Query : 2017ApJ...834..176N

2017ApJ...834..176N - Astrophys. J., 834, 176-176 (2017/January-2)

Chromospheric and coronal activity in the 500 Myr old open cluster M37: evidence for coronal stripping?


Abstract (from CDS):

We present the results of a spectroscopic survey to characterize chromospheric activity, as measured by Hαemission, in low-mass members of the 500 Myr old open cluster M37. Combining our new measurements of Hαluminosities (L) with previously cataloged stellar properties, we identify saturated and unsaturated regimes in the dependence of the L-to-bolometric luminosity ratio, L/Lbol, on the Rossby number Ro. All rotators with Ro smaller than 0.03 ± 0.01 converge to an activity level of L/Lbol=(1.27±0.02)×10–4. This saturation threshold (Ro,sat=0.03±0.01) is statistically smaller than that found in most studies of the rotation-activity relation. In the unsaturated regime, slower rotators have lower levels of chromospheric activity, with L/Lbol(Ro) following a power-law of index β=-0.51±0.02, slightly shallower than that found for a combined ≃650 Myr old sample of Hyades and Praesepe stars. By comparing this unsaturated behavior to that previously found for coronal activity in M37 (as measured via the X-ray luminosity, LX), we confirm that chromospheric activity decays at a much slower rate than coronal activity with increasing Ro. While a comparison of L and LX for M37 members with measurements of both reveals a nearly 1:1 relation, removing the mass-dependencies by comparing instead L/Lbol and LX/Lbol does not provide clear evidence for such a relation. Finally, we find that Ro,sat is smaller for our chromospheric than for our coronal indicator of activity (Ro,sat=0.03±0.01 versus 0.09 ± 0.01). We interpret this as possible evidence for coronal stripping.

Abstract Copyright: © 2017. The American Astronomical Society. All rights reserved.

Journal keyword(s): open clusters and associations: individual: M37 - stars: activity - stars: chromospheres - stars: low-mass - stars: low-mass

VizieR on-line data: <Available at CDS (J/ApJ/834/176): table2.dat>

Status at CDS : All or part of tables of objects could be ingested in SIMBAD with priority 2.

Simbad objects: 2

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Number of rows : 2
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
1 NGC 1490 GiG 03 53 34.200 -66 01 05.26   13.42   11.94 12.6 ~ 41 0
2 M 37 OpC 05 52 18 +32 33.2   6.19 5.6     ~ 346 2

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