Using the CIFIST grid of CO5BOLD 3D model atmospheres to study the effects of stellar granulation on photometric colours - II. The role of convection across the H-R diagram

• Verfasst von: Kucinskas, Arunas [VerfasserIn]
• Verfasst von: Klevas, Jonas [VerfasserIn]
• Verfasst von: Ludwig, Hans-Günter [VerfasserIn]
• Verfasst von: Bonifacio, Piercarlo [VerfasserIn]
• Verfasst von: Steffen, M. [VerfasserIn]
• Verfasst von: Caffau, Elisabetta [VerfasserIn]
• Titel: Using the CIFIST grid of CO5BOLD 3D model atmospheres to study the effects of stellar granulation on photometric colours - II. The role of convection across the H-R diagram
• Verf.angabe: A. Kučinskas, J. Klevas, H.-G. Ludwig, P. Bonifacio, M. Steffen, and E. Caffau
• E-Jahr: 2018
• Jahr: 25 May 2018
• Umfang: 12 S.
• Fussnoten: Die 5 im Text ist hochgestellt ; Gesehen am 18.11.2019
• Titel Quelle: Enthalten in: Astronomy and astrophysics
• Ort Quelle: Les Ulis : EDP Sciences, 1969
• Jahr Quelle: 2018
• Band/Heft Quelle: 613(2018) Artikel-Nummer A24, 12 Seiten
• ISSN Quelle: 1432-0746
• DOI: doi:10.1051/0004-6361/201732447
• Datenträger: Online-Ressource
• Sprache: eng
• K10plus-PPN: 1682009971

Abstract

<i>Aims.<i/> We studied the influence of convection on the spectral energy distributions (SEDs), photometric magnitudes, and colour indices of different types of stars across the H-R diagram.<i>Methods.<i/> The 3D hydrodynamical CO<sup>5<sup/>BOLD, averaged ⟨3D⟩, and 1D hydrostatic LHD model atmospheres were used to compute SEDs of stars on the main sequence (MS), main sequence turn-off (TO), subgiant branch (SGB), and red giant branch (RGB), in each case at two different effective temperatures and two metallicities, [M∕H] = 0.0 and − 2.0. Using the obtained SEDs, we calculated photometric magnitudes and colour indices in the broad-band Johnson-Cousins <i>UBVRI<i/> and 2MASS <i>JHK<i/><sub>s<sub/>, and the medium-band Strömgren <i>uvby<i/> photometric systems.<i>Results.<i/> The 3D-1D differences in photometric magnitudes and colour indices are small in both photometric systems and typically do not exceed ± 0.03 mag. Only in the case of the coolest giants located on the upper RGB are the differences in the <i>U<i/> and <i>u<i/> bands able reach ≈−0.2 mag at [M∕H] = 0.0 and ≈−0.1 mag at [M∕H] = −2.0. Generally, the 3D-1D differences are largest in the blue-UV part of the spectrum and decrease towards longer wavelengths. They are also sensitive to the effective temperature and are significantly smaller in hotter stars. Metallicity also plays a role and leads to slightly larger 3D-1D differences at [M∕H] = 0.0. All these patterns are caused by a complex interplay between the radiation field, opacities, and horizontal temperature fluctuations that occur due to convective motions in stellar atmospheres. Although small, the 3D-1D differences in the magnitudes and colour indices are nevertheless comparable to or larger than typical photometric uncertainties and may therefore cause non-negligible systematic differences in the estimated effective temperatures.