulations predict that the inner Galaxy was host to the first stars in the Universe, we see no chemical evidence of the ensuing massive supernova explosions: all of our targets exhibit halo-like, solar [Sc/Fe] ratios, which is in contrast to the low values predicted from Population III nucleosynthesis. One of the targets is a CEMP-s star at [Fe/H] = −2.52 dex, and another target is a moderately metal-poor ([Fe/H] = −1.53 dex) CH star with strong enrichment in s-process elements (e.g., [Ba/Fe] = 1.35). These individuals provide the first contenders of these classes of stars towards the bulge. Four of the carbon-normal stars exhibit abundance patterns reminiscent of halo star across a metallicity range spanning −2.0 to −2.6 dex, i.e., enhanced α-elements and solar Fe-peak and neutron-capture elements, and the remaining one is a regular metal-rich bulge giant. The position, distance, and radial velocity of one of the metal-poor HB stars coincides with simulations of the old trailing arm of the disrupted Sagittarius dwarf galaxy. While their highly uncertain proper motions prohibit a clear kinematic separation, the stars’ chemical abundances and distances suggest that these metal-poor candidates, albeit located towards the bulge, are not of the bulge, but rather inner halo stars on orbits that make them pass through the central regions. Thus, we caution similar claims of detections of metal-poor stars as true habitants of the bulge