Oxygen isotopic ratios in first dredge-up red giant stars and nuclear reaction rate uncertainties revisited

We describe a general yet simple method to analyse the propagation of nuclear reaction rate uncertainties in a stellar nucleosynthesis and mixing context. The method combines post-processing nucleosynthesis and mixing calculations with a Monte Carlo scheme. With this approach we reanalyze the dependence of theoretical oxygen isotopic ratio predictions in first dredge-up red giant branch stars in a systematic way. Such predictions are important to the interpretation of pre-solar Al_2 O_3 grains from meteorites. The reaction rates with uncertainties were taken from the NACRE compilation (Angulo etal., 1999). We include seven reaction rates in our systematic analysis of stellar models with initial masses from 1 to 3 M_sun. We find that the uncertainty of reaction rate for reaction O18(p,alpha)N15 typically causes an error in the theoretical O16/O18 ratio of about +20/-5 per cent. The error of the O16/O17 prediction is +-10 to 40 per cent depending on the stellar mass, and is persistently dominated by the comparatively small uncertainty of the O16(p,gamma)F17 reaction. With the new estimates on reaction rate uncertainties by the NACRE compilation, the p-capture reactions O17(p,alpha)N14 and O17(p,gamma)F18 have virtually no impact on theoretical predictions for stellar mass <= 1.5 M_sun. However, this is not the case for masses > 1.5 M_sun, where core mixing and subsequent envelope mixing interact. In these cases where core mixing complicates post-dredge-up surface abundances, uncertainty in other reactions have a secondary but noticeable effect on surface abundances.Comment: 11 pages (with figures and tables at the end), 8 figures (11 .eps files), submitted to MNRA

A different glance to the site testing above Dome C

Due to the recent interest shown by astronomers towards the Antarctic Plateau as a potential site for large astronomical facilities, we assisted in the last years to a strengthening of site testing activities in this region, particularly at Dome C. Most of the results collected so far concern meteorologic parameters and optical turbulence measurements based on different principles using different instruments. At present we have several elements indicating that, above the first 20-30 meters, the quality of the optical turbulence above Dome C is better than above whatever other site in the world. The challenging question, crucial to know which kind of facilities to build on, is to establish how much better the Dome C is than a mid-latitude site. In this contribution we will provide some complementary elements and strategies of analysis aiming to answer to this question. We will try to concentrate the attention on critical points, i.e. open questions that still require explanation/attention.Comment: 3 figures, EAS Publications Series, Volume 25, 2007, pp.5

Study of the winter 2005 Antarctica polar vortex

During winter and springtime, the flow above Antarctica at high altitude (upper troposphere and stratosphere) is dominated by the presence of a vortex centered above the continent. It lasts typically from August to November. This vortex is characterized by a strong cyclonic jet centered above the polar high. In a recent study of our group (Hagelin et al., 2008) of four different sites in the Antarctic internal plateau (South Pole, Dome C, Dome A and Dome F), it was made the hypothesis that the wind speed strength in the upper atmosphere should be related to the distance of the site to the center of the Antarctic polar vortex. This high altitude wind is very important from an astronomical point of view since it might trigger the onset of the optical turbulence and strongly affect other optical turbulence parameters. What we are interested in here is to localize the position of the minimum value of the wind speed at high altitude in order to confirm the hypothesis of Hagelin et al. (2008).Comment: 3rd ARENA conference, 11-15 May 2009 EAS Publication Serie

Mt. Graham: Optical turbulence vertical distribution at standard and high vertical resolution

A characterization of the optical turbulence vertical distribution and all the main integrated astroclimatic parameters derived from the CN2 and the wind speed profiles above Mt. Graham is presented. The statistic includes measurements related to 43 nights done with a Generalized Scidar (GS) used in standard configuration with a vertical resolution of ~1 km on the whole 20-22 km and with the new technique (HVR-GS) in the first kilometer. The latter achieves a resolution of ~ 20-30 m in this region of the atmosphere. Measurements done in different periods of the year permit us to provide a seasonal variation analysis of the CN2. A discretized distribution of the typical CN2 profiles useful for the Ground Layer Adaptive Optics (GLAO) simulations is provided and a specific analysis for the LBT Laser Guide Star system ARGOS case is done including the calculation of the 'gray zones' for J, H and K bands. Mt. Graham confirms to be an excellent site with median values of the seeing without dome contribution equal to 0.72", the isoplanatic angle equal to 2.5" and the wavefront coherence time equal to 4.8 msec. We provide a cumulative distribution of the percentage of turbulence developed below H* where H* is included in the (0,1 km) range. We find that 50% of the whole turbulence develops in the first 80 m from the ground. The turbulence decreasing rate is very similar to what has been observed above Mauna Kea.Comment: 12 pages, 6 figures, Proc. SPIE Conference "Ground-based and Airborne Telescopes III", 27 June 2010, San Diego, California, US

Optical turbulence vertical distribution with standard and high resolution at Mt. Graham

