TY - JOUR
T1 - Stellar flares versus luminosity
T2 - XUV-induced atmospheric escape and planetary habitability
AU - Atri, Dimitra
AU - Carberry Mogan, Shane R.
N1 - Funding Information:
DA acknowledges support from the New York University Abu Dhabi (NYUAD) Institute research grant G1502. SRCM acknowledges support from the NYUAD Global PhD Fellowship.
Publisher Copyright:
© 2020 The Author(s)
PY - 2021/1/1
Y1 - 2021/1/1
N2 - Space weather plays an important role in the evolution of planetary atmospheres. Observations have shown that stellar flares emit energy in a wide energy range (1030-1038 erg), a fraction of which lies in X-rays and extreme ultraviolet (XUV). These flares heat the upper atmosphere of a planet, leading to increased escape rates, and can result in atmospheric erosion over a period of time. Observations also suggest that primordial terrestrial planets can accrete voluminous H/He envelopes. Stellar radiation can Erode these protoatmospheres over time, and the extent of this erosion has implications for the planet's habitability. We use the energy-limited equation to calculate hydrodynamic escape rates from these protoatmospheres irradiated by XUV stellar flares and luminosity. We use the flare frequency distribution of 492 FGKM stars observed with TESS to estimate atmospheric loss in habitable zone planets. We find that for most stars, luminosity-induced escape is the main loss mechanism, with a minor contribution from flares. However, flares dominate the loss mechanism of ∼20 per cent M4-M10 stars. M0-M4 stars are most likely to completely Erode both their proto- and secondary atmospheres, and M4-M10 are least likely to Erode secondary atmospheres. We discuss the implications of these results on planetary habitability.
AB - Space weather plays an important role in the evolution of planetary atmospheres. Observations have shown that stellar flares emit energy in a wide energy range (1030-1038 erg), a fraction of which lies in X-rays and extreme ultraviolet (XUV). These flares heat the upper atmosphere of a planet, leading to increased escape rates, and can result in atmospheric erosion over a period of time. Observations also suggest that primordial terrestrial planets can accrete voluminous H/He envelopes. Stellar radiation can Erode these protoatmospheres over time, and the extent of this erosion has implications for the planet's habitability. We use the energy-limited equation to calculate hydrodynamic escape rates from these protoatmospheres irradiated by XUV stellar flares and luminosity. We use the flare frequency distribution of 492 FGKM stars observed with TESS to estimate atmospheric loss in habitable zone planets. We find that for most stars, luminosity-induced escape is the main loss mechanism, with a minor contribution from flares. However, flares dominate the loss mechanism of ∼20 per cent M4-M10 stars. M0-M4 stars are most likely to completely Erode both their proto- and secondary atmospheres, and M4-M10 are least likely to Erode secondary atmospheres. We discuss the implications of these results on planetary habitability.
KW - Astrobiology
KW - Hydrodynamics
KW - Planets
KW - Planets and satellites: atmospheres
KW - Radiation mechanisms: thermal
KW - Satellites: terrestrial planets
KW - Stars: flare
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U2 - 10.1093/mnrasl/slaa166
DO - 10.1093/mnrasl/slaa166
M3 - Article
AN - SCOPUS:85096980012
SN - 1745-3925
VL - 500
SP - L1-L5
JO - Monthly Notices of the Royal Astronomical Society: Letters
JF - Monthly Notices of the Royal Astronomical Society: Letters
IS - 1
ER -