2007A&A...468..657G


Query : 2007A&A...468..657G

2007A&A...468..657G - Astronomy and Astrophysics, volume 468, 657-662 (2007/6-3)

On the effect of helium enhancement on bolometric corrections and Teff-colour relations.

GIRARDI L., CASTELLI F., BERTELLI G. and NASI E.

Abstract (from CDS):

We evaluate the effects that variations in He content have on bolometric corrections and Teff-colour relations. To do this, we computed ATLAS9 model atmospheres and spectral energy distributions for effective temperatures ranging from 3500K to 40000K for dwarfs and from 3500K to 8000K for giants, considering both ``He-non-enhanced'' and ``He-enhanced'' compositions. The variations in He content that were considered are of ΔY=+0.1 and +0.2 for the metallicity [M/H]=+0.5 and ΔY = +0.1 for [M/H]=-0.5 and -1.5. Synthetic photometry was then carried out for the UBVRIJHK system. We conclude that the changes in bolometric corrections, caused by the adopted He-enhancements are in general too small (less than 0.01mag), for both dwarfs and giants, to be affecting present-day tables of bolometric corrections at a significant level. The only possible exceptions are found for the U-band at Teff between 4000K and 8000K, where |ΔBCU| amounts to ∼0.02mag, and for Teff equal to 3500K, where |ΔBCSλ| values clearly become much higher (up to 0.06mag for passbands from U to V). However, even in the latter case the overall uncertainty caused by variations in the He content may be not so significant, because the ATLAS9 results are still approximative at their lowest temperature limit.

Abstract Copyright:

Journal keyword(s): stars: atmospheres - stars: fundamental parameters

Simbad objects: 3

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Number of rows : 3
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 NGC 2808 GlC 09 12 03.10 -64 51 48.6           ~ 1356 0
2 NGC 5139 GlC 13 26 47.28 -47 28 46.1           ~ 3285 0
3 M 13 GlC 16 41 41.634 +36 27 40.75     5.8     ~ 2123 0

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2022.12.02-10:21:36

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