J/MNRAS/476/908 Chromospheric activity in 4 open clusters (Fang+, 2018)
Stellar activity with LAMOST. II. Chromospheric activity in open clusters.
Fang X.-S., Zhao G., Zhao J.-K., Bharat Kumar Y.
<Mon. Not. R. Astron. Soc., 476, 908-926 (2018)>
=2018MNRAS.476..908F 2018MNRAS.476..908F (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Stars, late-type ; Equivalent widths
Keywords: stars: activity - stars: chromospheres - stars: late-type -
stars: rotation
Abstract:
We use the LAMOST spectra of member stars in Pleiades, M34, Praesepe,
and Hyades to study how chromospheric activity varies as a function of
mass and rotation at different age. We measured excess equivalent
widths of Hα, Hβ, and CaII K based on estimated
chromospheric contributions from old and inactive field dwarfs, and
excess luminosities are obtained by normalizing bolometric luminosity,
for more than 700 late-type stars in these open clusters. Results
indicate two activity sequences in cool spot coverage and Hα
excess emission among GK dwarfs in Pleiades and M dwarfs in Praesepe
and Hyades, paralleling with well-known rotation sequences. A weak
dependence of chromospheric emission on rotation exists among
ultrafast rotators in saturated regime with Rossby number Ro≤0.1. In
the unsaturated regime, chromospheric and coronal emission show
similar dependence on Ro, but with a shift towards larger Ro,
indicating chromospheric emission gets easily saturated than coronal
emission, and/or convective turnover time-scales based on X-ray data
do not work well with chromospheric emission. More interestingly, our
analysis shows fully convective slow rotators obey the
rotation-chromospheric activity relation similar to hotter stars,
confirming the previous finding. We found correlations among Hα,
Hβ, and CaII K emissions, in which Hα losses are more
important than CaII K for cooler and more active stars. In addition, a
weak correlation is seen between chromospheric emission and
photospheric activity that shows dependence on stellar spectral type
and activity level, which provides some clues on how spot
configuration varies as a function of mass and activity level.
Description:
We have selected four nearby open clusters with a range of ages from
100 to 700Myr (Pleiades, M34, Praesepe, and Hyades), and retrieved
the available spectra of good quality from LAMOST DR3 archive.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablef1.dat 181 378 Measurements for stars in Pleiades
tablef2.dat 181 45 Measurements for stars in M34
tablef3.dat 181 176 Measurements for stars in Praesepe
tablef4.dat 181 142 Measurements for stars in Hyades
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See also:
V/153 : LAMOST DR4 catalogs (Luo+, 2018)
Byte-by-byte Description of file: tablef?.dat
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Bytes Format Units Label Explanations
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1- 25 A25 --- Name Star designation
27- 34 I8 K Teff Effective (quiescent) temperature
36- 45 F10.4 0.1nm EWHa ?=-9999 Equivalent width of Halpha line
47- 56 F10.4 0.1nm EWHb ?=-9999 Equivalent width of Hbeta line
58- 67 F10.4 0.1nm EWCaK ?=-9999 Equivalent width of Ca II K line
69- 78 F10.4 0.1nm EW'Ha ?=-9999 Excess equivalent width of Halpha line
80- 89 F10.4 0.1nm EW'Hb ?=-9999 Excess equivalent width of Hbeta line
91-100 F10.4 0.1nm EW'CaK ?=-9999 Excess equivalent width of Ca II K line
102-111 F10.4 [-] R'Ha ?=-9999 Fractional excess luminosity of
Halpha (1)
113-122 F10.4 [-] R'Hb ?=-9999 Fractional excess luminosity of
Hbeta (1)
124-133 F10.4 [-] R'CaK ?=-9999 Fractional excess luminosity of
Ca IIK (1)
135-144 F10.3 --- fs ?=-9999 Spot filling factor (based on TiO2)
146-153 I8 K Tspot ?=-9999 Spot temperature
158-159 I2 --- multi Photometric single/binary member/non-member (2)
161-170 F10.6 deg RAdeg Right ascension J2000)
172-181 F10.6 deg DEdeg Declination (J2000)
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Note (1): R'Ha, R'Hb, R'CaK are in log10 scale;
Note (2): multi notification as follows:
0 = candidate single members
1 = probable binary members
-1 = fainter probable non-members
10 = brighter probable non-members
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History:
From electronic version of the journal
References:
Fang et al., Paper I, 2016MNRAS.463.2494F 2016MNRAS.463.2494F
(End) Patricia Vannier [CDS] 13-Apr-2021