TY - JOUR
T1 - LINKING STELLAR CORONAL ACTIVITY and ROTATION at 500 MYR
T2 - A DEEP CHANDRA OBSERVATION of M37
AU - Núñez, Alejandro
AU - Agüeros, Marcel A.
AU - Covey, Kevin R.
AU - Hartman, Joel D.
AU - Kraus, Adam L.
AU - Bowsher, Emily C.
AU - Douglas, Stephanie T.
AU - López-Morales, Mercedes
AU - Pooley, David A.
AU - Posselt, Bettina
AU - Saar, Steven H.
AU - West, Andrew A.
N1 - Publisher Copyright:
© 2015. The American Astronomical Society. All rights reserved..
PY - 2015/8/20
Y1 - 2015/8/20
N2 - Empirical calibrations of the stellar age-rotation-activity relation (ARAR) rely on observations of the co-eval populations of stars in open clusters. We used the Chandra X-ray Observatory to study M37, a 500-Myr-old open cluster that has been extensively surveyed for rotation periods (). M37 was observed almost continuously for five days, for a total of 440.5 ks, to measure stellar X-ray luminosities (), a proxy for coronal activity, across a wide range of masses. The cluster's membership catalog was revisited to calculate updated membership probabilities from photometric data and each star's distance to the cluster center. The result is a comprehensive sample of 1699 M37 members: 426 with , 278 with X-ray detections, and 76 with both. We calculate Rossby numbers, , where τ is the convective turnover time, and ratios of the X-ray-to-bolometric luminosity, , to minimize mass dependencies in our characterization of the rotation-coronal activity relation at 500 Myr. We find that fast rotators, for which , show saturated levels of activity, with log(). For , activity is unsaturated and follows a power law of the form , where β = . This is the largest sample available for analyzing the dependence of coronal emission on rotation for a single-aged population, covering stellar masses in the range 0.4-1.3 , in the range 0.4-12.8 days, and in the range . Our results make M37 a new benchmark open cluster for calibrating the ARAR at ages of Myr.
AB - Empirical calibrations of the stellar age-rotation-activity relation (ARAR) rely on observations of the co-eval populations of stars in open clusters. We used the Chandra X-ray Observatory to study M37, a 500-Myr-old open cluster that has been extensively surveyed for rotation periods (). M37 was observed almost continuously for five days, for a total of 440.5 ks, to measure stellar X-ray luminosities (), a proxy for coronal activity, across a wide range of masses. The cluster's membership catalog was revisited to calculate updated membership probabilities from photometric data and each star's distance to the cluster center. The result is a comprehensive sample of 1699 M37 members: 426 with , 278 with X-ray detections, and 76 with both. We calculate Rossby numbers, , where τ is the convective turnover time, and ratios of the X-ray-to-bolometric luminosity, , to minimize mass dependencies in our characterization of the rotation-coronal activity relation at 500 Myr. We find that fast rotators, for which , show saturated levels of activity, with log(). For , activity is unsaturated and follows a power law of the form , where β = . This is the largest sample available for analyzing the dependence of coronal emission on rotation for a single-aged population, covering stellar masses in the range 0.4-1.3 , in the range 0.4-12.8 days, and in the range . Our results make M37 a new benchmark open cluster for calibrating the ARAR at ages of Myr.
UR - https://www.scopus.com/pages/publications/84939804974
UR - https://www.scopus.com/pages/publications/84939804974#tab=citedBy
U2 - 10.1088/0004-637X/809/2/161
DO - 10.1088/0004-637X/809/2/161
M3 - Article
AN - SCOPUS:84939804974
SN - 0004-637X
VL - 809
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 161
ER -