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Title: HAZMAT. I. The evolution of far-UV and near-UV emission from early M stars

Abstract

The spectral energy distribution, variability, and evolution of the high-energy radiation from an M dwarf planet host is crucial in understanding the planet's atmospheric evolution and habitability and in interpreting the planet's spectrum. The star's extreme-UV (EUV), far-UV (FUV), and near-UV (NUV) emission can chemically modify, ionize, and erode the atmosphere over time. This makes determining the lifetime exposure of such planets to stellar UV radiation critical for both the evolution of a planet's atmosphere and our potential to characterize it. Using the early M star members of nearby young moving groups, which sample critical ages in planet formation and evolution, we measure the evolution of the GALEX NUV and FUV flux as a function of age. The median UV flux remains at a 'saturated' level for a few hundred million years, analogous to that observed for X-ray emission. By the age of the Hyades Cluster (650 Myr), we measure a drop in UV flux by a factor of 2-3 followed by a steep drop from old (several Gyrs) field stars. This decline in activity beyond 300 Myr follows roughly t {sup –1}. Despite this clear evolution, there remains a wide range, of 1-2 orders of magnitude, in observed emissionmore » levels at every age. These UV data supply the much-needed constraints to M dwarf upper-atmosphere models, which will provide empirically motivated EUV predictions and more accurate age-dependent UV spectra as inputs to planetary photochemical models.« less

Authors:
 [1]
  1. Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001 (United States)
Publication Date:
OSTI Identifier:
22342250
Resource Type:
Journal Article
Journal Name:
Astronomical Journal (New York, N.Y. Online)
Additional Journal Information:
Journal Volume: 148; Journal Issue: 4; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1538-3881
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ATMOSPHERES; AVAILABILITY; EMISSION; ENERGY SPECTRA; EVOLUTION; FAR ULTRAVIOLET RADIATION; FORECASTING; LIFETIME; LIMITING VALUES; NEAR ULTRAVIOLET RADIATION; PHOTOCHEMISTRY; PLANETS; STARS; ULTRAVIOLET RADIATION; ULTRAVIOLET SPECTRA; X RADIATION

Citation Formats

Shkolnik, Evgenya L., and Barman, Travis S., E-mail: shkolnik@lowell.edu, E-mail: barman@lpl.arizona.edu. HAZMAT. I. The evolution of far-UV and near-UV emission from early M stars. United States: N. p., 2014. Web. doi:10.1088/0004-6256/148/4/64.
Shkolnik, Evgenya L., & Barman, Travis S., E-mail: shkolnik@lowell.edu, E-mail: barman@lpl.arizona.edu. HAZMAT. I. The evolution of far-UV and near-UV emission from early M stars. United States. https://doi.org/10.1088/0004-6256/148/4/64
Shkolnik, Evgenya L., and Barman, Travis S., E-mail: shkolnik@lowell.edu, E-mail: barman@lpl.arizona.edu. 2014. "HAZMAT. I. The evolution of far-UV and near-UV emission from early M stars". United States. https://doi.org/10.1088/0004-6256/148/4/64.
@article{osti_22342250,
title = {HAZMAT. I. The evolution of far-UV and near-UV emission from early M stars},
author = {Shkolnik, Evgenya L. and Barman, Travis S., E-mail: shkolnik@lowell.edu, E-mail: barman@lpl.arizona.edu},
abstractNote = {The spectral energy distribution, variability, and evolution of the high-energy radiation from an M dwarf planet host is crucial in understanding the planet's atmospheric evolution and habitability and in interpreting the planet's spectrum. The star's extreme-UV (EUV), far-UV (FUV), and near-UV (NUV) emission can chemically modify, ionize, and erode the atmosphere over time. This makes determining the lifetime exposure of such planets to stellar UV radiation critical for both the evolution of a planet's atmosphere and our potential to characterize it. Using the early M star members of nearby young moving groups, which sample critical ages in planet formation and evolution, we measure the evolution of the GALEX NUV and FUV flux as a function of age. The median UV flux remains at a 'saturated' level for a few hundred million years, analogous to that observed for X-ray emission. By the age of the Hyades Cluster (650 Myr), we measure a drop in UV flux by a factor of 2-3 followed by a steep drop from old (several Gyrs) field stars. This decline in activity beyond 300 Myr follows roughly t {sup –1}. Despite this clear evolution, there remains a wide range, of 1-2 orders of magnitude, in observed emission levels at every age. These UV data supply the much-needed constraints to M dwarf upper-atmosphere models, which will provide empirically motivated EUV predictions and more accurate age-dependent UV spectra as inputs to planetary photochemical models.},
doi = {10.1088/0004-6256/148/4/64},
url = {https://www.osti.gov/biblio/22342250}, journal = {Astronomical Journal (New York, N.Y. Online)},
issn = {1538-3881},
number = 4,
volume = 148,
place = {United States},
year = {Wed Oct 01 00:00:00 EDT 2014},
month = {Wed Oct 01 00:00:00 EDT 2014}
}