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Title: First Detection of Radio Emission Associated with a Classical Cepheid

We report the detection of 15 GHz radio continuum emission associated with the classical Cepheid variable starδCephei (δCep) 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 phaseϕ≈ 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 phaseϕ= 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 thatδCep undergoes periodic increases in X-ray flux during pulsation phaseϕ≈ 0.43. The lack of radio detection in two out of three observing epochs atϕ≈ 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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DOI PREFIX: 10.3847
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Journal Name:
The Astronomical Journal
Medium: X Size: Article No. 92
["Article No. 92"]
Sponsoring Org:
National Science Foundation
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