J/MNRAS/514/4781 Active stars in the LAMOST-K2 field (Xiang+, 2022)
Investigation of stellar magnetic activity using variational autoencoder based
on low-resolution spectroscopic survey.
Xiang Y., Gu S., Cao D.
<Mon. Not. R. Astron. Soc., 514, 4781-4793 (2022)>
=2022MNRAS.514.4781X 2022MNRAS.514.4781X (SIMBAD/NED BibCode)
ADC_Keywords: Stars, late-type ; Stars, variable ; Equivalent widths
Keywords: methods: data analysis - techniques: spectroscopic - stars: activity -
stars: chromospheres
Abstract:
We apply the variational autoencoder (VAE) to the LAMOST-K2
low-resolution spectra to detect the magnetic activity of the stars in
the K2 field. After the training on the spectra of the selected
inactive stars, the VAE model can efficiently generate the synthetic
reference templates needed by the spectral subtraction procedure,
without knowing any stellar parameters. Then, we detect the peculiar
spectral features, such as chromospheric emissions, strong nebular
emissions, and lithium absorptions, in our sample. We measure the
emissions of the chromospheric activity indicators, Hα and CaII
infrared triplet (IRT) lines, to quantify the stellar magnetic
activity. The excess emissions of Hα and CaII IRT lines of the
active stars are correlated well to the rotational periods and the
amplitudes of light curves derived from the K2 photometry. We degrade
the LAMOST spectra to simulate the slitless spectra of the China Space
Station Telescope (CSST) and apply the VAE to the simulated data. For
cool active stars, we reveal a good agreement between the equivalent
widths of Hα line derived from the spectra with two resolutions.
The result indicates the ability of identifying the magnetically
active stars in the future CSST survey, which will deliver an
unprecedented large data base of low-resolution spectra as well as
simultaneous multiband photometry of stars.
Description:
Table 1 lists the stellar parameters derived from LASP and the
quantities of the residual emissions of the chromospheric indicators
for the detected active stars in the LAMOST-K2 (LK2) field. The
residual equivalent widths were measured after subtraction of the
inactive spectra generated by VAE.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 103 1176 Stellar parameters and chromospheric emissions
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See also:
IV/34 : K2 Ecliptic Plane Input Catalog (EPIC) (Huber+, 2017)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 I9 --- Obsid LAMOST obsid
13- 21 I9 --- EPIC K2 Ecliptic Plane Input Catalog number
27- 30 I4 K Teff Effective temperature
33- 36 F4.2 [cm/s2] logg Surface gravity
39- 43 F5.2 --- [Fe/H] Metallicity
45- 49 F5.2 0.1nm EWHa Residual equivalent width of Hα
52- 55 F4.2 0.1nm EW8498 Residual equivalent width of Ca 8498
58- 61 F4.2 0.1nm EW8542 Residual equivalent width of Ca II 8542
64- 67 F4.2 0.1nm EW8662 Residual equivalent width of Ca II 8662
73- 76 F4.2 [mW/m2] logFHa Hα line surface flux
82- 85 F4.2 [mW/m2] logFCa Ca II IRT line surface flux
90- 94 F5.2 --- logR'Ha Ratio of Hα emission to the
bolometric luminosity
99-103 F5.2 --- logR'Ca Ratio of Ca II IRT emission to the
bolometric luminosity
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Acknowledgements:
Yue Xiang, xy(at)ynao.ac.cn
(End) Patricia Vannier [CDS] 25-Jul-2022