J/ApJS/280/24 Halpha emission-line stars & YSOs from LAMOST MRS (Tan+, 2025)
A catalog of Hα emission-line stars and 785 newly identified young stellar
object candidates from LAMOST based on a deep learning method.
Tan L., Mei Y., Qian J., Wang X., Cui Y., Huang A., Wang F., Deng H.,
Liu C., Chi H.
<Astrophys. J. Suppl. Ser., 280, 24 (2025)>
=2025ApJS..280...24T 2025ApJS..280...24T
ADC_Keywords: Spectra, optical; YSOs; Stars, emission
Keywords: Stellar spectral types ; Stellar classification ;
Young stellar objects ; Convolutional neural networks ;
Astronomy data analysis ; Emission line stars
Abstract:
The Hα emission line commonly appears in the spectra of many
stars and serves as a key indicator for tracing ionized interstellar
gas, investigating stellar activity, and studying gas dynamics. Young
stellar objects (YSOs), representing the early evolutionary stages of
stars, typically exhibit the Hα emission line in their spectra.
In this paper, we use bidirectional long short-term memory networks
and convolutional neural networks to identify Hα emission-line
stars in medium-resolution spectra from the Large Area Multi-Target
Fiber Optic Spectroscopic Telescope (LAMOST) survey, and further
search for YSO candidates via the Li absorption line. We constructed a
data set by crossmatching previously published data sets with LAMOST
data and performing manual verification. Using this data set, we built
an identification model that achieved an accuracy of 97.58% on the
testing set. Application of this model to the full survey yielded
46,867 Hα emission-line star candidates, with 41,996 visually
confirmed detections (15,329 of which are recorded in SIMBAD). To
further identify YSOs, we developed a dedicated Li absorption line
detector, identifying 4618 preliminary candidates from the Hα
emission-line stars. Rigorous vetting confirmed 4255 YSO candidates,
comprising 3470 previously cataloged objects and 785 new discoveries.
All catalogs (Hα emission-line stars and YSOs) and the code of
the proposed model are publicly released to facilitate community
research.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 105 41996 Basic information of the 41,996 Hα emission
line stars
table4.dat 90 4333 Basic information of the 4,255 YSO candidates and
the 78 sources potentially contaminated by LPV
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See also:
II/360 : Gaia DR2 x AllWISE catalogue (Marton+, 2019)
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
VII/293 : Classifier catalogue of class II YSO posteriors (Wilson+, 2023)
V/162 : LAMOST DR11 catalogs (Luo+, 2026)
J/A+A/333/619 : Upper Scorpius OB assoc. Lithium survey (Preibisch+ 1998)
J/ApJ/688/1142 : Star formation in W5: Spitzer observations (Koenig+, 2008)
J/A+A/504/461 : YSOs in L1630N and L1641 (Fang+, 2009)
J/ApJS/184/18 : Spitzer survey of young stellar clusters (Gutermuth+, 2009)
J/AJ/144/192 : Spitzer survey of Orion A and B. I. YSOs (Megeath+, 2012)
J/ApJ/794/124 : Young forming region NGC2264 Spitzer sources (Rapson+, 2014)
J/ApJ/827/96 : WISE census of YSOs in Canis Major (Fischer+, 2016)
J/MNRAS/458/3479 : SVM selection of WISE YSO Candidates (Marton+, 2016)
J/MNRAS/493/4463 : Crystalline silicate absorption at 11.1µm (Do-Duy+, 2020)
J/A+A/643/A122 : Active deep learning in large sp. surveys (Skoda+, 2020)
J/A+A/638/A21 : New Herbig Ae/Be & classical Be stars cat. (Vioque+, 2020)
J/A+A/647/A116 : YSO candidate catalog from ANN (Cornu+, 2021)
J/MNRAS/500/4849 : GALAH emission-line stars (Cotar+, 2021)
J/ApJS/254/33 : Gal. midplane Spitzer/IRAC cand. YSOs (SPICY) (Kuhn+, 2021)
J/AJ/162/282 : Untangling Galaxy. III. PMS stars (Mcbride+, 2021)
