J/ApJS/276/12 Blue horizontal-branch stars from LAMOST (Ju+, 2025)
The blue horizontal-branch stars from the LAMOST survey: atmospheric parameters.
Ju J., Zhang Bo, Cui W., Huo Z., Liu C., Huang Y., Shi J.
<Astrophys. J. Suppl. Ser., 276, 12 (2025)>
=2025ApJS..276...12J 2025ApJS..276...12J
ADC_Keywords: Stars, horizontal branch; Spectra, optical; Abundances, [Fe/H]
Keywords: Horizontal branch stars ; Fundamental parameters of stars ; Surveys
Abstract:
Blue horizontal-branch (BHB) stars are crucial for studying the
structure of the Galactic halo. Accurate atmospheric parameters of BHB
stars are essential for investigating the formation and evolution of
the Galaxy. In this work, a data-driven technique named Stellar Label
Machine (SLAM) is used to estimate the atmospheric parameters of Large
Sky Area Multi-Object Fiber Spectroscopic Telescope low-resolution
spectra for BHB stars with a set of A-type theoretical spectra as the
training data set. We add color indexes ((BP-G), (G-RP), (BP-RP),
(J-H)) during the training process to constrain the stellar
temperature further. Finally, we derive the atmospheric parameters
(Teff, logg, [Fe/H]) for 5355 BHB stars. Compared to existing
literature results, our results are more robust, and after taking the
color index into account the resulting precision of Teff and logg is
significantly improved, especially for the spectrum with a low
signal-to-noise ratio (S/N). Based on the duplicate observations with
an S/N difference <20%, the random errors are around 30K, 0.1dex, and
0.12dex for Teff, logg, and [Fe/H], respectively. The stellar labels
provided by SLAM are also compared to those from the high-resolution
spectra in the literature. The standard deviation between the
predicted star labels and the published values from the
high-resolution spectra is adopted as the statistical uncertainty of
our results. They are σ(Teff)=76K, σ(logg)=0.04dex, and
σ([Fe/H])=0.09dex, respectively.
Description:
LAMOST is a unique 4m quasi-meridian reflecting Schmidt telescope, and
the LAMOST low-resolution spectra cover a wavelength range of
370-900nm with R∼1800.
Ju+ (2024ApJS..270...11J 2024ApJS..270...11J) identified 5436 blue horizontal-branch (BHB)
stars by measuring the equivalent widths of multiple absorption line
profiles and spectral line features based on the LAMOST low-resolution
spectra. In this study, we adopt 5355 BHB stars as our final sample.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 60 5355 The predicted stellar labels of 5355 LAMOST blue
horizontal-branch (BHB) stars
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See also:
VII/233 : 2MASS All-Sky Extended Source Catalog (XSC) (IPAC/UMass, 2003-2006)
J/AJ/103/267 : Spectroscopy of hot stars in galactic halo (Beers+ 1992)
J/AJ/117/2308 : Spectroscopy of hot stars in the halo (Wilhelm+, 1999)
J/A+A/364/102 : Abundances of field BHB star candidates (Kinman+, 2000)
J/AJ/127/899 : Blue HB stars in SDSS (Sirko+, 2004)
J/ApJ/684/1143 : BHB candidates in the Milky Way (Xue+, 2008)
J/ApJ/738/79 : SDSS-DR8 BHB stars in the Milky Way's halo (Xue+, 2011)
J/ApJ/808/16 : Cannon: a new approach to determine abundances (Ness+, 2015)
J/ApJS/226/1 : Carbon stars from LAMOST DR2 data (Ji+, 2016)
J/AcA/66/405 : Gal. bulge eclipsing & ellipsoidal binaries (Soszynski+, 2016)
J/ApJS/232/16 : Mira stars discovered in LAMOST DR4 (Yao+, 2017)
J/ApJS/234/31 : Carbon stars from LAMOST using machine learning (Li+, 2018)
J/ApJS/241/32 : OB stars from the LAMOST DR5 spectra (Liu+, 2019)
J/ApJS/246/9 : Stellar parameters of LAMOST stars using SLAM (Zhang+, 2020)
J/A+A/654/A107 : Catalogues of Blue Horizontal Branch Stars (Culpan+, 2021)
J/ApJS/257/54 : Early-type star param. from LAMOST LRS & MRS (Guo+, 2021)
J/ApJS/253/22 : Ks absolute magnitudes from LAMOST for OB stars (Xiang+, 2021)
J/A+A/662/A66 : Hot stars from LAMOST DR6 (Xiang+, 2022)
J/A+A/685/A134 : Blue Horizontal Branch stars catalog (Culpan+, 2024)
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 [107128/585113083] LAMOST spectrograph identifier
11- 21 F11.7 deg RAdeg Right Ascension in decimal degrees (J2000)
23- 33 F11.8 deg DEdeg [-10/62] Declination in decimal degrees (J2000)
35- 40 F6.2 --- SN [10/988] Signal to noise in the g band
42- 49 F8.2 K Teff [4496/12806] Effective temperature
51- 54 F4.2 [cm/s2] log(g) [1.47/5.68] log surface gravity
56- 60 F5.2 [Sun] [Fe/H] [-4.04/1.14] Metallicity
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 24-Oct-2025