J/MNRAS/491/874 Abundance analyses of hot subdwarfs with Subaru (Naslim+, 2020)
A search for heavy-metal stars: abundance analyses of hot subdwarfs with Subaru.
Naslim N., Jeffery C.S., Woolf V.M.
<Mon. Not. R. Astron. Soc., 491, 874-888 (2020)>
=2020MNRAS.491..874N 2020MNRAS.491..874N (SIMBAD/NED BibCode)
ADC_Keywords: Stars, subdwarf ; Abundances, peculiar ; Spectra, optical ;
Effective temperatures ; Radial velocities
Keywords: stars: abundances - stars: chemically peculiar -
stars: fundamental parameters - stars: individual: FBS 1749+373 -
stars: individual: PG 1559+048 - subdwarfs
Abstract:
The discovery of extremely zirconium- and lead-rich surfaces amongst a
small subgroup of hot subdwarfs has provoked questions pertaining to
chemical peculiarity in hot star atmospheres and about their
evolutionary origin. With only three known in 2014, a limited search
for additional 'heavy-metal' subdwarfs was initiated with the Subaru
Telescope. Five hot subdwarfs having intermediate to high surface
enrichment of helium were observed at high resolution and analysed for
surface properties and abundances. This paper reports the analyses of
four of these stars. PG 1559+048 and FBS 1749+373, having only
intermediate helium enrichment, show strong lines of triply ionized
lead. PG 1559+048 also shows a strong overabundance of germanium and
yttrium. With more helium-rich surfaces, Ton 414 and J17554+5012, do
not show evidence of heavy-metal enrichment. This limited survey
suggests that extreme enrichment of 'heavy metals' by selective
radiative levitation in hot subdwarf atmospheres is suppressed if the
star is too helium rich.
Description:
Observations of five Helium subdwarfs (He-sds) were obtained on 2015
June 3 with the HDS on the Subaru Telescope in service mode (program
S15A-206S). The sample analysed in this paper comprised PG 1559+048,
Ton 414, FBS 1749+373, and GALEX J175548.50+501210.77. These stars
were identified as He-sds sufficiently bright for high-resolution high
signal-to-noise spectroscopy, and with Teff in a range similar to
that in which heavy metals had been discovered previously (Naslim et
al. 2011MNRAS.412..363N 2011MNRAS.412..363N, 2013MNRAS.434.1920N 2013MNRAS.434.1920N).
Two exposures were made consecutively for each star, with exposure
times of 1200s, except for the brighter GALEX J175548.50+501210.77,
where an exposure times of 300s was used. A slit width of 0.4mm was
used, corresponding to a projected resolution R=45000. The data were
reduced as described by Jeffery et al. (2017MNRAS.465.3101J 2017MNRAS.465.3101J, section
2.3).
Objects:
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RA (ICRS) DE Designation(s)
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16 01 31.27 +04 40 27.0 PG 1559+048 = 2MASS J16013127+0440270
17 51 37.32 +37 19 51.1 FBS 1749+373 = 2MASS J17513733+3719511
09 24 40.07 +30 50 12.5 Ton 414 = 2MASS J09244006+3050124
17 55 48.57 +50 12 11.5 GALEX J175548.5+501210 = 2MASS J17554857+5012116
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 76 11 Atmospheric parameters for the programme stars
table2.dat 214 7 Elemental abundances in the form logεi
tablea2.dat 154 8 Comparison of abundances logεi for
microturbulent velocities vt= 0.0 and 5.0km/s
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Name Star name
14- 16 A3 --- Grid [m10/sbd] Model atmosphere grid (1)
18- 22 I5 K Teff Effective temperature
24- 27 I4 K e_Teff ? Error on Teff
29- 32 F4.2 [cm/s2] logg Surface gravity
34- 37 F4.2 [cm/s2] e_logg ? Error on logg
39- 42 F4.2 --- nHe ? Fractional helium abundance
44- 47 F4.2 --- e_nHe ? Error on nHe
49- 53 F5.2 [-] logy ? Logarithm of helium-to-hydrogen ratio
55- 58 F4.2 [-] e_logy ? Error on logy
60 I1 km/s vsini Projected equatorial rotation velocity (2)
62- 64 F3.1 km/s e_vsini Error on vsini
66- 70 F5.1 km/s RV Radial velocity (3)
72- 74 F3.1 km/s e_RV Error on RV
76 I1 --- ref Reference for Teff, logg, logy and nHe (4)
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Note (1): Grid as follows:
m10 = 1/10 solar for all Z>2 ([X/H]=-1)
sbd = 1/10 solar for 2<Z<26 and solar for Z≥26
Note (2): The projected equatorial rotation velocity (vsini) was measured by
optimizing fits to the profiles of carbon and nitrogen lines
Note (3): Radial velocities measured for all four stars were reported by
Martin et al. (2017MNRAS.467...68M 2017MNRAS.467...68M). However those measurements
omitted a correction to the heliocentric rest frame, which has
included here.
