1,563 research outputs found
The WFCAM Multi-wavelength Variable Star Catalog
Stellar variability in the near-infrared (NIR) remains largely unexplored.
The exploitation of public science archives with data-mining methods offers a
perspective for the time-domain exploration of the NIR sky. We perform a
comprehensive search for stellar variability using the optical-NIR multi-band
photometric data in the public Calibration Database of the WFCAM Science
Archive (WSA), with the aim of contributing to the general census of variable
stars, and to extend the current scarce inventory of accurate NIR light curves
for a number of variable star classes. We introduce new variability indices
designed for multi-band data with correlated sampling, and apply them for
pre-selecting variable star candidates, i.e., light curves that are dominated
by correlated variations, from noise-dominated ones. Pre-selection criteria are
established by robust numerical tests for evaluating the response of
variability indices to colored noise characteristic to the data. We find 275
periodic variable stars and an additional 44 objects with suspected variability
with uncertain periods or apparently aperiodic variation. Only 44 of these
objects had been previously known, including 11 RR~Lyrae stars in the outskirts
of the globular cluster M3 (NGC~5272). We provide a preliminary classification
of the new variable stars that have well-measured light curves, but the
variability types of a large number of objects remain ambiguous. We classify
most of the new variables as contact binary stars, but we also find several
pulsating stars, among which 34 are probably new field RR~Lyrae and 3 are
likely Cepheids. We also identify 32 highly reddened variable objects close to
previously known dark nebulae, suggesting that these are embedded young stellar
objects. We publish our results and all light-curve data as the WFCAM Variable
Star Catalog.Comment: 21 pages, 11 figure
Gapped Excitations in the High-Pressure Antiferromagnetic Phase of URuSi
We report a neutron scattering study of the magnetic excitation spectrum in
each of the three temperature and pressure driven phases of URuSi. We
find qualitatively similar excitations throughout the (H0L) scattering plane in
the hidden order and large moment phases, with no changes in the
-widths of the excitations at the = (1.407,0,0) and =
(1,0,0) points, within our experimental resolution. There is, however, an
increase in the gap at the point from 4.2(2) meV to 5.5(3) meV,
consistent with other indicators of enhanced antiferromagnetism under pressure.Comment: 5 pages, 3 figures, 1 tabl
Static and dynamic Jahn-Teller effect in the alkali metal fulleride salts A4C60 (A = K, Rb, Cs)
We report the temperature dependent mid- and near-infrared spectra of K4C60,
Rb4C60 and Cs4C60. The splitting of the vibrational and electronic transitions
indicates a molecular symmetry change of C604- which brings the fulleride anion
from D2h to either a D3d or a D5d distortion. In contrast to Cs4C60, low
temperature neutron diffraction measurements did not reveal a structural phase
transition in either K4C60 and Rb4C60. This proves that the molecular
transition is driven by the molecular Jahn-Teller effect, which overrides the
distorting potential field of the surrounding cations at high temperature. In
K4C60 and Rb4C60 we suggest a transition from a static to a dynamic Jahn-Teller
state without changing the average structure. We studied the librations of
these two fullerides by temperature dependent inelastic neutron scattering and
conclude that both pseudorotation and jump reorientation are present in the
dynamic Jahn-Teller state.Comment: 13 pages, 10 figures, to be published in Phys. Rev.
Biometria e métodos para superação da dormência de sementes de faveira-rósea (Parkia oppositifolia Spruce ex Benth.) Fabaceae-mimosoideae.
Resumo 131
Identificação de carotenoides em polpa de goiaba microencapsulada utilizando cromatografia líquida de alta eficiência.
Título: goaiba [i.e. goiaba]
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