4,391 research outputs found
Desempenho de cultivares de cenoura no inverno em sistema orgânico de cultivo no Vale do São Francisco.
bitstream/item/53848/1/COT147.pd
Response of hybrid squash Tetsukabuto to water depths and doses of nitrogen.
O objetivo deste trabalho foi avaliar a resposta da abóbora híbrida tipo Tetsukabuto a diferentes lâminas de água e doses de nitrogênio (N), nas condições de Cerrado do Brasil Central
Optical and Near-Infrared UBVRIJHK Photometry for the RR Lyrae stars in the Nearby Globular Cluster M4 (NGC 6121)
We present optical and near-infrared UBVRIJHK photometry of stars in the
Galactic globular cluster M4 (NGC 6121) based upon a large corpus of
observations obtained mainly from public astronomical archives. We concentrate
on the RR Lyrae variable stars in the cluster, and make a particular effort to
accurately reidentify the previously discovered variables. We have also
discovered two new probable RR Lyrae variables in the M4 field: one of them by
its position on the sky and its photometric properties is a probable member of
the cluster, and the second is a probable background (bulge?) object. We
provide accurate equatorial coordinates for all 47 stars identified as RR
Lyraes, new photometric measurements for 46 of them, and new period estimates
for 45. We have also derived accurate positions and mean photometry for 34 more
stars previously identified as variable stars of other types, and for an
additional five non-RR Lyrae variable stars identified for the first time here.
We present optical and near-infrared color-magnitude diagrams for the cluster
and show the locations of the variable stars in them. We present the Bailey
(period-amplitude) diagrams and the period-frequency histogram for the RR Lyrae
stars in M4 and compare them to the corresponding diagrams for M5 (NGC 5904).
We conclude that the RR Lyrae populations in the two clusters are quite similar
in all the relevant properties that we have considered. The mean periods,
pulsation-mode ratios, and Bailey diagrams of these two clusters show support
for the recently proposed "Oosterhoff-neutral" classification.Comment: 33 pages, 16 figures, 7 table
Weak Galactic Halo--Fornax dSph Connection from RR Lyrae Stars
For the first time accurate pulsation properties of the ancient variable
stars of the Fornax dwarf spheroidal galaxy (dSph) are discussed in the broad
context of galaxy formation and evolution. Homogeneous multi-band optical
photometry of spanning {\it twenty} years has allowed us to identify and
characterize more than 1400 RR Lyrae stars (RRLs) in this galaxy. Roughly 70\%
are new discoveries. We investigate the period-amplitude distribution and find
that Fornax shows a lack of High Amplitude (A_V\gsim0.75 mag) Short Period
fundamental-mode RRLs (P\lsim0.48 d, HASPs). These objects occur in stellar
populations more metal-rich than [Fe/H]-1.5 and they are common in the
Galactic halo (Halo) and in globulars. This evidence suggests that old (age
older than 10 Gyr) Fornax stars are relatively metal-poor.
A detailed statistical analysis of the role of the present-day Fornax dSph in
reproducing the Halo period distribution shows that it can account for only a
few to 20\% of the Halo when combined with RRLs in massive dwarf galaxies
(Sagittarius dSph, Large Magellanic Cloud). This finding indicates that
Fornax-like systems played a minor role in building up the Halo when compared
with massive dwarfs. We also discuss the occurrence of HASPs in connection with
the luminosity and the early chemical composition of nearby dwarf galaxies. We
find that, independently of their individual star formation histories, bright
(M_V\lsim-13.5 mag) galaxies have HASPs, whereas faint ones (M_V\gsim-11
mag) do not. Interestingly enough, Fornax belongs to a luminosity range
(--11M--13.5 mag) in which the occurrence of HASPs appears to be
correlated with the early star formation and chemical enrichment of the host
galaxy.Comment: 7 pages, 5 figures, A&A, accepte
Aplicação da metodologia definida pela OCDE para o cálculo de população urbana e rural nos municípios do Brasil
Não existe, à escala internacional, um consenso sobre a definição do conceito de “rural”, apesar de ser
usado quer pelo senso comum quer pelos cientistas das ciências sociais. Com o objetivo de aplicar o
critério de delimitação do rural da OCDE no território brasileiro, a presente comunicação utilizou
dados do censo demográfico brasileiro de 2010, fornecidos pelo IBGE. Procurando seguir a tipologia
da OCDE foi determinada a densidade demográfica de cada um dos 314.018 setores censitários e
classificados como urbano ou rural. Com esses dados os 5.565 municípios foram qualificados como
