J/A+A/640/A40 1002 mCP stars from LAMOST DR4 (Hummerich+, 2020)
A plethora of new, magnetic chemically peculiar stars from LAMOST DR4.
Hummerich S., Paunzen E., Bernhard K.
<Astron. Astrophys. 640, A40 (2020)>
=2020A&A...640A..40H 2020A&A...640A..40H (SIMBAD/NED BibCode)
ADC_Keywords: Stars, Ap ; Stars, Bp ; Stars, peculiar ; Spectral types ;
MK spectral classification ; Stars, ages ; Stars, masses
Keywords: stars: chemically peculiar - stars: abundances - binaries: eclipsing
Abstract:
The present work is aimed at identifying new mCP stars using spectra
collected by the Large Sky Area Multi-Object Fiber Spectroscopic
Telescope (LAMOST). Suitable candidates were selected by searching
LAMOST DR4 spectra for the presence of the characteristic 5200Å
flux depression. Spectral classification was carried out with a
modified version of the MKCLASS code and the accuracy of the
classifications was estimated by comparison with results from manual
classification and the literature. Using parallax data and photometry
from Gaia DR2, we investigated the space distribution of our sample
stars and their properties in the colour-magnitude diagram. Our final
sample consists of 1002 mCP stars, most of which are new discoveries
(only 59 common entries with the Catalogue of Ap, HgMn and Am stars).
Traditional mCP star peculiarities have been identified in all but 36
stars, highlighting the efficiency of the code's peculiarity
identification capabilities. The derived temperature and peculiarity
types are in agreement with manually derived classifications and the
literature. Our sample stars are between 100Myr and 1Gyr old, with the
majority having masses between 2M☉ and 3M☉. Our results
could be considered as strong evidence for an inhomogeneous age
distribution among low-mass (M<3M☉) mCP stars; however, we
caution that our sample has not been selected on the basis of an
unbiased, direct detection of a magnetic field. We identified several
astrophysically interesting objects: the mCP stars LAMOST
J122746.05+113635.3 and LAMOST J150331.87+093125.4 have distances and
kinematical properties in agreement with halo stars; LAMOST
J034306.74+495240.7 is an eclipsing binary system
(Porb=5.1435±0.0012d) hosting an mCP star component; and LAMOST
J050146.85+383500.8 was found to be an SB2 system likely comprising of
an mCP star and a supergiant component. With our work, we
significantly increase the sample size of known Galactic mCP stars,
paving the way for future in-depth statistical studies.
Description:
We present essential data for the 1002 mCP stars identified in this
study, which include LAMOST identifier and alternative identifier,
positional information, spectral type (as derived in this study), S/N
ratio of the analysed spectrum, G magnitudes and parallax information
from GAIA DR2, dereddened colour index (BP-RP)0, absorption in the G
band, and intrinsic absolute magnitude in the G band (Table A1). For
spectral classification, we used an altered version of Richard O.
Gray's MKCLASS code (http://www.appstate.edu/~grayro/mkclass/) that we
specifically tailored to classify magnetic chemically peculiar stars
using low-resolution spectra from LAMOST DR4. We evaluated our results
by spotchecking with manually derived spectral types and comparison to
samples from the literature. We also give masses and fractional ages
on the main sequence (tau) for the 903 sample stars fulfilling the
imposed accuracy criteria (Table B1; cf. Section 4.2.2 of the source
paper) and provide information on the liblamost library (Table C1),
which, together with three other standard star libraries (libr18,
libnor36, libsynth; cf. Section 3 in the source paper), was used in
the classification process.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 173 1002 Essential data for the 1002 mCP stars identified
in the present study
tableb1.dat 32 903 Masses and fractional ages on the main sequence
for the 903 sample stars fulfilling the
accuracy criteria
tablec1.dat 98 38 *Standard stars of the liblamost library
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Note on tablec1.dat: Although it contains a very suitable grid of dwarf spectra,
we note that the liblamost library is far from being a perfect set of standard
star spectra and we explicitly caution against using the liblamost library as
a standard star library out of the context of the present investigation.
