The P-L-relations on the AGB
Learning outcome
• Knowledge of the observed P-L-relations for AGB stars
• Knowledge of the interpretation of the various sequences
• Knowledge of the relation between P-L and other parameters
Why?
L ~ R²Teff4
~ 1/R³ (for M const)
L ~ 1/2/3
.constP
Period – Luminosity Relation
Miras
• Field stars• Observed logP-colour
relation (at 0.25)• Combine with colour-
luminosity relation
Mbol = +0.5 mag – 2.25 log PEggen (1975)
Miras
Robertson & Feast 1981
Miras - LMC
Wood et al. 1983
Miras - LMC
Feast et al. 1989
K = 19.7 mag – 3.57 log PMbol = 19.86 mag – 2.34 log P
PC- and PLC-relation
• Period-Colour-RelationO-rich: (J-K) = 0.56 log P – 0.12C-rich: (J-K) = 2.32 log P – 3.77
• Period-Luminosity-Colour-Relation (LMC)O-rich: K = -4.58 log P + 2(J-K) + 19.71C-rich: K = -2.88 log P -0.14(J-K) +18.22
Feast et al. 1989
Bedding & Zijlstra 1998
SRVs
Long period variables - LMC
Wood et al.1999
Long period variables - LMCIta et al. 2004OGLE/SIRIUS surveyJ-K: temp / chemistrytheta: lc regularity
F, G: Cepheids
LMC
SMC
Long period variables - LMCIta et al. 2004OGLE/SIRIUS survey
P-L and amplitudeI-
band
am
plitu
des
from
OG
LEK
iss
& B
eddi
ng 2
003
Sequence E
Soszynski et al. 2004
ellipsoidal/eclipting variables
confirmed from rv variations
Sequence DWood et al. 2004
Origin?
• binary• rotation of spotted star• non-radial pulsation• episodic dust formation
no satisfying solution yet
LPVs in Clusters
47 Tuc
Lebzelter & Wood2005
Linear/non-linear models
Wood 2007
LPVs in Clusters
NGC 1846 (LMC cluster)
Lebzelter & Wood2007
Lebzelter et al. 2005
P-L-relations in comparison
Glass & van Leeuwen 2007
Other P-L-studies
• Glass et al. 1995 (Galactic Bulge)• Groenewegen & Whitelock 1996 (Field)• Cioni et al. 2001 (LMC)• Noda et al. 2002 (LMC)• Lebzelter et al. 2002 (LMC)• Rejkuba et al. 2003 (Cen A)• Groenewegen 2004 (MCs)• Schultheis et al. 2004 (MCs, Bulge)• Fraser et al. 2005 (LMC)
Distance determinationUsing the relation by Feast et al. 1989 with Zero-Point = 1.0:
Object AGB dist. Other dist.
LMC 18.48m±0.1m 18.52m (Cep)
LMC - SMC 0.4m 0.44m (RGB-Tip)
Gal. Centre 8.5±0.7 kpc 8.5±0.5 kpc (Cep)
Cen A 28.0m±0.2m 27.9m±0.2m
(RGB-Tip)
Feast 2004