J/AJ/162/126 FUV and optical absorption in 47 Tucanae (Dixon+, 2021)
Observations of the Bright Star in the globular cluster 47 Tucanae (NGC 104).
Dixon W.V., Chayer P., Miller Bertolami M.M., Sosa Fiscella S.V.,
Benjamin R.A., Dupree A.
<Astron. J., 162, 126-126 (2021)>
=2021AJ....162..126D 2021AJ....162..126D (SIMBAD/NED BibCode)
ADC_Keywords: Stars, bright; Spectra, ultraviolet; Spectra, optical; Abundances;
Clusters, globular
Keywords: Stellar abundances; Stellar atmospheres; Ultraviolet astronomy
Spectroscopy; Post-asymptotic giant branch stars; Stellar evolution
Abstract:
The Bright Star in the globular cluster 47Tucanae (NGC104) is a
post-asymptotic giant branch (post-AGB) star of spectral type B8III.
The ultraviolet spectra of late-B stars exhibit myriad absorption
features, many due to species unobservable from the ground. The Bright
Star thus represents a unique window into the chemistry of 47Tuc. We
have analyzed observations obtained with the Far Ultraviolet
Spectroscopic Explorer, the Cosmic Origins Spectrograph aboard the
Hubble Space Telescope, and the Magellan Inamori Kyocera Echelle
Spectrograph on the Magellan Telescope. By fitting these data with
synthetic spectra, we determine various stellar parameters
(Teff=10850±250K, logg=2.20±0.13) and the photospheric
abundances of 26 elements, including Ne, P, Cl, Ga, Pd, In, Sn, Hg,
and Pb, which have not previously been published for this cluster.
Abundances of intermediate-mass elements (Mg through Ga) generally
scale with Fe, while the heaviest elements (Pd through Pb) have
roughly solar abundances. Its low C/O ratio indicates that the star
did not undergo third dredge-up and suggests that its heavy elements
were made by a previous generation of stars. If so, this pattern
should be present throughout the cluster, not just in this star.
Stellar-evolution models suggest that the Bright Star is powered by a
He-burning shell, having left the AGB during or immediately after a
thermal pulse. Its mass (0.54±0.16M☉) implies that single
stars in 47Tuc lose 0.1-0.2M☉ on the AGB, only slightly less than
they lose on the red giant branch.
Description:
Far Ultraviolet Spectroscopic Explorer (FUSE) provides
medium-resolution spectroscopy from 1187Å to the Lyman limit. The
Bright Star was observed through the FUSE 30"x30" aperture. The data
were retrieved from the Mikulski Archive for Space Telescopes (MAST).
The signal-to-noise ratio (S/N) per resolution element is <5 at
wavelengths shorter than 1026Å and 10-15 at longer wavelengths.
Cosmic Origins Spectrograph (COS/HST) enables high-sensitivity,
medium- and low-resolution spectroscopy in the 1150-3200Å
wavelength range. The Bright Star was observed with COS using both the
G130M and G160M gratings.
The Bright Star was observed with the Magellan/Clay telescope at the
Las Campanas Observatory using the Magellan Inamori Kyocera Echelle
(MIKE) spectrograph with a 0.70x5" slit. The S/N per resolution
element varies within each spectral order and with wavelength,
reaching a maximum of about 450 at 4700Å on the blue side and
7500Å on the red.
Objects:
-----------------------------------------------
RA (2000) DE Designation(s)
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00 24 05.36 -72 04 53.2 47 Tucanae = NGC 104
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 53 150 Selected FUV absorption features
tablea2.dat 52 103 Selected optical absorption features
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See also:
VI/39 : Model Atmospheres (Kurucz, 1979)
VII/195 : Globular Clusters in the Milky Way (Harris, 1996)
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
J/AJ/143/121 : UV properties Galactic globulars with GALEX. (Schiavon+, 2012)
J/A+A/572/A108 : 47 Tuc red giants chemical composition (Thygesen+, 2014)
J/ApJ/780/94 : Abundances of red giants in 47 Tuc (Cordero+, 2014)
J/A+A/588/A25 : Post-AGB & CSPNe evolutionary models (Miller Bertolami, 2016)
J/A+A/594/A116 : HI4PI spectra and column density maps (HI4PI team+, 2016)
J/A+A/604/A128 : S abundances for 1301 stars from GES (Duffau+, 2017)
J/A+A/628/A54 : Fe, Mg, Ti in Galactic clusters (Kovalev+, 2019)
J/MNRAS/485/3042 : UBVRI photometry in 48 globular clusters (Stetson+, 2019)
J/A+A/649/A3 : Gaia Early DR3 photometric passbands (Riello+, 2021)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Ion Element
8- 16 A9 0.1nm Wave Wavelength; Angrstom
18 A1 --- f_Wave [a] Flag on Wave (1)
20- 24 F5.2 --- loggf [-5.25/0.55]? Oscillator strength
26- 34 F9.3 /cm El [0/82885]? Energy level
36- 42 F7.3 --- Abund [-11.31/-3.27]? Abundance relative to hydrogen
44- 47 F4.2 --- e_Abund [0.05/0.7]? Error on Anbund
49- 53 A5 --- Grating Grating
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Note (1): Flag as follows:
a = Spectral region with multiple features. See the discussion in the text.
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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- 5 A5 --- Ion Element
7- 14 F8.3 0.1nm Wave [3736/8719] Wavelength; Angstrom
16- 20 F5.2 --- loggf [-3.78/0.83] Oscillator strength
22- 31 F10.3 /cm El [0/149188] Energy level
33- 37 F5.1 0.1pm EW [3.4/232.6]? Equivalent width; in milli-Angstrom
39- 41 F3.1 0.1pm e_EW [0.8/3.3]? Error in EW
43- 47 F5.2 --- Abund [-8.57/-3.3]? Abundance relative to Hydrogen
49- 52 F4.2 --- e_Abund [0.01/0.3]? Error in Abund
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 17-Jan-2022