A characterization of the optical turbulence vertical distribution (Cn2 profiles) and all the main integrated astroclimatic parameters derived from the Cn2 and the wind speed profiles above the site of the Large Binocular Telescope (Mt. Graham, Arizona, US) is presented. The statistic includes measurements related to 43 nights done with a Generalized Scidar (GS) used in standard configuration with a vertical resolution Delta(H)~1 km on the whole 20 km and with the new technique (HVR-GS) in the first kilometer. The latter achieves a resolution Delta(H)~20-30 m in this region of the atmosphere. Measurements done in different periods of the year permit us to provide a seasonal variation analysis of the Cn2. A discretized distribution of Cn2 useful for the Ground Layer Adaptive Optics (GLAO) simulations is provided and a specific analysis for the LBT Laser Guide Star system ARGOS (running in GLAO configuration) case is done including the calculation of the 'gray zones' for J, H and K bands. Mt. Graham confirms to be an excellent site with median values of the seeing without dome contribution epsilon = 0.72", the isoplanatic angle theta0 = 2.5" and the wavefront coherence time tau0= 4.8 msec. We find that the optical turbulence vertical distribution decreases in a much sharper way than what has been believed so far in proximity of the ground above astronomical sites. We find that 50% of the whole turbulence develops in the first 80+/-15 m from the ground. We finally prove that the error in the normalization of the scintillation that has been recently put in evidence in the principle of the GS technique, affects these measurements with an absolutely negligible quantity (0.04").Comment: 11 figures. MNRAS, accepte

Methodological Decisions in Undertaking Academic Integrity Policy Analysis: Considerations for Future Research

Purpose: The purpose of this article is to share details of the methodological decisions regarding data collection that a researcher or research team may want to consider when undertaking a policy analysis. Methods: We have undertaken a meticulous documentation of our decision-making processes throughout the research design process. Results: We provide narrative evidence of what worked for us as a collaborative research team. Implications: Understanding the decisions we made throughout our research design and implementation may help other research teams, particularly those working as virtual collaborations and/or those undertaking academic integrity policy analysis

Book Reviews

BOOK REVIEWS Poverty amidst affluence: Britain and the United States, Vic George and Irving Howards, Aldershot,England, Edward Elgar Publishers, 1991, Reviewed by James Midgley Separate societies: Poverty and inequality in American cities. William W. Goldsmith and Edward J. Blakely,Philadelphia, Temple University Press, 1992, Reviewed by James Midgley The new politics of poverty: The non-working poor in America Lawrence M. Mead, New York, Basic Books, 1992, Reviewed by James Midgley The End of Equality. Mickey Kaus. New York: Basic Books, 1992, Reviewed by David Stoesz The Moral Construction of Poverty: Welfare Reform in America. Joel F. handler and Yeheskel HasenfeldNewbury Park: Sage Publications, 1991, Reviewed by Howard Jacob Karger The Dispossessed: American Underclasses from the Civil War to the Present. Jacqueline Jones, New York: Basic Books, 1992, Reviewed by Henry J. D\u27Souza. 213 Poor Women and Their Families: Hard Working Charity Cases. Beverly Stadum, Albany, New York, State University of New York Press, 1992, Reviewed by Leslie Leighninger From Middle Income to Poor: Downward mobility Among Displaced Steelworkers. Allisojn Zippay, New York, Praeger, 1992, Reviewed by Joel Bla

Deep Near-Infrared Imaging of a Field in the Outer Disk of M82 with the ALTAIR Adaptive Optics System on Gemini North

Deep H and K' images, recorded with the ALTAIR adaptive optics system and NIRI imager on Gemini North, are used to probe the red stellar content in a field with a projected distance of 1 kpc above the disk plane of the starburst galaxy M82. The data have an angular resolution of 0.08 arcsec FWHM, and individual AGB and RGB stars are resolved. The AGB extends to at least 1.7 mag in K above the RGB-tip, which occurs at K = 21.7. The relative numbers of bright AGB stars and RGB stars are consistent with stellar evolution models, and one of the brightest AGB stars has an H-K color and K brightness that is consistent with it being a C star. The brightnesses of the AGB stars suggest that they formed during intermediate epochs, possibily after the last major interaction with M81. Therefore, star formation in M82 during intermediate epochs may not have been restricted to the plane of the disk.Comment: 16 pages of text plus 7 postscript figures; to appear in the PAS

Ground-layer wavefront reconstruction from multiple natural guide stars

Observational tests of ground layer wavefront recovery have been made in open loop using a constellation of four natural guide stars at the 1.55 m Kuiper telescope in Arizona. Such tests explore the effectiveness of wide-field seeing improvement by correction of low-lying atmospheric turbulence with ground-layer adaptive optics (GLAO). The wavefronts from the four stars were measured simultaneously on a Shack-Hartmann wavefront sensor (WFS). The WFS placed a 5 x 5 array of square subapertures across the pupil of the telescope, allowing for wavefront reconstruction up to the fifth radial Zernike order. We find that the wavefront aberration in each star can be roughly halved by subtracting the average of the wavefronts from the other three stars. Wavefront correction on this basis leads to a reduction in width of the seeing-limited stellar image by up to a factor of 3, with image sharpening effective from the visible to near infrared wavelengths over a field of at least 2 arc minutes. We conclude that GLAO correction will be a valuable tool that can increase resolution and spectrographic throughput across a broad range of seeing-limited observations.Comment: 25 pages, 8 figures, to be published in Astrophys.