220 research outputs found

    A Comment on Open Access: the Whipping Boy for Problems in Scholarly Publishing

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    This is a commentary as part of the debate on Open Access

    The mid- and far-infrared colours of AGB and post-AGB stars

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    With the advent of space missions, like SPITZER and ASTRO-F, with sensitive detectors in the near- and mid-infra red covering a reasonable field-of-view and having a good spatial resolution, it will be possible to detect individual AGB stars in Local Group galaxies. The filters used by these missions are non-standard and different from mission to mission. In this paper, the colours of mass-losing AGB and post-AGB stars are calculated in the broad-band filters of the SPITZER and ASTRO-F missions, as well as Bessell V,I and 2MASS J,H,K to connect these results to existing ground-based data. The models are calculated for carbon- and oxygen-rich chemistry and cover different effective temperatures and dust compositions.Comment: A&A, accepted: 27 October 200

    The distribution of H13CN in the circumstellar envelope around IRC+10216

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    H13CN J=8-7 sub-millimetre line emission produced in the circumstellar envelope around the extreme carbon star IRC+10216 has been imaged at sub-arcsecond angular resolution using the SMA. Supplemented by a detailed excitation analysis the average fractional abundance of H13CN in the inner wind (< 5E15 cm) is estimated to be about 4E-7, translating into a total HCN fractional abundance of 2E-5 using the isotopic ratio 12C/13C=50. Multi-transitional single-dish observations further requires the H13CN fractional abundance to remain more or less constant in the envelope out to a radius of about 4E16 cm, where the HCN molecules are effectively destroyed, most probably, by photodissociation. The large amount of HCN present in the inner wind provides effective line cooling that can dominate over that generated from CO line emission. It is also shown that great care needs to be taken in the radiative transfer modelling where non-local, and non-LTE, effects are important and where the radiation field from thermal dust grains plays a major role in exciting the HCN molecules. The amount of HCN present in the circumstellar envelope around IRC+10216 is consistent with predicted photospheric values based on equilibrium chemical models and indicates that any non-equilibrium chemistry occurring in the extended pulsating atmosphere has no drastic net effect on the fractional abundance of HCN molecules that enters the outer envelope. It further suggests that few HCN molecules are incorporated into dust grains.Comment: Accepted for publication in ApJ. 20 pages, 7 figure

    Luminosities and mass-loss rates of SMC and LMC AGB stars and Red Supergiants

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    (Abridged) Dust radiative transfer models are presented for 101 carbon stars and 86 oxygen-rich evolved stars in the Magellanic Clouds for which 5-35 \mum\ {\it Spitzer} IRS spectra are available. The spectra are complemented with available optical and infrared photometry to construct the spectral energy distribution. A minimisation procedure is used to fit luminosity, mass-loss rate and dust temperature at the inner radius. Different effective temperatures and dust content are also considered. Periods from the literature and from new OGLE-III data are compiled and derived. The O-rich stars are classified in foreground objects, AGB stars and Red Super Giants. For the O-rich stars silicates based on laboratory optical constants are compared to "astronomical silicates". Overall, the grain type by Volk & Kwok (1988) fit the data best. However, the fit based on laboratory optical constants for the grains can be improved by abandoning the small-particle limit. The influence of grain size, core-mantle grains and porosity are explored. Relations between mass-loss rates and luminosity and pulsation period are presented and compared to the predictions of evolutionary models, those by Vassiliadis & Wood (1993) and their adopted mass-loss recipe, and those based on a Reimers mass-loss law with a scaling of a factor of five. The Vassiliadis & Wood models describe the data better, although there are also some deficiencies, in particular to the maximum adopted mass-loss rate. The OGLE-III data reveal an O-rich star in the SMC with a period of 1749 days. Its absolute magnitude of Mbol=−8.0M_{\rm bol}= -8.0 makes it a good candidate for a super-AGB star.Comment: A&A accepte

    Research Information Management: Defining RIM and the Library\u27s Role

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    Research information management (RIM) is the aggregation, curation, and utilization of information about research and is emerging as an area of increasing interest and relevance in many university libraries. RIM intersects with many aspects of traditional library services in discovery, acquisition, dissemination, and analysis of scholarly activities, and does so through the nexus with institutional data systems, faculty workflows, and institutional partners. RIM adoption offers libraries new opportunities to support institutional and researcher goals. In this paper prepared by Rebecca Bryant, OCLC Research Senior Program Officer, and a working group of librarians representing OCLC Research Library Partnership institutions, learn more about what RIM is, what is driving RIM adoption, and the library’s role in RIM. The publication is intended to help libraries and other institutional stakeholders understand developing research information management practices—and particularly the value add that libraries can offer in a complex ecosystem. This work is part of a suite of publications and resources around RIM practices. Read more about upcoming research and reports in the area of research information management

    Adding Value by Taking a National and Institutional Approach to Research Data: The ANDS Experience

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    The Australian National Data Service (ANDS) has been working to add value to Australia’s research data environment since 2009. This paper looks at the changes that have occurred over this time, ANDS’ role in those changes and the current state of the Australian research sector at this time, using case studies of selected institutions

    The ARROW Project

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    DRFIC2008 Session 3. Various initiatives driving institutional repositories forwardDRFIC2008 ă‚»ăƒƒă‚·ăƒ§ăƒł3:æ©Ÿé–ąăƒȘポゾトăƒȘă‚’æŽšé€Čă™ă‚‹ć€šæ§˜ăȘă‚€ăƒ‹ă‚·ăƒŁăƒăƒ– 栱摊

    A Submillimeter HCN Laser in IRC+10216

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    We report the detection of a strong submillimeter wavelength HCN laser line at a frequency near 805 GHz toward the carbon star IRC+10216. This line, the J=9-8 rotational transition within the (04(0)0) vibrationally excited state, is one of a series of HCN laser lines that were first detected in the laboratory in the early days of laser spectroscopy. Since its lower energy level is 4200 K above the ground state, the laser emission must arise from the inner part of IRC+10216's circumstellar envelope. To better characterize this environment, we observed other, thermally emitting, vibrationally excited HCN lines and find that they, like the laser line, arise in a region of temperature approximately 1000 K that is located within the dust formation radius; this conclusion is supported by the linewidth of the laser. The (04(0)0), J=9-8 laser might be chemically pumped and may be the only known laser (or maser) that is excited both in the laboratory and in space by a similar mechanism.Comment: 11 pages, 3 figure
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