J/MNRAS/431/2063 UV/X-ray activity of M dwarfs within 10pc (Stelzer+, 2013)
The UV and X-ray activity of the M dwarfs within 10pc of the Sun.
Stelzer B., Marino A., Micela G., Lopez-Santiago J., Liefke C.
<Mon. Not. R. Astron. Soc., 431, 2063-2079 (2013)>
=2013MNRAS.431.2063S 2013MNRAS.431.2063S
ADC_Keywords: Stars, nearby ; Stars, dwarfs ; Stars, M-type ; Ultraviolet ;
X-ray sources
Keywords: stars: activity- stars: chromospheres- stars: coronae -
stars: late-type - ultraviolet: stars - X-rays: stars
Abstract:
M dwarfs are the most numerous stars in the Galaxy. They are
characterized by strong magnetic activity. The ensuing high-energy
emission is crucial for the evolution of their planets and the
eventual presence of life on them. We systematically study the X-ray
and ultraviolet emission of a subsample of M dwarfs from a recent
proper-motion survey, selecting all M dwarfs within 10pc to obtain a
nearly volume-limited sample (∼90 percent completeness). Archival
ROSAT, XMM-Newton and GALEX data are combined with published
spectroscopic studies of Hα emission and rotation to obtain a
broad picture of stellar activity on M dwarfs. We make use of
synthetic model spectra to determine the relative contributions of
photospheric and chromospheric emission to the ultraviolet flux. We
also analyse the same diagnostics for a comparison sample of young M
dwarfs in the TW Hya association (∼10Myr). We find that generally the
emission in the GALEX bands is dominated by the chromosphere but the
photospheric component is not negligible in early-M field dwarfs. The
surface fluxes for the Hα, near-ultraviolet, far-ultraviolet and
X-ray emission are connected via a power-law dependence. We present
here for the first time such flux-flux relations involving broad-band
ultraviolet emission for M dwarfs. Activity indices are defined as
flux ratio between the activity diagnostic and the bolometric flux of
the star in analogy to the CaII R'HK index. For given spectral
type, these indices display a spread of 2-3dex which is largest for
M4 stars. Strikingly, at mid-M spectral types, the spread of rotation
rates is also at its highest level. The mean activity index for fast
rotators, likely representing the saturation level, decreases from
X-rays over the FUV to the NUV band and Hα, i.e. the fractional
radiation output increases with atmospheric height. The comparison to
the ultraviolet and X-ray properties of TWHya members shows a drop of
nearly three orders of magnitude for the luminosity in these bands
between ∼10Myr and few Gyr age. A few young field dwarfs (<1Gyr) in
the 10-pc sample bridge the gap indicating that the drop in magnetic
activity with age is a continuous process. The slope of the age decay
is steeper for the X-ray than for the UV luminosity.
Description:
Our sample is based on the All-Sky Catalog of bright M dwarfs
published by Lepine & Gaidos (2011AJ....142..138L 2011AJ....142..138L, Cat. J/AJ/142/138,
hereafter LG11). We have selected all 163 stars from LG11 within 10pc.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 60 159 Stellar parameters for 10-pc sample
table2.dat 81 159 Observed NUV, FUV, and X-ray fluxes for 10-pc sample
from erratum 2014 (MNRAS 442, 343)
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See also:
V/101 : Nearest stars until 10pc (Zakhozhaj, 1979-1996)
J/A+A/325/159 : Companions to M dwarfs within 5pc (Leinert+ 1997)
J/A+A/421/643 : New nearby stars in the LEHPMS (Reyle+, 2004)
J/AJ/132/866 : New M dwarfs in solar neighborhood (Riaz+, 2006)
J/MNRAS/373/705 : New M dwarfs within 10pc (Reyle+, 2006)
J/MNRAS/383/831 : New DENIS nearby L and late-M dwarfs (Phan-Bao+, 2008)
J/AJ/142/138 : All-sky catalog of bright M dwarfs (Lepine+, 2011)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- --- [PM]
4- 16 A13 --- PM PM name (IHHMMm+DDMM)
18- 27 A10 --- Gl/GJ Gliese designation of star
29- 32 F4.2 pc d [1.8/10] Heliocentric distance of star
34- 37 F4.2 pc e_d rms uncertainty on d
39- 42 A4 --- SpType MK spectral type
44- 47 I4 K Teff [2555/3800] Effective temperature
49- 53 F5.2 [mW/m2] logFb [-9.5/-7.0] Bolometric flux at Earth
55 A1 --- l_vsini [<] Limit flag on vsini
56- 60 F5.2 km/s vsini [1/35]?=- Rotational velocity
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- --- [PM]
4- 16 A13 --- PM PM name (IHHMMm+DDMM)
18- 23 F6.2 [mW/m2] logFnuv ? Near-uv flux from Galex (177-283nm)
25- 30 F6.2 [mW/m2] b_logFnuv ? Lower value of logFnuv interval
32- 37 F6.2 [mW/m2] B_logFnuv ? Upper value of logFnuv interval
39 A1 --- l_logFfuv Limit flag on logFfuv
40- 45 F6.2 [mW/m2] logFfuv ? Far-UV flux from Galex (134-179nm)
47- 52 F6.2 [mW/m2] b_logFfuv ? Lower value of logFfuv interval
54- 59 F6.2 [mW/m2] B_logFfuv ? Upper value of logFfuv interval
61 A1 --- l_logFx Limit flag on logFx
62- 67 F6.2 [mW/m2] logFx X-ray flux (0.2-2.0keV)
69- 74 F6.2 [mW/m2] b_logFx ? Lower value of logFx interval
76- 81 F6.2 [mW/m2] B_logFx ? Upper value of logFx interval
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 11-Jun-2014