J/A+A/550/A103 Model 1D (LHD) and 3D (CO5BOLD) spectra (Allende Prieto+, 2013)
Convective line shifts for the Gaia RVS spectral range from the CIFIST 3D
model atmosphere grid.
Allende Prieto C., Koesterke L. Ludwig H.-G., Freytag B., Caffau E.
<Astron. Astrophys. 550, A103 (2013)>
=2013A&A...550A.103A 2013A&A...550A.103A
ADC_Keywords: Atlases ; Line Profiles ; Models, atmosphere ; Radial velocities
Keywords: stars: atmospheres - line: formation - convection -
techniques: radial velocities - stars: solar-type - stars: late-type
Abstract:
To derive space velocities of stars along the line of sight from
wavelength shifts in stellar spectra requires accounting for a number
of second-order effects. For most stars, gravitational redshifts,
convective blueshifts, and transverse stellar motion are the dominant
contributors. We provide theoretical corrections for the net velocity
shifts due to convection expected for the measurements from the Gaia
Radial Velocity Spectrometer (RVS). We used a set of three-dimensional
time-dependent simulations of stellar surface convection computed with
CO5BOLD to calculate spectra of late-type stars in the Gaia RVS range
and to infer the net velocity offset that convective motions will
induce in radial velocities derived by cross-correlation. The net
velocity shifts derived by cross-correlation depend both on the
wavelength range and spectral resolution of the observations.
Convective shifts for Gaia RVS observations are less than 0.1km/s for
late-K-type stars, and they increase with stellar mass, reaching about
0.3km/s or more for early F-type dwarfs. This tendency is the result
of an increase with effective temperature in both temperature and
velocity fluctuations in the line-forming region. Our simulations also
indicate that the net RVS convective shifts can be positive (i.e.
redshifts) in some cases. Overall, the blueshifts weaken slightly with
increasing surface gravity, and are enhanced at low metallicity.
Gravitational redshifts amount up to 0.7km/s and dominate convective
blueshifts for dwarfs, but become much weaker for giants.
Description:
Model spectral fluxes for late-type stars computed from 3D
hydrodynamical simulations of surface convection performed with the
CO5BOLD code. Their 1D hydrostatic counterparts are included, based on
the LHD code, sharing the same microphysics as the CO5BOLD models. The
fluxes for both the 3D and 1D models are calculated with the same
opacities and radiative transfer code (ASSET).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
info.dat 39 84 Identifiers and parameters for the models
flux.fit 2880 63851 *3D array of fluxes Flambda (erg/cm2/s/Å)
wavelength.fit 2880 382 Array of wavelengths (8440 to 8770Å)
wavelength.txt 10 136820 The array of wavelengths as a text file
sp1d/* . 84 Fluxes for the 1D model as text files
sp3d/* . 84 Fluxes for the 3D model as text files
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Note on flux.fit: FITS file containing a (2x84x136820) array of 2x84 spectra,
each of 136820 points (range 0.844-13.682µm); the first dimension
corresponds to 1=1D, 2=3D models, and the second dimension to the model
number (see info.dat, or table A.1 in the paper)
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Byte-by-byte Description of file: info.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- ID Simulation ID (as in Table A.1)
17- 23 A7 --- ID2 Internal ID
25- 28 I4 K Teff [3790/6730] Effective temperature
30- 33 F4.2 [cm/s2] logg [1.5/4.5] Decimal log of the surface gravity (cgs)
35- 39 F5.2 [Sun] [Fe/H] [-3/0] Iron abundance
(log10 scale normalized to sun)
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Acknowledgements:
Carlos Allende Prieto, callende(at)iac.es
(End) Carlos Allende Prieto [IAC, Spain], Patricia Vannier [CDS] 18-Dec-2012