220 research outputs found
A Comment on Open Access: the Whipping Boy for Problems in Scholarly Publishing
This is a commentary as part of the debate on Open Access
The mid- and far-infrared colours of AGB and post-AGB stars
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
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
(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 makes it a good candidate
for a super-AGB star.Comment: A&A accepte
Research Information Management: Defining RIM and the Library\u27s Role
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 libraryâs role in RIM.
The publication is intended to help libraries and other institutional stakeholders understand developing research information management practicesâand 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
The Australian National Data Service (ANDS) has been working to add value to Australiaâs research data environment since 2009. This paper looks at the changes that have occurred over this time, ANDSâ 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
DRFIC2008 Session 3. Various initiatives driving institutional repositories forwardDRFIC2008 ă»ăă·ă§ăł3:æ©éąăȘăăžăăȘăæšéČăăć€æ§ăȘă€ăă·ăŁăă ć ±ć
A Submillimeter HCN Laser in IRC+10216
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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