J/AJ/164/110 HST/COS far-UV spectra of AU Microscopii flares (Feinstein+, 2022)
AU Microscopii in the Far-UV; Observations in Quiescence, during Flares, and
Implications for AU Mic b and c.
Feinstein A.D., France K., Youngblood A., Duvvuri G.M., Teal D.J.,
Cauley P.W., Seligman D.Z., Gaidos E., Kempton E.M.-R., Bean J.L.,
Diamond-Lowe H., Newton E., Ginzburg S., Plavchan P., Gao P., Schlichting H.
<Astron. J., 164, 110 (2022)>
=2022AJ....164..110F 2022AJ....164..110F
ADC_Keywords: Stars, M-type; Stars, flare; Spectra, ultraviolet
Keywords: Stellar activity ; Stellar flares ; Hubble Space Telescope ;
Ultraviolet astronomy ; M dwarf stars ; Exoplanet atmospheres
Abstract:
High-energy X-ray and ultraviolet (UV) radiation from young stars
impacts planetary atmospheric chemistry and mass loss. The active
∼22Myr M-dwarf AU-Mic hosts two exoplanets orbiting interior to its
debris disk. Therefore, this system provides a unique opportunity to
quantify the effects of stellar X-ray and UV irradiation on planetary
atmospheres as a function of both age and orbital separation. In this
paper, we present over 5hr of far-UV (FUV) observations of AU-Mic
taken with the Cosmic Origins Spectrograph (COS; 1070-1360Å) on the
Hubble Space Telescope (HST). We provide an itemization of 120
emission features in the HST/COS FUV spectrum and quantify the flux
contributions from formation temperatures ranging from 104 to 107K. We
detect 13 flares in the FUV white-light curve with energies ranging
from 1029 to 1031erg/s. The majority of the energy in each of these
flares is released from the transition region between the chromosphere
and the corona. There is a 100x increase in flux at continuum
wavelengths λ<1100Å in each flare, which may be caused by
thermal Bremsstrahlung emission. We calculate that the baseline
atmospheric mass-loss rate for AU-Micb is ∼108g/s, although this rate
can be as high as ∼1014g/s during flares with Lflare∼1033erg/s.
Finally, we model the transmission spectra for AU-Micb and c with a
new panchromatic spectrum of AU Mic and motivate future JWST
observations of these planets.
Description:
We observed AU-Mic over two visits with Hubble Space Telescope Cosmic
Origins Spectrograph (HST/COS) under GO program 16164 (PI Cauley). We
used the COS G130M grating centered at 1222Å for both visits with
R∼12000-17000. The configuration provides coverage from approximately
1060-1360Å with a detector gap from 1210-1225Å, masking the
bright Lyα mission feature to avoid detector saturation. The
same COS setting was used for both visits. The visits were executed on
2021 May 28 and 2021 September 23 during transit events of AU-Micb.
Objects:
---------------------------------------------
RA (2000) DE Designation(s)
---------------------------------------------
20 45 09.53 -31 20 27.2 AU Mic = V* AU Mic
---------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 77 119 Complete line list for emission features in our
Hubble/COS spectra for AU Mic
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/A+AS/125/149 : CHIANTI - Atomic Database For Emission Lines I. (Dere+ 1997)
J/AJ/141/50 : White-light flares on cool stars from Kepler (Walkowicz+, 2011)
J/ApJS/207/15 : M dwarf flare spectra (Kowalski+, 2013)
J/ApJ/829/23 : Stellar flares from Q0-Q17 Kepler LCs (Davenport, 2016)
J/ApJ/843/31 : MUSCLES Treasury Survey IV Mdwarf UV fluxes (Youngblood+, 2017)
J/ApJ/881/9 : EvryFlare. I. Cool stars flares in southern sky (Howard+, 2019)
J/A+A/622/A133 : M45, M44 and M67 flare stars (Ilin+, 2019)
J/AJ/159/60 : 8695 flares; 1228 stars in TESS sectors 1 & 2 (Gunther+, 2020)
J/ApJ/895/140 : EvryFlare. II. Parameters 122 cool flare stars (Howard+, 2020)
J/ApJ/890/23 : NUV and FUV measurements of planet host stars (Loyd+, 2020)
J/A+A/645/A42 : Flares in 5 open clusters (Ilin+, 2021)
J/AJ/163/121 : Radial velocity and light curve of Kepler 1627A (Bouma+, 2022)
J/AJ/163/156 : THYME. VI. TOI-1227 radial velocity (Mann+, 2022)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Ion Ion
9 A1 --- f_Ion [*] Flag on Ion (1)
11- 17 F7.2 0.1nm Waver [1083/1360] Measured rest wavelength
(λrest; Å)
19- 25 F7.2 0.1nm Wave [1083/1360] Observation wavelength
(λobs; Å)
27- 32 F6.2 km/s dVel [-22.9/25.4] Velocity shift
34- 39 F6.2 --- FluxQ [0.43/150] Flux Quiescent (10-15erg/s/cm2)
41- 44 F4.2 --- e_FluxQ [0.1/6] Error on Flux-Q
46- 49 F4.2 km/s FWHMQ [0.19/0.77] FWHM Quiescent
51- 54 F4.2 km/s e_FWHMQ [0/0.06] Error on FWHM-Q
56- 61 F6.2 --- FluxB [0.61/223] Flux flare B (10-15erg/s/cm2)
63- 67 F5.2 --- e_FluxB [0.3/22] Error on Flux-B
69- 72 F4.2 km/s FWHMB [0.17/1.68] FWHM flare B
74- 77 F4.2 km/s e_FWHMB [0.01/3] Error on FWHM-B
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Note (1): Ions flagged are optically thick lines used when fitting the
DEM models following the methods of Duvvuri+, 2021ApJ...913...40D 2021ApJ...913...40D (1
occurrence).
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History:
From electronic version of the journal
(End) Prepared by Coralie Fix [CDS], 16-Jan-2023