The Blazhko modulation of RRab The Blazhko modulation of RRab starsstars

Recent resultsRecent results

Johanna JurcsikJohanna Jurcsik Konkoly Observatory Konkoly Observatory

JENAM 2008, VIENNA, AustriaAsteroseismology and Stellar Evolution

Full access to an automatized 60cm Full access to an automatized 60cm telescopetelescope

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 Astrophysical importance of RR Lyrae starsstars

Observations can be accurately modelled

Theoretical calibrating objects ofStellar pulsationStellar evolution

Indicators of Universal distance scale Chemical composition distribution

The physics of radial mode stellar pulsation is well knownTheir 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 (2003-2008)The Konkoly Blazhko Survey (2003-2008)

Aims: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 Modulation frequencies in the Fourier

spectrumspectrum Previously found:

symmetric or asymmetric equidistant triplets at the pulsation frequency components

The fm moduation frequency was not undaubtedly detected

triplet kf0 ± fmquintuplet kf0 ± 2fmseptuplet kf0 ± 4fm kf0 ± 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 2f0

The colour behaviour (AB/AV, AV/AI) of fm is discrepantfrom 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 Detection of small-amplitude modulationsmodulations

BR Tau Pmod=19.3d RR Gem Pmod=7.2 d

DM Cyg Pmod=10.6d SS Cnc Pmod=5.3 d

StatisticsStatistics ~50% (14/30) of RRab 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, 15-30% was detected in previous surveys (MACHO, OGLE)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 Temporal occurrence and significant changes in the significant changes in the

modulationmodulationRY Com 2007 2008

RR Gem

1935-36 1938-53 1958-59 1965-83 2004-05 Amplitude of

phasemodulation

amplitude modulation

Is Blazhko modulation a Is Blazhko modulation a common property of RRab common property of RRab

stars ?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 pulsationof MW Lyr in 20 phases of the modulation

V – (B-V)

V – (V-IC)

(B-V) – (V-IC)

MW Lyrae

2006 2007

Complex phase and amplitude modulations

MW Lyrae

Phase modulation = pulsation period changes

With a simple transformation according to the phase of f0 the modulation become pure amplitude modulation

Changes in theobserved derived

mean quantities of MW Lyr

(B-V

)

(

V-I

)

<

B-V

>

<

V-I

>

<

B>

-<V

>

<V

>-<

I> (

V)

<V

> P

er p

uls

A

mp

pu

ls

derived

Pulsation phase

<T

eff>

<

L/L

Su

n>

<V

m>

<V

i> <

log

ge

ff>

<R

/RS

un>

R

/Rs

un

Vra

d

L

/Ls

un

Te

ff

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 fm 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 varyduring 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 :• 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 Is light-curve modulation a common property of RRab stars?stars? 2008, ApJ, submitted• 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 An extensive photometric study of the Blazhko RR Lyrae star MW Lyr: II. Changes in the physical parameters,study of the Blazhko RR Lyrae star MW Lyr: II. Changes in the physical parameters, 2008, MNRAS, submitted• 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 An extensive photometric study of the Blazhko RR Lyrae star MW Lyr: I. Light curve solution,Blazhko RR Lyrae star MW Lyr: I. Light curve solution, 2008, MNRAS, in press• Sódor, Á., Jurcsik, J., Szeidl, B.: A new method for determining physical parameters of A new method for determining physical parameters of fundamental mode RR~Lyrae stars from multicolour light curvesfundamental mode RR~Lyrae stars from multicolour light curves 2008, MNRAS, submitted• Hurta, Zs., Jurcsik, J., Szeidl, B., Sódor, Á.: First Quintuplet Frequency Solution of a First Quintuplet Frequency Solution of a Blazhko Variable: Light Curve Analysis of RV Uma,Blazhko Variable: Light Curve Analysis of RV Uma, 2008, AJ, 135, 957• Hurta, Zs.: The Blazhko behavior of RV Uma,The Blazhko behavior of RV Uma, 2007, AN, 328, 841•Sódor, Á., Szeidl, B., Jurcsik, J.: The Blazhko behaviour of RR Geminorum II. Long-term The Blazhko behaviour of RR Geminorum II. Long-term photometric results,photometric results, 2007, A&A, 469, 1033• 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 CncThe shortest modulation period Blazhko RR Lyrae star: SS Cnc 2006, AJ, 132, 61• 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, The Blazhko behaviour of RR Geminorum I, CCD photometric results in 2004,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 starsMulticolour light curves of RRab stars, 2005-2008, IBVS No 5709, 5793, 5844, 5846