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
V/153 : LAMOST DR4 catalogs (Luo+, 2018)
J/AJ/151/13 : LAMOST-Kepler MKCLASS spectral classification (Gray+, 2016)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Seq [1/1002] Internal identification number
6- 24 A19 --- LAMOST LAMOST identifier (JHHMMSS.ss+DDMMSS.s)
26- 53 A28 --- AName Alternative identifier (1)
55- 56 I2 h RAh Right Ascension (J2000.0) (2)
58- 59 I2 min RAm Right Ascension (J2000.0) (2)
61- 65 F5.2 s RAs Right Ascension (J2000.0) (2)
67 A1 --- DE- Declination sign (J2000.0) (2)
68- 69 I2 deg DEd Declination (J2000.0) (2)
71- 72 I2 arcmin DEm Declination (J2000.0) (2)
74- 78 F5.2 arcsec DEs Declination (J2000.0) (2)
80-109 A30 --- SpType Spectral type as derived in this study (3)
110 A1 --- n_SpType [abc] Note on SpType (4)
112-114 I3 --- S/Ng Sloan g band S/N of analysed spectrum
116-122 F7.4 mag Gmag G magnitude (GAIA DR2)
124-129 F6.4 mag e_Gmag Gmag error (GAIA DR2)
131-137 F7.3 mas Plx ? Parallax (GAIA DR2)
139-143 F5.3 mas e_Plx ? Parallax error (GAIA DR2)
145-151 F7.3 mag (BP-RP)0 ? Dereddened BP-RP colour index
153-157 F5.3 mag e_(BP-RP)0 ? Dereddened BP-RP colour index error
159-162 F4.2 mag AG ? Absorption in G band
164-168 F5.2 mag GMAG0 ? Intrinsic absolute magnitude in G band
170-173 F4.2 mag e_GMAG0 ? Intrinsic absolute magnitude in G band error
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Note (1): HD number, TYC identifier or GAIA DR2 number.
Note (2): All positional information was taken from GAIA DR2.
Note (3): The given spectral type corresponds to the output of the MKCLASS_mCP
code. All further additions to the spectral type that are not directly
based on the MKCLASS_mCP output are been placed in square brackets.
(In the source paper, this information has been highlighted using italics).
For an easy identification, manually altered spectral types are indicated
by asterisks.
We note that the "p" denoting peculiarity was omitted from the spectral
classifications.
For more information on the spectral classifications, please refer to
Section 3 of the source paper.
Note (4): Note on SpType as follows:
a = Star contained in the sample of strongly magnetic Ap stars of
Scholz et al.(2019A&A...628A..81S 2019A&A...628A..81S)
b = Enhanced metal-lines but no traditional Si, Cr, Sr, or Eu peculiarities
present
c = Spectrum indicative of an SB2 system (cf. Section 4.8 of paper)
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Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Seq [1/1001] Internal identification number
6- 10 F5.3 Msun Mass Mass (1)
12- 16 F5.3 Msun e_Mass Error on mass, lower limit of 1σ
error interval
18- 22 F5.3 Msun E_Mass Error on Mass, upper limit of 1σ
error interval
24- 26 I3 % tau Fractional age on the main sequence (1)
28- 29 I2 % e_tau Error on tau, lower limit of 1σ
error interval
31- 32 I2 % E_tau Error on tau, upper limit of 1σ
error interval
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Note (1): Values have been calculated assuming solar metallicity [Z]=0.020.
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Byte-by-byte Description of file: tablec1.dat
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Bytes Format Units Label Explanations
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1- 38 A38 --- IDspec Original LAMOST spectrum FITS file name
41- 43 A3 --- --- [KIC]
44- 51 I8 --- KIC Kepler input catalogue identification number
53- 68 A16 --- 2MASS 2MASS identifier (HHMMSSss+DDMMsSSs)
70- 82 A13 --- SpType Spectral type (1)
84- 86 I3 --- S/Ng Sloan g band S/N of spectrum (1)
88- 92 A5 --- Qual Quality flag (1)
94- 96 A3 --- suitab Suitable as an MKK standard? (2)
98 A1 --- n_suitab Note on suitability estimate (3)
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Note (1): excel or vgood, as derived by Gray et al. (2016AJ....151...13G 2016AJ....151...13G,
Cat. J/AJ/151/13).
Note (2): Suitable as an MKK standard star as follows:
1 = suitable to a lesser extent
2 = suitable
3 = fully suitable
Note (3): Note on suitability estimate as follows:
a = Interstellar contribution to the Ca II K line. DIB at 4130Å
b = Slightly broadened lines - rapid rotator? Glitch at 4315Å
c = He lines slightly strong. Glitch at 4307Å
d = Slightly metal-weak?
e = Characteristica of luminosity class III only weakly expressed
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Acknowledgements:
Stefan Hummerich, ernham(at)rz-online.de
(End) Stefan Hummerich [BAV, Germany], Patricia Vannier [CDS] 05-Jun-2020