The Blazhko modulation of RRab stars Recent results Johanna Jurcsik Konkoly Observatory JENAM 2008, VIENNA, Austria Asteroseismology and Stellar Evolution

Full access to an automatized 60cm telescope 90% of the telescope time is dedicated to observations of RR Lyrae stars 5 years ~700 nights of observations ~4000 hours Konkoly Observatory, Svábhegy, Budapest

Astrophysical importance of RR Lyrae stars Observations can be accurately modelled Theoretical calibrating objects of Stellar pulsation Stellar evolution Indicators of Universal distance scale Chemical composition distribution The physics of radial mode stellar pulsation is well known Their evolutionary state is well known

The Blazhko effect Its reason is still unknown! The residual light curve after the removal of the mean pulsation light curve has large amplitude at around maximum/minimum light Its amplitude can be commensurable with the amplitude of the pulsation

The Konkoly Blazhko Survey ( ) Aims: To define the true incidence rate of the modulation To obtain extended, accurate, multicolour light curves of modulated and unmodulated RRab stars

Modulation frequencies in the Fourier spectrum Previously found: symmetric or asymmetric equidistant triplets at the pulsation frequency components The f m moduation frequency was not undaubtedly detected triplet kf 0 ± fm quintuplet kf 0 ± 2fm septuplet kf 0 ± 4fm kf 0 ± 12.5fm The modulation frequency appears in the spectra of all the Blazhko stars with extended obervations spectrum of MW Lyr in the vicinity of 2f 0 The colour behaviour (A B /A V, A V /A I ) of f m is discrepant from the colour behaviour of the pulsation and modulation side frequencies The real frequency of the modulation is most probably the modulation frequency and not any of the side lobe frequencies !

Detection of small-amplitude modulations Detection of small-amplitude modulations BR Tau Pmod=19.3d RR Gem Pmod=7.2 d DM Cyg Pmod=10.6d SS Cnc Pmod=5.3 d

Statistics ~50% (14/30) of RR ab stars show the Blazhko effect The selection of targets was to observe stars with no previous accurate light curves 15-30% was detected in previous surveys (MACHO, OGLE) 15-30% was detected in previous surveys (MACHO, OGLE) The modulation has SMALL amplitude in half of the Blazhko stars Small-amplitude modulations were not detected in any of the previous surveys Histograms of the amplitude distributions of the highest modulation frequency components

Temporal occurrence and significant changes in the modulation RY Com RR Gem Amplitude of phase modulation amplitude modulation

Is Blazhko modulation a common property of RRab stars ? -- mmag amplitude of the modulation is also possible -- the modulation may occur temporarily

We obtained extended multicolour light curves of large modulation Blazhko stars for the first time The light curves cover the whole pulsation light curve in different phases of the modulation

colour-magnitude and two-colour loops of the pulsation of MW Lyr in 20 phases of the modulation V – (B-V) V – (V-I C ) (B-V) – (V-I C )

MW Lyrae Complex phase and amplitude modulations

MW Lyrae Phase modulation = pulsation period changes With a simple transformation according to the phase of f 0 the modulation become pure amplitude modulation

Changes in the observed derived mean quantities of MW Lyr (B-V) (V-I) - - (V) Per puls Amp puls derived Pulsation phase R/R sun V rad L/L sun T eff

Previously known Recent results of the Konkoly Survey Only large amplitude modulations were known Discovery of small amplitude modulations Modulation appears in the spectrum as doublets/triplets, the modulation frequency was not definitely identified Quintuplets, septuplets and f m identified in the spectra The occurrence rate of the modulation was estimated 15-30% The detected incidence rate is ~50% The global mean physical parameters of the star do vary during the Blazhko cycle based on our colour observations No observations covering the whole pulsation in different phases of the modulation were previously obtained

References of the Konkoly Blazhko Survey : Is light-curve modulation a common property of RRab stars? Jurcsik, J., Sódor, Á., Szeidl, B., Váradi, M., Hurta, Zs., Posztobányi, K., Vida, K., Dékány, I., Hajdu, G., Kővári, Zs., Nagy, I.: Is light-curve modulation a common property of RRab stars? 2008, ApJ, submitted An extensive photometric study of the Blazhko RR Lyrae star MW Lyr: II. Changes in the physical parameters, Jurcsik, J., Sódor, Á., Szeidl, B., Kolláth, Z., Smith, H. A., Hurta, Zs., Váradi, M., Henden, A., Dékány, I., Nagy, I., Posztobányi, K., Szing, A., Vida, K., Vityi, N.: An extensive photometric study of the Blazhko RR Lyrae star MW Lyr: II. Changes in the physical parameters, 2008, MNRAS, submitted An extensive photometric study of the Blazhko RR Lyrae star MW Lyr: I. Light curve solution, Jurcsik, J., Sódor, Á., Hurta, Zs., Váradi, M., Szeidl, B., Smith, H. A., Henden, A., Dékány, I., Nagy, I., Posztobányi, K., Szing, A., Vida, K., Vityi, N.: An extensive photometric study of the Blazhko RR Lyrae star MW Lyr: I. Light curve solution, 2008, MNRAS, in press A new method for determining physical parameters of fundamental mode RR~Lyrae stars from multicolour light curves Sódor, Á., Jurcsik, J., Szeidl, B.: A new method for determining physical parameters of fundamental mode RR~Lyrae stars from multicolour light curves 2008, MNRAS, submitted First Quintuplet Frequency Solution of a Blazhko Variable: Light Curve Analysis of RV Uma, Hurta, Zs., Jurcsik, J., Szeidl, B., Sódor, Á.: First Quintuplet Frequency Solution of a Blazhko Variable: Light Curve Analysis of RV Uma, 2008, AJ, 135, 957 The Blazhko behavior of RV Uma, Hurta, Zs.: The Blazhko behavior of RV Uma, 2007, AN, 328, 841 The Blazhko behaviour of RR Geminorum II. Long-term photometric results,Sódor, Á., Szeidl, B., Jurcsik, J.: The Blazhko behaviour of RR Geminorum II. Long-term photometric results, 2007, A&A, 469, 1033 The shortest modulation period Blazhko RR Lyrae star: SS Cnc J. Jurcsik, B. Szeidl, Á. Sódor, I. Dékány, Zs. Hurta, K. Posztobányi, K. Vida, M. Váradi, and A. Szing: The shortest modulation period Blazhko RR Lyrae star: SS Cnc 2006, AJ, 132, 61 The Blazhko behaviour of RR Geminorum I, CCD photometric results in 2004, J. Jurcsik, Á. Sódor, M. Váradi, B. Szeidl, A. Washüettl, M. Weber, I. Dékány, Zs. Hurta, B. Lakatos, K. Posztobányi, A. Szing, and K. Vida: The Blazhko behaviour of RR Geminorum I, CCD photometric results in 2004, 2005, A&A, 430, 1049 Jurcsik, J., Sódor, Á., Szeidl, B., Váradi, M., Hurta, Zs., Posztobányi, K., Vida, K., Dékány, I., Hajdu, G., Kővári, Zs., Nagy, I., Koponyás, B., Vityi, N., Szing, A., Kun,.E.: Multicolour light curves of RRab stars Multicolour light curves of RRab stars, , IBVS No 5709, 5793, 5844, 5846