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Your search keyword '"Carfantan, H."' showing total 2 results
Start Over Author "Carfantan, H." Topic spectrum analysis
2 results on '"Carfantan, H."'

1. Long-term magnetic field stability of Vega.

Author

Alina, D., Petit, P., Lignières, F., Wade, G. A., Fares, R., Aurière, M., Böhm, T., and Carfantan, H.

Subjects
COSMIC magnetic fields, BRIGHTEST stars, ASTROPHYSICAL spectropolarimetry, ASTRONOMICAL observations, TIME series analysis, SPECTRUM analysis, LEAST squares
Abstract

We present new spectropolarimetric observations of the normal A-type star Vega, obtained during the summer of 2010 with NARVAL at Télescope Bernard Lyot (Pic du Midi Observatory). This new time-series is constituted of 615 spectra collected over 6 different nights. We use the Least-Square-Deconvolution technique to compute, from each spectrum, a mean line profile with a signal-to-noise ratio close to 20,000. After averaging all 615 polarized observations, we detect a circularly polarized Zeeman signature consistent in shape and amplitude with the signatures previously reported from our observations of 2008 and 2009. The surface magnetic geometry of the star, reconstructed using the technique of Zeeman-Doppler Imaging, agrees with the maps obtained in 2008 and 2009, showing that most recognizable features of the photospheric field of Vega are only weakly distorted by large-scale surface flows (differential rotation or meridional circulation). [ABSTRACT FROM AUTHOR]

Published
2012
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2. Estimating the p-mode frequencies of the solar twin 18 Scorpii.

Author

Bazot, M., Campante, T. L., Chaplin, W. J., Carfantan, H., Bedding, T. R., Dumusque, X., Broomhall, A.-M., Petit, P., Théado, S., Van Grootel, V., Arentoft, T., Castro, M., Christensen-Dalsgaard, J., do Nascimento Jr, J.-D., Dintrans, B., Kjeldsen, H., Monteiro, M. J. P. F. G., Santos, N. C., Sousa, S., and Vauclair, S.

Subjects
SOLAR research, SPECTRUM analysis, SOLAR oscillations, ASTROPHYSICS, MATHEMATICAL optimization
Abstract

Solar twins have been a focus of attention for more than a decade, because their structure is extremely close to that of the Sun. Today, thanks to high-precision spectrometers, it is possible to use asteroseismology to probe their interiors. Our goal is to use time series obtained from the HARPS spectrometer to extract the oscillation frequencies of 18 Sco, the brightest solar twin. We used the tools of spectral analysis to estimate these quantities. We estimate 52 frequencies using an MCMC algorithm. After examination of their probability densities and comparison with results from direct MAP optimization, we obtain a minimal set of 21 reliable modes. The identification of each pulsation mode is straightforwardly accomplished by comparing to the well-established solar pulsation modes. We also derived some basic seismic indicators using these values. These results offer a good basis to start a detailed seismic analysis of 18 Sco using stellar models. [ABSTRACT FROM AUTHOR]

Published
2012
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