Potential of regular spacings for mode identification:

case of a CoRoT Scuti star

Margit PaparóZs. Bognár, J.M. Benkő, D. Gandolfi, A. Moya, J.C. Suárez, Á. Sódor, M. Hareter, E. Poretti, M. Auvergne, A. Baglin, W.W. Weiss and E.W.

Guenther

CoRoT Week 1119 – 22 March, 2013, Tenerife, Spain

Konkoly Observatory, MTA CSFK, Budapest, Hungary

Mode identification

• Cornerstone of asteroseismology• Asymptotic regime: patterns exist (solar type oscillation

and white dwarfs Scuti stars: outside of the asymptotic regime, no exact

patterns are expected• Mode selection mechanism – few observed, more

theoretically predicted modes• Ways of identification: multi-colour photometry and

spectroscopy• Space data: many targets, limited amount of observing

time for additional data• Hope: some kind of regularity exists due to the long,

continuous and high precision measurements

How to pick a CoRoT Scuti star up for investigation

• Hungarian Asteroseimological Group (HAG) joined the CoRoT preparatory work via the ESA PECS project with multi-colour photometry (http://www.konkoly.hu/HAG/)

• Different kind of pulsating stars were observed: RR Lyrae, Scuti, Doradus and Cephei stars

• Photomeric characterisation of targets and discovery of new variables on the exo-field were our main activity

• The most promising variable candidate was 21st on the field around HD 292192 (http://www.konkoly.hu/HAG/research/sel21.html)

• Official CoRoT ID became 102749568 (Konkoly 21 is kept as nickname)

Observations of CoRoT 102749568discovered at Konkoly Observatory in 2005 by József Benkő

CoRoT: LRa01

24 Oct. – 3 March, 2008

CoRoT team

Photometry

Multi-colour follow-up at Konkoly Observatory11 nights at 2010/2011 and 2011/2012 winter season

Observer: Zsófia Bognár

Spectroscopy

AAOmega multi-object spectrograph at 3.9 m telescope of Australian Astr. Obs. at 2009

Davide Gandolfi and E. W. Guenther

Mercator+HERMES

in 2013, observer: Ádám Sódor

contributor: Markus Hareter

Fourier analyses of CoRoT data

52 independent modes were found above the S/N=4 significance level

(Linear combination modes were omitted)

Fits are given with 3 and 67 frequencies. The pulsational energy is concentrated in a few modes

We perfomed a standard Fourier analysis in white light

Frequency spacing of 52 independent modes

- More than one radial period ratio were found in the early analyses

- A sequence of consecutive radial orders separated by the large separation were expected

- We got very clean spacing diagram with some dominant peaks

- The values were used to prepare the echelle diagrams

2.2 2.7 (31.48Hz)

0.84

0.66

0.2

Echelle diagrams – I. Can we use them in the non-asymptotic regime?

Folded by 0.2 c/d (2.35Hz)

Folded by 0.66 c/d (7.64 mHz)

Folded by 0.84 c/d (9.8 Hz)

- Blue circles are mostly the highest amplitude modes- Red points represent the lowest amplitude modes of the 52 independent modes

No obvious, clear patterns exist

Echelle diagram – II. Can we use it for getting the large separation in the non-asymptotic regime?

Folded by 2.20 c/d (25.46Hz)

Folded by 2.72 c/d (31.48Hz)

No clear patterns exist for the low amplitude modes (red points). A few points are arranged along curved lines in both panels.

The blue circles are distributed along three inclined „straight” lines in both panels. The inclinations are different for the different value of the possible large separations.

Is there a different way to get more information about the modes (both l and n

values)?

A paper titled:CoRoT 1027495568: mode identification of a Scuti

star based on regular spacings with the same co-authors as this presentation will be

submitted to A&A in a few weeks

- We constructed a different diagram to use all the regular spacings of the highest amplitude modes

- Regularity helped the interpretation of the spacings up to the identification of modes

- We used spectroscopy, multi-colour photometry and modelling for confirmation

Conclusion on spacings

• Although we are out of the asymptotic regime, quasi-equidistancies can be found among the frequencies of space data.

• The potential of the mode identification based only on the frequency regularities is highly valuable.

• We have started a systematic search for spacings in Scuti, Dor and hybrid stars observed by CoRoT.

Period ratios – new observablethat space missions can serve for many

stars• Period ratios are the most precise values derived from the

frequencies• Thousands of different kind of pulsating stars have list of

increased number of frequencies thanks to the space missions• We may start a new way of investigation using the period

ratios if the theoretical calibration is going to be solved• The period ratios of CoRoT 102749568 were used for

independent mode identification in the paper: Frequency regularities in d Scuti stars M. Paparó and J.M. Benkő in ASP Conf. Ser., The 61B Fujihara Seminar: Progress in

Physics of Sun and Stars, A New Era in Helio- and Asteroseismology, ed. H. Shibahashi & A.E. Lynas-Gray (ASP, San Fransisco), in press

copy request: paparo@konkoly.hu

Behaviour of the near radial period ratio region

Near radial period ratio of 102749568. Closely spaced period ratios create vertical lines due to grouping of frequencies

Systematic search for 22 Scuti stars.

a. Cep, b. KIC 9700322, c. HD 50844, d. KIC 4840675 (fast rotator)

Vertical lines generally appears

Mode identification based only on period ratios

Whole range of the period ratios for 102749568 and selected segments for mode identification. The missing frequencies exclude the quantum numbers used for the segments.

Comparison of the distribution of period ratios for 102749568 and some randomly generated frequency sets (KS test proves the difference).

Identification: 3-3-3-2 modes with 100-83-75-60 %. The real identification was excluded only in one case. Theoretical calibration is needed for a general use of peiod ratio

Thank you