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Changes in Mean Global Physical Parameters of Blazhko RR Lyrae stars derived from

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. The IP Method (IPM). Telescope.

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Changes in Mean Global Physical Parameters of Blazhko RR Lyrae stars derived from

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  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. The IP Method (IPM) Telescope The Inverse Photometric Baade–Wesselink Method(Sódor, Jurcsik & Szeidl, 2009, MNRAS, 394, 261) Input:– multicolour light curves [B(j), V(j), IC(j) or V(j), IC(j), where j 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:– Teff (j), Vp (j), R(j), L(j), (M), distance: d, reddening.

  3. How IPM works? Telescope Using a least squares fitting method IPM looks for those Teff (j) and Vp(j) curves [geff ( ∫Vp(j)dj, dVp(j)/dj, M, R0 ) and R( ∫Vp(j)dj, R0)], M, R0, d,and colour zero point values that, utilising synthetic magnitudes and colours of static atmosphere model grids, fit the input multicolour light curves the best.

  4. The initial Teff(j) and Vp(j) curves Telescope The non-linear fitting method needs appropriate initial curves. Teff(j): Teff – (V – IC) relation(Bessel et al., 1998, A&A, 333, 231, Table 8) Vp(j): Liu’s template Our Vrad – IC relation (1991, PASP, 103, 205) based on20 RRab’sVp and IC curves

  5. Test results Telescope 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.

  6. Test results Telescope Output radial velocity curves

  7. Test results Telescope Comparison with earlier Baade–Wesselink results andwith empirical relations black symbols – IPM resultsgrey symbols – earlier BW results empirical relations from Catelan et al. (2004, ApJS, 154, 633, Eq. 3) Sandage & Tammann (2006, ARA&A, 44, 93, Eq. 9)

  8. Applying IPM for Blazhko variables 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 phaseare 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 Teff(j, F), R(j, F), L(j, F) where F denotes Blazhko phase. 3. Averaging by pulsation phase, variations only with Blazhko phase remain: Teff(F), R(F), L(F).

  9. Results Telescope MW Lyr XY And DM Cyg RR Gem SS Cnc DA / <A> DP / <P> DR / <R> DL / <L> DT / <T> 1% 4% 1%

  10. Thank you!

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