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تسجيل مستخدم جديدFlat Spectrum Radio Continuum Emission Associated with $epsilon$ Eridani
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We present Very Large Array observations at 33.0 GHz that detect emission coincident with $epsilon$ Eridani to within $0rlap.{}07$ (0.2 AU at the distance of this star), with a positional accuracy of $0rlap.{}05$. This result strongly supports the suggestion of previous authors that the quiescent centimeter emission comes from the star and not from a proposed giant exoplanet with a semi-major axis of $sim1rlap.{}0$ (3.4 AU). The centimeter emission is remarkably flat and is consistent with optically thin free-free emission. In particular, it can be modeled as a stellar wind with a mass loss rate of the order of $6.6 times 10^{-11}~ M_odot ~yr^{-1}$, which is 3,300 times the solar value, exceeding other estimates of this stars wind. However, interpretation of the emission in terms of other thermal mechanisms like coronal free-free and gyroresonance emission cannot be discarded.
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As part of a wider search for radio emission from nearby systems known or suspected to contain extrasolar planets $epsilon$ Eridani was observed by the Jansky Very Large Array (VLA) in the 2-4 GHz and 4-8 GHz frequency bands. In addition, as part of
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The nearby star $rm epsilon Eridani$ has been a frequent target of radio surveys for stellar emission and extraterrestial intelligence. Using deep $rm 2-4 GHz$ observations with the Very Large Array, we have uncovered a $29 mu {rm Jy}$ compact, st
eady continuum radio source coincident with $rm epsilon Eridani$ to within 0.06 arcseconds ($lesssim 2sigma$; 0.2 au at the distance of the star). Combining our data with previous high frequency continuum detections of $rm epsilon Eridani$, our observations reveal a spectral turnover at $rm 6 GHz$. We ascribe the $rm 2-6 GHz$ emission to optically thick, thermal gyroresonance radiation from the stellar corona, with thermal free-free opacity likely becoming relevant at frequencies below $rm 1 GHz$. The steep spectral index ($alpha simeq 2$) of the $rm 2-6 GHz$ spectrum strongly disfavors its interpretation as stellar wind-associated thermal bremsstrahlung ($alpha simeq 0.6$). Attributing the entire observed $rm 2-4 GHz$ flux density to thermal free-free wind emission, we thus, derive a stringent upper limit of $3 times 10^{-11} M_{odot} {rm yr}^{-1}$ on the mass loss rate from $rm epsilon Eridani$. Finally, we report the non-detection of flares in our data above a $5sigma$ threshold of $rm 95 mu Jy$. 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 $rm epsilon Eridani$.
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