Rapidly oscillating M giant stars?

Koen, C.; Laney, D.

doi:10.1046/j.1365-8711.2000.03127.x

Cited by 47 publications

(60 citation statements)

References 27 publications

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“…As stated above, the results of Koen & Laney (2000) support the presence of rapid oscillations in M-giants derived from Hipparcos photometry. For the only star in common with us, RV Cam, we already showed that no comparable short period is present in our APT material.…”

Section: Rapid Oscillations?supporting

confidence: 80%

“…It even should easily allow the detection of rapid variations (<10 days!) proposed recently by Koen & Laney (2000) for some M-giants having Hipparcos photometry (see below). Table 1 gives an overview of the resulting time scales.…”

Section: Period Findingmentioning

confidence: 84%

“…Finally an additional 132 day period is needed to fit the data set to a still not fully satisfactory extent. Recently, Koen & Laney (2000) reported on the discovery of rapid oscillations in M-giants derived from Hipparcos photometry. For the only star in common with us, RV Cam, they find a very short periodicity of only 7.67 days, in addition to the 96.4 day variation from the Hipparcos catalogue.…”

Section: Rv Cammentioning

confidence: 99%

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Multi-colour light variation of AGB stars observed with ISO

Kerschbaum¹,

Lebzelter²,

Lázaro

2001

A&A

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Abstract. New visual light curves and infrared multi-epoch photometry are presented for a sample of AGBstars spectroscopically observed with ISO. While the ISO work is or will be presented elsewhere, the aim of this paper is to give an overview of the properties of the light change of the objects. This information is crucial for the interpretation of the valuable ISO material. Using the University of Vienna Twin Automatic Photoelectric Telescope (APT) we monitored the stars of our sample in the photometric bands V and IC. We present the light curve of each object and derive the parameters of the current light change, such as period(s) and amplitude. Furthermore we give V −IC colours and colour variations for these objects. Our results allow us to derive some general results on semiregular and irregular variables. Only in less than 50% of the cases could we confirm the GCVS period. Moreover, we did not find any pronounced difference between SRb and Lb variables in the regularity of the light curve. The existence of rapid oscillations indicated by Hipparcos data could not be confirmed. In addition to the visual light changes we present new near infrared photometry data. Although typically only few data points are available, they can be viewed relative to the better-monitored visual light curves providing information on possible phase shifts and differences in amplitude in different parts of the spectrum. Furthermore, multi-epoch photometry allows us to derive mean colours for these objects.

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Section: Rapid Oscillations?supporting

confidence: 80%

Section: Period Findingmentioning

confidence: 84%

Section: Rv Cammentioning

confidence: 99%

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Multi-colour light variation of AGB stars observed with ISO

Kerschbaum¹,

Lebzelter²,

Lázaro

2001

A&A

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“…While Φ for the 9 period fit is slightly higher, we have to compensate for the fact that we have added an extra period. Reduced χ 2 's and the Bayes information criterion (BIC, Koen & Laney 2000) both indicate that the two fits are equivalent in quality. Occam's razor favors the 9 period fit (no need for a magnetic field in that case).…”

Section: Asteroseismological Fitsmentioning

confidence: 99%

Preliminary Asteroseismology of EC20058-5234 and Limits on Plasmon Neutrinos

Bischoff-Kim¹

2009

cia

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We present results from a preliminary asteroseismological analysis of the hot DBV EC20058-5234 based on an extensive grid of models. EC20058 is the only known stable DBV and also the hottest and provides an ideal laboratory to constrain the emission rate of plasmon neutrinos. In a Whole Earth Telescope (WET) campaign in 1997, Sullivan et al. (2008) have found 11 independent modes. We use the results of their work to perform a 6 parameter fit of the observed period spectrum. We find a best fit model consistent with the spectroscopically determined effective temperature and surface gravity for EC20058. We find that the periods can be fit successfully without invoking an uneven split of the 281s mode due to a magnetic field. Based on our best fit model, we compute rates of change for the two stable modes observed in the star, which in turn can be used to place tight constraints on plasmon neutrino emission. Astrophysical ContextAbove a temperature of about 26000 K, more than half of the luminosity of an average white dwarf comes from neutrino emission (Figure 1). In that temperature range, the neutrinos are mainly produced by the decay of photons coupled to a plasma (plasmons). If we measure a neutrino luminosity in hot white dwarfs, we are measuring plasmon neutrino rates. One can use the change in the pulsation periods over time to measure the neutrino luminosity. As a white dwarf cools, the period of a given mode increases because the interior is becoming less and less compressible. The faster the cooling, the faster the period increases. Mestel theory (Mestel 1952) predictsṖ if the white dwarf is leaking energy exclusively through photons. A higherṖ than expected means

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“…The authors thank the anonymous referee for the constructive comments and recommendations on the manuscript. We thank Gerald Handler for providing the KUV 05134+2605 data obtained in 1988 , 1992, 2000 October, 2001, and during the Whole Earth Telescope campaign in 2000 (XCov20). The authors also acknowledge the contribution of L. Molnár, E. Plachy, H. Ollé and E. Verebélyi to the observations of KUV 05134+2605.…”

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confidence: 99%

Revealing the pulsational properties of the V777 Herculis star KUV 05134+2605 by its long-term monitoring

Bognár

Paparó

Córsico

et al. 2014

A&A

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Context. KUV 05134+2605 is one of the 21 pulsating DB white dwarfs (V777 Her or DBV variables) known so far. The detailed investigation of the short-period and low-amplitude pulsations of these relatively faint targets requires considerable observational efforts from the ground, long-term single-site or multi-site observations. The observed amplitudes of excited modes undergo short-term variations in many cases, which makes determining pulsation modes difficult. Aims. We aim to determine the pulsation frequencies of KUV 05134+2605, find regularities between the frequency and period components, and perform an asteroseismic investigation for the first time. Methods. We re-analysed the published data and collected new measurements. We compared the frequency content of the different datasets from the different epochs and performed various tests to check the reliability of the frequency determinations. The mean period spacings were investigated with linear fits to the observed periods, Kolmogorov-Smirnov and inverse variance significance tests, and with a Fourier analysis of different period sets, including a Monte Carlo test that simulated the effect of alias ambiguities. We employed fully evolutionary DB white dwarf models for the asteroseismic investigations. Results. We identified 22 frequencies between 1280 and 2530 μHz. These form 12 groups, which suggests at least 12 possible frequencies for the asteroseismic investigations. Thanks to the extended observations, KUV 05134+2605 joined the group of rich white dwarf pulsators. We identified one triplet and at least one doublet with a ≈9 μHz frequency separation, from which we derived a stellar rotation period of 0.6 d. We determined the mean period spacings of ≈31 s and 18 s for the modes we propose as dipole and quadrupole. We found an excellent agreement between the stellar mass derived from the = 1 period spacing and the period-to-period fits, all providing M * = 0.84−0.85 M solutions. Our study suggests that KUV 05134+2605 is the most massive amongst the known V777 Her stars.

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Rapidly oscillating M giant stars?

Cited by 47 publications

References 27 publications

Multi-colour light variation of AGB stars observed with ISO

Multi-colour light variation of AGB stars observed with ISO

Preliminary Asteroseismology of EC20058-5234 and Limits on Plasmon Neutrinos

Revealing the pulsational properties of the V777 Herculis star KUV 05134+2605 by its long-term monitoring

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