The Search for Super-saturation in Chromospheric Emission

Abstract

We investigate if the super-saturation phenomenon observed at X-ray wavelengths for the corona, exists in the chromosphere for rapidly rotating late-type stars. Moderate resolution optical spectra of fast rotating EUV- and X-ray- selected late-type stars were obtained. Stars in alpha Per were observed in the northern hemisphere with the Isaac Newton 2.5 m telescope and IDS spectrograph. Selected objects from IC 2391 and IC 2602 were observe in the southern hemisphere with the Blanco 4m telescope and R-C spectrograph at CTIO. Ca II H & K fluxes were measured for all stars in our sample. We find the saturation level for Ca II K at log(L_CaK/L_bol) = -4.08. The Ca II K flux does not show a decrease as a function of increased rotational velocity or smaller Rossby number as observed in the X-ray. This lack of "super-saturation" supports the idea of coronal-stripping as the cause of saturation and super-saturation in stellar chromospheres and corona, but the detailed underlying mechanism is still under investigation.

28 Pages, 6 figures, 1 Table; Accepted in ApJ for Aug 2011

References in corpus (8)

• Evidence for Magnetic Flux Saturation in Rapidly Rotating M Stars
• X-rays in the Orion Nebula Cluster: Constraints on the origins of magnetic activity in pre-main sequence stars
• The theoretical calculation of the Rossby number and the `non-local' convective overturn time for pre-main sequence and early post-main sequence stars
• X-ray Emission From Nearby M-dwarfs: the Super-saturation Phenomenon
• Investigating coronal saturation and super-saturation in fast-rotating M-dwarf stars
• The chromospheric emission of solar-type stars in the young open clusters IC 2391 and IC 2602
• Coronal stripping in supersaturated stars
• Chromospheric activity among fast rotating M-dwarfs in the open cluster NGC 2516

Cited by in corpus (6)

• Magnetism, rotation, and nonthermal emission in cool stars -- Average magnetic field measurements in 292 M dwarfs
• Supersaturation and activity-rotation relation in PMS stars: the young Cluster h Per
• The Rotation-Activity Correlations in K and M dwarfs. I. Stellar parameters, compilations of $v\sin i$ and $P/\sin i$ for a large sample of late-K and M dwarfs
• The Rotation-Activity Correlations in K and M dwarfs. II. New constraints on the dynamo mechanisms in late-K and M dwarfs before and at the transition to complete convection
• Chromospheric and Coronal Activity in the 500-Myr-old Open Cluster M37: Evidence for Coronal Stripping?
• The corona -- chromosphere connection studied with simultaneous eROSITA and TIGRE observations