J/ApJ/882/27 Metal-poor stars with APF obs. II. MW halo stars (Mardini+, 2019)
Metal-poor stars observed with the Automated Planet Finder Telescope.
II. Chemodynamical analysis of six low-metallicity stars in the halo system of
the Milky Way.
Mardini M.K., Placco V.M., Taani A., Li H., Zhao G.
<Astrophys. J., 882, 27 (2019)>
=2019ApJ...882...27M 2019ApJ...882...27M
ADC_Keywords: Milky Way; Stars, halo; Equivalent widths; Stars, metal-deficient;
Radial velocities; Abundances
Keywords: Galaxy: halo ; stars: abundances ; stars: atmospheres ;
stars: fundamental parameters ; stars: kinematics and dynamics ;
techniques: imaging spectroscopy
Abstract:
In this work, we study the chemical compositions and kinematic
properties of six metal-poor stars with [Fe/H]<-2.5 in the Galactic
halo. From high-resolution (R∼110000) spectroscopic observations
obtained with the Lick/Automated Planet Finder, we determined
individual abundances for up to 23 elements, to quantitatively
evaluate our sample. We identify two carbon-enhanced metal-poor stars
(J1630+0953 and J2216+0246) without enhancement in neutron-capture
elements (CEMP-no stars), while the rest of our sample stars are
carbon-intermediate. By comparing the light-element abundances of the
CEMP stars with predicted yields from nonrotating zero-metallicity
massive-star models, we find that the possible progenitors of
J1630+0953 and J2216+0246 could be in the 13-25M☉ mass range,
with explosion energies (0.3-1.8)x1051erg. In addition, the
detectable abundance ratios of light and heavy elements suggest that
our sample stars are likely formed from a well-mixed gas cloud, which
is consistent with previous studies. We also present a kinematic
analysis, which suggests that most of our program stars likely belong
to the inner-halo population, with orbits passing as close as ∼2.9kpc
from the Galactic center. We discuss the implications of these results
on the critical constraints on the origin and evolution of CEMP stars,
as well as the nature of the Population III progenitors of the
lowest-metallicity stars in our Galaxy.
Description:
High-resolution spectroscopic observations for 12 stars were carried
out using the Levy Spectrometer on the Automated Planet Finder (APF)
Telescope at Lick Observatory. The observing setup included a 0.5"
slit, yielding a resolving power of R∼110000 across a wavelength range
of 3730-9989Å.
For more information about the target selection and observations we
refer the reader to Paper I (Mardini+, 2019, J/ApJ/875/89) in which
six stars have been studied. In this paper, we present the remaining
stars.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 72 6 Log of the Lick/APF observations
table2.dat 66 358 Equivalent widths of our sample
table3.dat 87 6 Stellar parameters of the program stars
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See also:
I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/A+A/305/245 : Fe I in metal-poor stars (Magain+, 1996)
J/A+A/416/1117 : Abundances in the early Galaxy (Cayrel+, 2004)
J/ApJ/655/492 : Equivalent widths of 26 metal-poor stars (Aoki+, 2007)
J/ApJ/696/797 : Evolution and yields of low-mass AGB stars (Cristallo+, 2009)
J/ApJS/182/80 : Rare earth abundances (Sneden+, 2009)
J/A+A/512/A54 : Teff and Fbol from Infrared Flux Method (Casagrande+, 2010)
J/ApJ/724/341 : Nucleosynthesis of massive metal-free stars (Heger+, 2010)
J/MNRAS/418/284 : s-process in low-metallicity stars. II. (Bisterzo+, 2011)
J/ApJ/742/54 : CASH project II. Extremely metal-poor stars (Hollek+, 2011)
J/AJ/141/175 : Abundances in M15 RGB/RHB stars (Sobeck+, 2011)
J/AJ/145/13 : Metal-poor stars from SDSS/SEGUE. I. Abundances (Aoki+, 2013)
J/ApJ/769/57 : Equivalent widths of metal-poor stars (Frebel+, 2013)
J/ApJ/773/33 : Metal-poor subgiant BD+44 493 abundances (Ito+, 2013)
J/ApJ/762/26 : Most metal-poor stars. II. Galactic halo stars (Yong+, 2013)
J/ApJ/788/180 : Metal-poor stars in the Milky Way's halo (Carollo+, 2014)
