J/MNRAS/490/2219 s-process enhanced stars in the LAMOST survey (Norfolk+, 2019)
Discovery of s-process enhanced stars in the LAMOST survey.
Norfolk B.J., Casey A.R., Karakas A.I., Miles M.T., Kemp A.J.,
Schlaufman K.C., Ness M., Ho A.Y.Q., Lattanzio J.C., Ji A.P.
<Mon. Not. R. Astron. Soc., 490, 2219-2227 (2019)>
=2019MNRAS.490.2219N 2019MNRAS.490.2219N (SIMBAD/NED BibCode)
ADC_Keywords: Stars, giant ; Stars, peculiar ; Abundances, peculiar ;
Positional data ; Parallaxes, trigonometric ; Proper motions ;
Radial velocities ; Space velocities ; Effective temperatures ;
Optical
Keywords: stars: abundances - stars: chemically peculiar
Abstract:
Here we present the discovery of 895 s-process-rich candidates from
454180 giant stars observed by the Large Sky Area Multi-Object Fibre
Spectroscopic Telescope (LAMOST) using a data-driven approach. This
sample constitutes the largest number of s-process enhanced stars ever
discovered. Our sample includes 187 s-process-rich candidates that are
enhanced in both barium and strontium, 49 stars with significant
barium enhancement only and 659 stars that show only a strontium
enhancement. Most of the stars in our sample are in the range of
effective temperature and logg typical of red giant branch (RGB)
populations, which is consistent with our observational selection bias
towards finding RGB stars. We estimate that only a small fraction
(∼0.5 per cent) of binary configurations are favourable for s-process
enriched stars. The majority of our s-process-rich candidates (95 per
cent) show strong carbon enhancements, whereas only five candidates
(<3 per cent) show evidence of sodium enhancement. Our kinematic
analysis reveals that 97 per cent of our sample are disc stars, with
the other 3 per cent showing velocities consistent with the Galactic
halo. The scaleheight of the disc is estimated to be
zh=0.634±0.063kpc, comparable with values in the literature. A
comparison with yields from asymptotic giant branch (AGB) models
suggests that the main neutron source responsible for the Ba and Sr
enhancements is the 13C(α,n)16O reaction. We conclude that
s-process-rich candidates may have received their overabundances via
mass transfer from a previous AGB companion with an initial mass in
the range 1-3M☉.
Description:
The LAMOST survey released low-resolution (R∼1800) optical spectra
(3700-9000Å) for 2207189 stars in their second data release (Bai et
al. 2016RAA....16..107B 2016RAA....16..107B). For details regarding the LAMOST atmospheric
parameters and error analysis, we direct the reader to the LAMOST
Stellar Parameter pipeline (Wu et al. 2011RAA....11..924W 2011RAA....11..924W, Cat.
J/other/RAA/11.924, 2011A&A...525A..71W 2011A&A...525A..71W, Cat. J/A+A/525/A71). Stellar
parameters and abundances (Teff, logg, [M/H], [α/M]) were
derived by Ho et al. (2017ApJ...836....5H 2017ApJ...836....5H, Cat. J/ApJ/836/5) using The
Cannon (Ness et al. 2015ApJ...808...16N 2015ApJ...808...16N, Cat. J/ApJ/808/16,
2016ApJ...823..114N 2016ApJ...823..114N, Cat. J/ApJ/823/114; Casey et al.
2016arXiv160303040C 2016arXiv160303040C).
The s-process-rich candidates in this work were identified by
filtering for significant flux residuals at the Sr and Ba lines. We
fit a Gaussian function with amplitude A to the residuals of the
observed flux and the data-driven model from The Cannon at wavelengths
4554Å (BaII) and 4077Å (SrII) for s-process-rich candidates, at
wavelengths 4554Å (BaII) and 4934Å (BaII) for Ba-enriched
candidates, and at wavelengths 4077Å (SrII) and 4215Å (SrII) for
Sr-enriched candidates.
