J/ApJS/264/12 Chromospheric activities from LAMOST and K2 (Han+, 2023)
Stellar chromospheric activities revealed from the LAMOST-K2 time-domain survey.
Han H., Wang S., Bai Yu, Yang H., Fang X., Liu J.
<Astrophys. J. Suppl. Ser., 264, 12 (2023)>
=2023ApJS..264...12H 2023ApJS..264...12H
ADC_Keywords: Stars, late-type; Equivalent widths; Abundances, [Fe/H];
Spectra, optical; Photometry
Keywords: Late-type stars ; Stellar activity ; Stellar rotation
Abstract:
By using the LAMOST time-domain survey data, we study stellar
activities based on the Hα lines for about 2000 stars in four K2
plates. Two indices, R'Hα and R+Hα, are computed
from LAMOST spectra, the former of which is derived by excluding the
photospheric contributions to the Hα lines, while the latter is
derived by further subtracting the non-dynamo-driven chromospheric
emission. Meanwhile, the periodicity and variation amplitudes are
computed from K2 light curves. Both the R'Hα-Ro relation and
R+Hα-Ro relation show complicated profiles in the
nonsaturated decay region. Hot stars show flatter slopes and a higher
activity level than cool stars, and the behavior is more notable in
the R+Hα-Ro relation. This is consistent with recent studies
using other activity proxies, including Lx/Lbol, R'HK, and
amplitudes of optical light curves. This may suggest different kinds
of stars follow different power laws in the decay region. Most of our
targets have multiple observations, and some of them exhibit
significant variability of Hα emissions, which may cause the
large scatters shown in the decay region. We find three targets
exhibiting positive correlation in a rotational phase, possibly
indicating that their optical light curves are dominated by hot
faculae rather than cool starspots.
Description:
The Large Sky Area Multi-Object Fiber Spectroscopic Telescope
(hereafter LAMOST, also named as the Guoshoujing Telescope) is a
quasi-meridian Schmidt telescope with a 4m aperture and a field of
view of 5°. With 4000 fibers on its focus surface, tens of
millions of spectra have been gathered with high efficiency.
Since 2012, the LAMOST-Kepler/K2 projects have been carried out, which
performed both time-domain and non-time-domain sky surveys of the
Kepler field and the K2 campaigns, releasing both the
medium-resolution spectral (MRS) and low-resolution spectral (LRS)
data for tens of thousands of targets (Fu+ 2020RAA....20..167F 2020RAA....20..167F ;
Zong+ 2020, J/ApJS/251/15). Recently, LAMOST has started the second
5yr sky survey, which performs both LRS and MRS observations with
R∼1800 and ∼7500, respectively. The MRS observations provide spectra
covering the wavelength range from 4950Å to 5930Å for the blue
arm and from 6300Å to 6800Å for the red arm, respectively.
Spectra of the LRS observations cover the wavelength range of
3650-9000Å.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 47 58798 Medium-resolution EWs of the Hα lines
table2.dat 47 125428 Low-resolution EWs of the Halpha lines
table3.dat 111 1556 All the quantities calculated from the
Medium-Resolution data together with
stellar parameters
table4.dat 111 1678 All the quantities calculated from the
Low-Resolution data together with stellar parameters
--------------------------------------------------------------------------------
See also:
V/146 : LAMOST DR1 catalogs (Luo+, 2015)
