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We report the detection of three large millimeter flaring events from the nearby Sun-like,ϵ Eridani, found in archival Atacama Large Millimeter/submillimeter Array (ALMA) 12 m and Atacama Compact Array observations at 1.33 mm taken from 2015 January 17 to 18 and 2016 October 24 to November 23, respectively. This is the first time that flares have been detected from a Sun-like star at millimeter wavelengths. The largest flare among our data was detected in the ALMA observations on 2015 January 17 from 20:09:10.4–21:02:49.3 UT with a peak flux density of 28 ± 7 mJy and a duration of 9 s. The peak brightness of the largest flare is 3.4 ± 0.9 × 10^14 erg s^−1 Hz^−1, a factor of >50× times brighter than the star’s quiescent luminosity and >10× brighter than solar flares observed at comparable wavelengths. We find changes in the spectral index (F ν ∝ ν α ) at the flare peak, with α = 1.81 ± 1.94 and a lower limit on the fractional linear polarization ∣Q/I∣ = 0.08 ± 0.12. This positive spectral index is more similar to millimeter solar flares, differing from M-dwarf flares also detected at millimeter wavelengths that exhibit steeply negative spectral indices.
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Science development study for the Atacama Large Aperture Submillimeter Telescope (AtLAST): Solar and stellar observations
Observations at (sub-)millimeter wavelengths offer a complementary perspective on our Sun and other stars, offering significant insights into both the thermal and magnetic composition of their chromospheres. Despite the fundamental progress in (sub-)millimeter observations of the Sun, some important aspects require diagnostic capabilities that are not offered by existing observatories. In particular, simultaneously observations of the radiation continuum across an extended frequency range would facilitate the mapping of different layers and thus ultimately the 3D structure of the solar atmosphere. Mapping large regions on the Sun or even the whole solar disk at a very high temporal cadence would be crucial for systematically detecting and following the temporal evolution of flares, while synoptic observations, i.e., daily maps, over periods of years would provide an unprecedented view of the solar activity cycle in this wavelength regime. As our Sun is a fundamental reference for studying the atmospheres of active main sequence stars, observing the Sun and other stars with the same instrument would unlock the enormous diagnostic potential for understanding stellar activity and its impact on exoplanets. The Atacama Large Aperture Submillimeter Telescope (AtLAST), a single-dish telescope with 50m aperture proposed to be built in the Atacama desert in Chile, would be able to provide these observational capabilities. Equipped with a large number of detector elements for probing the radiation continuum across a wide frequency range, AtLAST would address a wide range of scientific topics including the thermal structure and heating of the solar chromosphere, flares and prominences, and the solar activity cycle. In this white paper, the key science cases and their technical requirements for AtLAST are discussed.
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- Award ID(s):
- 2206424
- PAR ID:
- 10637338
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- Open Research Europe
- Date Published:
- Journal Name:
- Open Research Europe
- Volume:
- 4
- ISSN:
- 2732-5121
- Page Range / eLocation ID:
- 140
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.12688/openreseurope.17453.1
