J/MNRAS/501/5927 New classical Ae stars using LAMOST DR5 (Anusha+, 2021)
Identification of new classical Ae stars in the Galaxy using LAMOST DR5.
Anusha R., Mathew B., Shridharan B., Arun R., Nidhi S., Banerjee G.,
Kartha S.S., Paul K.T., Bhattacharyya S.
<Mon. Not. R. Astron. Soc., 501, 5927-5937 (2021)>
=2021MNRAS.501.5927A 2021MNRAS.501.5927A (SIMBAD/NED BibCode)
ADC_Keywords: Stars, emission ; Milky Way ; Extinction ; Spectral types ;
Spectra, optical ; Infrared
Keywords: stars: emission-line, Be - techniques: photometric -
techniques: spectroscopic - circumstellar matter
Abstract:
We report the first systematic study to identify and characterize a
sample of classical Ae stars in the Galaxy. The spectra of these stars
were retrieved from the A-star catalogue using the Large sky Area
Multi-Object fibre Spectroscopic Telescope (LAMOST) survey. We
identified the emission-line stars in this catalogue from which 159
are confirmed as classical Ae stars. This increases the sample of
known classical Ae stars by about nine times from the previously
identified 21 stars. The evolutionary phase of classical Ae stars in
this study is confirmed from the relatively small mid- and
far-infrared excess and from their location in the optical
colour-magnitude diagram. We estimated the spectral type using MILES
spectral templates and identified classical Ae stars beyond A3, for
the first time. The prominent emission lines in the spectra within the
wavelength range 3700-9000Å are identified and compared with the
features present in classical Be stars. The Hα emission strength
of the stars in our sample show a steady decrease from late-B type to
Ae stars, suggesting that the disc size may be dependent on the
spectral type. Interestingly, we noticed emission lines of FeII, OI,
and Paschen series in the spectrum of some classical Ae stars. These
lines are supposed to fade out by late B-type and should not be
present in Ae stars. Further studies, including spectra with better
resolution, is needed to correlate these results with the rotation
rates of classical Ae stars.
Description:
The Large sky Area Multi-Object fibre Spectroscopic Telescope (LAMOST)
is a 4-m reflecting type Schmidt telescope, located in Xinglong
Station in China and run by the Chinese Academy of Sciences. It has an
effective aperture of 3.6-4.9m and a wide field-of-view (FoV) of
5° (Cui et al. 2012RAA....12.1197C 2012RAA....12.1197C). There are 4000 optical fibres
accommodated on the focal plane, each measuring 320 microns in
diameter and covering 3.3arcsec in the sky. These fibres are fed into
16 low-resolution spectrographs and then registered on to a 4kx4k CCD.
The spectrum obtained for each object covers a wavelength range of
3650-9000Å, with a resolving power of ∼1800 around g band (Wang et
al. 2013SCPMA..56.1833W 2013SCPMA..56.1833W).
We retrieved the spectra of 439920 stars from LAMOST DR5 A-star
catalogue (Luo et al. 2019yCat.5164....0L 2019yCat.5164....0L, Cat. V/164), which were
used for this study.
We studied a sample of 2931 A-type stars showing Hα in emission,
obtained from LAMOST DR5 and report the detection of 159 CAe stars
through spectral analysis, all of which can be considered as new
detection. Our primary motivation was to identify CAe stars from this
sample, which is a rare class of objects that demands attention.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 242 220 List of the classical Ae stars identified from
this study
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See also:
V/164 : LAMOST DR5 catalogs (Luo+, 2019)
II/336 : AAVSO Photometric All Sky Survey (APASS) DR9 (Henden+, 2016)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ID [1/159] Internal identifier
5- 23 A19 --- Name LAMOST designation (JHHMMSS.ss+DDMMSS.s)
25- 27 F3.1 mag Av Visual extinction from Green et al.
(2019ApJ...887...93G 2019ApJ...887...93G)
29- 33 F5.2 mag H-K0 Extinction corrected 2MASS color
35- 39 A5 --- SpTypeE Estimated spectral type obtained from
template matching with MILES library spectra
41- 45 A5 --- SpTypeL Spectral type given by LAMOST
47- 51 F5.2 mag Bmag ? B-band magnitude from Henden et al.
(2015AAS...22533616H, Cat. II/336)
53- 57 F5.2 mag Vmag ? V-band magnitude from Henden et al.
(2015AAS...22533616H, Cat. II/336)
59- 63 F5.2 --- n(K-W2) Spectral index from 2MASS Ks to WISE W2
calculated from the spectral energy
distribution
65- 74 I10 "Y:M:D" Date Observation date
76- 81 F6.2 0.1nm EWHa ? Hα equivalent width corrected for
underlying photospheric absorption
83-136 A54 --- URL URL to visualize the LAMOST spectra
138-242 A105 --- Features Other spectral features present (1)
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Note (1): (e)-emission profile; (a)-absorption profile
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 23-Oct-2023