Note (4): References as follows:
1 = This work
2 = Nemeth et al. (2012MNRAS.427.2180N 2012MNRAS.427.2180N)
3 = Thejll et al. (1994ApJ...433..819T 1994ApJ...433..819T)
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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- 12 A12 --- Name Star name
14 A1 --- f_Name Flag on Name (1)
16- 20 F5.2 [-] loge(H) Hydrogen abundance (G1)
22- 26 F5.2 [-] loge(He) Helium abundance (G1)
28- 31 F4.2 [-] loge(C) Carbon abundance (G1)
33- 36 F4.2 [-] e_loge(C) ? Error on loge(C)
38- 41 F4.2 [-] loge(N) Nitrogen abundance (G1)
43- 46 F4.2 [-] e_loge(N) ? Error on loge(N)
48 A1 --- l_loge(O) Limit flag on loge(O)
50- 53 F4.2 [-] loge(O) Oxygen abundance (G1)
55- 58 F4.2 [-] e_loge(O) ? Error on loge(O)
60 A1 --- l_loge(Ne) Limit flag on loge(Ne)
62- 65 F4.2 [-] loge(Ne) Neon abundance (G1)
67- 70 F4.2 [-] e_loge(Ne) ? Error on loge(Ne)
72 A1 --- l_loge(Mg) Limit flag on loge(Mg)
74- 77 F4.2 [-] loge(Mg) Magnesium abundance (G1)
79 A1 --- l_loge(Al) Limit flag on loge(Al)
81- 84 F4.2 [-] loge(Al) Aluminium abundance (G1)
86- 89 F4.2 [-] e_loge(Al) ? Error on loge(Al)
91- 94 F4.2 [-] loge(Si) Silicon abundance (G1)
96- 99 F4.2 [-] e_loge(Si) ? Error on loge(Si)
101-104 F4.2 [-] loge(S) Sulfur abundance (G1)
106-109 F4.2 [-] e_loge(S) ? Error on loge(S)
111 A1 --- l_loge(Cl) Limit flag on loge(Cl)
113-116 F4.2 [-] loge(Cl) Chlorine abundance (G1)
118-121 F4.2 [-] e_loge(Cl) ? Error on loge(Cl)
123 A1 --- l_loge(Ar) Limit flag on loge(Ar)
125-128 F4.2 [-] loge(Ar) Argon abundance (G1)
130 A1 --- l_loge(Ca) Limit flag on loge(Ca)
132-135 F4.2 [-] loge(Ca) Calcium abundance (G1)
137-140 F4.2 [-] e_loge(Ca) ? Error on loge(Ca)
142 A1 --- l_loge(Ti) Limit flag on loge(Ti)
144-147 F4.2 [-] loge(Ti) Titanium abundance (G1)
149-152 F4.2 [-] e_loge(Ti) ? Error on loge(Ti)
154 A1 --- l_loge(V) Limit flag on loge(V)
156-159 F4.2 [-] loge(V) Vanadium abundance (G1)
161-164 F4.2 [-] e_loge(V) ? Error on loge(V)
166 A1 --- l_loge(Fe) Limit flag on loge(Fe)
168-171 F4.2 [-] loge(Fe) Iron abundance (G1)
173 A1 --- l_loge(Ge) Limit flag on loge(Ge)
175-178 F4.2 [-] loge(Ge) Germanium abundance (G1)
180-183 F4.2 [-] e_loge(Ge) ? Error on loge(Ge)
185 A1 --- l_loge(Y) Limit flag on loge(Y)
187-190 F4.2 [-] loge(Y) Yttrium abundance (G1)
192-195 F4.2 [-] e_loge(Y) ? Error on loge(Y)
197 A1 --- l_loge(Zr) Limit flag on loge(Zr)
199-202 F4.2 [-] loge(Zr) Zirconium abundance (G1)
204 A1 --- l_loge(Pb) Limit flag on loge(Pb)
