P. de Ponthière, M. Bonnardeau, F-J. Hambsch, T. … · P. de Ponthière, M. Bonnardeau, ... RR Lyrae with Blazhko effect behave differently ... Pierre Created Date:

P. de Ponthière, M. Bonnardeau, F-J. Hambsch, T. Krajci ,

K. Menzies, R. Sabo

RACA 2014 – RCANES 2014

AAVSO Fall Meeting 2013 - Woburn

RR Lyrae (RRab) in a nutshell

Pulsating stars Periods: 0.3 to 0.8 days

Mass 0.7 M☼

Diameter 4 to 6 D☼

At brightness minimum

Lower temperature

Redder

Radius shrinks

At brightness maximum

Higher temperature

Bluer

Radius expands (15%)

Blazhko effect

Folded light curve

Two periods

○ Pulsation period 0.3 to 0.8 days

○ Blazhko period 10 to 1000 days

Blazhko effect = Amplitude and Phase

modulations

Blazhko effect

RR Lyrae (RRab)

Some with multiple Blazhko modulations

○ Three periods

Pulsation

Blazhko 1

Blazhko 2

Blazhko modulations are in resonance or not

Blazhko effect: frequently irregular

The successive cycles are not identical

KV Cnc observation challenges

Pulsation period 0.50208 day (12hr + 3min)

Maxima delayed by 6 min / day

Observation time windows for a particular site

Multi-longitude campaign

Belgium

France

Framingham MA

Cloudcroft NM (AAVSONet W28)

Bozeman MT

T = Tr + P * n

Observation time windows

Local horizons (trees) not used in this graph except for Belgium

KV Cnc observation campaign

Two observation seasons

January 2012 to May 2012

October 2012 to May 2013

158 observation nights

Total time span 480 days

32 280 light curve data points (differential photometry)

92 pulsation maxima recorded

(O-C)

Magnitude at maximum

Tc = Tr + P * n

O – C = To - Tc

(O-C) and Magnitude at Maximum

Maxima analysis

Linear regression of the (O-C) values

Pulsation period of 0.50208 day

Folded light curve

(O-C) and Mmax

folded with Blazhko period

Spectral analysis Period04 : (O-C) and Mmax

Main Blazhko period 77.6 d

Secondary Blazhko period 40.5 d

Folded light curves for different

Blazhko phases 11.5

12

12.5

13

13.5

0 0.5 1 1.5 2

0.0 - 0.1

11.5

12

12.5

13

13.5

0 0.5 1 1.5 2

0.3 - 0.4

11.5

12.0

12.5

13.0

13.5

0 0.5 1 1.5 2

0.5 - 0.6

11.5

12

12.5

13

13.5

0 0.5 1 1.5 2

0.7 - 0.8

Astonishing slope in ascending

branch : 2.5 mag / hour

Blazhko effect – similar to

AM radio communication 2 sin P sin M = cos(P-M) – cos(P+M)

Temporal space

sin P sin M

P = pulsation

M = Blazhko modulation

Frequency or spectral space

cos(P-M) – cos(P+M)

measured with Fourier tools

(Period04)

Blazhko effect – similar to

AM radio communication 2 sin P sin M = cos(P-M) – cos(P+M)

Fourier transformation

mathematical tool converting light

curve i.e. temporal data

to spectral data

Used software : Period04 available on Internet

Fp = Pulsation frequency

= 1 / 0.5 day

Fm = Blazhko frequency

= 1 / 77 days

Light curve spectral analysis

Triplets as ( n fo ± fx )

detected for fb and fb2

fo = 1.99169 d-1 (0.50209 d)

fb = 0.01285 d-1 (77.8 d)

fb2 = 0.02359 d-1 (42.4 d) Mag at maximum analysis

→ 40.5 d

42 d from Northern Sky Survey

P.Wils et al.

Why didn’t they detect fb??

fb2 statistically

not a harmonic of fb

Quintuplets as ( n fo ± 2 fb )

were not detected

Light curve spectral analysis

Triplets as ( n fo ± fx )

detected for fb and fb2

fo = 1.99169 d-1 (0.50209 d)

fb = 0.01285 d-1 (77.8 d)

fb2 = 0.02359 d-1 (42.4 d) Mag at maximum analysis

→ 40.5 d

42 d from Northern Sky Survey

P.Wils et al.

Why didn’t they detect fb??

fb2 statistically

not a harmonic of fb

Quintuplets as ( n fo ± 2 fb )

were not detected

Listening 2 RR Lyrae Blazhko stars

Create a synthetic light curve

(from Fourier components)

Convert it to an audio file

Compression 7 106

1 day 11 msec

Without Blazhko effect (AL Pic)

With Blazhko effect (AL Pic) 34 days

With Blazhko effect (KV Cnc) 77.6 days Song duration = 300 days

Conclusions

RRab Blazhko characterisation needs

Time series over long time span

Multi-longitude observations

RR Lyrae with Blazhko effect behave differently

Plenty of surprises

Not boring stars

Other RR Lyrae campaigns are running

Don’ t hesitate to join the group