J/A+A/651/A20 Gaia RVS benchmark stars. I. (Caffau+, 2021)
The Gaia RVS benchmark stars.
I. Chemical inventory of the first sample of evolved stars and its Rb NLTE
investigation.
Caffau E., Bonifacio P., Korotin S.A., Francois P., Lallement R.,
Matas Pinto A.M., Di Matteo P., Steffen M., Mucciarelli A., Katz D.,
Haywood M., Chemin L., Sartoretti P., Sbordone L., Andrievsky S.M.,
Kovtyukh V.V., Spite M., Spite F., Panuzzo P., Royer F., Thevenin F.,
Ludwig H.-G., Marchal O., Plum G.
<Astron. Astrophys. 651, A20 (2021)>
=2021A&A...651A..20C 2021A&A...651A..20C (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stars, late-type ; Abundances
Keywords: stars: abundances - Galaxy: abundances - Galaxy: evolution -
Galaxy: formation
Abstract:
The Radial Velocity Spectrometer (RVS) on board the Gaia satellite is
not provided with a wavelength calibration lamp. It uses its
observations of stars with known radial velocity to derive the
dispersion relation. To derive an accurate radial velocity
calibration, a precise knowledge of the line spread function (LSF) of
the RVS is necessary. Good-quality ground-based observations in the
wavelength range of the RVS are highly desired to determine the LSF.
Several radial velocity standard stars are available to the Gaia
community. The highest possible number of calibrators will surely
allow us to improve the accuracy of the radial velocity. Because the
LSF may vary across the focal plane of the RVS, a large number of
high-quality spectra for the LSF calibration may allow us to better
sample the properties of the focal plane.
We selected a sample of stars to be observed with UVES at the Very
Large Telescope, in a setting including the wavelength range of RVS,
that are bright enough to allow obtaining high-quality spectra in a
short time. We also selected stars that lack chemical investigation in
order to increase the sample of bright, close by stars with a complete
chemical inventory.
We here present the chemical analysis of the first sample of 80
evolved stars. The quality of the spectra is very good, therefore we
were able to derive abundances for 20 elements. The metallicity range
spanned by the sample is about 1dex, from slightly metal-poor to
solar metallicity. We derived the Rb abundance for all stars and
investigated departures from local thermodynamical equilibrium (NLTE)
in the formation of its lines.
The sample of spectra is of good quality, which is useful for a Gaia
radial velocity calibration. The Rb NLTE effects in this stellar
parameters range are small but sometimes non-negligible, especially
for spectra of this good quality.
Description:
For this project on the UVES spectrograph, we selected the setting
437+760. The choices on the setting were that (i) the 760 range
completely covers the RVS range without any gaps, and (ii) the 437
range is the reddest setting that can be coupled with the 760 setting.
For metal-rich stars (the majority of our targets), observations in
blue settings provide very crowded spectra, and a higher S/N can be
achieved in this selected setting than in bluer settings such as the
390 setting.
We chose the highest UVES resolution (slit 0.4" in the blue arm and
0.3" in the red arm). For all observations, the DIC2 437+760 setting
was used. For the stars brighter than V magnitude 8.5, an observing
block comprises ten observations of 77.5s to avoid detector
saturation. For the stars fainter than 8.5, five exposures of 202 s
allow avoiding detector saturation. In this program, 90 stars have
been observed, 80 of which are evolved stars and are analysed here.
