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$alpha$ Centauri A in the far infrared | | R. Liseau
; B. Montesinos
; G. Olofsson
; G. Bryden
; J. P. Marshall
; D. Ardila
; A. Bayo Aran
; W. C. Danchi
; C. del Burgo
; C. Eiroa
; S. Ertel
; M. C. W. Fridlund
; A. V. Krivov
; G. L. Pilbratt
; A. Roberge
; P. Thébault
; J. Wiegert
; G. J. White
; | | Date: |
17 Dec 2012 | | Abstract: | Chromospheres and coronae are common phenomena on solar-type stars.
Understanding the energy transfer to these heated atmospheric layers requires
direct access to the relevant empirical data. Study of these structures has, by
and large, been limited to the Sun thus far. The region of the temperature
reversal can be directly observed only in the far infrared and submm. We aim at
the determination of the characteristics of the atmosphere in the region of the
temperature minimum of the solar sister star alpha Cen A. For the nearby binary
system alpha Centauri, stellar parameters are known with high accuracy from
measurements. For the basic model parameters Teff, log g and [Fe/H], we
interpolate in the grid of GAIA/PHOENIX stellar model atmospheres and compute
the corresponding model for the G2 V star alpha Cen A. Comparison with
photometric measurements shows excellent agreement between observed
photospheric data in the optical and infrared. For longer wavelengths, the
modelled spectral energy distribution is compared to MIPS, PACS, SPIRE and
LABOCA photometry. A specifically tailored Uppsala model based on the MARCS
code and extending further in wavelength is used to gauge the emission
characteristics of alpha Cen A in the FIR. Similar to the Sun, the FIR emission
of alpha Cen A originates in the minimum temperature region above the stellar
photosphere in the visible. However, in comparison with the solar case, the FIR
photosphere of alpha Cen A appears marginally cooler, Tmin=T160mu=3920+/-375 K.
Beyond the minimum near 160mu, the brightness temperatures increase and this
radiation likely originates in warmer regions of the chromosphere of alpha Cen
A. To the best of our knowledge this is the first time a temperature minimum
has been directly measured on a main-sequence star other than the Sun. | | Source: | arXiv, 1212.3954 | | Services: | Forum | Review | PDF | Favorites | |
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