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The surface differential rotation of active solar-type stars can be investigated by means of Doppler and Zeeman-Doppler Imaging, both techniques enabling one to estimate the short-term temporal evolution of photospheric structures (cools…

Astrophysics · Physics 2009-11-10 P. Petit , J. -F. Donati , A. Collier Cameron

We use Doppler imaging techniques to determine the dependence of starspot rotation rates on latitude in an homogeneous sample of young, rapidly-rotating solar analogues. A solar-like differential rotation law is used, where the rotation…

Astrophysics · Physics 2009-11-10 J. R. Barnes , A. Collier Cameron , J. -F. Donati , D. J. James , S. C. Marsden , P. Petit

Rapid gamma-ray flares pose an astrophysical puzzle, requiring mechanisms both to accelerate energetic particles and to produce fast observed variability. These dual requirements may be satisfied by collisionless relativistic magnetic…

High Energy Astrophysical Phenomena · Physics 2020-08-26 J. M. Mehlhaff , G. R. Werner , D. A. Uzdensky , M. C. Begelman

We give a simple, but accurate method that can be used to account for illumination in compact binary systems which have a low-mass companion, even if spherically symmetric illumination of the secondary star (not necessarily on the main…

Astrophysics · Physics 2009-10-28 J. -M. Hameury , H. Ritter

In this talk, I will show how to determine the biasing factor $b$ from the high-order moments of galaxies. The determination is based on the analytical modeling of primordial peaks and virialized halos and is independent of the currently…

Astrophysics · Physics 2007-05-23 Y. P. JING

We consider the effect of rapid rotation on the light curves of neutron stars with hot polar caps. For $P \approx 3$ms spin periods, the pulse fractions can be as much as an order of magnitude larger than with simple slowly-rotating…

Astrophysics · Physics 2009-10-31 Timothy M. Braje , Roger W. Romani , Kevin P. Rauch

Extended source effects can be seen in gravitational lensing events when sources cross critical lines. Those events probe the stellar intensity profile and could be used to measure limb darkening coefficients to test stellar model…

Instrumentation and Methods for Astrophysics · Physics 2019-08-14 Hans J. Witt , F. Atrio-Barandela

Over the past years, thousands of stellar flares have been detected by harvesting data from large photometric surveys. These detections, however, do not account for potential sources of contamination such as background stars appearing in…

With increasingly large data sets, weak lensing measurements are able to measure cosmological parameters with ever greater precision. However this increased accuracy also places greater demands on the statistical tools used to extract the…

Astrophysics · Physics 2015-05-13 S. Pires , J. -L. Starck , A. Amara , R. Teyssier , A. Refregier , J. Fadili

Superradiance in black holes is well-understood but a general treatment for superradiance in stars has until now been lacking. This is surprising given the ease with which we can observe isolated neutron stars and the array of signatures…

High Energy Physics - Phenomenology · Physics 2022-12-14 Francesca Chadha-Day , Björn Garbrecht , Jamie McDonald

Modelling of stellar radiative intensities in various spectral pass-bands plays an important role in stellar physics. At the same time the direct calculations of the high-resolution spectrum and then integrating it over the given spectral…

Solar and Stellar Astrophysics · Physics 2021-06-30 L. S. Anusha , A. I. Shapiro , V. Witzke , M. Cernetic , S. K. Solanki , L. Gizon

The velocity distribution function (VDF) of the hypothetical Weakly Interacting Massive Particles (WIMPs), currently the most favored candidate for the Dark Matter (DM) in the Galaxy, is determined directly from the circular speed…

Astrophysics of Galaxies · Physics 2013-05-01 Pijushpani Bhattacharjee , Soumini Chaudhury , Susmita Kundu , Subhabrata Majumdar

The phenomenon of beam focusing of microwaves in a plasma near a turning-point caustic is discussed in the context of the analytical solution to the Gaussian beam-tracing equations in the 2D linear-layer problem. The location of maximum…

Stellar magnetic activity is a source of noise in the study of the transits of extrasolar planets. It induces flux variations which affect significantly the transit depth determination and the derivations of planetary and stellar…

Earth and Planetary Astrophysics · Physics 2015-06-03 P. Ballerini , G. Micela , A. F. Lanza , I. Pagano

We introduce and test a new and highly efficient method for treating the thermal and radiative effects influencing the energy equation in SPH simulations of star formation. The method uses the density, temperature and gravitational…

Astrophysics · Physics 2009-11-13 D. Stamatellos , A. P. Whitworth , T. Bisbas , S. Goodwin

Most extrasolar planets have been detected by their influence on their parent star, typically either gravitationally (the Doppler method) or by the small dip in brightness as the planet blocks a portion of the star (the transit method).…

Earth and Planetary Astrophysics · Physics 2014-05-06 Fabienne A. Bastien , Keivan G. Stassun , Joshua Pepper

Gamma-ray binaries could be compact pulsar wind nebulae formed when a young pulsar orbits a massive star. The pulsar wind is contained by the stellar wind of the O or Be companion, creating a relativistic comet-like structure accompanying…

High Energy Astrophysical Phenomena · Physics 2015-05-18 G. Dubus , B. Cerutti , G. Henri

The beaming pattern of thermal annihilation radiation is broader than the beaming pattern produced by isotropic nonthermal electrons and positrons in the jets of radio-emitting active galactic nuclei which Compton scatter photons from an…

Astrophysics · Physics 2009-10-30 J. G. Skibo , C. D. Dermer , R. Schlickeiser

We have incorporated the oblate distortion of the shape of the star due to the stellar rotation, which modifies the finite disk correction factor (f_D) in the m-CAK hydrodynamical model. We implement a simplified version for the f_D…

Solar and Stellar Astrophysics · Physics 2015-05-20 Ignacio Araya , Michel Curé , Anahí Granada , Lydia Cidale

We present a new implementation of the magnetic Doppler imaging technique, which aims at self-consistent temperature and magnetic mapping of the surface structures in cool active stars. Our magnetic imaging procedure is unique in its…

Astrophysics · Physics 2009-06-23 O. Kochukhov , N. Piskunov