206-209 F4.2 [-] loge(Pb) Lead abundance (G1)
211-214 F4.2 [-] e_loge(Pb) ? Error on loge(Pb)
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Note (1): Flag as follows:
a = Model: Teff=38000K, logg=6.0, nHe=0.200, m10
b = Model: Teff=38000K, logg=6.0, nHe=0.200, sdb
c = Model: Teff=36000K, logg=6.0, nHe=0.300, m10
d = Model: Teff=36000K, logg=6.0, nHe=0.300, sdb
e = Model: Teff=38000K, logg=6.0, nHe=0.699, m10
f = Model: Teff=40000K, logg=6.0, nHe=0.949, m10
g = Asplund et al. (2009ARA&A..47..481A 2009ARA&A..47..481A); photospheric except helium
(helioseismic), neon, and argon (coronal)
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Name Star Name
14 A1 --- f_Name [ab] Flag on Name (1)
16- 19 F4.2 [-] loge(C) Carbon abundance (G1)
21- 24 F4.2 [-] e_loge(C) Error on loge(C)
26- 29 F4.2 [-] loge(N) Nitrogen abundance (G1)
31- 34 F4.2 [-] e_loge(N) Error on loge(N)
36- 39 F4.2 [-] loge(O) ? Oxygen abundance (G1)
41- 44 F4.2 [-] e_loge(O) ? Error on loge(O)
46- 49 F4.2 [-] loge(Ne) ? Neon abundance (G1)
51- 54 F4.2 [-] e_loge(Ne) ? Error on loge(Ne)
56- 59 F4.2 [-] loge(Al) ? Aluminium abundance (G1)
61- 64 F4.2 [-] e_loge(Al) ? Error on loge(Al)
66- 69 F4.2 [-] loge(Si) Silicon abundance (G1)
71- 74 F4.2 [-] e_loge(Si) Error on loge(Si)
76- 79 F4.2 [-] loge(S) Sulfur abundance (G1)
81- 84 F4.2 [-] e_loge(S) Error on loge(S)
86- 89 F4.2 [-] loge(Cl) ? Chlorine abundance (G1)
91- 94 F4.2 [-] e_loge(Cl) ? Error on loge(Cl)
96- 99 F4.2 [-] loge(Ca) ? Calcium abundance (G1)
101-104 F4.2 [-] e_loge(Ca) ? Error on loge(Ca)
106-109 F4.2 [-] loge(Ti) ? Titanium abundance (G1)
111-114 F4.2 [-] e_loge(Ti) ? Error on loge(Ti)4
116-119 F4.2 [-] loge(V) ? Vanadium abundance (G1)
121-124 F4.2 [-] e_loge(V) ? Error on loge(V)
126-129 F4.2 [-] loge(Ge) ? Germanium abundance (G1)
131-134 F4.2 [-] e_loge(Ge) ? Error on loge(Ge)
136-139 F4.2 [-] loge(Y) ? Yttrium abundance (G1)
141-144 F4.2 [-] e_loge(Y) ? Error on loge(Y)
146-149 F4.2 [-] loge(Pb) ? Lead abundance (G1)
151-154 F4.2 [-] e_loge(Pb) ? Error on loge(Pb)
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Note (1): Flag as follows:
a = The abundances are given for a microturbulent velocity vt=0km/s
b = The abundances are given for a microturbulent velocity vt=5km/s
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Global Notes:
Note (G1): The mean surface abundances of measured elements are shown in the
form logεi=logni+c
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 13-Feb-2023