More light on RV Tauri variables
نویسنده
چکیده
This study confirms the results of the preliminary study (Russell, 1997) indicating that RV Tau variables in globular clusters don’t show the kind of anomalous abundances seen in RV Tau variables observed in the field. By making comparisons with red giants in the same clusters, it has been possible, for the first time, to identify precisely how each element deviates from the normal abundance ratios of evolved giants. The apparent systematic deficiency in s-process elements reported for RVTau variables in the literature is not confirmed in the present study. Either the stars observed here are of such low metallicity, that what ever process causes s-process deficiencies in more metal rich field stars doesn’t operate; or the systematic deficiency in s-process elements is simply an illusion of small number statistics.
منابع مشابه
The RV Tauri phenomenon and binarity
We present accurate radial velocity measurements on the pulsating extremely iron-deficient post-AGB object HD 52961 and the RV Tauri star EN TrA (HD 131356) proving them to be binaries. Our long-term photometric monitoring campaign shows that the RV Tauri photometric class “b” phenomenon in HD 52961 is due to variable circumstellar extinction during orbital motion. By comparing carefully the ob...
متن کاملUVES spectra of young brown dwarfs in Cha I: radial and rotational velocities
Based on high-resolution UVES spectra we found that the radial velocity (RV) dispersion of nine of twelve known young bona fide and candidate brown dwarfs in the Cha I dark cloud is 2.0 kms, i.e. significantly smaller than the RV dispersion of T Tauri stars in Cha I (3.6 km/s) and only slightly larger than the dispersion of the surrounding molecular gas (1.2 km/s) (Mizuno et al. 1999). This res...
متن کاملFirst detection of photospheric depletion in the LMC ⋆
Context. Recent photospheric abundance studies of galactic field RV Tauri stars show that depletion of refractory elements is rather common in these evolved objects. Aims. The process that creates this chemical anomaly is not understood well, but it probably requires the presence of gravitationally bound dust in a binary system. We test for the presence of depletion in extra-galactic objects. M...
متن کاملUltra-low Amplitude Variables in the Lmc – Classical Cepheids, Pop. Ii Cepheids, Rv Tau Stars and Binary Variables
A search for variable stars with ultra-low amplitudes (ULA), in the millimag range, has been made in the combined MACHO and OGLE data bases in the broad vicinity of the Cepheid instability strip in the HR diagram. A total of 25 singly periodic and 4 multiply periodic ULA objects has been uncovered. Our analysis does not allow us to distinguish between pulsational and ellipsoidal (binary) variab...
متن کاملThe binary RV Tauri star AC Her and evidence for a long-lived dust-disc
We present in this letter a homogeneous set of CORAVEL radial velocity measurements of the well studied RV Tauri star AC Her showing it to be a binary with a period of 1196 ± 6 days. The photospheric abundances are deduced using high resolution, high signal-to-noise optical spectra and prove that AC Her is another RV Tauri star displaying depletion of refractory elements, strengthening the rela...
متن کامل