Probing the mass-loss history of the unusual Mira variable R Hydrae through its infrared CO wind

Context. The unusual Mira variable R Hya is well known for its declining period between AD 1770 and 1950, which is possibly attributed to a recent thermal pulse. Aims. The goal of this study is to probe the circumstellar envelope (CSE) around R Hya and to check for a correlation between the derived density structure and the declining period. Methods. We investigate the CSE around R Hya by performing an in-depth analysis of (1.) the photospheric light scattered by three vibration-rotation transitions in the fundamental band of CO at 4.6 $mu$m; and (2.) the pure rotational CO J = 1-0 through 6-5 emission lines excited in the CSE. The vibrational-rotational lines trace the inner CSE within 3.5´´, whereas the pure rotational CO lines are sensitive probes of the cooler gas further out in the CSE. Results. The combined analysis bear evidence of a change in mass-loss rate some 220 yr ago (at ~150 $R_{star}$ or ~1.9 arcsec from the star). While the mass-loss rate before AD 1770 is estimated to be ~ 2 imes 10^ $M_{odot}$/yr, the present day mass-loss rate is a factor of ~20 lower. The derived mass-loss history nicely agrees with the mass-loss rate estimates by Zijlstra et al. (2002) on the basis of the period decline. Moreover, the recent detection of an AGB-ISM bow shock around R Hya at 100 arcsec to the west by Wareing et al. (2006) shows that the detached shell seen in the 60 $mu$m IRAS images can be explained by a slowing-down of the stellar wind by surrounding matter and that no extra mass-loss modulation around 1-2 arcmin needs to be invoked. Conclusions. Our results give empirical evidence to the thermal-pulse model, which is capable of explaining both the period evolution and the mass-loss history of R Hya

The MOLspheres of Mira Variables

Time series of near-IR spectra are used to explore the cool molecular region between the photosphere and expanding circumstellar shell in large amplitude (Mira) AGB variables. The ∼1000 K Mira “MOLsphere” is shown to undergo large amplitude velocity changes that are aperiodic with time scales many times longer than the photospheric pulsation

High-resolution 3 microns spectroscopy of IRC+10216

Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe

Chemical Abundances of Symbiotic Giants

High resolution (R ∼ 50000), near-IR spectra were used to measure photospheric abundances of CNO and elements around the iron peak for 24 symbiotic giants. Spectrum synthesis was employed using local thermal equilibrium and hydrostatic model atmospheres. The metallicities are distributed in a wide range with maximum around [Fe/H] ∼−0.4 – − 0.3 dex. Enrichment in 14N indicates that all the sample giants have experienced the first dredge-up. The relative abundance of [Ti/Fe] is generally large in red symbiotic systems

An Archive of Spectra from the Mayall Fourier Transform Spectrometer at Kitt Peak

We describe the SpArc science gateway for spectral data obtained during the period from 1975 through 1995 at the Kitt Peak National Observatory using the Fourier Transform Spectrometer (FTS) in operation at the Mayall 4-m telescope. SpArc is hosted by Indiana University Bloomington and is available for public access. The archive includes nearly 10,000 individual spectra of more than 800 different astronomical sources including stars, nebulae, galaxies, and Solar System objects. We briefly describe the FTS instrument itself, and summarize the conversion of the original interferograms into spectral data and the process for recovering the data into FITS files. The architecture of the archive is discussed, and the process for retrieving data from the archive is introduced. Sample use cases showing typical FTS spectra are presented