Five criteria detailed in Section 2 of the article were used for each
spectrum in order to identify potential s-process enrichment. This
approach yielded 895 candidates, out of which 871 have positive
parallaxes and parallax S/N of five or above in Gaia DR2 (Gaia
Collaboration, 2018A&A...616A...1G 2018A&A...616A...1G, Cat. I/345). Properties of these
candidates are presented in Table 1.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 1280 871 Properties of 895 s-process-rich candidates
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See also:
J/ApJ/836/5 : Abundances of LAMOST giants from APOGEE DR12 (Ho+, 2017)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
V/149 : LAMOST DR2 catalogs (Luo+, 2016)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 43 A43 --- IDsp Object spectral identifier from LAMOST
45- 52 F8.3 K Teffc Effective temperature from
Ho et al. (2017ApJ...836....5H 2017ApJ...836....5H) (1)
54- 62 F9.7 [cm/s2] loggc Surface gravity from
Ho et al. (2017ApJ...836....5H 2017ApJ...836....5H) (1)
64- 73 F10.7 [-] [M/H]c Metallicity from
Ho et al. (2017ApJ...836....5H 2017ApJ...836....5H) (1)
75- 84 F10.7 [-] [a/M]c Abundance of α-elements relative
to overall metallicity from
Ho et al. (2017ApJ...836....5H 2017ApJ...836....5H) (1)
86- 92 F7.4 K e_Teffc Error on Teffc (1)
94- 103 F10.8 [cm/s2] e_loggc Error on loggc (1)
105- 114 F10.8 [-] e_[M/H]c Error on [M/H]c (1)
116- 125 F10.8 [-] e_[a/M]c Error on [a/M]c (1)
127- 134 F8.6 --- chi2c Reduced chi-squared from The Cannon (1)
136- 145 F10.6 deg RAdeg Right ascension (J2000)
147- 155 F9.6 deg DEdeg Declination (J2000)
157- 162 F6.2 pix-1 S/N Signal to noise ratio of the LAMOST
spectra
164- 169 I6 --- codeindex [1553/449248] Code index
171- 175 A5 --- Baonly [true /false] Star with only Ba
enhancements (48/871 stars)
177- 181 A5 --- Sronly [true /false] Star with only Sr
enhancements (645/871 stars)
183- 187 A5 --- BaSr [true /false] Enhancement in both Ba
and Sr (178/871 stars)
189- 197 F9.6 [-] [Ba/Fe]1 Ba/Fe abundance ratio for the 4554Å
line
199- 207 F9.7 [-] e_[Ba/Fe]1 ?=0 Error on [Ba/Fe]1
209- 221 F13.9 --- K[Ba/Fe]1 Kernel density estimate of [Ba/Fe]1
223- 236 F14.10 --- e_K[Ba/Fe]1 Error on K[Ba/Fe]1
238- 246 F9.6 [-] [Ba/Fe]2 Ba/Fe abundance ratio for the 4934Å
line
248- 256 F9.7 [-] e_[Ba/Fe]2 ?=0 Error on [Ba/Fe]2
258- 270 F13.9 --- K[Ba/Fe]2 Kernel density estimate of [Ba/Fe]2
272- 285 F14.10 --- e_K[Ba/Fe]2 Error on K[Ba/Fe]2
287- 295 F9.6 [-] [Sr/Fe]1 Sr/Fe abundance ratio for the 4077Å
line
297- 307 F11.7 [-] e_[Sr/Fe]1 ?=0 Error on [Sr/Fe]1
309- 322 F14.9 --- K[Sr/Fe]1 Kernel density estimate of [Sr/Fe]1
324- 337 F14.10 --- e_K[Sr/Fe]1 Error on K[Sr/Fe]1
339- 347 F9.6 [-] [Sr/Fe]2 Sr/Fe abundance ratio for the 4215Å
line
349- 358 F10.7 [-] e_[Sr/Fe]2 ?=0 Error on [Sr/Fe]2
360- 372 F13.9 --- K[Sr/Fe]2 Kernel density estimate of [Sr/Fe]2
374- 387 F14.10 --- e_K[Sr/Fe]2 Error on K[Sr/Fe]2
389- 407 I19 --- GaiaDR2 Gaia DR2 source identifier (2)
409- 418 F10.6 deg RAgdeg Right ascension (ICRS) at Ep=2015.5 (2)
420- 428 F9.6 deg DEgdeg Declination (ICRS) at Ep=2015.5 (2)
