10.5281/zenodo.4567598
https://zenodo.org/records/4567598
oai:zenodo.org:4567598
Linsky, Jeffrey
Jeffrey
Linsky
0000-0003-4446-3181
JILA, University of Colorado and NIST
Wood, Brian E.
Brian E.
Wood
Naval Research Laboratory
Youngblood, Allison
Allison
Youngblood
LASP, University of Colorado
Brown, Alexander
Alexander
Brown
CASA, University of Colorado
Froning, Cynthia S.
Cynthia S.
Froning
McDonald Obs.,University of Texas
France, Kevin
Kevin
France
LASP, University of Colorado
Buccino, Andrea P.
Andrea P.
Buccino
FCEN, Universidad de Buenos Aires
Cranmer, Steven S.
Steven S.
Cranmer
LASP, University of Colorado
Mauas, Pablo
Pablo
Mauas
FCEN, Universidad de Buenos Aires
Miguel, Yamila
Yamila
Miguel
Leiden Observatory
Pineda, J. Sebastian
J. Sebastian
Pineda
LASP, University of Colorado
Rugheimer, Sarah
Sarah
Rugheimer
University of Oxford
Vieytes, Mariela
Mariela
Vieytes
CONICET, Universidad Buenos Aires
Wheatley, Peter J.
Peter J.
Wheatley
University of Warwick
Wilson, David J.
David J.
Wilson
McDonald Obs., University of Texas
The Relative Emission from Chromospheres and Coronae: Dependence on Spectral Type and Age
Zenodo
2021
Cool Stars on the main sequence
Chromospheres
Coronae
Magnetic heating
Wolk, Scott
Scott
Wolk
CFA, Harvard University
2021-02-27
eng
Poster
10.5281/zenodo.4567597
https://zenodo.org/communities/coolstars20half
Creative Commons Attribution 4.0 International
We present a comprehensive picture of the relative emission and heating of the chromospheres and coronae of stars with spectral types F2 - M7.5 V as a function of effective temperature and age. At chromospheric temperatures the dominant emission is in the Lyman-alpha line, which we take as representative of the total emission from chromospheres. At coronal temperatures the dominant emission is by X-rays, which we take a representative of the total emission from coronae. We include in this study 79 dwarf stars for which there are X-ray fluxes and Lyman-alpha fluxes corrected for interstellar absorption. The Lyman-alpha fluxes are from HST/STIS spectra obtained with the MUSCLES, Mega-MUSCLES, and other surveys and programs. The X-ray fluxes are from XMM-Newton, Chandra, and ROSAT.
We find that Lyman-alpha and X-ray fluxes for F, G, and K stars lie on the same trend line with active stars near the top and inactive stars near the bottom. As stars evolve, they systematically descend the trend line. M stars depart from the FGK trend line in the sense of relatively weak Lyman-alpha emission. The ratio of the Lyman-alpha to bolometric luminosity, L(Lya)/L(bol), increases to lower effective temperature for stars at all ages. The ratio of X-ray to bolometric luminosity, L(X)/L(bol), follows a different pattern with young stars (t<450 Myr) showing X-ray saturation for effective temperatures less than 5200 K and stronger L(X)/L(bol) than L(Lya/L(bol). For older stars (t>4 Gyr), L(Lya)/L(bol) exceeds L(X)/L(bol), but L(X)/L(bol) increases to lower effective temperatures much faster than L(Lya)/L(bol). We discuss the implications of these results concerning the relative heating rates at coronal and chromospheric temperatures.
This work is supported by grants from the Space Telescope Science Institute for programs HST-GO-12475, 12596, 13650, 14640, and 15071.