Chow-Choong Ngeow, Marcella Marconi, Ilaria Musella, Michele Cignoni, Shashi M. Kanbur
In this paper the synthetic period-luminosity (P-L) relations in Spitzer's
IRAC bands, based on a series of theoretical pulsation models with varying
metal and helium abundance, were investigated. Selected sets of these synthetic
P-L relations were compared to the empirical IRAC band P-L relations recently
determined from Galactic and Magellanic Clouds Cepheids. For the Galactic case,
synthetic P-L relations from model sets with (Y = 0.26, Z = 0.01), (Y = 0.26, Z
= 0.02) and (Y = 0.28, Z = 0.02) agree with the empirical Galactic P-L
relations derived from the Hubble Space Telescope parallaxes. For Magellanic
Cloud Cepheids, the synthetic P-L relations from model sets with (Y = 0.25, Z =
0.008) agree with both of the empirical Large Magellanic Cloud (LMC) and Small
Magellanic Cloud (SMC) P-L relations. Analysis of the synthetic P-L relations
from all model sets suggested that the IRAC band P-L relations may not be
independent of metallicity, as the P-L slopes and intercepts could be affected
by the metallicity and/or helium abundance. We also derive the synthetic period
color(P-C) relations in the IRAC bands. Non-vanishing synthetic P-C relations
were found for certain combinations of IRAC band filters and metallicity.
However, the synthetic P-C relations disagreed with the [3.6]-[8.0] P-C
relation recently found for the Galactic Cepheids. The synthetic [3.6]-[4.5]
P-C slope from (Y = 0.25, Z = 0.008) model set, on the other hand, is in
excellent agreement to the empirical LMC P-C counterpart, if a period range of
1.0 < log(P) < 1.8 is adopted.
View original:
http://arxiv.org/abs/1111.1791
No comments:
Post a Comment