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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
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:
FileName Lrecl Records Explanations
ReadMe 80 . This file stars.dat 82 12 Main properties of the studied Miras (from the table2 of the paper and Simbad) sp/* 31 12 Individual combined spectra
Byte-by-byte Description of file: stars.dat
Bytes Format Units Label Explanations
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
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
Byte-by-byte Description of file: sp/*
Bytes Format Units Label Explanations
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
Acknowledgements: Stefan Uttenthaler, stefan.uttenthaler(at)
(End) S. Uttenthaler [Univ. of Vienna, Austria], P. Vannier [CDS] 12-May-2011
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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