48 citations · 346 across the 31 of their papers we have counts for
25 papers · 1 filter
Hemispheric asymmetry in the sunspot cycle as a nonextensive phenomenon
Leonardo F. G. Batista, Thiago M. Santiago, Paulo C. F. da Silva Filho +2
The appearance of dark sunspots over the solar photosphere is not considered to be symmetric between the northern and southern hemispheres. Among the different conclusions obtained…
Fractal signature as a rotational modulation and stellar noise classifier based on the active Kepler stars
Paulo Cleber Farias da Silva Filho, Jose Ribamar Dantas Silveira Junior, Bricio Warney de Freitas Alves +5
In this study, we report on the analysis of 701 stars in a solar vicinity defined in three categories namely subsolar, solar, and supersolar with rotation periods between 1 and 70…
Measuring deviation from Skumanich braking index in active stars observed by Kepler mission
D. B. de Freitas, F. J. Cavalcante, T. M. Santiago
The aim of this work is to determine the deviation of the value of magnetic braking index from Skumanich canonical value for giant and main-sequence stars. In this contex…
Stellar age dependence of the nonextensive magnetic braking index: a test for the open cluster Per
Daniel B. de Freitas
Using a generalized function of the stellar spin-down law, we investigate the age dependence of the magnetic braking index (). Our survey includes 9 open clusters aged lower tha…
On the multiscale behaviour of stellar activity and rotation of the planet host Kepler-30
D. B. de Freitas, A. F. Lanza, F. O. da Silva Gomes +1
Kepler-30 is a unique target to study stellar activity and rotation in a young solar-like star accompanied by a compact planetary system. We use about 4 years of high-precision pho…
Non-extensive processes associated with heating of the Galactic disc
C. A. P. Viana, D. B. de Freitas
We analyse the mechanisms ruling galactic disc heating through the dynamics of space velocities , and , extracted from the Geneva-Copenhagen catalogue. To do this, we use…
New Suns in the Cosmos V: Stellar rotation and multifractality in active \textit{Kepler} stars
D. B. de Freitas, M. M. F. Nepomuceno, L. D. Alves Rios +2
In the present study, high-precision time series photometry for the active \emph{Kepler} stars is described in the language of multifractals. We explore the potential of using the…
A nonextensive insight to the stellar initial mass function
D. B. de Freitas, R. T. Eufrasio, M. M. F. Nepomuceno +1
the present paper, we propose that the stellar initial mass distributions as known as IMF are best fitted by -Weibulls that emerge within nonextensive statistical mechanics. As…
New Suns in the Cosmos IV: the multifractal nature of stellar magnetic activity in \textit{Kepler} cool stars
D. B. de Freitas, M. M. F. Nepomuceno, M. Gomes de Souza +5
In the present study, we investigate the multifractal nature of a long-cadence time series observed by the \textit{Kepler} mission for a sample of 34 M dwarf stars and the Sun in i…
On the incidence of \textit{WISE} infrared excess among solar analog, twin and sibling stars
Antônio D. Costa, Bruno L. Canto Martins, Izan C. Leão +4
This study presents a search for IR excess in the 3.4, 4.6, 12 and 22 m bands in a sample of 216 targets, composed of solar sibling, twin and analog stars observed by the \texti…
New Suns in the Cosmos III: multifractal signature analysis
D. B. de Freitas, M. M. F. Nepomuceno, P. R. V. de Moraes Junior +7
In present paper, we investigate the multifractality signatures in hourly time series extracted from CoRoT spacecraft database. Our analysis is intended to highlight the possibilit…
Rotation period distribution of CoRoT and Kepler Sun-like stars
I. C. Leão, L. Pasquini, C. E. Ferreira Lopes +9
We study the distribution of the photometric rotation period (Prot), which is a direct measurement of the surface rotation at active latitudes, for three subsamples of Sun-like sta…
Stellar Cycles from Photometric Data: CoRoT Stars
C. E. Ferreira Lopes, I. C. Leão, D. B. de Freitas +3
Until a few years ago, the amplitude variation in the photometric data had been limitedly explored mainly because of time resolution and photometric sensitivity limitations. This i…
The variability behavior of CoRoT M-giant Stars
C. E. Ferreira Lopes, V. Neves, I. C. Leão +8
For 6 years the Convection, Rotation, and Planetary Transits (CoRoT) space mission has acquired photometric data from more than one hundred thousand point sources towards and direc…
A nonextensive view of the stellar braking indices
D. B. de Freitas, F. J. Cavalcante, B. B. Soares +1
The present work is based on a description for the angular mometum loss rate due to magnetic braking for main-sequence stars on the relationship between stellar rotation and age. I…
The rotational behavior of Kepler Stars with Planets
F. Paz-Chinchón, I. C. Leão, J. P. Bravo +6
We analyzed the host stars of the present sample of confirmed planets detected by Kepler and Kepler Objects of Interest (KOI) to compute new photometric rotation periods and to stu…
Chandrasekhar's relation and the stellar rotation in the Kepler field
J. R. P. Silva, B. B. Soares, D. B. de Freitas
According to the statistical law of large numbers, the expected mean of identically distributed random variables of a sample tends toward the actual mean as the sample increases. U…
Strong evidences for a nonextensive behavior of the rotation period in Open Clusters
D. B. de Freitas, M. M. F. Nepomuceno, B. B. Soares +1
Time-dependent nonextensivity in a stellar astrophysical scenario combines nonextensive entropic indices derived from the modified Kawaler's parametrization, and , obtai…
Time-dependent nonextensivity arising from the rotational evolution of solar-type stars
Jose R. P. Silva, Mackson M. F. Nepomuceno, Braulio B. Soares +1
Nonextensive formalism is a generalization of the Boltzmann-Gibbs statistics. In this formalism the entropic index q is a quantity characterizing the degree of nonextensivity, and…
New Suns in the Cosmos?
D. B. de Freitas, I. C. Leão, C. E. F. Lopes +5
The present work reports on the discovery of three stars that we have identified to be rotating Sun-like stars, based on rotational modulation signatures inferred from light curves…
Overview of semi-sinusoidal stellar variability with the CoRoT satellite
J. R. De Medeiros, C. E. Ferreira Lopes, I. C. Leao +13
To date, the CoRoT space mission has produced more than 124,471 light curves. Classifying these curves in terms of unambiguous variability behavior is mandatory for obtaining an un…
A nonextensive approach to the stellar rotational evolution I. F and G type stars
D. B. de Freitas, J. R. De Medeiros
The pioneering study by Skumanich (1972) showed that the rotational velocity of G-type Main-Sequence (MS) stars decreases with stellar age according to $t^{-…
Nonextensivity in the Solar Neighborhood
D. B. de Freitas, J. R. De Medeiros
In the present study, we analyze the radial velocity distribution as a function of different stellar parameters such as stellar age, mass, rotational velocity and distance to the S…
Wavelet analysis of stellar rotation and other periodicities
D. B. de Freitas, I. de C. Leão, B. L. Canto Martins +1
The wavelet transform has been used for numerous studies in astrophysics, including signal--noise periodicity and decomposition as well as the signature of differential rotation in…