Issue |
A&A
Volume 468, Number 2, June III 2007
The XMM-Newton extended survey of the Taurus molecular cloud
|
|
---|---|---|
Page(s) | 657 - 662 | |
Section | Stellar atmospheres | |
DOI | https://doi.org/10.1051/0004-6361:20077129 | |
Published online | 26 March 2007 |
On the effect of helium enhancement on bolometric corrections and Teff-colour relations
1
Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova, Italy e-mail: leo.girardi@oapd.inaf.it
2
Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, 34131 Trieste, Italy
Received:
19
January
2007
Accepted:
21
February
2007
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 3500 K to 40 000 K for dwarfs
and from 3500 K to 8000 K for giants, considering both
“He-non-enhanced” and “He-enhanced” compositions. The variations
in He content that were considered are of = +0.1 and +0.2
for the metallicity [M/H] = +0.5 and
= +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 0.01 mag), 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 4000 K and 8000 K, where
amounts to ~0.02 mag, and for Teff equal to 3500 K, where
values clearly become much higher (up to
0.06 mag 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.
Key words: stars: atmospheres / stars: fundamental parameters
© ESO, 2007
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