5,786 research outputs found
Nonextensivity in the solar magnetic activity during the increasing phase of solar Cycle 23
In this paper we analyze the behavior of the daily Sunspot Number from the
Sunspot Index Data Center (SIDC), the mean Magnetic Field strength from the
National Solar Observatory/Kitt Peak (NSO/KP) and Total Solar Irradiance means
from Virgo/SoHO, in the context of the --Triplet which emerges within
nonextensive statistical mechanics. Distributions for the mean solar Magnetic
Field show two different behaviors, with a --Gaussian for scales of 1 to 16
days and a Gaussian for scales longer than 32 days. The latter corresponds to
an equilibrium state. Distributions for Total Solar Irradiance also show two
different behaviors (approximately Gaussian) for scales of 128 days and longer,
consistent with statistical equilibrium and --Gaussian for scales 128
days. Distributions for the Sunspot Number show a --Gaussian independent of
timescales, consistent with a nonequilibrium state. The values obtained
("--Triplet",,)
demonstrate that the Gaussian or --Gaussian behavior of the aforementioned
data depends significantly on timescales. These results point to strong
multifractal behavior of the dataset analyzed, with the multifractal level
decreasing from Sunspot Number to Total Solar Irradiance. In addition, we found
a numerically satisfied dual relation between and .Comment: 6 pages, 4 figure
Power-law statistics and stellar rotational velocities in the Pleiades
In this paper we will show that, the non-gaussian statistics framework based
on the Kaniadakis statistics is more appropriate to fit the observed
distributions of projected rotational velocity measurements of stars in the
Pleiades open cluster. To this end, we compare the results from the
and -distributions with the Maxwellian.Comment: 13 pages, 3 figure
Mass generation for non-Abelian antisymmetric tensor fields in a three-dimensional space-time
Starting from a recently proposed Abelian topological model in (2+1)
dimensions, which involve the Kalb-Ramond two form field, we study a
non-Abelian generalization of the model. An obstruction for generalization is
detected. However we show that the goal is achieved if we introduce a vectorial
auxiliary field. Consequently, a model is proposed, exhibiting a non-Abelian
topological mass generation mechanism in D=3, that provides mass for the
Kalb-Ramond field. The covariant quantization of this model requires ghosts for
ghosts. Therefore in order to quantize the theory we construct a complete set
of BRST and anti-BRST equations using the horizontality condition.Comment: 8 pages. To appear in Physical Review
On the link between rotation, chromospheric activity and Li abundance in subgiant stars
The connection rotation-CaII emission flux-lithium abundance is analyzed for
a sample of bona fide subgiant stars, with evolutionary status determined from
HIPPARCOS trigonometric parallax measurements and from the Toulouse-Geneva
code.Comment: 9 pages, 8 figure
A snapshot of the inner dusty regions of a RCrB-type variable
R Coronae Borealis variable stars are suspected to sporadically eject
optically thick dust clouds causing, when one of them lies on the
line-of-sight, a huge brightness decline in visible light. Mid-infrared
interferometric observations of RYSgr allowed us to explore the circumstellar
regions very close to the central star (~20-40 mas) in order to look for the
signature of any heterogeneities. Using the VLTI/MIDI instrument, five
dispersed visibility curves were recorded with different projected baselines
oriented towards two roughly perpendicular directions. The large spatial
frequencies visibility curves exhibit a sinusoidal shape whereas, at shorter
spatial frequencies visibility curves follow a Gaussian decrease. These
observations are well interpreted with a geometrical model consisting in a
central star surrounded by an extended circumstellar envelope in which one
bright cloud is embedded. Within this simple geometrical scheme, the inner
110AU dusty environment of RYSgr is dominated at the time of observations by a
single dusty cloud which, at 10mic represents ~10% of the total flux of the
whole system. The cloud is located at about 100stellar radii from the centre
toward the East-North-East direction (or the symmetric direction with respect
to centre) within a circumstellar envelope which FWHM is about 120stellar
radii. This first detection of a cloud so close to the central star, supports
the classical scenario of the RCrB brightness variations in the optical
spectral domain
Measuring territorial cohesion trends in Europe: A correlation with EU Cohesion Policy
Territorial cohesion is a formal EU policy goal since 2010, when it
was placed in the Lisbon Treaty, alongside the long-term EU
goals of economic and social cohesion. Understandably, by itself,
a policy goal is irrelevant if it cannot be assessed. In this light,
this article discusses potential methodological approaches to
measure territorial cohesion trends in a given territory, their
advantages and limitations, based on existing literature. It uses
European NUTS 2 and the Portuguese and Polish NUTS 3 as
concrete case studies to assess territorial cohesion trends from
2005 to 2020 via a Territorial Cohesion Index. As such, it presents
an updated and unique picture on the territorial cohesion trends
in Europe and in two specific EU member states, based on
available data. It concludes that measuring territorial cohesion
trends is challenging mainly due to lack of available data in
certain key dimensions of territorial cohesion, but it is possible
and needed.info:eu-repo/semantics/publishedVersio
Lithium and magnetic fields in giants. HD 232862 : a magnetic and lithium-rich giant star
We report the detection of an unusually high lithium content in HD 232862, a
field giant classified as a G8II star, and hosting a magnetic field. With the
spectropolarimeters ESPaDOnS at CFHT and NARVAL at TBL, we have collected high
resolution and high signal-to-noise spectra of three giants : HD 232862, KU Peg
and HD 21018. From spectral synthesis we have inferred stellar parameters and
measured lithium abundances that we have compared to predictions from
evolutionary models. We have also analysed Stokes V signatures, looking for a
magnetic field on these giants. HD 232862, presents a very high abundance of
lithium (ALi = 2.45 +/- 0.25 dex), far in excess of the theoretically value
expected at this spectral type and for this luminosity class (i.e, G8II). The
evolutionary stage of HD 232862 has been precised, and it suggests a mass in
the lower part of the [1.0 Msun ; 3.5 Msun ] mass interval, likely 1.5 to 2.0
solar mass, at the bottom of the Red Giant Branch. Besides, a time variable
Stokes V signature has been detected in the data of HD 232862 and KU Peg,
pointing to the presence of a magnetic field at the surface of these two
rapidly rotating active stars.Comment: 11 pages, 9 figures ; accepted by Astronomy and Astrophysic
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