J/A+A/690/A393 Optical spectra of Mira variables (Uttenthaler+, 2024)
The impact of third dredge-up on the mass loss of Mira variables.
Uttenthaler S., Shetye S., Nanni A., Aringer B., Eriksson K., McDonald I.,
Gobrecht D., Hoefner S., Wolter U., Cristallo S., Bernhard K.
<Astron. Astrophys. 690, A393 (2024)>
=2024A&A...690A.393U 2024A&A...690A.393U (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Stars, late-type ; Stars, M-type ; Stars, S ;
Spectra, infrared ; Optical
Keywords: stars: AGB and post-AGB - stars: evolution - stars: late-type -
stars: oscillations - stars: winds - outflows
Abstract:
The details of the mass-loss process in the late stages of low- and
intermediate-mass stellar evolution are not well understood,
in particular its dependence on stellar parameters. Mira variables are
highly suitable targets for studying this mass-loss process.
Here, we follow up on our earlier finding that a near-to-mid-infrared
(NIR-MIR) colour versus pulsation period diagram shows two sequences
of Miras that can be distinguished by the third dredge-up (3DUP)
indicator technetium in those stars. While IR colours are good
indicators of the dust mass-loss rate (MLR) from Miras, no
corresponding sequences have been found using the gas MLR. However,
investigations of the gas MLR have been hampered by data limitations.
We aim to alleviate these limitations with new observational data.
We present new optical spectra of a well-selected sample of Miras. We
searched these spectra for absorption lines of Tc and other 3DUP
indicators, and combine our findings with gas MLRs and expansion
velocities from the literature. Furthermore, we extend the analysis of
the MIR emission to WISE data and compare the broadband spectral
energy distributions (SEDs) of Miras with and without Tc.
We find no systematic difference in gas MLRs between Miras with and
without Tc. However, the gas envelopes of Tc-poor Miras appear to have
a higher terminal expansion velocity than those of Miras with Tc.
Furthermore, our analysis of the IR photometry strongly corroborates
the earlier finding that Tc-poor Miras have a higher MIR emission than
Tc-rich ones, by as much as a factor of two.We model the IR colours
with DARWIN and stationary wind models and conclude that Miras with
and without Tc have different dust content or dust properties.
We discuss several hypotheses and interpretations of the observations
and conclude that the reduction of free oxygen by 3DUP of carbon and
iron-depleted dust grains in Tc-rich stars are the most convincing
explanations for our observations.
Description:
Optical high-resolution spectra of 17 M- and S-type Miras are
presented. Five of them (R Aur, U Aur, R Cas, WY Cas, U Her) have been
observed with the HERMES spectrograph mounted on the Mercator
telescope and the remaining 12 stars (T Ari, U Ari, S CMi, W Cnc, X
Hya, R Leo, R LMi, R Lyn, X Oph, R Peg, ST Sgr, R Tau) have been
observed with the HEROS spectrograph mounted on the TIGRE telescope.
The spectra obtained with HERMES/Mercator are provided as plain ascii
files containing the wavelength and the flux in a two-column array.
The spectra obtained with HEROS/TIGRE are provided as fits files that
report the wavelength scale in the fits header. The HEROS/TIGRE
spectra are devided into a blue and a red arm, indicated by "B" and
"R" in the file name. The flux is given in arbitrary units in all
cases. No correction for telluric absorption or radial velocity has
been applied. For details on the observations, see Section 2 of the
paper.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 63 19 Observational results and parameters of the
new sample stars
list.dat 160 62 List of fits HEROS/TIGRE spectra
fits/* . 62 Individual fits HEROS/TIGRE spectra
raur.dat 31 335538 R Aur HERMES/Mercator spectrum
rcas.dat 31 335530 R Cas HERMES/Mercator spectrum
uaur.dat 31 335490 U Aur HERMES/Mercator spectrum
uher.dat 31 335541 U Her HERMES/Mercator spectrum
wycas.dat 31 335531 WY Cas HERMES spectrum
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- Name Variable name
8- 10 A3 --- Tc Tc content (0 = Tc absent, 1 = Tc present)
12- 16 F5.1 km/s HRV ?=- Heliocentric radial velocity
18- 20 I3 d Per Pulsation period
22 A1 --- SpType Spectral type
24- 29 F6.3 mag Ksmag Mean KS-band magnitude
31- 36 F6.3 mag W4mag WISE 4 magnitude
38- 43 E6.2 Msun/yr dMgas/dt Gas mass-loss rate
45- 48 F4.1 km/s v1 Terminal expansion velocity
50 A1 --- Ref Reference for the gas MLR and v1 (1)
52- 60 A9 --- Sp Name of the table with spectrum data
62- 63 I2 --- spFits ? Number of fits spectra
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Note (1): References as follows:
a = Knapp & Morris (1985ApJ...292..640K 1985ApJ...292..640K)
b = Knapp (1986ApJ...311..731K 1986ApJ...311..731K)
c = Olofsson et al. (1988A&A...196L...1O 1988A&A...196L...1O)
d = Young (1995ApJ...445..872Y 1995ApJ...445..872Y)
e = Knapp et al. (1998ApJS..117..209K 1998ApJS..117..209K)
f = Schoier et al. (2002A&A...391..577S 2002A&A...391..577S)
g = Scicluna et al. (2022MNRAS.512.1091S 2022MNRAS.512.1091S)
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Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- Name Variable name
8- 12 I5 --- Nx Number of pixels along X-axis
14- 36 A23 "datime" Obs.date Observation date
38- 44 F7.2 0.1nm blambda Lower value of wavelength interval
46- 52 F7.2 0.1nm Bblambda Upper value of wavelength interval
54- 61 F8.6 0.1nm dblambda Wavelength resolution
63- 65 I3 Kibyte size Size of FITS file
67-115 A49 --- FileName Name of FITS file, in subdirectory fits
117-160 A44 --- Title Title of the FITS file
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Byte-by-byte Description of file: raur.dat rcas.dat uaur.dat uher.dat wycas.dat
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Bytes Format Units Label Explanations
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1- 14 E14.9 0.1nm lambda Wavelength
17- 31 E15.9 --- Flux ?=- Flux in arbitrary units
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Acknowledgements:
Stefan Uttenthaler, stefan.uttenthaler(at)gmail.com
(End) Patricia Vannier [CDS] 11-Oct-2024