J/MNRAS/444/392 : Synthetic Stellar Photometry. I. (Casagrande+, 2014)
J/ApJ/797/21 : Carbon-enhanced metal-poor stars (Placco+, 2014)
J/ApJ/833/20 : Carbon-enhanced metal-poor star abundances (Yoon+, 2016)
J/ApJ/835/81 : Bright metal-poor stars from HES Survey. II. (Beers+, 2017)
J/A+A/604/A129 : Formation of MW halo and its satellites (Mashonkina+, 2017)
J/A+A/614/A68 : Carbon-enhanced metal-poor stars sample (Caffau+, 2018)
J/ApJ/857/46 : Modelled vs observed abund. of EMP stars (Ishigaki+, 2018)
J/ApJS/238/16 : LAMOST-DR3 very metal-poor star catalog (Li+, 2018)
J/ApJ/875/89 : Metal-poor stars with APF. I. EMP stars (Mardini+, 2019)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 I1 --- Seq [1/6] Running sequence number
3- 12 A10 --- ID Identifier (JHHMM+DDMM)
14- 24 A11 "D/M/Y" Date Date of observation (UT)
26- 27 I2 h RAh Hour of right ascension (J2000)
29- 30 I2 min RAm Minute of right ascension (J2000)
32- 36 F5.2 s RAs Second of right ascension (J2000)
38 A1 --- DE- Sign of declination (J2000)
39- 40 I2 deg DEd Degree of declination (J2000)
42- 43 I2 arcmin DEm Arcminute of declination (J2000)
45- 48 F4.1 arcsec DEs Arcsecond of declination (J2000)
50- 54 F5.2 mag rmag [11.5/13] r-band magnitude
56- 61 A6 s Exp Exposure time
63- 64 I2 pix-1 S/N [30/45] Signal-to-noise ratio (1)
66- 72 F7.2 km/s RV [-114.7/284.1] Radial velocity (2)
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Note (1): The S/N ratio per pixel was measured using IRAF at λ∼4500Å.
Note (2): Our observed radial velocities were measured by cross-correlating the
high-resolution reduced spectra against synthesized templates of the
same spectral type, making use of the MgI triplet at 5160-5190Å.
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 F7.2 0.1nm lambda [4023/6717.7] Wavelength; in Angstroms units (1)
9- 13 A5 --- Ion Species identifier (1)
15- 18 F4.2 eV ExPot [0/4.65] Excitation potential
20- 24 F5.2 [-] log(gf) [-5.7/0.6] log oscillator strength
26- 31 F6.2 0.1pm EW1 [1/122]? J0326+0202 equivalent width;
in mÅ units
33- 38 F6.2 0.1pm EW2 [1.6/133]? J1108+2530 equivalent width;
in mÅ units
40- 45 F6.2 0.1pm EW3 [1/147]? J1256+3440 equivalent width;
in mÅ units
47- 52 F6.2 0.1pm EW4 [1/179]? J1413+1727 equivalent width;
in mÅ units
54- 59 F6.2 0.1pm EW5 [1/144]? J1630+0953 equivalent width;
in mÅ units
61- 66 F6.2 0.1pm EW6 [1/142.3]? J2216+0246 equivalent width;
in mÅ units
-------------------------------------------------------------------------------
Note (1): The molecules C(CH) λ=4312Å, C(CH) λ=4323Å, and
N(CN) λ=4214Å all have spectrum synthetic.
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- ID Identifier (JHHMM+DDMM)
12- 15 I4 K Teff [4783/5215] Lick/APF (corrected & adopted)
effective temperature
17- 20 F4.2 [cm/s2] logg [1.02/2.05] Lick/APF (corrected & adopted)
log of surface gravity
22- 26 F5.2 [-] [Fe/H] [-3.11/-2.52] Lick/APF (corrected &
adopted) [Fe/H] abundance
28- 31 F4.2 km/s Vt [1.08/2.37] Lick/APF (corrected & adopted)
microturbulent velocity
33- 36 I4 K TeffS [4570/5050] Lick/APF (spectroscopic)
effective temperature
38- 41 F4.2 [cm/s2] loggS [0.4/1.59] Lick/APF (spectroscopic) log of
surface gravity
43- 47 F5.2 [-] [Fe/H]S [-3.26/-2.67] Lick/APF (spectroscopic)
[Fe/H] abundance
49- 52 F4.2 km/s VtS [1.09/2.3] Lick/APF (spectroscopic)
microturbulent velocity
54- 57 I4 K Teffp1 [4693/5136] Photometric effective
temperature from (V-J)
59- 62 I4 K Teffp2 [4704/5187] Photometric effective
temperature from (V-K)
64- 67 F4.2 [cm/s2] loggDR2 [1.23/2.15] Log of surface gravity from
Gaia DR2
69-87 I19 --- Gaia Gaia DR2 ID from Table 6 (column added by CDS)
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History:
From electronic version of the journal
References:
Mardini et al. Paper I. 2019ApJ...875...89M 2019ApJ...875...89M Cat. J/ApJ/875/89
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 09-Feb-2021