Discovery of 2716 hot emission-line stars from LAMOST DR5

Shridharan, B.; Mathew, Blesson; Nidhi, S.; Anusha, R; Kartha, Sreeja S.; Kumar, Yerra Bharat

doi:10.1088/1674-4527/21/11/288

Cited by 12 publications

(9 citation statements)

References 86 publications

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“…These statistics, summarised in Table 2, 2021) with mass determinations. However, other less famous objects of the class do exist in the literature, like the recently proposed 58 Herbig Ae/Be sources from the LAMOST survey (Shridharan et al 2021;Zhang et al 2021), the 13 proposed Herbig Ae/Be stars in the Small Magellanic Cloud (Keller et al 2019), or the 77 IMTTs found in the Carina Nebula (Nuñez et al 2021).…”

Section: General Remarksmentioning

confidence: 99%

Identification and spectroscopic characterization of 128 new Herbig stars

Vioque,

Oudmaijer,

Wichittanakom

et al. 2022

Preprint

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We present optical spectroscopy observations of 145 high-mass pre-main sequence candidates from the catalogue of . From these, we provide evidence for the Herbig nature of 128 sources. This increases the number of known objects of the class by ∼ 50%. We determine the stellar parameters of these sources using the spectra and Gaia EDR3 data. The new sources are well distributed in mass and age, with 23 sources between 4-8 M and 32 sources above 8 M . Accretion rates are inferred from Hα and Hβ luminosities for 104 of the new Herbigs. These accretion rates, combined with previous similar estimates, allow us to analyze the accretion properties of Herbig stars using the largest sample ever considered. We provide further support to the existence of a break in accretion properties at ∼ 3-4 M , which was already reported for the previously known Herbig stars. We re-estimate the potential break in accretion properties to be at 3.87 +0.38 −0.96 M . As observed for the previously known Herbig stars, the sample of new Herbig stars independently suggests intense innerdisk photoevaporation for sources with masses above ∼ 7 M . These observations provide robust observational support to the accuracy of the Vioque et al. (2020) catalogue of Herbig candidates.

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Section: General Remarksmentioning

confidence: 99%

Identification and spectroscopic characterization of 128 new Herbig stars

Vioque,

Oudmaijer,

Wichittanakom

et al. 2022

Preprint

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“…For 686 stars in the LEMC, we could not estimate the spectral type due to the low signal-to-noise ratio (S/N) in the bluer region of the LAMOST spectra. Due to the observation strategy of LAMOST DR5, the majority of our sample is towards the galactic anti-centre direction (Figure 1 of Shridharan et al 2021). Limited photometric survey footprints towards this region inhibited us from studying these stars photometrically or using SEDs to estimate their stellar parameters.…”

Section: Synthetic Photometry From Bp/rp Spectramentioning

confidence: 99%

Emission line star catalogues post-Gaia DR3

Shridharan

Mathew

Bhattacharyya

et al. 2022

A&A

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Aims. Gaia Data Release 3 (DR3) and further releases have the potential to identify and categorise new emission-line stars in the Galaxy. We perform a comprehensive validation of astrophysical parameters from Gaia DR3 with the spectroscopically estimated emission-line star parameters from the LAMOST OBA emission catalogue. Methods. We compare different astrophysical parameters provided by Gaia DR3 with those estimated using LAMOST spectra. By using a larger sample of emission-line stars, we performed a global polynomial and piece-wise linear fit to update the empirical relation to convert the Gaia DR3 pseudo-equivalent width to the observed equivalent width, after removing the weak emitters from the analysis. Results. We find that the emission-line source classifications given by DR3 is in reasonable agreement with the classification from the LAMOST OBA emission catalogue. The astrophysical parameters estimated by the esphs module from Gaia DR3 provides a better estimate when compared to gspphot and gspspec. A second degree polynomial relation is provided along with piece-wise linear fit parameters for the equivalent width conversion. We notice that the LAMOST stars with weak Hα emission are not identified to be in emission from BP/RP spectra. This suggests that emission-line sources identified by Gaia DR3 are incomplete. In addition, Gaia DR3 provides valuable information about the binary and variable nature of a sample of emission-line stars.

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“…Recently, the study of these objects benefited greatly from the advent of large-scale spectroscopic surveys (e.g. Chojnowski et al 2015;Anusha et al 2021;Zhang et al 2022;Shridharan et al 2021).…”

Section: Introductionmentioning

confidence: 99%

“…This is particulary helpful for the identification of (cool) objects that do not show conspicuous Balmer-line profiles, let alone any appreciable Balmer-line emission. However, most recent surveys that target emission-line and shell stars specifically search for emission signatures in the Hα line (Anusha et al 2021;Zhang et al 2022;Shridharan et al 2021), and these objects will consequently be missed.…”

Section: Introductionmentioning

confidence: 99%

Searching for shell stars in LAMOST DR4 by probing the Fe 42 multiplet lines

Hümmerich

Paunzen

Bernhard

2022

Monthly Notices of the Royal Astronomical Society

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Shell stars, in particular the cooler ones, often do not show conspicuous Balmer-line emission and may consequently be missed in surveys that specifically search for emission signatures in the Hα line. The present work is aimed at identifying stars with shell-signatures via a search for strong Fe ii multiplet 42 lines at λλ4924, 5018, 5169 Å in archival LAMOST spectra. Candidates were selected by probing the Fe ii (42) lines in the spectra of a sample of colour-preselected early-type stars using a modified version of the MKCLASS code and then categorised by visual inspection of their spectra. We identified 75 stars showing conspicuous shell features, 43 Am/CP1 stars, 12 Ap/CP2 stars, and three objects with composite spectra. Spectral types and equivalent width measurements of the Fe ii (42) lines are presented for the sample of shell stars. Except for three objects, all shell stars appear significantly removed from the ZAMS in the colour-magnitude diagram, which is likely due to extinction by circumstellar material. We find a correlation between the equivalent width of the λ5169 Å line and the distance to the locus of the main-sequence stars (the larger the IR-excess, the stronger the λ5169 Å line) and studied the variability of the shell star sample using TESS data, identifying a very high proportion of double stars. All but 14 shell stars are new discoveries, which highlights the efficiency of the here presented novel approach to identify stars with subtle shell features. This study may be used as a blueprint for discovering these objects in massive spectral databases.

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Discovery of 2716 hot emission-line stars from LAMOST DR5

Cited by 12 publications

References 86 publications

Identification and spectroscopic characterization of 128 new Herbig stars

Identification and spectroscopic characterization of 128 new Herbig stars

Emission line star catalogues post-Gaia DR3

Searching for shell stars in LAMOST DR4 by probing the Fe 42 multiplet lines

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