Multicolour photometry of Balloon 090100001: linking the two classes of pulsating hot subdwarfs

Baran, A.; Pigulski, A.; Kozieł, D.; Ogłoza, W.; Silvotti, R.; Zoła, S.

doi:10.1111/j.1365-2966.2005.09066.x

Cited by 55 publications

(54 citation statements)

References 44 publications

(66 reference statements)

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“…Interestingly, two members of the class of SPsdBVs with pulsations in the range 340−380 s have now been found to also show g-mode pulsations: HS 0702+6043 (Schuh et al 2005(Schuh et al , 2006 and Balloon 090100001 (Oreiro et al 2005;Baran et al 2005).…”

Section: Introductionmentioning

confidence: 99%

Time-resolved spectroscopy of the bright sdBV Balloon 090100001

Telting

Østensen

2006

A&A

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We have obtained 2552 useful low-resolution spectra of the bright sdBV Balloon 090100001, which form the first large time-resolved spectroscopic dataset of this brightest known pulsating subdwarf B star. The data were obtained at the Nordic Optical Telescope during 7 nights in August/September 2004 over a total time base of 38 nights, aiming to derive pulsational characteristics of this star. In this paper we present the observations and the results obtained from frequency analyses. In our data we find clear evidence for 8 independent frequencies, that were all previously reported in photometric monitoring studies, allowing future asteroseismological studies of this star to be constrained by combined photometric and spectroscopic observations of as much as 8 pulsation modes. We do not find conclusive evidence for new frequencies. We present the first determination of the pulsational radial-velocity amplitudes of this star, and find that the radial-velocity amplitude of the main pulsation mode ( f 1 = 2.80749 mHz) in Balloon 090100001 is 18.9 km s −1 , which is the largest radial-velocity amplitude found in sdB-star pulsations so far. For all spectra, the radial velocities are published electronically.

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Section: Introductionmentioning

confidence: 99%

Time-resolved spectroscopy of the bright sdBV Balloon 090100001

Telting

Østensen

2006

A&A

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“…Especially interesting are the sdB pulsators that exhibit both p-and g-mode pulsations. Three of these so-called hybrid pulsators have been found at the intersection of the V361 Hya and V1093 Her stars (Oreiro et al 2005;Baran et al 2005;Schuh et al 2006;Lutz et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Impact of helium diffusion and helium-flash-induced carbon production on gravity-mode pulsations in subdwarf B stars

Nelemans²,

Aerts

et al. 2009

A&A

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Context. Realistic stellar models are essential to the forward modelling approach in asteroseismology. For practicality however, certain model assumptions are also required. For example, in the case of subdwarf B stars, one usually starts with zero-age horizontal branch structures without following the progenitor evolution. Aims. We analyse the effects of common assumptions in subdwarf B models on the g-mode pulsational properties. We investigate if and how the pulsation periods are affected by the H-profile in the core-envelope transition zone. Furthermore, the effects of Cproduction and convective mixing during the core helium flash are evaluated. Finally, we reanalyse the effects of stellar opacities on the mode excitation in subdwarf B stars. Methods. We computed detailed stellar evolutionary models of subdwarf B stars, and their non-adiabatic pulsational properties. Atomic diffusion of H and He is included consistently during the evolution calculations. The number fractions of Fe and Ni are gradually increased by up to a factor of 10 around log T = 5.3. This is necessary for mode excitation and to approximate the resulting effects of radiative levitation. We performed a pulsational stability analysis on a grid of subdwarf B models constructed with OPAL and OP opacities. Results. We find that helium settling causes a shift in the theoretical blue edge of the g-mode instability domain to higher effective temperatures. This results in a closer match to the observed instability strip of long-period sdB pulsators, particularly for l ≤ 3 modes. We show further that the g-mode spectrum is extremely sensitive to the H-profile in the core-envelope transition zone. If atomic diffusion is efficient, details of the initial shape of the profile become less important in the course of evolution. Diffusion broadens the chemical gradients, and results in less effective mode trapping and different pulsation periods. Furthermore, we report on the possible consequences of the He-flash for the g-modes. The outer edge of a flash-induced convective region introduces an additional chemical transition in the stellar models, and the corresponding spike in the Brünt-Väisälä frequency produces a complicated mode trapping signature in the period spacings.

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“…Its preliminary Q 2.3 data from the Kepler exploratory phase was initially analysed by Østensen et al (2010) and Reed et al (2010), while Van Grootel et al (2010) derived KIC 5807616's stellar parameters from spectroscopic observations. The star pulsates in both gravity (g-) and pressure (p-) modes, therefore it is a hybrid sdBV (Schuh et al 2005;Baran et al 2005). Its 27 730 ± 270 K effective temperature, log g = 5.52 ± 0.03 surface gravity, and 0.496 ± 0.002 M mass (Van Grootel et al 2010) are typical of this class of objects.…”

Section: Introductionmentioning

confidence: 99%

Planetary candidates around the pulsating sdB star KIC 5807616 considered doubtful

Krzesiński

2015

A&A

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Context. It has been suggested that two weak signals observed in the low frequency region of the Fourier transform amplitude spectra from the KIC 5807616 Q5-Q8 data can be interpreted as a result of the light reflection from planets orbiting the host star. Ever since the last results on KIC 5807616 were presented, the Kepler spacecraft has collected over two years of additional data, which we analysed using asteroseismological methods. Aims. To verify and improve on previous results, we used the Q 5-Q 17 Kepler data to identify pulsational modes, determine multiplet splitting, and to re-analyse the low frequency region between 33−49 μHz where two frequencies, claimed as the planetary signature, were found. Methods. Since Fourier transform amplitude spectra of the KIC 5807616 data do not show any clear multiplets, we used two stable acoustic modes to determine the theoretical width of gravity mode multiplets and their splittings. The period spacing and histograms of common multiplet component separations were used to identify pulsation modes and the observed gravity mode splittings. In the low frequency region, we analysed the amplitude variations of two planetary signature frequencies over the whole observing run. Results. We determined the rotational period of the star from the splittings. Analysis of the low frequency region shows that the amplitude and frequency change of the signals found there have similar characteristics to other gravity modes. Conclusions. New data allow for identifying gravity modes in a limited period range, as well as better rotational period estimations. We suggest that the so-called planetary signature frequencies found in previous work might instead be pulsation modes visible beyond the cut-off frequency of the star.

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Multicolour photometry of Balloon 090100001: linking the two classes of pulsating hot subdwarfs

Cited by 55 publications

References 44 publications

Time-resolved spectroscopy of the bright sdBV Balloon 090100001

Time-resolved spectroscopy of the bright sdBV Balloon 090100001

Impact of helium diffusion and helium-flash-induced carbon production on gravity-mode pulsations in subdwarf B stars

Planetary candidates around the pulsating sdB star KIC 5807616 considered doubtful

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