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

Wood 2007

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