J/ApJ/921/67 High-dispersion sp. of 8 Phoenix stream red giants (Casey+, 2021)
Signature of a massive rotating metal-poor star imprinted in the Phoenix stellar
stream.
Casey A.R., Ji A.P., Hansen T.T., Li T.S., Koposov S.E., Da Costa G.S.,
Bland-Hawthorn J., Cullinane L., Erkal D., Lewis G.F., Kuehn K.,
Mackey D., Martell S.L., Pace A.B., Simpson J.D., Zucker D.B.
<Astrophys. J., 921, 67 (2021)>
=2021ApJ...921...67C 2021ApJ...921...67C
ADC_Keywords: Spectra, optical; Stars, giant; Abundances
Keywords: Stellar streams
Abstract:
The Phoenix stellar stream has a low intrinsic dispersion in velocity
and metallicity that implies the progenitor was probably a low-mass
globular cluster. In this work we use Magellan/Magellan Inamori
Kyocera Echelle (MIKE) high-dispersion spectroscopy of eight Phoenix
stream red giants to confirm this scenario. In particular, we find
negligible intrinsic scatter in metallicity
(σ([FeII/H])=0.04-0.03+0.11) and a large peak-to-peak range
in [Na/Fe] and [Al/Fe] abundance ratios, consistent with the light
element abundance patterns seen in the most metal-poor globular
clusters. However, unlike any other globular cluster, we also find an
intrinsic spread in [SrII/Fe] spanning ∼1dex, while [BaII/Fe] shows
nearly no intrinsic spread (σ([BaII/H])=0.03-0.02+0.10).
This abundance signature is best interpreted as slow-neutron-capture
element production from a massive fast-rotating metal-poor star
(15-20M☉, vini/vcrit=0.4, [Fe/H]=-3.8). The low inferred
cluster mass suggests the system would have been unable to retain
supernovae ejecta, implying that any massive fast-rotating metal-poor
star that enriched the interstellar medium must have formed and
evolved before the globular cluster formed. Neutron-capture element
production from asymptotic giant branch stars or magneto-rotational
instabilities in core-collapse supernovae provide poor fits to the
observations. We also report one Phoenix stream star to be a
lithium-rich giant (A(Li)=3.1±0.1). At [Fe/H]=-2.93; it is among the
most metal-poor lithium-rich giants known.
Description:
We observed the brightest eight Phoenix stream members between
2018-September-30 and 2019-October-19 with the Magellan Inamori
Kyocera Echelle (MIKE) spectrograph on the 6.5m Magellan Clay
telescope at Las Campanas Observatory, Chile.
Objects:
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RA (ICRS) DE Designation(s)
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01 34 59.99 -49 53 24.0 Phoenix stream = NAME Phoenix Stream
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 86 8 Sky positions and exposure times for all stars observed
table2.dat 44 8 Stellar parameters for all targets
table3.dat 79 203 Summary of stellar abundances, including differences
due to a 1σ change in stellar parameters
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See also:
II/357 : The Dark Energy Survey (DES): Data Release 1 (Abbott+, 2018)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
II/371 : The Dark Energy Survey (DES): Data Release 2 (Abbott+, 2021)
J/AJ/120/1841 : Abund. & Kinematics of Halo and Disk Stars (Fulbright 2000)
J/A+A/439/129 : HERES II. Spectroscopic analysis (Barklem+, 2005)
J/A+A/505/117 : Abund. of red giants in 15 GCs (Carretta+, 2009)
J/ApJ/708/560 : Spectroscopy of UMa II and Coma Ber (Frebel+, 2010)
J/ApJ/731/64 : Spectroscopy of 300 RGBs in ω Cen (Marino+, 2011)
J/AJ/141/175 : Abundances in M15 RGB/RHB stars (Sobeck+, 2011)
J/MNRAS/434/1681 : Extremely metal-poor stars CaII triplet (Carrera+, 2013)
