Detection of 2$-$4 GHz Continuum Emission from $\epsilon$ Eridani

Abstract

The nearby star $\epsilon \mathrm{Eridani}$ has been a frequent target of radio surveys for stellar emission and extraterrestial intelligence. Using deep $2-4\mathrm{GHz}$ observations with the Very Large Array, we have uncovered a $29\mu \mathrm{Jy}$ compact, steady continuum radio source coincident with $\epsilon \mathrm{Eridani}$ to within 0.06 arcseconds ($\lesssim 2\sigma$; 0.2 au at the distance of the star). Combining our data with previous high frequency continuum detections of $\epsilon \mathrm{Eridani}$, our observations reveal a spectral turnover at $6\mathrm{GHz}$. We ascribe the $2-6\mathrm{GHz}$ emission to optically thick, thermal gyroresonance radiation from the stellar corona, with thermal free-free opacity likely becoming relevant at frequencies below $1\mathrm{GHz}$. The steep spectral index ($\alpha \simeq 2$) of the $2-6\mathrm{GHz}$ spectrum strongly disfavors its interpretation as stellar wind-associated thermal bremsstrahlung ($\alpha \simeq 0.6$). Attributing the entire observed $2-4\mathrm{GHz}$ flux density to thermal free-free wind emission, we thus, derive a stringent upper limit of $3\times 10^{-11}{M}_{\odot }{\mathrm{yr}}^{-1}$ on the mass loss rate from $\epsilon \mathrm{Eridani}$. Finally, we report the non-detection of flares in our data above a $5\sigma$ threshold of $95\mu \mathrm{Jy}$. Together with the optical non-detection of the most recent stellar maximum expected in 2019, our observations postulate a likely evolution of the internal dynamo of $\epsilon \mathrm{Eridani}$.

arXiv comment13 pages, 4 figures, accepted to ApJ

References in corpus (32)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• The NumPy array: a structure for efficient numerical computation
• Gaia Data Release 2. Summary of the contents and survey properties
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• The Gaia mission
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics
• Measured Mass Loss Rates of Solar-like Stars as a Function of Age and Activity
• An Accurate Flux Density Scale from 50 MHz to 50 GHz
• The VLBA Calibrator Survey - VCS1
• Testing a Predictive Theoretical Model for the Mass Loss Rates of Cool Stars
• Evidence for a Long-period Planet Orbiting Epsilon Eridani
• The Extrasolar Planet epsilon Eridani b - Orbit and Mass
• Structure in the Epislon Eridani dusty disk caused by mean motion resonances with a 0.3 eccentricity planet at periastron
• Epsilon Eridani's Planetary Debris Disk: Structure and Dynamics based on Spitzer and CSO Observations
• A seismic signature of a second dynamo?
• Revising the ages of planet-hosting stars
• Magnetic Activity Cycles in the Exoplanet Host Star epsilon Eridani
• Stellar Coronal Mass Ejections I. Estimating occurrence frequencies and mass-loss rates
• Exoplanet-induced radio emission from M-dwarfs
• Deep exploration of $\epsilon$ Eridani with Keck Ms-band vortex coronagraphy and radial velocities: mass and orbital parameters of the giant exoplanet
• The Northern Arc of $\epsilon$ Eridani's Debris Ring as Seen by ALMA
• An X-ray activity cycle on the young solar-like star $\epsilon \mathrm{Eridani}$
• Radio emission and mass loss rate limits of four young solar-type stars
• The Epsilon Eridani System Resolved by Millimeter Interferometry
• First Detection of Thermal Radio Emission from Solar-Type Stars with the Karl G. Jansky Very Large Array
• Deep LMT/AzTEC millimeter observations of Epsilon Eridani and its surroundings
• The Inner 25 AU Debris Distribution in the epsilon Eri System
• Radio Emission from the Exoplanetary System $\epsilon$ Eridani
• MAMBO image of the debris disk around epsilon Eridani : robustness of the azimuthal structure
• Magnetic field measurements of $\epsilon$ Eridani from Zeeman broadening
• Transient Events in Archival Very Large Array Observations of the Galactic Center

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