J/MNRAS/441/2361 Stellar magnetism, age and rotation (Vidotto+, 2014)
Stellar magnetism: empirical trends with age and rotation.
Vidotto A.A., Gregory S.G., Jardine M., Donati J.F., Petit P., Morin J.,
Folsom C.P., Bouvier J., Cameron A.C., Hussain G., Marsden S., Waite I.A.,
Fares R., Jeffers S., Do Nascimento J.D.JR
<Mon. Not. R. Astron. Soc., 441, 2361-2374 (2014)>
=2014MNRAS.441.2361V 2014MNRAS.441.2361V (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Magnetic fields
Keywords: techniques: polarimetric; stars: activity; stars: evolution
stars: magnetic field; planetary systems; stars: rotation
Abstract:
We investigate how the observed large-scale surface magnetic fields of
low-mass stars (∼0.1-2M☉), reconstructed through Zeeman-Doppler
imaging, vary with age t, rotation and X-ray emission. Our sample
consists of 104 magnetic maps of 73 stars, from accreting pre-main
sequence to main-sequence objects (1Myr≲t≲10Gyr). For non-accreting
dwarfs we empirically find that the unsigned average large-scale
surface field is related to age as t-0.655±0.045. This relation
has a similar dependence to that identified by Skumanich, used as the
basis for gyrochronology. Likewise, our relation could be used as an
age-dating method ('magnetochronology'). The trends with rotation we
find for the large-scale stellar magnetism are consistent with the
trends found from Zeeman broadening measurements (sensitive to large-
and small-scale fields). These similarities indicate that the fields
recovered from both techniques are coupled to each other, suggesting
that small- and large-scale fields could share the same dynamo field
generation processes. For the accreting objects, fewer statistically
significant relations are found, with one being a correlation between
the unsigned magnetic flux and rotation period. We attribute this to a
signature of star-disc interaction, rather than being driven by the
dynamo.
Description:
The stars considered in this study consist of 73 late-F, G, K and M
dwarf stars, in the PMS to MS phases. All have had their large-scale
surface magnetic fields reconstructed using the ZDI technique, with
some having been observed at multiple epochs.
File table1.dat contains the objects in our sample. Columns are: star
name, spectral type, mass, radius, rotation period, Rossby number,
age, X-ray luminosity, X-ray-to-bolometric luminosity ratio, average
large-scale unsigned surface magnetic field and its observation epoch
(year and month). The measurement errors associated to these
quantities are described in Appendix A. References for the values
compiled in this table are shown in the last column, in the format
presented by CDS and SAO/NASA ADS, except for Petit2014, Folsom2014 and
Waite2014, which were in preparation by the time of writing.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 222 102 Stars with magnetic field measurements
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1 I1 --- Group [1/6] Group (1)
3- 17 A15 --- Star Star name
18- 29 A12 --- n_Star Note for Sun
31- 36 A6 --- SpType Spectral type
38- 41 F4.2 Msun Mass Stellar mass
43- 46 F4.2 Rsun Radius Stellar radius
48- 53 F6.3 d Prot Stellar rotation period
55 A1 --- l_Ro Limit flag on Ro
56- 60 F5.3 --- Ro ?=- Stellar rossby number
62- 67 F6.1 Myr Age ?=- Stellar age
69- 73 F5.2 [10-7W] log10(LX) ?=- Log10 of X-ray luminosity in erg/s
75- 79 F5.2 --- log10(LX/Lbol) ?=- Log10 of X-ray-to-bolometric
luminosities ratio
81- 88 F8.3 --- <|BV|> Average large-scale unsigned surface
magnetic field
90- 97 A8 --- Obs.Epoch Observation epoch of stellar magnetic
field (YYYY or YYY MMM)
99-222 A124 --- Ref Reference bibcode for the values
compiled in this table (2)
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Note (1): The objects are divided in 6 sub-groups as follows:
1 = solar-like stars
2 = young suns
3 = hot-Jupiter host stars
4 = M-dwarf stars
5 = Sun
6 = classical T Tauri stars
Note (2): Petit2014 still in preparation.
(Folsom2014 = 2016MNRAS.457..580F 2016MNRAS.457..580F, Waite2014 = 2015MNRAS.449....8W 2015MNRAS.449....8W)
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Acknowledgements:
Aline Vidotto, aline.vidotto(at)tcd.ie
(End) Patricia Vannier [CDS] 05-Aug-2016