1 AGB variables; Distance Indicators; Bolometric Magnitudes; Pulsation Modes. Michael Feast University of Cape Town and South African Astronomical Observatory

2 Topics 1. How good are Mira variables as distance indicators? 2. Problems in Bolometric Corrections and distances for C-Miras 3. Problems in determining pulsation modes and evolution for low amplitude AGB variables in the intermediate age cluster NGC419 (SMC)

3 Comparison of the Mira distance scale with other distance indicators including RR Lyrae variables. New HST trigonometrical parallaxes of 5 RR Lyrae variables gives RR Lyrae calibration to ±0.03 mag. Important also for absolute magnitudes of Miras

4 M K – Log P relations for LMC Miras Whitelock et al. (2008)

5 Zero Point Calibration for O-Miras M K = -3.51(Log P -2.38) + β β Trig. Parallaxes (Hipparcos) ± 0.10 OH Phase Lag VLBI OH ± 0.17 VLBI H 2 O (T Lep) -7.17± 0.28 Globular Clusters -7.34± 0.13 Adopted (Whitelock et al. 2008) ± 0.07

6 Distance Modulus of the LMC O-Miras (K) 18.49±0.07 RR Lyraes (K) 18.53±0.04 Cepheids (K&VI) 18.50±0.03 Eclipsers (OB) ~18.4 Eclipser (G) 18.50± (0.06) SN Ring 18.55± (0.05) Clump 18.47±0.02 δ Sct 18.48±0.1

7 Distance to the Galactic Centre (kpc) O-Miras (JHK) 8.39±0.54 Central orbits 8.28±0.33 Cepheids (JHK) 7.9±0.2 RR Lyraes (K) 8.32±0.62 Sgr B2 7.9±0.8 Clump 7.87±0.34 CephII (K) 7.63±0.21 Kinematics 7.6±0.5 RR Lyraes (V) with non-standard reddening law 9.3±(0.4)

8 Distance Modulus of NGC185 O-Miras (24 stars) (K) 24.16±0.08 (1) HB (V) 24.22±0.07 (2) RR Lyraes (V) 24.14±0.05 (3) (1) Lorenz et al. 2011, I amp ≥1.0mag, (2) Butler & Martinez-Delgado 2005 (3) Saha et al O-Mira Zero point Whitelock et al. (2008) HB and RR Lyrae zero-point (Benedict et al. 2011)

9 NGC 147 O-Miras (11 stars)(K) 24.32±0.09 HB(V) 24.49±(0.02) RR Lyraes(V) 24.18±0.10 Apparent Mags (V) HB (Butler et al.) RR Lyraes (Saha et al.)

10 Bolometric Correction for Carbon Stars (Whitelock et al. 2006)

11 M bol – Log P relation for LMC C-Miras Whitelock et al. (2006)

PL Relations for C-Miras in Local Group Fornax, LeoI, Phoenix, Sculptor, LeoII, WLM

13 Distance modulus of the Fornax Dwarf Spheroidal C-Miras (M bol ) RR Lyraes (clusters)(V) Clump (K) (20.75) Clump(I) δ Sct ([Fe/H] = –1.4) δ Sct ([Fe/H] = –1.0) 20.76

14 Distance Modulus of the LeoI Dwarf Spheroidal C-Miras (M bol ) 21.91±0.12 RR Lyraes ([Fe/H]=−1.82)(V) 22.09±0.14 ([Fe/H]=−1.4)(V) 22.00±0.14

15 Bolometric Correction for Carbon Stars (Whitelock et al. 2006)

16 Examples of Dust obscuration events Whitelock et al. (2006)

17 Reddening in Circumstellar shells ΔK/Δ(J−K) R For ~ 1.0 EV Eri ~1.0 DY Per ~ ~ ~1.4 and some suggestions of non-uniform absorption over surface. Apparent m bol from BC K – (J-K) falls in obscuration phases. e.g ΔK= 2.1, Δ(J-K)= 1.3, Δm bol = 0.90

18 Wood Sequences in the LMC (Ita et al. 2004)

19 NGC419 K – Log P Data from Kamath et al.

20 M bol – Log P for NGC419 (SMC) variables Kamath et al. (2010)

21 Distance Modulus of NGC419 (SMC) (LMC Mod = 18.50) Miras (2) (M bol ) 18.87±0.20 Oxygen SR (2 nd overtone)(K) 18.89± <0.01 Carbon SR (1 st overtone)(K) 18.81±0.05

22 Conclusions 1. Miras variables are robust distance indicators. However care must be taken with C-Miras with significant circumstellar shells, especially those of intermediate periods. 2. There is an apparent conflict between the interpretation of AGB variables in NGC419 depending on whether one uses K or m bol suggesting uncertainties in the derivation of the latter