1. Changes in Mean Global Physical Parameters of Blazhko RR Lyrae stars derived from multicolour photometry Ádám Sódor Konkoly Observatory Stellar Pulsation Meeting, Santa Fe – June 2, 2009

2. Ádám Sódor ● Stellar Pulsation Meeting ● Santa Fe ● June 2, 2009 ● 2 / 9 2 Telescope The Inverse Photometric Baade–Wesselink Method (Sódor, Jurcsik & Szeidl, 2009, MNRAS, 394, 261) Input: –multicolour light curves [B(  ), V(  ), I C (  ) or V(  ), I C (  ), where  denotes pulsation phase], –metallicity, –static atmosphere model grids of synthetic colours. (Castelli & Kurucz, 2003, IAUS, 210, 20) Not needed: –spectroscopic radial velocity measurements, –magnitude and colour zero points. Output: –T eff (  ), V p (  ), R (  ), L (  ), (M), distance: d, reddening.

3. Ádám Sódor ● Stellar Pulsation Meeting ● Santa Fe ● June 2, 2009 ● 3 / 9 3 Telescope

4. Ádám Sódor ● Stellar Pulsation Meeting ● Santa Fe ● June 2, 2009 ● 4 / 9 4 The non-linear fitting method needs appropriate initial curves. T eff (  ):T eff – (V – I C ) relation (Bessel et al., 1998, A&A, 333, 231, Table 8) V p (  ): Liu’s templateOur V rad – I C relation (1991, PASP, 103, 205)based on 20 RRab’s V p and I C curves Telescope

5. Ádám Sódor ● Stellar Pulsation Meeting ● Santa Fe ● June 2, 2009 ● 5 / 9 5 The IPM was tested on 9 non-modulated RRab stars, each subjected spectroscopic Baade–Wesselink analyses previously. Errors are estimated from runs with different internal settings. For good quality light curves the IPM gives similarly accurate results to direct B–W analyses. Telescope

6. Ádám Sódor ● Stellar Pulsation Meeting ● Santa Fe ● June 2, 2009 ● 6 / 9 6 Telescope Output radial velocity curves

7. Ádám Sódor ● Stellar Pulsation Meeting ● Santa Fe ● June 2, 2009 ● 7 / 9 7 Telescope Comparison with earlier Baade–Wesselink results and with empirical relations empirical relations from Catelan et al. (2004, ApJS, 154, 633, Eq. 3) Sandage & Tammann (2006, ARA&A, 44, 93, Eq. 9) black symbols – IPM results grey symbols – earlier BW results

8. Ádám Sódor ● Stellar Pulsation Meeting ● Santa Fe ● June 2, 2009 ● 8 / 9 8 Telescope – There is no available simultaneous photometric and spectroscopic observations of any Blazhko star extended enough to cover both the Blazhko and pulsation cycles sufficiently. – Today the IP Method provides the only possibility to determine the variation of the physical parameters of Blazhko stars with modulation. 1.Parameters independent from Blazhko phase are determined first, from the mean light curve: M, d, colour zero points (reddening). 2.With these values fixed, IPM is run for each Blazhko phase. We obtain T eff (  ), R(  ), L(  ) where  denotes Blazhko phase. 3.Averaging by pulsation phase  variations only with Blazhko phase remain: T eff (  ), R(  ), L(  ).

9. Ádám Sódor ● Stellar Pulsation Meeting ● Santa Fe ● June 2, 2009 ● 9 / 9 9 Telescope MW Lyr XY And DM Cyg RR Gem SS Cnc  A /  P /  R /  L /  T /   

10. Thank you!