2013ApJ...765..126M


C.D.S. - SIMBAD4 rel 1.7 - 2019.12.10CET08:23:29

2013ApJ...765..126M - Astrophys. J., 765, 126 (2013/March-2)

Magnetic effects and oversized M dwarfs in the young open cluster NGC 2516.

MacDONALD J. and MULLAN D.J.

Abstract (from CDS):

By combining rotation periods with spectroscopic determinations of projected rotation velocity, Jackson et al. have found that the mean radii for low-mass M-dwarfs in the young, open cluster NGC 2516 are larger than model predictions at a given absolute I magnitude or I - K color and also larger than measured radii of magnetically inactive M-dwarfs. The relative radius difference is correlated with magnitude, increasing from a few percent at MI= 7 to greater than 50% for the lowest luminosity stars in their sample at MI∼ 9.5. Jackson et al. have suggested that a two-temperature star spot model is capable of explaining the observations, but their model requires spot coverage fractions of at least 50% in rapidly rotating M-dwarfs. Here we examine these results in terms of stellar models that include the inhibiting effects of magnetic fields on convective energy transport, with and without the effects of star spots. We find that a pure spot model is inconsistent with the color-magnitude diagram. The observations of radii versus color and radii versus absolute magnitude in NGC 2516 are consistent with models which include only magnetic inhibition or a combination of magnetic inhibition and spots. At a given mass we find a large dispersion in the strength of the vertical component of the magnetic field in the stellar photosphere but the general trend is that the vertical field increases with decreasing mass from a few hundred Gauss at 0.65 M to 600-900 G, depending on spot coverage, in the lowest mass stars in the sample at 0.25 M.

Abstract Copyright:

Journal keyword(s): open clusters and associations: individual: NGC 2516 - stars: low-mass - stars: magnetic field

VizieR on-line data: <Available at CDS (J/ApJ/765/126): table2.dat table3.dat>

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 - 2020
#notes
1 V* CC Eri BY* 02 34 22.5662436236 -43 47 46.871752741 11.305 10.201 8.865 7.926 6.992 K7V 247 0
2 NGC 2516 OpC 07 58 04 -60 45.2           ~ 576 0
3 V* LQ Hya BY* 09 32 25.5684079124 -11 11 04.687410738 9.316 8.761 7.891 7.288 6.815 K1Vp 395 0
4 FBS 1109+767 EB* 11 12 42.3412918233 +76 26 56.388992336   16.1   14.8   M4V 47 0
5 HD 118100 Fl* 13 34 43.2063348511 -08 20 31.335294003 11.578 10.552 9.372 8.602 7.930 K5Ve 322 0
6 V* EK Dra BY* 14 39 00.2109485496 +64 17 29.977371998   8.243 7.604     G1.5V 370 0
7 V* CM Dra BY* 16 34 20.3299130309 +57 09 44.365524588   14.50 12.87 10.85 9.26 M4.5V 400 0
8 V* BY Dra BY* 18 33 55.7719224141 +51 43 08.903033617 10.22 9.23   8.733   K4Ve+K7.5Ve 592 0

    Equat.    Gal    SGal    Ecl

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2019.12.10-08:23:29

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