IV/34 : K2 Ecliptic Plane Input Catalog (EPIC) (Huber+, 2017)
V/156 : LAMOST DR7 catalogs (Luo+, 2019)
J/A+A/397/147 : Activity-rotation relationship in stars (Pizzolato+ 2003)
J/A+A/469/309 : Activity in late-type stars (Cincunegui+, 2007)
J/ApJ/687/1264 : Age estimation for solar-type dwarfs (Mamajek+, 2008)
J/ApJ/743/48 : Stars with rot. periods & X-ray lum. (Wright+, 2011)
J/ApJ/795/161 : Activity & rotation in Praesepe & Hyades (Douglas+, 2014)
J/A+A/566/A43 : EPOCH Project. EROS-2 LMC periodic variables (Kim+, 2014)
J/ApJ/851/116 : Long-term var. of Kepler sun-like stars (Montet+, 2017)
J/ApJ/834/85 : Hα emission in nearby M dwarfs (Newton+, 2017)
J/MNRAS/485/3457 : Rotational modulation in TESS B stars (Balona+, 2019)
J/A+A/628/A41 : KIC stars in Kepler/XMM-Newton (Pizzocaro+, 2019)
J/ApJS/241/29 : Flare cat. through LC data of Kepler DR25 (Yang+, 2019)
J/other/NatAs/4.03 : Rotation and activity across HR diagram (Lehtinen+, 2020)
J/other/NatAs/4.658 : Rotation and activity across HR diagram (Lehtinen+, 2020)
J/A+A/635/A43 : Stellar rot. periods from K2 (Reinhold+, 2020)
J/ApJ/902/114 : Stellar X-ray activity. I. (Wang+, 2020)
J/ApJS/246/9 : Stellar param. of LAMOST stars using SLAM (Zhang+, 2020)
J/ApJS/247/9 : FGK stars activity in LAMOST-Kepler (Zhang+, 2020)
J/ApJS/251/15 : LAMOST-Kepler/K2 survey (LK-MRS) 1st yr. (Zong+, 2020)
J/other/RAA/21.292 : LAMOST Time-Domain survey, first results (Wang+, 2021)
Byte-by-byte Description of file: table[12].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- LAMOST LAMOST identifier (JHHMMSS.ss+DDMMSS.s)
21- 28 F8.2 0.1nm EW [-180/21936]? Equivalent width; Angstroms
30- 38 F9.2 0.1nm e_EW [0/250977]? Uncertainty in EW
40- 47 F8.2 d BMJD [58784.6/58950.6] Barycentric Modified Julian Date
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table[34].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- LAMOST LAMOST identifier (JHHMMSS.ss+DDMMSS.s)
21- 25 F5.2 0.1nm EWHa [-6.7/1]? Hα equivalent width, EW' (1)
27- 30 F4.2 0.1nm e_EWHa [0/0.7]? Uncertainty in EWHa (1)
32- 36 F5.2 [-] logRHa [-8.5/-3.2]? Log of RHa index, log
(R'Hα) (1)
38- 41 F4.2 [-] e_logRHa [4/7]? Uncertainty in logRHa (1)
43- 46 F4.2 [-] DlogRHa [0/1.2]? Variability of logRHa (1)
48- 52 F5.2 0.1nm EWpHa [-7.7/0.3]? Hα equivalent width, EW+ (2)
54- 57 F4.2 0.1nm e_EWpHa [0/0.7]? Uncertainty in EWpHa (2)
59- 63 F5.2 [-] logRpHa [-7/-3.2]? Log of RHa index, log
(R+Hα) (2)
65- 68 F4.2 [-] e_logRpHa [4/7]? Uncertainty in logRpHa (2)
70- 73 F4.2 [-] DlogRpHa [0/0.7]? Variability of logRpHa (2)
75- 81 F7.2 K Teff [3366/8490] Effective temperature
83- 86 F4.2 [cm/s2] logg [3.5/4.9] Log surface gravity
88- 92 F5.2 [Sun] [Fe/H] [-2.5/0.6] Metallicity
94- 98 F5.2 [-] log(x) [-4.2/-3.9] Log of χ (3)
100- 105 F6.2 d tauC [2.7/139]? Convective turnover time
107- 111 F5.2 d PRot [0.29/30.58]? Rotational period
--------------------------------------------------------------------------------
Note (1): Excluding the photospheric contribution.
Note (2): Excluding the photospheric contribution and chromospheric emission
that are not related to magnetic activity.
Note (3): In this work, χ was estimated as (Equation (4)):
χ=fλ6564/fbol=fλ6564/σT4eff
The continuum flux fλ6564 was estimated based on the PHOENIX
synthetic spectra. See Section 3.1.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 07-Mar-2023