J/AJ/161/277 Sample of 45 HαEW outliers (Kiman+, 2021)
Calibration of the Hα age-activity relation for M dwarfs.
Kiman R., Faherty J.K., Cruz K.L., Gagne J., Angus R., Schmidt S.J.,
Mann A.W., Bardalez Gagliuffi D.C., Rice E.
<Astron. J., 161, 277-277 (2021)>
=2021AJ....161..277K 2021AJ....161..277K (SIMBAD/NED BibCode)
ADC_Keywords: Stars, M-type; Stars, dwarfs; Photometry, H-alpha; Spectral types
Keywords: Low mass stars; Astronomy data analysis; Catalogs; Stellar activity
Astrometric binary stars; Stellar evolution
Abstract:
In this work, we calibrate the relationship between Hα emission
and M-dwarf ages. We compile a sample of 892 M-dwarfs with Hα
equivalent width (HαEW) measurements from the literature that
are either comoving with a white dwarf of known age (21 stars) or in a
known young association (871 stars). In this sample we identify 7
M-dwarfs that are new candidate members of known associations. By
dividing the stars into active and inactive categories according to
their HαEW and spectral type (SpT), we find that the fraction of
active dwarfs decreases with increasing age, and the form of the
decline depends on SpT. Using the compiled sample of age calibrators,
we find that Hα EW and fractional Hα luminosity
(LHα/Lbol) decrease with increasing age. HαEW for
SpT≲M7 decreases gradually up until ∼1Gyr. For older ages, we found
only two early M dwarfs that are both inactive and seem to continue
the gradual decrease. We also found 14 mid-type M-dwarfs, out of which
11 are inactive and present a significant decrease in HαEW,
suggesting that the magnetic activity decreases rapidly after ∼1Gyr.
We fit LHα/Lbol versus age with a broken power law and find
an index of -0.11-0.01+0.02 for ages ≲776Myr. The index becomes
much steeper at older ages, but a lack of field age-calibrators
(≫1Gyr) leaves this part of the relation far less constrained.
Finally, from repeated independent measurements for the same stars, we
find that 94% of them have a level of HαEW variability ≲5Å
at young ages (<1Gyr).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 68 45 *Sample of HαEW outliers
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Note on table3.dat : Possibly accreting according to the criterion
from White & Basri, 2003ApJ...582.1109W 2003ApJ...582.1109W.
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See also:
J/MNRAS/447/1126 : Halpha measurements in Abell 2465 (Wegner+, 2015)
J/MNRAS/466/163 : Candidate Halpha sources in GBS (Wevers+, 2017)
J/A+A/624/A10 : Normalized Halpha line profiles of FGK stars (Giribaldi+, 2019)
J/A+A/630/A90 : Halpha emission-line stars in Canis Major (Pettersson+, 2019)
J/ApJS/253/19 : Halpha and other EWs of LAMOST M-type stars (Zhang+, 2021)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 17 A17 --- 2MASS 2MASS identifier
19- 22 F4.1 --- SpT ?=-1 Spectral type
24- 42 F19.15 0.1nm EWHa [11.5/250] Equivalent width, Hα
44- 61 F18.16 0.1nm e_EWHa [0.05/9.8]? Uncertainty in EWHa
63- 68 F6.2 --- dHa [0.43/230] Delta above the Hα EW limit
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History:
From electronic version of the journal
(End) Prepared by Coralie Fix [CDS], 17-Aug-2021