430- 439 F10.6 deg GLON Galactic longitude
441- 450 F10.6 deg GLAT Galactic latitude
452- 461 F10.6 deg ELON Ecliptic longitude
463- 472 F10.6 deg ELAT Ecliptic latitude
474- 482 F9.6 mas Plx ? Gaia DR2 parallax (2)
484- 493 F10.6 mas/yr pmRA ? Gaia DR2 proper motion in right
ascension (2)
495- 504 F10.6 mas/yr pmDE ? Gaia DR2 proper motion in
declination (2)
506- 514 F9.6 mag Gmag Gaia DR2 G-band magnitude (2)
516- 524 F9.6 mag BPmag Gaia DR2 BP-band magnitude (2)
526- 534 F9.6 mag RPmag Gaia DR2 RP-band magnitude (2)
536- 544 F9.7 deg e_RAgdeg Error on RAgdeg (2)
546- 554 F9.7 deg e_DEgdeg Error on DEgdeg (2)
556- 564 F9.7 mas e_Plx ? Error on Plx (2)
566- 574 F9.7 mas/yr e_pmRA ? Error on pmRA (2)
576- 584 F9.7 mas/yr e_pmDE ? Error on pmDE (2)
586- 591 F6.4 mag b_AG ? Lower bound on AG (2)
593- 598 F6.4 mag B_AG ? Upper bound on AG (2)
600- 605 F6.4 mag AG ? Estimate of extinction in the G band
from Apsis-Priam (2)
607- 619 F13.5 --- chi2AL AL chi-square value (2)
621- 627 F7.4 mas epsi ?=0 Excess noise of the source (2)
629- 639 E11.5 --- sepsi ?=0 Significance of excess noise (2)
641- 649 F9.5 --- gofAL Goodness of fit statistic of model wrt
along-scan observations (2)
651- 652 I2 --- MatchObsA Matched FOV transits used in the AGIS
solution (2)
654- 655 I2 --- NbAL Number of bad observations AL (2)
657- 659 I3 --- NgAL Number of good observations AL (2)
661- 663 I3 --- NAC Total number of observations AC (2)
665- 667 I3 --- NAL Total number of observations AL (2)
669- 670 I2 --- Solved Number of astrometric parameters
solved (2)
672- 680 F9.7 um-1 pscol ? Astrometrically determined
pseudocolour of the source (2)
682- 691 F10.8 um-1 e_pscol ? Error on pscol
693- 702 F10.8 mas amax The longest semi-major axis of the 5-d
error ellipsoid (2)
704- 715 F12.8 mas-2 WAL Mean astrometric weight of the
source (2)
717- 725 F9.7 mag BP-G BP-G colour index (2)
727- 735 F9.7 mag BP-RP BP-RP colour index (2)
737- 747 F11.8 --- DEPlxcor ? Correlation between declination and
parallax (2)
749- 759 F11.8 --- DEpmDEcor ? Correlation between declination and
proper motion in declination (2)
761- 771 F11.8 --- DEpmRAcor ? Correlation between declination and
proper motion in right ascension (2)
773- 778 F6.4 mag b_E(BP-RP) ? Lower bound on E(BP-RP) (2)
780- 785 F6.4 mag B_E(BP-RP) ? Upper bound on E(BP-RP) (2)
787- 792 F6.4 mag E(BP-RP) ? Estimate of redenning E(BP-RP) from
Apsis-Priam (2)
794- 802 F9.7 mag G-RP G-RP colour index (2)
804- 815 F12.8 [Lsun] b_Lum ? Lower bound on Lum (2)
817- 829 F13.8 [Lsun] B_Lum ? Upper bound on Lum (2)
831- 842 F12.7 [Lsun] Lum ? Esimate of luminosity from
Apsis-FLAME (2)
844- 845 I2 --- MatchObs The total number of FOV transits
matched to this source (2)
847- 858 F12.9 --- fvarpi Mean Parallax factor AL (2)
860- 870 F11.7 --- RPlx ? Parallax divided by its error (2)
872- 882 F11.8 --- PlxpmDEcor ? Correlation between parallax and
proper motion in declination (2)
884- 894 F11.8 --- PlxpmRAcor ? Correlation between parallax and
proper motion in right ascension (2)
896- 908 F13.5 e-/s FBP Mean flux in the integrated BP band (2)
