TY - JOUR
T1 - HAZMAT. V. The Ultraviolet and X-Ray Evolution of K Stars
AU - Richey-Yowell, Tyler
AU - Shkolnik, Evgenya L.
AU - Schneider, Adam C.
AU - Osby, Ella
AU - Barman, Travis
AU - Meadows, Victoria S.
N1 - Funding Information:
The authors would like to acknowledge support from the NASA Habitable Worlds grant NNX16AB62G. We wish to thank the anonymous referee for an insightful and helpful report. This work is based on observations made with the NASA Galaxy Evolution Explorer and ROSAT. GALEX is operated for NASA by the California Institute of Technology under NASA contract NAS5-98034. This research utilized the public data from the second ROSAT All-sky Survey (https:// heasarc.gsfc.nasa.gov/W3Browse/rosat/rass2rxs.html). This work makes use of data products from the Two Micron All-sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/ gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/ dpac/consortium).
Funding Information:
The authors would like to acknowledge support from the NASA Habitable Worlds grant NNX16AB62G. We wish to thank the anonymous referee for an insightful and helpful report. This work is based on observations made with the NASA Galaxy Evolution Explorer and ROSAT. GALEX is operated for NASA by the California Institute of Technology under NASA contract NAS5-98034. This research utilized the public data from the second ROSAT All-sky Survey (https://heasarc.gsfc.nasa.gov/W3Browse/rosat/rass2rxs.html). This work makes use of data products from the Two Micron Allsky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/ gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/ dpac/consortium).
Publisher Copyright:
© 2019. The American Astronomical Society. All rights reserved.
PY - 2019/2/10
Y1 - 2019/2/10
N2 - Knowing the high-energy radiation environment of a star over a planet's formation and evolutionary period is critical in determining if that planet is potentially habitable and if any biosignatures could be detected, as UV radiation can severely change or destroy a planet's atmosphere. Current efforts for finding a potentially habitable planet are focused on M stars, yet K stars may offer more habitable conditions due to decreased stellar activity and more distant and wider habitable zones (HZs). While M star activity evolution has been observed photometrically and spectroscopically, there has been no dedicated investigation of K star UV evolution. We present the first comprehensive study of the near-UV, far-UV, and X-ray evolution of K stars. We used members of young moving groups and clusters ranging in age from 10 to 625 Myr combined with field stars and their archived GALEX UV and ROSAT X-ray data to determine how the UV and X-ray radiation evolve. We find that the UV and X-ray flux incident on an HZ planet is 5-50 times lower than that of HZ planets around early-M stars and 50-1000 times lower than those around late-M stars, due to both an intrinsic decrease in K dwarf stellar activity occurring earlier than for M dwarfs and the more distant location of the K dwarf HZ.
AB - Knowing the high-energy radiation environment of a star over a planet's formation and evolutionary period is critical in determining if that planet is potentially habitable and if any biosignatures could be detected, as UV radiation can severely change or destroy a planet's atmosphere. Current efforts for finding a potentially habitable planet are focused on M stars, yet K stars may offer more habitable conditions due to decreased stellar activity and more distant and wider habitable zones (HZs). While M star activity evolution has been observed photometrically and spectroscopically, there has been no dedicated investigation of K star UV evolution. We present the first comprehensive study of the near-UV, far-UV, and X-ray evolution of K stars. We used members of young moving groups and clusters ranging in age from 10 to 625 Myr combined with field stars and their archived GALEX UV and ROSAT X-ray data to determine how the UV and X-ray radiation evolve. We find that the UV and X-ray flux incident on an HZ planet is 5-50 times lower than that of HZ planets around early-M stars and 50-1000 times lower than those around late-M stars, due to both an intrinsic decrease in K dwarf stellar activity occurring earlier than for M dwarfs and the more distant location of the K dwarf HZ.
KW - stars: evolution
KW - stars: low-mass
UR - http://www.scopus.com/inward/record.url?scp=85062020304&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85062020304&partnerID=8YFLogxK
U2 - 10.3847/1538-4357/aafa74
DO - 10.3847/1538-4357/aafa74
M3 - Article
AN - SCOPUS:85062020304
VL - 872
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 1
M1 - A17
ER -