Fleming, Scott W., Million, Chase, Osten, Rachel A., Kolotkov, Dmitrii Y. and Brasseur, C. E. (2022) New time-resolved, multi-band flares in the GJ 65 system with gPhoton. The Astrophysical Journal, 928 (1). 8. doi:10.3847/1538-4357/ac5037 ISSN 1538-4357.

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Abstract

Characterizing the distribution of flare properties and occurrence rates is important for understanding habitability of M-dwarf exoplanets. The Galaxy Evolution Explorer (GALEX) space telescope observed the GJ 65 system, composed of the active, flaring M stars BL Cet and UV Cet, for 15,900 s (∼4.4 hr) in two ultraviolet (UV) bands. The contrast in flux between flares and the photospheres of cool stars is maximized at UV wavelengths, and GJ 65 is the brightest and nearest flaring M-dwarf system with significant GALEX coverage. It therefore represents the best opportunity to measure low-energy flares with GALEX. We construct high-cadence lightcurves from calibrated photon events and find 13 new flare events with near-UV (NUV) energies ranging from 1028.5–1029.5 erg and recover one previously reported flare with an energy of 1031 erg. The newly reported flares are among the smallest M-dwarf flares observed in the UV with sufficient time resolution to discern lightcurve morphology. The estimated flare frequency at these low energies is consistent with extrapolation from the distributions of higher-energy flares on active M dwarfs measured by other surveys. The largest flare in our sample is bright enough to exceed the local nonlinearity threshold of the GALEX detectors, which precludes color analysis. However, we detect quasi-periodic pulsations during this flare in both the far-UV and NUV bands at a period of ∼50 s, which we interpret as a modulation of the flare’s chromospheric thermal emission through periodic triggering of reconnection by external MHD oscillations in the corona.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science, Engineering and Medicine > Science > Physics
SWORD Depositor:	Library Publications Router
Library of Congress Subject Headings (LCSH):	Flare stars, M stars, Solar flares, Ultraviolet astronomy
Journal or Publication Title:	The Astrophysical Journal
Publisher:	The American Astronomical Society
ISSN:	1538-4357
Official Date:	22 March 2022
Dates:	Date Event 22 March 2022 Published 28 January 2022 Accepted
Volume:	928
Number:	1
Article Number:	8
DOI:	10.3847/1538-4357/ac5037
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Open Access (Creative Commons)
Copyright Holders:	© 2022. The Author(s). Published by the American Astronomical Society
Date of first compliant deposit:	28 April 2022
Date of first compliant Open Access:	28 April 2022
RIOXX Funder/Project Grant:	Project/Grant ID RIOXX Funder Name Funder ID 80NSSC18K0084 [NASA] National Aeronautics and Space Administration http://dx.doi.org/10.13039/100000104 ST/T000252/1 [STFC] Science and Technology Facilities Council http://dx.doi.org/10.13039/501100000271 UNSPECIFIED [MES] Ministry of Education and Science of the Russian Federation http://dx.doi.org/10.13039/501100003443
Related URLs:	http://creativecommons.org/licenses/by/4...

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