910- 920 F11.6 e-/s e_FBP Error on FBP (2)
922- 931 F10.5 --- RFBP Integrated BP mean flux divided by its
error (2)
933- 934 I2 --- o_BPmag Number of observations contributing to
BP photometry (2)
936- 944 F9.7 --- E(BP/RP) BP/RP excess factor (2)
946- 958 F13.5 e-/s FG G-band mean flux (2)
960- 970 F11.6 e-/s e_FG Error on FG (2)
972- 981 F10.5 --- RFG G-band mean flux divided by its
error (2)
983- 985 I3 --- o_Gmag Number of observations contributing to
G photometry (2)
987 I1 --- Mode Photometry processing mode (2)
989-1001 F13.5 e-/s FRP Mean flux in the integrated RP band (2)
1003-1013 F11.6 e-/s e_FRP Error on FRP (2)
1015-1024 F10.5 --- RFRP Integrated RP mean flux divided by its
error (2)
1026-1027 I2 --- o_RPmag Number of observations contributing to
RP photometry (2)
1029-1040 F12.9 --- pmRApmDEcor ? Correlation between proper motion in
right ascension and proper motion in
declination (2)
1042-1047 I6 --- fPriam ? Flags for the Apsis-Priam results (2)
1049-1060 F12.9 --- RADEcor Correlation between right ascension
and declination (2)
1062-1071 F10.5 km/s RV ? Radial velocity (2)
1073-1081 F9.6 km/s e_RV ? Error on RV (2)
1083-1092 F10.7 [Rsun] b_Rad ? Lower bound on Rad (2)
1094-1103 F10.7 [Rsun] B_Rad ? Upper bound on Rad (2)
1105-1113 F9.6 [Rsun] Rad ? Estimate of radius from
Apsis-FLAME (2)
1115-1124 I10 --- RandomI Random index used to select subsets (2)
1126-1137 F12.9 --- RAPlxcor ? Correlation between right ascension
and parallax (2)
1139-1150 F12.9 --- RApmDEcor ? Correlation between right ascension
and proper motion in declination (2)
1152-1163 F12.9 --- RApmRAcor ? Correlation between right ascension
and proper motion in right
ascension (2)
1165-1170 F6.1 yr Epoch [2015.5] Reference epoch (2)
1172-1173 I2 --- o_RV Number of transits used to compute
radial velocity (2)
1175-1178 F4.1 [-] [Fe/H]temp ? Fe/H of the template used to compute
radial velocity (2)
1180-1182 F3.1 [cm/s2] loggtemp ? logg of the template used to compute
radial velocity (2)
1184-1187 I4 K Tefftemp ? Teff of the template used to compute
radial velocity (2)
1189-1197 F9.4 K b_Teff ? Lower bound on Teff (2)
1199-1207 F9.4 K B_Teff ? Upper bound on Teff (2)
1209-1216 F8.3 K Teff ? Stellar effective temperature
(estimate from Apsis-Priam) (2)
1218-1219 I2 --- Nper Visibility periods used in astrometric
solution (2)
1221-1230 F10.5 km/s U U component of space velocity
1232-1241 F10.5 km/s V V component of space velocity
1243-1252 F10.5 km/s W W component of space velocity
1254-1262 F9.5 kpc X ? Galactic position X
1264-1271 F8.5 kpc Y ? Galactic position Y
1273-1280 F8.5 kpc Z ? Galactic position Z
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Note (1): Parameters derived by Ho et al. (2017ApJ...836....5H 2017ApJ...836....5H), using
The Cannon (Ness et al. 2015ApJ...808...16N 2015ApJ...808...16N, 2016ApJ...823..114N 2016ApJ...823..114N;
Casey et al. 2016arXiv160303040C 2016arXiv160303040C)
Note (2): Values from Gaia DR2 (Gaia Collaboration, 2018A&A...616A...1G 2018A&A...616A...1G,
Cat. I/345)
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 27-Jan-2023