2009A&A...496..787R


Query : 2009A&A...496..787R

2009A&A...496..787R - Astronomy and Astrophysics, volume 496, 787-790 (2009/3-4)

On the magnetic topology of partially and fully convective stars.

REINERS A. and BASRI G.

Abstract (from CDS):

We compare the amount of magnetic flux measured in Stokes V and Stokes I in a sample of early- and mid-M stars around the boundary to full convection (∼M 3.5). Early-M stars possess a radiative core, mid-M stars are fully convective. While Stokes V is sensitive to the net polarity of magnetic flux arising mainly from large-scale configurations, Stokes I measurements can see the total mean flux. We find that in early-M dwarfs, only ∼6% of the total magnetic flux is detected in Stokes V. This ratio is more than twice as large, ∼14%, in fully convective mid-M dwarfs. The bulk of the magnetic flux on M-dwarfs is not seen in Stokes V. This is presumably because magnetic flux is mainly stored in small scale components. There is also more to learn about the effect of the weak-field approximation on the accuracy of strong field detections. In our limited sample, we see evidence for a change in magnetic topology at the boundary to full convection. Fully convective stars store a 2-3 times higher fraction of their flux in fields visible to Stokes V. We estimate the total magnetic energy detected in Stokes I and compare it to results from Stokes V. We find that in early-M dwarfs only ∼0.5% of the total magnetic energy is detected in Stokes V while this fraction is ∼2.5% in mid-M dwarfs.

Abstract Copyright:

Journal keyword(s): stars: late-type - stars: magnetic fields - stars: activity

Simbad objects: 8

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Number of rows : 8
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 G 158-27 PM* 00 06 43.1973190107 -07 32 17.019101068     13.837 13.605 10.15 M5.5V 189 0
2 V* V1005 Ori BY* 04 59 34.8342878424 +01 47 00.669818328   11.48 10.107 9.603 8.239 M0Ve 322 0
3 V* YZ CMi Er* 07 44 40.1723046464 +03 33 08.875227574 13.761 12.831 11.225 9.958 8.263 M4.0Ve 826 0
4 BD+20 2465 Er* 10 19 36.2808181226 +19 52 12.010446571   10.82 9.52 9.19   dM3 1225 0
5 BD+13 2618 Er* 13 00 46.5566863405 +12 22 32.677229903 12.314 11.233 9.750 8.785 7.653 M0V 324 1
6 BD+16 2708 Er* 14 54 29.2361840107 +16 06 03.797990080 12.86 11.686 10.150 9.116 7.872 M3V 258 1
7 Ross 154 Er* 18 49 49.3637762005 -23 50 10.447375350 13.528 12.19 10.43 10.23 7.703 M3.5Ve 351 0
8 V* EV Lac Er* 22 46 49.7312610268 +44 20 02.374381562   11.85 10.26 9.89   M4.0V 847 2

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2022.05.28-10:36:59

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