The 10 unevolved stars will be analysed with stars of similar stellar
parameters that are observed or are scheduled to be observed for the
following two ESO periods (P105 and P106).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb3.dat 480 80 Detailed chemical abundances
tablec.dat 53 42914 Lines used in the chemical investigation for
each element and for each star in the sample
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See also:
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
Byte-by-byte Description of file: tableb3.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- RVS Stellar identifier (RVSNNN)
8- 11 I4 K Teff Effective temperature
13- 16 F4.2 [cm/s2] logg log surface gravity
18- 24 F7.5 km/s xi Microturbulence velocity
26- 32 F7.5 --- A(FeI) A(Fe) derived from FeI lines
34- 41 F8.6 --- e_A(FeI) Uncertainty on A(Fe) derived from FeI lines
43- 45 I3 --- o_FeI ? Number of FeI lines
47- 53 F7.5 --- A(FeII) A(Fe) derived from FeII lines (1)
55- 62 F8.6 --- e_A(FeII) Uncertainty on A(Fe) derived from FeII lines
64 I1 --- o_FeII ? Number of FeII lines (1)
66- 72 F7.5 --- A(C) A(C) abundance (1)
74- 80 F7.5 --- A(O) A(O) abundance (1)
82- 88 F7.5 --- A(Na) A(Na) abundance (1)
90- 97 F8.6 --- e_A(Na) ?=- Uncertainty on A(Na)
99 I1 --- o_Na ? Number of Na lines (1)
101-107 F7.5 --- A(Mg) A(Mg) abundance (1)
109-116 F8.6 --- e_A(Mg) ?=- Uncertainty on A(Mg)
118-119 I2 --- o_Mg ? Number of MgI lines (1)
121-127 F7.5 --- A(Al) A(Al) abundance (1)
129-136 F8.6 --- e_A(Al) Uncertainty on A(Al)
138 I1 --- o_Al ? Number of AlI lines (1)
140-146 F7.5 --- A(Si) A(Si) abundance (1)
148-155 F8.6 --- e_A(Si) Uncertainty on A(Si)
157-158 I2 --- o_si ? Number of SiI lines
160-166 F7.5 --- A(S) ?=- A(S) abundance (1)
168-175 F8.6 --- e_A(S) ?=- Uncertainty on A(S)
177-185 F9.5 --- A(Ca) A(Ca) abundance (1)
187-194 F8.6 --- e_A(Ca) Uncertainty on A(Ca)
196 I1 --- o_Ca ? Number of Ca lines
198-204 F7.5 --- A(ScI) A(Sc) abundance derived from ScI lines (1)
206-213 F8.6 --- e_A(ScI) ?=- Uncertainty on A(Sc) derived from
ScI lines
215 I1 --- o_ScI ? Number of ScI lines
217-223 F7.5 --- A(ScII) A(Sc) abundance derived from ScII lines (1)
225-232 F8.6 --- e_A(ScII) ?=- Uncertainty on A(Sc) derived from
ScII lines
234 I1 --- o_ScII ? Number of ScII lines
236-242 F7.5 --- A(TiI) A(Ti) abundance derived from TiI lines (1)
244-251 F8.6 --- e_A(TiI) Uncertainty on A(Ti) derived from TiI lines
253-254 I2 --- o_TiI ? Number of TiI lines
256-262 F7.5 --- A(TiII) A(Ti) derived from TiII lines (1)
264-271 F8.6 --- e_A(TiII) ?=- Uncertainty on A(Ti) derived from
TiII lines
273 I1 --- o_TiII ? Number of TiII lines
275-281 F7.5 --- A(V) A(V) abundance (1)
283-290 F8.6 --- e_A(V) Uncertainty on A(V)
292-293 I2 --- o_V ? Number of VI lines
295-301 F7.5 --- A(CrI) A(Cr) abundance (1)
303-310 F8.6 --- e_A(CrI) Uncertainty on A(Cr)
312-313 I2 --- o_CrI ? Number of CrI lines
315-321 F7.5 --- A(Mn) A(Mn) abundance (1)
323-330 F8.6 --- e_A(Mn) Uncertainty on A(Mn
332 I1 --- o_Mn ? Number of MnI lines
334-340 F7.5 --- A(Co) A(Co) abundance (1)
342-349 F8.6 --- e_A(Co) Uncertainty on A(Co)
351-352 I2 --- o_Co ? Number of CoI lines
354-360 F7.5 --- A(Ni) A(Ni) abundance (1)
362-369 F8.6 --- e_A(Ni) Uncertainty on A(Ni)
371-372 I2 --- o_Ni ? Number of NiI lines
374-380 F7.5 --- A(Rb)NLTE A(Rb) abundance under NLTE assumption (1)
382-388 F7.5 --- A(Rb)LTE A(Rb) abundance under LTE assumption (1)
390-396 F7.5 --- A(Sr) A(Sr) abundance (1)
398-404 F7.5 --- A(Y) A(Y) abundance (1)
406-412 F7.5 --- A(Ba) A(Ba) abundance (1)
414-420 F7.5 --- A(Eu) A(Eu) abundance (1)
422-430 F9.5 deg RAodeg Observed right ascension
432-440 F9.5 deg DEodeg Observed declination
442-450 F9.5 deg RAdeg Right ascension (J2000)
452-460 F9.5 deg DEdeg Declination (J2000)
462-480 I19 --- GaiaEDR3 GaiaEDR3 source_id
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Note (1): A(X) is defined as: A(X)=log(N(X)/N(H))+12.
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Byte-by-byte Description of file: tablec.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- El Element (1)
5- 6 I2 --- Z Element number
10 I1 --- Ion [0/1]
13- 18 A6 --- RVS Star name (RVSNNN)
25- 32 F8.4 nm lambda Wavelength
34- 40 F7.3 [-] loggf Oscillator strength
43- 53 F11.4 cm-1 Elow LowerEnergy
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Note (1): Elements considered are:
Mg, Al, Si, Ca, ScI, ScII, TiI, TiII, V, Cr, Mn, FeI, FeII, Co, Ni
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Acknowledgements:
Elisabetta Caffau, Elisabetta.Caffau(at)obspm.fr
(End) Patricia Vannier [CDS] 20-May-2021