Theoretical Modes Fitting on Miras Light Curves

Barthès, D.; Tuchman, Y.; Mennessier, M. O.; Mattei, J. A.

doi:10.1007/978-94-011-1062-4_15

Cited by 14 publications

(20 citation statements)

References 1 publication

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“…The humps seen in the CoRoT lightcurves may, therefore, well be related to surface variations, although we note that other explanations exist as well (see e.g. Barthes et al 1998, who discuss the possibility of a low-order, two-mode resonance in the pulsation of LPVs).…”

Section: Discussionmentioning

confidence: 72%

Long-period variables in the CoRoT fields

Lebzelter

2011

A&A

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Aims. We searched the first set of data released by the CoRoT mission for red stars showing long-period variability (LPV). These stars are likely highly evolved stars on the upper giant branch. The high time resolution of the CoRoT data allows us to study the light curves of these variables in unprecedented detail. Methods. Light curves of the reddest stars were extracted from the CoRoT public archive. The search for LPV was done by visual inspection. Instrumental artefacts were removed, and the final light curves were inspected for signs of variability on time scales of hours to a few days. Such abrupt and irregular light curve changes have been reported in the literature to occur in these stars, but their origin is not yet understood. Results. We detected 52 LPV candidates in four CoRoT fields, most of them previously unknown. No signs of any short-time light changes on time scales between 20 min and a few days and an amplitude exceeding a few mmag could be detected. We conclude that if these short-time variations are physical reality, they must be quite rare events, and we derive a 95% confidence upper limit of 0.15 events per star per year. Any deviations from a perfectly smooth long-time variation are occurring on time scales longer than approximately 10 days.

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Section: Discussionmentioning

confidence: 72%

Long-period variables in the CoRoT fields

Lebzelter

2011

A&A

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“…But it is also clear that only a fraction of all miras show this behaviour. The humps may be analogs of the humps seen on bump Cepheid light curves and likely result from a 2-to-1 resonance between the fundamental and the first overtone mode (Barthes et al 1998, Wood et al 1999, Lebzelter et al 2005. A few miras have been reported to show even double maxima in their light curve (e.g.…”

Section: Introductionmentioning

confidence: 88%

The shapes of light curves of Mira‐type variables

Lebzelter

2011

Astron Nachr

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Using a sample of 454 mira light curves from the ASAS survey we study the shape of the light variations in this kind of variable stars. Opposite to earlier studies, we choose a general approach to identify any deviation from a sinusoidal light change. We find that about 30% of the studied light curves show a significant deviation from the sinusoidal reference shape. Among these stars two characteristic light curve shapes of comparable frequency could be identified. Some hint for a connection between atmospheric chemistry and light curve shape was found, but beside that no or only very weak relations between light curve shape and other stellar parameters seem to exist.

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“…Even for a strictly harmonic excitation, the shell does not necessarily mimic the stellar pulsation, but instead exhibits its own normal modes (cf. Barthés & Tuchman 1994). Superimposed upon the excitation period that is in the range of approximately (10 2 −10 3 ) d (Whitelock et al 1991), the envelope typically shows oscillations with periods of up to a few 10 4 d. This could explain, at least in part, the observed cycle-to-cycle variation in the periods of some Miras (Eddington & Plakidis 1929).…”

Section: Introductionmentioning

confidence: 91%

Circumstellar dust shells around long-period variables

Dreyer¹,

Hegmann²,

Sedlmayr³

2010

A&A

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Context. Long-period variables (LPVs) and Miras exhibit a pronounced variability in their luminosity with a more or less well-defined period, and they suffer large mass loss in the form of stellar winds. Owing to this extensive mass loss, they are surrounded by extended circumstellar dust shells (CDSs). The dynamics of these envelopes is the result of a complex interplay via an external excitation by the pulsating central star, dust formation, and radiative transfer. Aims. Our study is aimed at an understanding of the dynamics of CDSs around carbon-rich, standard luminous LPVs and Miras. These shells often show multiperiodicity with secondary periods as high as a few 10 4 d superimposed on a main period that is in the range of approximately 10 2 −10 3 d. Such secondary periods may be caused at least in part by the presence of dust. Methods. We consider an excitation of the CDSs either by a harmonic force, provided by the oscillation of the central star, or by a stochastic force with a continuous power spectrum. The resulting numerically computed dynamical behaviour of the shell is analysed with the help of Fourier analysis and stroboscopic maps. Results. CDSs may be described as multioscillatory systems that are driven by the pulsating stars. A set of normal modes can be identified. The obtained periods of these modes are some 10 3 d, which is a characteristic timescale for dust nucleation, growth, and elemental enrichment in the dust formation zone. Depending on the oscillation period and strength of the central star, the envelope reacts periodically, multi-periodically, or irregularly.

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Theoretical Modes Fitting on Miras Light Curves

Cited by 14 publications

References 1 publication

Long-period variables in the CoRoT fields

Long-period variables in the CoRoT fields

The shapes of light curves of Mira‐type variables

Circumstellar dust shells around long-period variables

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