Asteroseismology of the <i>β</i> Cep star <i>ν</i> Eri: initial results

Handler, G.; Aerts, C.

doi:10.1017/s0252921100010654

Cited by 12 publications

(6 citation statements)

References 8 publications

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“…It would thus be the second example of a star exhibiting two different types of pulsation. The high‐order g‐modes of the first such star, HD 209295, are however believed to be triggered by tidal effects (Handler et al 2002). As we have no evidence for binarity of ν Eri, it may therefore be the first star in which two types of pulsation with time‐scales more than an order of magnitude different are intrinsically excited.…”

Section: Discussionmentioning

confidence: 99%

“…Experience with δ Scuti stars has shown that the more the detection level for periodic light variations is pushed down, the more pulsation modes are detected (e.g. see the sequence of papers by Handler et al 1996, 1997, 2000). In fact, most of the pulsation modes of these stars have light amplitudes around or below 1 mmag, an amplitude quite easily detected with the large data sets of 2–3 mmag precision differential photometry obtained during these campaigns.…”

Section: Introductionmentioning

confidence: 99%

“…We therefore organized a multisite campaign for ν Eri, applying both observing methods mentioned above (Handler & Aerts 2002). In the following, we report on the results from the photometric measurements.…”

Section: Introductionmentioning

confidence: 99%

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Asteroseismology of the Cephei star Eridani - I. Photometric observations and pulsational frequency analysis

Handler

Shobbrook

Jerzykiewicz

et al. 2004

Monthly Notices of the Royal Astronomical Society

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We undertook a multisite photometric campaign for the β Cephei star ν Eridani. More than 600 h of differential photoelectric uvyV photometry were obtained with 11 telescopes during 148 clear nights.The frequency analysis of our measurements shows that the variability of ν Eri can be decomposed into 23 sinusoidal components, eight of which correspond to independent pulsation frequencies between 5 and 8 cd −1 . Some of these are arranged in multiplets, which suggests rotational m-mode splitting of non-radial pulsation modes as the cause. If so, the rotation period of the star must be between 30 and 60 d.One of the signals in the light curves of ν Eri has a very low frequency of 0.432 cd −1 . It can be a high-order combination frequency or, more likely, an independent pulsation mode. In the latter case, ν Eri would be both a β Cephei star and a slowly pulsating B (SPB) star.The photometric amplitudes of the individual pulsation modes of ν Eri appear to have increased by about 20 per cent over the last 40 years. So have the amplitudes of the dominant combination frequencies of the star. Among the latter, we could only identify sum frequencies with certainty, not difference frequencies, which suggests that neither light-curve distortion in its simplest form nor resonant mode coupling is their single cause.One of our comparison stars, µ Eridani, turned out to be variable with a dominant time-scale of 1.62 d. We believe either that it is an SPB star just leaving its instability strip or that its variations are of rotational origin.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Asteroseismology of the Cephei star Eridani - I. Photometric observations and pulsational frequency analysis

Handler

Shobbrook

Jerzykiewicz

et al. 2004

Monthly Notices of the Royal Astronomical Society

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“…The research domain of asteroseismology has received a strong impetus since its successful application to the Sun (helioseismology), to several white dwarfs (for recent applications, see Vauclair et al 2002; Handler, Metcalfe & Wood 2002) and also to solar‐like stars (for a review, see Bedding & Kjeldsen 2003). So far, seismic studies have concentrated mainly on such stars because they have very rich frequency spectra consisting of short‐period oscillations.…”

Section: Introductionmentioning

confidence: 99%

“…The latter have been performed for many bright β Cephei stars (Aerts & De Cat 2003) but 16 (EN) Lac is one of the few multiperiodic objects for which both photometry and spectroscopy point towards the same mode identification for the detected non‐radial modes (Aerts et al 2003c). In an effort to improve this situation, and with the goal to perform the most in‐depth seismic application on a β Cephei star, Handler & Aerts (2002) set up a large spectroscopic and photometric multisite campaign for the star ν Eridani (HD 29248, V mag 3.92, spectral type B2 III). This campaign took place between 2002 October and 2003 January.…”

Section: Introductionmentioning

confidence: 99%

Asteroseismology of the Cephei star Eridani - II. Spectroscopic observations and pulsational frequency analysis

Aerts

Cat

Handler

et al. 2004

Monthly Notices of the Royal Astronomical Society

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We undertook a multisite spectroscopic campaign for the β Cephei star ν Eridani. A total of 2294 high-resolution spectra were obtained from telescopes at 11 different observatories around the world. The time base of dedicated multisite observations is 88 d. To this data set we have added 148 older, previously unpublished spectra, such that the overall time-span of the 2442 spectra is 430 d. The analysis of the radial velocity variations derived from the Si III triplet centred on 4560 Å leads to 19 significant frequencies, of which seven correspond to independent pulsation frequencies. Five of these are members of multiplets with an average spacing of 0.018 ± 0.002 cd −1 . Our spectroscopic results agree well with those derived from a simultaneous multisite photometric campaign of the star, albeit that we do not recover their low frequency at 0.43218 cd −1 . We find three different candidate frequencies below 1 cd −1 instead. We also find that the radial velocity amplitude of the main mode has increased by some 30 per cent over the last 15 years, which is consistent with the photometry data. We derive a relative equivalent width variation of 6.5 per cent, which is completely dominated by the main radial mode. The phase difference between the radial velocity and light variations for the main frequency is 97. • 9 ± 1. • 8, which is clearly deviant from the adiabatic value and confirms the radial nature of the dominant mode. The spectral line broadening leads to an upper limit of 20 km s −1 for v sin i, which is consistent with the long rotation period derived from the frequency splittings.

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