Região Predominantemente Rural; Região Intermediária e Região Predominantemente Urbana. Os
resultados apontam para a maioria das cidades brasileiras como sendo consideradas regiões
intermediárias
Theoretical study of molecular electronic excitations and optical transitions of C60
We report results on ab initio calculations of excited states of the
fullerene molecule by using configuration interaction (CI) approach with singly
excited determinants (SCI). We have used both the experimental geometry and the
one optimized by the density functional method and worked with basis sets at
the cc-pVTZ and aug-cc-pVTZ level. Contrary to the early SCI semiempirical
calculations, we find that two lowest electron
optical lines are situated at relatively high energies of ~5.8 eV (214 nm) and
~6.3 eV (197 nm). These two lines originate from two transitions: from HOMO to (LUMO+1) () and from (HOMO--1)
to LUMO (). The lowest molecular excitation, which is the level, is found at ~2.5 eV. Inclusion of doubly excited determinants
(SDCI) leads only to minor corrections to this picture. We discuss possible
assignment of absorption bands at energies smaller than 5.8 eV (or
larger than 214 nm).Comment: 6 pages, 1 figure, 9 Table
Discovery of optical pulsations in V2116 Ophiuchi/GX 1+4
We report the detection of pulsations with s period in V2116 Oph,
the optical counterpart of the low-mass X-ray binary GX 1+4. The pulsations are
sinusoidal with modulation amplitude of up to 4% in blue light and were
observed in ten different observing sessions during 1996 April-August using a
CCD photometer at the 1.6-m and 0.6-m telescopes of Laborat\'orio Nacional de
Astrof\'{\i}sica, in Brazil. The pulsations were also observed with the
fast photometer. With only one exception the observed optical periods are
consistent with those observed by the BATSE instrument on board the Compton
Gamma Ray Observatory at the same epoch. There is a definite correlation
between the observability of pulsations and the optical brightness of the
system: V2116~Oph had magnitude in the range when the pulsed
signal was detected, and when no pulsations were present. The
discovery makes GX 1+4 only the third of accretion-powered X-ray
pulsars to be firmly detected as a pulsating source in the optical. The
presence of flickering and pulsations in V2116 Oph adds strong evidence for an
accretion disk scenario in this system. The absolute magnitude of the pulsed
component on 1996 May 27 is estimated to be . The implied
dimensions for the emitting region are 1.1 R_{\sun}, 3.2 R_{\sun}, and 7.0
R_{\sun}, for black-body spectral distributions with K, K, and K, respectively.Comment: 9 pages, 3 figures in PostScript, latex, accepted for publication on
the Astrophysical Journal Letter
The Carina Project IX: on Hydrogen and helium burning variables
We present new multi-band (UBVI) time-series data of helium burning variables
in the Carina dwarf spheroidal galaxy. The current sample includes 92 RR
Lyrae-six of them are new identifications-and 20 Anomalous Cepheids, one of
which is new identification. The analysis of the Bailey diagram shows that the
luminosity amplitude of the first overtone component in double-mode variables
is located along the long-period tail of regular first overtone variables,
while the fundamental component is located along the short-period tale of
regular fundamental variables. This evidence further supports the transitional
nature of these objects. Moreover, the distribution of Carina double-mode
variables in the Petersen diagram (P_1/P_0 vs P_0) is similar to metal-poor
globulars (M15, M68), to the dwarf spheroidal Draco and to the Galactic Halo.
This suggests that the Carina old stellar population is metal-poor and affected
by a small spread in metallicity. We use trigonometric parallaxes for five
field RR Lyrae stars to provide an independent estimate of the Carina distance
using the observed reddening free Period--Wesenheit [PW, (BV)] relation. Theory
and observations indicate that this diagnostic is independent of metallicity.
We found a true distance modulus of \mu=20.01\pm0.02 (standard error of the
mean) \pm0.05 (standard deviation) mag. We also provided independent estimates
of the Carina true distance modulus using four predicted PW relations (BV, BI,
VI, BVI) and we found: \mu=(20.08\pm0.007\pm0.07) mag,
\mu=(20.06\pm0.006\pm0.06) mag, \mu=(20.07\pm0.008\pm0.08) mag and
\mu=(20.06\pm0.006\pm0.06) mag. Finally, we identified more than 100 new SX
Phoenicis stars that together with those already known in the literature (340)
make Carina a fundamental laboratory to constrain the evolutionary and
pulsation properties of these transitional variables.Comment: 44 pages, 13 tables, 13 figures, Accepted for publication in Ap
- …