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Category/Subcategory: Natural Sciences/Astronomy

Testing the Gallavotti-Cohen Fluctuation Theorem on the Solar Photosphere

Author: Giorgio Viavattene
The understanding of fluctuations in systems far from equilibrium is one of the key issues of non-equilibrium statistical thermodynamics. The Fluctuation Theorem of Gallavotti and Cohen (1995) [GCFT] portrays some symmetry featur ... more

Views: 17

Stellar Parameters in an Instant with Machine Learning

Author: Earl Bellinger
We use machine learning to build a constrained multiple regression model for rapidly estimating the fundamental stellar parameters of main-sequence solar-like stars (Bellinger & Angelou 2016). We train a random forest of decision ... more

Views: 476

Modelling the Line-of-Sight Projection and Filtering-Induced Leakage in Time-Distance Helioseismology

Author: Vincent Böning
In current approaches to time-distance helioseismology, the line-of-sight projection effect on the traveltimes is not fully taken into account. Furthermore, filtering of full-disc data induces leakage due to the projection onto ... more

Views: 466

Looking for Magnetic Field in Kepler Red Giants

Author: Jérôme Ballot
Spectropolarimetric measurements allow us to detect and measure magnetic field through Zeeman effect in stellar photospheres. We observed with the spectropolarimeters Narval (at Telescope Bernard Lyot) and ESPADONS (at CFHT) a few ... more

Views: 382

Measurements of helioseismic travel times

Author: Markus Roth
In time-distance helioseismology wave travel times are measured from the cross-correlation between Doppler velocities recorded at any two locations on the solar surface. All local helioseismology inferences rely critically on the ... more

Views: 402

Spherical Born Kernels for Flows in Time-Distance Helioseismology

Author: Vincent Böning
We extend an existing Born approximation model for calculating the linear sensitivity of helioseismic travel-times to flows from Cartesian to spherical geometry. This development is necessary to use the Born approximation for in ... more

Views: 484

The Envelope Spectrum

Author: René Kiefer
Solar-like oscillations exhibit a regular pattern of frequencies. This pattern is dominated by the small and large frequency separations between modes. The accurate determination of these parameters is of great interest, because ... more

Views: 526

Kepler observation of HD 176465, a binary system with overlapping pulsation frequencies

Author: Othman Benomar
Binary stars systems are crucial to better understand the physics of stars, because they might share a common history, enabling us to assume that they have the same age and composition. Furthermore, using the Kepler laws, the orbi ... more

Views: 328

Asteroseismic signature of a starspot

Author: Emanuele Papini
Stellar acoustic oscillations are affected by magnetic activity, however it is unclear how a single starspot would affect the power spectrum of oscillations. Since the starspot rotates with the star, it causes a perturbation that ... more

Views: 343

The K2 RR Lyrae survey

Author: Robert Szabo
We have initiated a large survey with K2, to observe thousands of RR Lyrae stars along the ecliptic. The high photometric precision and the 80-90-day continuous coverage will allow us to investigate the light variation of these ga ... more

Views: 382