J/A+A/663/A133 : YSOs toward IRAS 22147+5948 in outer Galaxy (Karska+, 2022)
J/A+A/664/A175 : MW low mass young stars from Gaia EDR3 (Prisinzano+, 2022)
J/ApJS/260/35 : Classical Be stars from LAMOST MRS DR7 (Wang+, 2022)
J/ApJS/259/38 : Ha emission-line stars & Herbig Ae/Be (Zhang+, 2022)
J/A+A/674/A21 : KYSO - The Konkoly Optical YSO catalogue (Marton+, 2023)
J/ApJS/267/7 : YSO candidates from LAMOST LRS DR9 & ZTF (Zhang+, 2023)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 10 I10 --- OBSID [588903058/1127014206] LAMOST observation identifier
12- 30 A19 --- LAMOST LAMOST designation (JHHMMSS.ss+DDMMSS.s)
32- 42 F11.7 deg RAdeg Right Ascension (J2000)
44- 54 F11.7 deg DEdeg [-11/88.5] Declination (J2000)
56- 74 I19 --- Gaia ?=-9999 Gaia DR3 identifier
76- 97 A22 --- OType Type from SIMBAD cross-matching
99-105 A7 --- Type Type from visual inspection (1)
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Note (1): Overview of the 10 subcategories of Hα emission-line profiles
as follows:
type1.1 = no absorption features (10750 occurrences)
type1.2 = medium asborption. This profile exhibits a broad and shallow
absorption component overlaid on the emission line, with the
emission peak situated above the pseudocontinuum line
(3137 occurrences).
type1.3 = deep absorption. This profile features an emission peak embedded
within a deep absorption component, with the peak lying below
the pseudocontinuum line, distinguishing it from Type 1.2
(410 occurrences).
type2.1 = Double peaks above continuum. both peaks are above the
pseudocontinuum line. The distinction between Types 2.1 and
2.2 lies in the obviousness of the double peaks (4931 occurrences).
type2.2 = Double peaks above continuum. Both peaks are above the
pseudocontinuum line. The distinction between Types 2.1 and
2.2 lies in the obviousness of the double peaks (2430 occurrences).
type2.3 = Double peaks below continuum (301 occurrences).
type2.4 = Strong double peaks with deep absorption. This profile resembles
Types 2.1, but feature a sharp and deep absorption line
between the two peaks (1266 occurrences).
type2.5 = Strong double peaks with deep absorption. This profile resembles
Types 2.3, but feature a sharp and deep absorption line
between the two peaks (7 occurrences).
type3.1 = P Cygni profile characterized by an absorption component on
the left side of the emission line (7388 occurrences).
type3.2 = Inverse P Cygni profile: features an absorption component on
the right side of the emission line (7381 occurrences).
See Section 2.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 10 I10 --- OBSID [589105026/1126212122] LAMOST observation
identifier
11 A1 --- f_OBSID [*?] Flag on OBSID (1)
13- 31 A19 --- LAMOST LAMOST designation (JHHMMSS.ss+DDMMSS.s)
33- 43 F11.7 deg RAdeg Right Ascension (J2000)
45- 54 F10.7 deg DEdeg [-10/79.2] Declination (J2000)
56- 74 I19 --- Gaia ?=-9999 Gaia DR3 identifier
76 I1 --- [NII] [0/1] Detection of the [NII]6548+6583A lines
(1=line was observed; 0=not detected)
78 I1 --- [OI] [0/1] Detection of the [OI]6300+6364A lines
(1=line was observed; 0=not detected)
80 I1 --- HeI [0/1] Detection of the HeI6678A line
(1=line was observed; 0=not detected)
82 I1 --- [SII] [0/1] Detection of the [SII]6717+6731A lines
(1=line was observed; 0=not detected)
84- 90 F7.2 0.1nm EW [-242.7/0] Hα equivalent width; Angstroms
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Note (1): Flag as follows:
? = potential confusion with LPV (78 occurrences)
* = newly identified YSO candidate (785 occurrences)
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History:
From electronic version of the journal
License: CC-BY-4.0
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 22-May-2026