J/A+A/531/A88 Optical spectra of 12 Miras (Uttenthaler+, 2011)
The evolutionary state of Miras with changing pulsation periods.
Uttenthaler S., Van Stiphout K., Voet K., Van Winckel H., Van Eck S.,
Jorissen A., Kerschbaum F., Raskin G., Prins S., Pessemier W.,
Waelkens C., Fremat Y., Hensberge H., Dumortier L., Lehmann H.
<Astron. Astrophys. 531, A88 (2011)>
=2011A&A...531A..88U 2011A&A...531A..88U
ADC_Keywords: Stars, variable ; Spectroscopy
Keywords: stars: AGB and post-AGB - stars: oscillations - stars: evolution -
stars: abundances
Abstract:
Miras are long-period variables thought to be in the asymptotic giant
branch (AGB) phase of evolution. In about one percent of known Miras,
the pulsation period is changing. It has been speculated that this
changing period is the consequence of a recent thermal pulse in these
stars. We aim to clarify the evolutionary state of these stars, and to
determine in particular whether or not they are in the
thermally-pulsing (TP-)AGB phase. One important piece of information
that has been neglected so far when determining the evolutionary state
is the presence of the radio-active s-process element technetium (Tc).
We obtained high-resolution, high signal-to-noise-ratio optical
spectra of a dozen prominent Mira variables with changing pulsation
period to search for this indicator of TPs and dredge-up. We also use
the spectra to measure lithium (Li) abundances. Furthermore, we
establish the evolutionary states of our sample stars by means of
their present-day periods and luminosities. Among the twelve sample
stars observed in this programme, five were found to show absorption
lines of Tc. BH Cru is found to be a carbon-star, its period increase
in the past decades possibly having stopped by now. We report a
possible switch in the pulsation mode of T UMi from Mira-like to
semi-regular variability in the past two years. R Nor, on the other
hand, is probably a fairly massive AGB star, which could be true for
all meandering Miras. Finally, we assign RU Vul to the metal-poor
thick disk with properties very similar to the short-period,
metal-poor Miras. We conclude that there is no clear correlation
between period change type and Tc presence. The stars that are most
likely to have experienced a recent TP are BH Cru and R Hya, although
their rates of period change are quite different.
Description:
The tables contain the combined high-resolution optical spectra of the
12 sample stars. The combining of the spectra was optimised for the
wavelength of the technetium lines, i.e. between 420 and 430nm. At
long wavelengths, the combined spectrum could show some artifacts. The
wavelength is in nm, and not necessarily shifted to the rest frame.
The estimated SNR is most realistic for the range 420-430nm.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 82 12 Main properties of the studied Miras (from
the table2 of the paper and Simbad)
sp/* . 12 Individual combined spectra
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Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- FileName Name of the file containing the spectrum
11- 16 A6 --- Name Simbad name of the Mira
19- 20 I2 h RAh Simbad Hour of Right Ascension (J2000.0)
22- 23 I2 min RAm Simbad Minute of Right Ascension (J2000.0)
25- 28 F4.1 s RAs Simbad Second of Right Ascension (J2000.0)
30 A1 --- DE- Simbad Sign of the Declination (J2000.0)
31- 32 I2 deg DEd Simbad Degree of Declination (J2000.0)
34- 35 I2 arcmin DEm Simbad Arcminute of Declination (J2000.0)
37- 38 I2 arcsec DEs Simbad Arcsecond of Declination (J2000.0)
40- 44 A5 --- PCh Period change type: SCh, CCh or MCh (1)
47- 53 A7 --- SpT Range of spectral type
55- 59 F5.1 km/s HRV Heliocentric radial velocity
61- 63 A3 --- Tc [yes no ?] Presence of Technecium
66- 69 I4 K Teff Effective temperature
71 A1 --- l_Li Limit flag on Li
72- 75 F4.1 [---] Li Abundance of Lithium (logε(Li), H=12)
78- 82 F5.1 d P Period, this study
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Note (1): Period change types are as follows:
CCh = Continuous change: a continuous decrease or increase in the period
over a century or more, with no indication for epochs of astable
period. The change is large, 15% or more over 100years.
SCh = Sudden change: after a long phase of stability, the period suddenly
begins to either decrease or increase at a large rate; the total
change in period is similar to that of the CCh class, but the rate
is ten times faster.
MCh = Meandering change: the periods change by 10% over several decades,
followed by a return to the previous period. The rate of change is
comparable to that of the CCh Miras, but the total change is
somewhat smaller than that of the other two classes.
const = constant period
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Byte-by-byte Description of file: sp/*
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Bytes Format Units Label Explanations
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1- 9 F9.5 nm lambda [376/901] Wavelength
10- 22 F13.4 --- Flux Flux in arbitrary units
23- 31 F9.3 --- SNR Estimated signal-to-noise ratio
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Acknowledgements:
Stefan Uttenthaler, stefan.uttenthaler(at)univie.ac.at
(End) S. Uttenthaler [Univ. of Vienna, Austria], P. Vannier [CDS] 12-May-2011