6,562 research outputs found
A multi-color and Fourier study of RR Lyrae variables in the globular cluster NGC 5272 (M3)
We have performed a detailed study of the pulsational and evolutionary
characteristics of 133 RR Lyrae stars in the globular cluster NGC5272 (M3)
using highly accurate BVI data taken on 5 separate epochs. M3 seems to contain
no less than ~32% of Blazhko stars, and the occurrence and characteristics of
the Blazhko effect have been analyzed in detail. We have identified a good
number (~ 14%) of overluminous RR Lyrae stars that are likely in a more
advanced evolutionary stage off the Zero Age Horizontal Branch (ZAHB). Physical
parameters (i.e. temperature, luminosity, mass) have been derived from (B--V)
colors and accurate color-temperature calibration, and compared with Horizontal
Branch evolutionary models and with the requirements of stellar pulsation
theory. Additional analysis by means of Fourier decomposition of the V light
curves confirms, as expected, that no metallicity spread is present in M3.
Evolution off the ZAHB does not affect [Fe/H] determinations, whereas Blazhko
stars at low amplitude phase do affect [Fe/H] distributions as they appear more
metal-rich. Absolute magnitudes derived from Fourier coefficients might provide
useful average estimates for groups of stars, if applicable, but do not give
reliable {\em individual} values. Intrinsic colors derived from Fourier
coefficients show significant discrepancies with the observed ones, hence the
resulting temperatures and temperature-related parameters are unreliable.Comment: 86 pages, 19 figures, 13 tables, in press A
Tenzing and the importance of tool development for research efficiency
The way science is done is changing. While some tools are facilitating this change, others lag behind. The resulting mismatch between tools and researchers' workflows can be inefficient and delay the progress of research. As an example, information about the people associated with a published journal article was traditionally handled manually and unsystematically. However, as large-scale collaboration, sometimes referred to as “team science,” is now common, a more structured and easy-to-automate approach to managing meta-data is required. In this paper we describe how the latest version of tenzing (A.O. Holcombe et al., Documenting contributions to scholarly articles using CRediT and tenzing, PLOS One 15(12) (2020)) helps researchers collect and structure contributor information efficiently and without frustration. Using tenzing as an example, we discuss the importance of efficient tools in reforming science and our experience with tool development as researchers.</p
Crossover from stationary to aging regime in glassy dynamics
We study the non-equilibrium dynamics of the spherical p-spin models in the
scaling regime near the plateau and derive the corresponding scaling functions
for the correlators. Our main result is that the matching between different
time regimes fixes the aging function in the aging regime to
. The exponent is related to the one giving the
length of the plateau. Interestingly is quickly very small when one
goes away from the dynamic transition temperature in the glassy phase. This
gives new light on the interpretation of experiments and simulations where
simple aging was found to be a reasonable but not perfect approximation, which
could be attributed to the existence of a small but non-zero stretching
exponent.Comment: 7 pages+2 figure
Sorption of Water and Polar-Nonpolar Organic Vapors on Microporous Chromia
High surface area, narrow particle size distribution chromic;t
was investigated for its microporosity. Adsorption studies with
argon, water vapor, methanol, isopropanol, butane, isobutane, neopentane,
and heptane indicated alternative approaches to the
determination of micropore volume
RR LYRAE VARIABLE STARS: PULSATIONAL CONSTRAINTS RELEVANT TO THE OOSTERHOFF CONTROVERSY
A solution to the old Oosterhoff controversy is proposed on the basis of a
new theoretical pulsational scenario concerning RR Lyrae cluster variables
(Bono and coworkers). We show that the observed constancy of the lowest
pulsation period in both Oosterhoff type I (OoI) and Oosterhoff type II (OoII)
prototypes (M3, M15) can be easily reproduced only by assuming the canonical
evolutionary horizontal-branch luminosity levels of these Galactic globular
clusters and therefore by rejecting the Sandage period shift effect (SPSE).Comment: postscript file of 7 pages and 2 figures; one non postcript figure is
available upon request; for any problem please write to
[email protected]
IMAGE PRE-PROCESSING STRATEGIES FOR ENHANCING PHOTOGRAMMETRIC 3D RECONSTRUCTION OF UNDERWATER SHIPWRECK DATASETS
Although underwater photogrammetry has become widely adopted, there are still significant unresolved issues that are worthy of attention. This article focuses on the 3D model generation of underwater shipwrecks and intends explicitly to address the problem of dealing with sub-optimal datasets. Even if the definition of best practices and standards to be adopted during the acquisition phase appears to be crucial, there is a massive amount of data gathered so far by professionals and the scientific community all over the world that cannot be ignored. The compelling idea is to attempt to achieve the best reconstruction results possible, even from sub-optimal or less-than-ideal image datasets. This work focuses on the investigation of different strategies and approaches for balancing the quality of the photogrammetric products, without neglecting their reliability concerning the surveyed object. The case study of this research is the Mandalay MHT, a 34 m long steel-hulled auxiliary schooner that sank in 1966 and now lies in the Biscayne National Park (Florida - USA). The dataset has been provided by the Submerged Resources Center (SRC) of the US National Park Service, in order to develop an experimental image enhancement method functional to the virtualization and visualization of the generated products, as a part of a sustainable, affordable, and reliable method of studying submerged artefacts and sites. The original images have been processed using different image enhancement approaches, and the outputs have been compared and analysed
Aging, memory and rejuvenation: some lessons from simple models
Many recent experiments probed the off equilibrium dynamics of spin glasses
and other glassy systems through temperature cycling protocols and observed
memory and rejuvenation phenomena. Here we show through numerical simulations,
using powerful algorithms, that such features can already be observed to some
extent in simple models such as two dimensional ferromagnets. We critically
discuss these results and review some aspects of the literature in the light of
our findings.Comment: 10 pages, 8 figures. Contribution to the Proceedings of the
Summerschool "Ageing and the glass transition", Luxembourg 14-25 Sept. 200
Equilibrium and out of equilibrium thermodynamics in supercooled liquids and glasses
We review the inherent structure thermodynamical formalism and the
formulation of an equation of state for liquids in equilibrium based on the
(volume) derivatives of the statistical properties of the potential energy
surface. We also show that, under the hypothesis that during aging the system
explores states associated to equilibrium configurations, it is possible to
generalize the proposed equation of state to out-of-equilibrium conditions. The
proposed formulation is based on the introduction of one additional parameter
which, in the chosen thermodynamic formalism, can be chosen as the local minima
where the slowly relaxing out-of-equilibrium liquid is trapped.Comment: 7 pages, 4 eps figure
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