Chromospheric and Coronal Activity in the 500-Myr-old Open Cluster M37: Evidence for Coronal Stripping?

Abstract

We present the results of a spectroscopic survey to characterize chromospheric activity, as measured by H$\alpha$ emission, in low-mass members of the 500-Myr-old open cluster M37. Combining our new measurements of H$\alpha$ luminosities ($L_{H\alpha }$) with previously cataloged stellar properties, we identify saturated and unsaturated regimes in the dependence of the $L_{H\alpha }$-to-bolometric-luminosity ratio, $L_{H\alpha }/L_{bol}$, on the Rossby number $R_o$. All rotators with Ro smaller than 0.03$\pm$0.01 converge to an activity level of $L_{H\alpha }/L_{bol}$ = (1.27$\pm$0.02) x 10${}^{-4}$. This saturation threshold ($R_{o,sat}$ = 0.03$\pm$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 $L_{H\alpha }/L_{bol}$($R_o$) following a power-law of index $\beta$ = -0.51$\pm$0.02, slightly shallower than the one found for a combined $\approx$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, $L_X$), we confirm that chromospheric activity decays at a much slower rate than coronal activity with increasing $R_o$. While a comparison of $L_{H\alpha }$ and $L_X$ for M37 members with measurements of both reveals a nearly 1:1 relation, removing the mass-dependencies by comparing instead $L_{H\alpha }/L_{bol}$ and $L_X/L_{bol}$ does not provide clear evidence for such a relation. Finally, we find that $R_{o,sat}$ is smaller for our chromospheric than for our coronal indicator of activity ($R_{o,sat}$ = 0.03$\pm$0.01 versus 0.09$\pm$0.01). We interpret this as possible evidence for coronal stripping.

arXiv commentAccepted for publication on the Astrophysical Journal

References in corpus (32)

• emcee: The MCMC Hammer
• The Sloan Digital Sky Survey: Technical Summary
• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• A new extensive library of PHOENIX stellar atmospheres and synthetic spectra
• A terrestrial planet candidate in a temperate orbit around Proxima Centauri
• The stellar activity-rotation relationship and the evolution of stellar dynamos
• The Fifth Data Release of the Sloan Digital Sky Survey
• The SDSS View of the Palomar-Green Bright Quasar Survey
• Keck Spectra of Pleiades Brown Dwarf Candidates and a Precise Determination of the Lithium Depletion Edge in the Pleiades
• Hectospec, the MMT's 300 Optical Fiber-Fed Spectrograph
• The Kepler Catalog of Stellar Flares
• The Stellar Populations of Praesepe and Coma Berenices
• The evolution of X-ray emission in young stars
• On the angular momentum evolution of fully-convective stars: rotation periods for field M-dwarfs from the MEarth transit survey
• Theoretical isochrones in several photometric systems II. The Sloan Digital Sky Survey ugriz system
• Planetary Nebulae: Observational Properties, Mimics, and Diagnostics
• The UV and X-ray activity of the M dwarfs within 10pc of the Sun
• The Factory and The Beehive II. Activity and Rotation in Praesepe and the Hyades
• The Age-Activity-Rotation Relationship in Solar-Type Stars
• Deep MMT Transit Survey of the Open Cluster M37 II: Variable Stars
• K2 Rotation Periods for low-mass Hyads and the Implications for Gyrochronology
• Deep MMT Transit Survey of the Open Cluster M37 III: Stellar Rotation at 550 Myr
• Ca II H and K Chromospheric Emission Lines in Late K and M Dwarfs
• Deep MMT Transit Survey of the Open Cluster M37 I: Observations and Cluster Parameters
• X-Ray-Emitting Stars Identified from the ROSAT All-Sky Survey and the Sloan Digital Sky Survey
• Supersaturation and activity-rotation relation in PMS stars: the young Cluster h Per
• The ultracool dwarf DENIS-P J104814.7-395606. Chromospheres and coronae at the low-mass end of the main-sequence
• Chromospheric activity among fast rotating M-dwarfs in the open cluster NGC 2516
• Linking Stellar Coronal Activity and Rotation at 500 Myr: A Deep Chandra Observation of M37
• RACE-OC Project: Rotation and variability in the open cluster NGC2099 (M37)
• The X-ray luminosity function of M37 and the evolution of coronal activity in low-mass stars
• The Search for Super-saturation in Chromospheric Emission

Cited by in corpus (7)

• The Evolution of Flare Activity with Stellar Age
• Relation of X-ray activity and rotation in M dwarfs and predicted time-evolution of the X-ray luminosity
• A New Look at an Old Cluster: The Membership, Rotation, and Magnetic Activity of Low-Mass Stars in the 1.3-Gyr-Old Open Cluster NGC 752
• Calibration of the Halpha Age-Activity relation for M dwarfs
• The Planetary Nebula in the 500 Myr old Open Cluster M37
• The Factory and the Beehive. IV. A Comprehensive Study of the Rotation X-ray Activity Relation in Praesepe and the Hyades
• The Factory and the Beehive. V. Chromospheric and Coronal Activity and Its Dependence on Rotation in Praesepe and the Hyades