J/ApJ/778/56 : Hamburg/ESO Survey extremely metal-poor stars (Cohen+, 2013)
J/MNRAS/444/392 : Synthetic Stellar Photometry. I. (Casagrande+, 2014)
J/ApJ/797/44 : Evolution and nucleosynthesis of AGB stars (Fishlock+, 2014)
J/AJ/147/136 : Stars of very low metal abundance. VI. (Roederer+, 2014)
J/ApJ/807/171 : SkyMapper Survey metal-poor star sp. (Jacobson+, 2015)
J/ApJ/837/176 : Sp. obs. of 2 red giant stars in omega Cen (Yong+, 2017)
J/ApJS/237/13 : Yields of 13-120M☉ massive stars (Limongi+, 2018)
J/ApJ/870/83 : Abundances in GruI & TriII (Ji+, 2019)
J/MNRAS/490/3508 : The Southern Stellar Stream Sp. Survey (S5) (Li+, 2019)
J/AJ/158/14 : Stellar pop. of GCs using APOGEE (Nataf+, 2019)
J/ApJ/885/3 : Membership in 12 stellar streams from DES (Shipp+, 2019)
J/AJ/160/181 : Chemical abundances in red giants with Magellan (Ji+, 2020)
J/other/Nat/583.768 : 2050 red giants CaII EWs (Wan+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name Star name (G1)
12- 13 I2 h RAh Hour of right ascension (J2000)
15- 16 I2 min RAm Minute of right ascension (J2000)
18- 22 F5.2 s RAs Second of right ascension (J2000)
24 A1 --- DE- Sign of declination (J2000)
25- 26 I2 deg DEd Degree of declination (J2000)
28- 29 I2 arcmin DEm Arcminute of declination (J2000)
31- 34 F4.1 arcsec DEs Arcsecond of declination (J2000)
36- 54 I19 --- Gaia Gaia DR2 identifier
56- 66 A11 "Y/M/D" Date Date of observation (UT)
68- 70 I3 min Exp [30/134] Exposure time
72- 76 F5.2 mag gmag [15.96/17.71] g-band magnitude
78- 80 F3.1 arcsec Slit [0.7/1] Slit
82- 83 I2 pix-1 SN450 [12/25] Signal-to-noise ratio at 450nm
85- 86 I2 pix-1 SN650 [20/44] Signal-to-noise ratio at 650nm
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Star name (G1)
12- 15 I4 K Teff [4905/5292] Effective temperature
17- 18 I2 K e_Teff [43/71] Teff uncertainty
20- 23 F4.2 [cm/s2] logg [1.64/2.56] Log of surface gravity
25- 28 F4.2 [cm/s2] e_logg [0.16/0.17] logg uncertainty
30- 33 F4.2 km/s Vt [1.47/2.11] Microturbulent velocity
35- 38 F4.2 km/s e_Vt [0.07/0.6] Vt uncertainty
40- 44 F5.2 Sun [M/H] [-2.93/-2.52] Mean stellar metallicity (1)
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Note (1): Note that [M/H] refers to the mean stellar metallicity, derived
from FeII lines (Ji+ 2020, J/AJ/160/181).
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Star name (G1)
12- 16 A5 --- Ion Element and ionisation state
18- 20 I3 --- N [1/100] Number of transitions measured
22 A1 --- ul Indicator that the measurement is an upper
limit
24- 28 F5.2 [-] loge [-1.8/9.02] The log(epsilon) abundance
30- 34 F5.2 [-] [X/H] [-3.82/1.01] The [X/H] abundance ratio
36- 39 F4.2 [-] e_[X/H] [0.04/0.6]? The 1-sigma uncertainty in [X/H]
abundance ratio
41- 45 F5.2 [-] [X/Fe] [-1.2/3.7] The [X/Fe] abundance ratio
47- 50 F4.2 [-] e_[X/Fe] [0/0.6]? The 1-sigma uncertainty in [X/Fe]
abundance ratio
52- 56 F5.2 [-] logeDelT [-0.03/0.14]? The abundance change due to a
1-sigma shift in effective temperature,
ΔT
58- 62 F5.2 [-] logeDelg [-0.28/0.13]? The abundance change due to a
1-sigma shift in log (surface gravity),
Δg
64- 68 F5.2 [-] logeDelVt [-0.38/0.05]? The abundance change due to a
1-sigma shift in microturbulence, Δv
70- 74 F5.2 [-] logeDelM [-0.05/0.04]? The abundance change due to a
1-sigma shift in metallicity, ΔM
76- 79 F4.2 [-] s_loge [0/0.5]? The total uncertainty in
log(epsilon) abundance, SX
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Global notes:
Note (G1): Designations from Wan+ 2020Natur.583..768W 2020Natur.583..768W (see J/other/Nat/583.768)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 07-Feb-2023