Preliminary Asteroseismology of EC20058-5234 and Limits on Plasmon Neutrinos

Bischoff-Kim, A.

doi:10.1553/cia154s16

Cited by 9 publications

(10 citation statements)

References 7 publications

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“…f7 could also be a mode of its own that happens to lie close to where the m =+1 member of the (f5, f6) multiplet would be if it were present. Preliminary work (Bischoff‐Kim 2008) did not find that fits excluding the f7 mode (e.g. invoking a magnetic field) were significantly better than fits that included the f7 mode as an independent mode.…”

Section: Clues From Observationsmentioning

confidence: 96%

Asteroseismic constraints on diffusion in white dwarf envelopes

Kim¹,

Metcalfe²

2011

Monthly Notices of the Royal Astronomical Society

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The asteroseismic analysis of white dwarfs allows us to peer below their photospheres and determine their internal structure. At ∼28 000 K EC20058−5234 is the hottest known pulsating helium atmosphere white dwarf. As such, it constitutes an important link in the evolution of white dwarfs down the cooling track. It is also astrophysically interesting because it is at a temperature where white dwarfs are expected to cool mainly through the emission of plasmon neutrinos. In the present work, we perform an asteroseismic analysis of EC20058−5234 and place the results in the context of stellar evolution and time‐dependent diffusion calculations. We use a parallel genetic algorithm complemented with targeted grid searches to find the models that fit the observed periods best. Comparing our results with similar modelling of EC20058−5234’s cooler cousin CBS114, we find a helium envelope thickness consistent with time‐dependent diffusion calculations and obtain a precise mode identification for EC20058−5234.

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Section: Clues From Observationsmentioning

confidence: 96%

Asteroseismic constraints on diffusion in white dwarf envelopes

Kim¹,

Metcalfe²

2011

Monthly Notices of the Royal Astronomical Society

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“…The O − C diagram of all 10 pulsation frequencies showed structure that was not consistent with scatter. It was also apparent that for some frequencies, O − C was changing by a large fraction of the period, and that none of the O − C diagrams were consistent with the parabolic trend of a simple neutrino plus photon-cooling model (Bischoff-Kim 2008).…”

Section: Building the O − C Diagramsmentioning

confidence: 98%

PERIODIC VARIATIONS IN THEO–CDIAGRAMS OF FIVE PULSATION FREQUENCIES OF THE DB WHITE DWARF EC 20058–5234

Dalessio

Sullivan

Provençal

et al. 2013

ApJ

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Variations in the pulsation arrival time of five independent pulsation frequencies of the DB white dwarf EC 20058−5234 individually imitate the effects of reflex motion induced by a planet or companion but are inconsistent when considered in unison. The pulsation frequencies vary periodically in a 12.9 year cycle and undergo secular changes that are inconsistent with simple neutrino plus photon-cooling models. The magnitude of the periodic and secular variations increases with the period of the pulsations, possibly hinting that the corresponding physical mechanism is located near the surface of the star. The phase of the periodic variations appears coupled to the sign of the secular variations. The standards for pulsation-timing-based detection of planetary companions around pulsating white dwarfs, and possibly other variables such as subdwarf B stars, should be re-evaluated. The physical mechanism responsible for this surprising result may involve a redistribution of angular momentum or a magnetic cycle. Additionally, variations in a supposed combination frequency are shown to match the sum of the variations of the parent frequencies to remarkable precision, an expected but unprecedented confirmation of theoretical predictions.

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“…a Analysis based on Q7 data (Østensen et al 2011). b Analysis based on Q10-Q12 data (Østensen 2013 with EC 20058-5234 (Dalessio et al 2010;Bischoff-Kim 2008), but without much success because none of the modes were stable over evolutionary timescales. With the exception of KIC 8626021, none of the other known DBVs observed so far show modes stable on evolutionary timescales.…”

Section: Astrophysical Contextmentioning

confidence: 99%

SEVEN-PERIOD ASTEROSEISMIC FIT OF THEKEPLERDBV

Kim

Østensen

Hermes

et al. 2014

ApJ

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We present a new, better-constrained asteroseismic analysis of the helium-atmosphere (DB) white dwarf discovered in the field of view of the original Kepler mission. Observations obtained over the course of 2 yr yield at least seven independent modes, two more than were found in the discovery paper for the object. With several triplets and doublets, we are able to fix the and m identification of several modes before performing the fitting, greatly reducing the number of assumptions we must make about mode identification. We find a very thin helium layer for this relatively hot DB, which adds evidence to the hypothesis that helium diffuses outward during DB cooling. At least a few of the modes appear to be stable on evolutionary timescales and could allow us to obtain a measurement of the rate of cooling with monitoring of the star over the course of the next few years with ground-based follow-up.

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Preliminary Asteroseismology of EC20058-5234 and Limits on Plasmon Neutrinos

Cited by 9 publications

References 7 publications

Asteroseismic constraints on diffusion in white dwarf envelopes

Asteroseismic constraints on diffusion in white dwarf envelopes

PERIODIC VARIATIONS IN THEO–CDIAGRAMS OF FIVE PULSATION FREQUENCIES OF THE DB WHITE DWARF EC 20058–5234

SEVEN-PERIOD ASTEROSEISMIC FIT OF THEKEPLERDBV

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