Cooling time of shock-heated gas in the atmospheres of Mira Ceti long-period variable stars

Belova, O. M.; Bychkov, K. V.; Rudnitskii, G. M.

doi:10.1134/s1063772914120026

Cited by 3 publications

(2 citation statements)

References 5 publications

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“…Given the relatively low surface gravity of δ Cep (log g=1.91 in cgs units, i.e., ∼0.30% that of the Sun), its high inferred mass-loss rate (up to Ṁ ∼ 10 −6 M yr −1 ), the presence of circumstellar H i 21 cm emission, and the rather low outflow velocity estimated for the wind (V out ≈ 35 km s −1 ), Matthews et al (2012) postulated that δ Cep's wind is likely to be predominantly cool and neutral (see also Holzer & MacGregor 1985;Glassgold & Huggins 1983). Nonetheless, the pulsations suspected of driving Cepheid outflows (e.g., Willson & Bowen 1986) are predicted to generate shocks that may propagate beyond the photosphere and lead to partial (and time-variable) ionization of the wind (Fokin et al 1996;Marengo et al 2002;Nardetto et al 2006;Belova et al 2014). In this case, free-free emission may be detectable at centimeter wavelengths from the partially ionized wind.…”

Section: Free-free Emission From a Partially Ionized Windmentioning

confidence: 99%

First Detection of Radio Emission Associated with a Classical Cepheid

Matthews¹,

Evans²,

Rupen³

2023

Preprint

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We report the detection of 15 GHz radio continuum emission associated with the classical Cepheid variable star δ Cephei based on observations with the Karl G. Jansky Very Large Array. Our results constitute the first probable detection of radio continuum emission from a classical Cepheid. We observed the star at pulsation phase φ ≈0.43 (corresponding to the phase of maximum radius and minimum temperature) during three pulsation cycles in late 2018 and detected statistically significant emission (> 5σ) during one of the three epochs. The observed radio emission appears to be variable at a > ∼ 10% level on timescales of days to weeks. We also present an upper limit on the 10 GHz flux density at pulsation phase φ = 0.31 from an observation in 2014. We discuss possible mechanisms that may produce the observed 15 GHz emission, but cannot make a conclusive identification from the present data. The emission does not appear to be consistent with originating from a close-in, late-type dwarf companion, although this scenario cannot yet be strictly excluded. Previous X-ray observations have shown that δ Cephei undergoes periodic increases in X-ray flux during pulsation phase φ ≈ 0.43. The lack of radio detection in two out of three observing epochs at φ ≈ 0.43 suggests that either the radio emission is not linked with a particular pulsation phase, or else that the strength of the generated radio emission in each pulsation cycle is variable.

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Section: Free-free Emission From a Partially Ionized Windmentioning

confidence: 99%

First Detection of Radio Emission Associated with a Classical Cepheid

Matthews¹,

Evans²,

Rupen³

2023

Preprint

View full text Add to dashboard Cite

show abstract

“…yr −1 ), the presence of circumstellar H I 21 cm emission, and the rather low outflow velocity estimated for the wind (V out ≈ 35 km s −1 ), Matthews et al (2012) postulated that δ Cep's wind is likely to be predominantly cool and neutral (see also Glassgold & Huggins 1983;Holzer & MacGregor 1985). Nonetheless, the pulsations suspected of driving Cepheid outflows (e.g., Willson & Bowen 1986) are predicted to generate shocks that may propagate beyond the photosphere and lead to partial (and time-variable) ionization of the wind (Fokin et al 1996;Marengo et al 2002;Nardetto et al 2006;Belova et al 2014). In this case, free-free emission may be detectable at centimeter wavelengths from the partially ionized wind.…”

Section: Free-free Emission From a Partially Ionized Windmentioning

confidence: 99%

First Detection of Radio Emission Associated with a Classical Cepheid

Matthews

Evans

Rupen

2023

View full text Add to dashboard Cite

We report the detection of 15 GHz radio continuum emission associated with the classical Cepheid variable star δ Cephei (δ Cep) based on observations with the Karl G. Jansky Very Large Array. Our results constitute the first probable detection of radio continuum emission from a classical Cepheid. We observed the star at pulsation phase ϕ ≈ 0.43 (corresponding to the phase of maximum radius and minimum temperature) during three pulsation cycles in late 2018 and detected statistically significant emission (>5σ) during one of the three epochs. The observed radio emission appears to be variable at a ≳10% level on timescales of days to weeks. We also present an upper limit on the 10 GHz flux density at pulsation phase ϕ = 0.31 from an observation in 2014. We discuss possible mechanisms that may produce the observed 15 GHz emission, but cannot make a conclusive identification from the present data. The emission does not appear to be consistent with originating from a close-in, late-type dwarf companion, although this scenario cannot yet be strictly excluded. Previous X-ray observations have shown that δ Cep undergoes periodic increases in X-ray flux during pulsation phase ϕ ≈ 0.43. The lack of radio detection in two out of three observing epochs at ϕ ≈ 0.43 suggests that either the radio emission is not linked with a particular pulsation phase, or else that the strength of the generated radio emission in each pulsation cycle is variable.

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Mira Variables. Molecular Spectra

Панчук

Клочкова

2023

Astrophys. Bull.

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Cooling time of shock-heated gas in the atmospheres of Mira Ceti long-period variable stars

Cited by 3 publications

References 5 publications

First Detection of Radio Emission Associated with a Classical Cepheid

First Detection of Radio Emission Associated with a Classical Cepheid

First Detection of Radio Emission Associated with a Classical Cepheid

Mira Variables. Molecular Spectra

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