Dynamo-generated magnetic fields in fast rotating single giants

Red giants offer a good opportunity to study the interplay of magnetic fields and stellar evolution. Using the spectro-polarimeter NARVAL of the Telescope Bernard Lyot (TBL), Pic du Midi, France and the LSD technique, we began a survey of magnetic fields in single G-K-M giants. Early results include 6 MF-detections with fast rotating giants, and for the first time a magnetic field was detected directly in an evolved M-giant: EK Boo. Our results could be explained in the terms of $\alpha$--$\omega$ dynamo operating in these giants.Comment: 2 pages, 1 figure, proceedings of IAUS259: Cosmic Magnetic Field

The phase-dependent Ca II K emission of zeta Aur K-type supergiants: chromospheric heating versus irradiation-induced emission

Zeta Aur systems, wide eclipsing binaries with K supergiants, have been given special attention in stellar astrophysics over the past 80 years, since their hot companions serve as probing light sources during chromospheric eclipse phases and provide us with unique information. On the other hand, at the same time their hot irradiation raises the question as to how representative the physical conditions found in zeta Aur type K supergiant chromospheres are for this class of objects. We here present, using high quality (20.000 resolution, s/n = 120 to 160) TIGRE-spectra, the Ca II K emission of the K4 II supergiants of zeta Aur and 32 Cyg in different, orbital phases, representing different degrees of irradiation by the hot companion. To extract the K giant spectra from each composite spectrum, we subtract each secondary's contribution by using a matching PHOENIX model spectrum as template. By the variation of the Ca II K emission with orbital phase, and by comparison with eclipse spectra of the K supergiants, we find that the irradiation induced contribution is of the order of at least 2.3 times larger than the intrinsic chromospheric emission caused by chromospheric heating processes common to all K supergiants

Comparison of two- and three-dimensional echocardiography with cineventriculography for measurement of left ventricular volume in patients

AbstractObjectives. We compared two- and three-dimensional echocardiopaphy with cineventriculography for measurement of left ventricular volume in patients.Background. Three-dimensional echocardiography has been shown to be highly accurate and superior to two-dimensional echocardiography in measuring left ventricular volume in vitro. However, there has been little comparison of the two methods in patients.Methods. Two- and three-dimensional echocardiography were performed in 35 patients (mean age 48 years) 1 to 3 h before left ventricular cineventriculography. Three-dimensional echocardiography used an acoustic spatial locator to register image position. Volume was computed using a polyhedral surface reconstruction algorithm based on multiple nonparallel, unevenly spaced short-axis cross sections. Two-dimensional echocardiography used the apical biplane summation of disks method. Single-plane cineventriculographic volumes were calculated using the summation of disks algorithm. The methods were compared by linear regression and a limits of agreement analysis. For the latter, systematic error was assessed by the mean of the deferences (cineventriculography minus echocardiography), and the limits of agreement were defined as ±2 SD from the mean difference.Results. Three-dimensional echocardiographic volumes demonstrated excellent correlation (end-diastole r = 0.97; end-systole r = 0.98) with cineventriculography. Standard errors of the estimate were approximately half those of two-dimensional echocardiography (end-diastole ±11.0 ml vs. ±21.5 ml; end-systole ±10.2 ml vs. ±17.0 ml). By limits of agreement analysis the end-diastolic mean diferences for two- and three-dimensional echocardiography were 21.1 and 12.9 ml, respectively. The limits of agreement (±2 SD) were ±54.0 and ±24.8 ml, respectively. For end-systole, comparable improvement was obtained by three-dimensional echocardiography. Results for ejection fraction by the two methods were similar.Conclusions. Three-dimensional echocardiography correlates highly with cineventriculography for estimation of ventricular volumes in patients and has approximately half the variability of two-dimensional echocardiography for these measurements. On the basis of this study, three-dimensional echocardiography is the preferred echocardiographic technique for measurement of ventricular volume. Three-dimensional echocardiography is equivalent to two-dimensional echocardiography for measuring ejection fraction

Magnetic fields in single late-type giants in the Solar vicinity: How common is magnetic activity on the giant branches?

We present our first results on a new sample containing all single G, K and M giants down to V = 4 mag in the Solar vicinity, suitable for spectropolarimetric (Stokes V) observations with Narval at TBL, France. For detection and measurement of the magnetic field (MF), the Least Squares Deconvolution (LSD) method was applied (Donati et al. 1997) that in the present case enables detection of large-scale MFs even weaker than the solar one (the typical precision of our longitudinal MF measurements is 0.1-0.2 G). The evolutionary status of the stars is determined on the basis of the evolutionary models with rotation (Lagarde et al. 2012; Charbonnel et al., in prep.) and fundamental parameters given by Massarotti et al. (1998). The stars appear to be in the mass range 1-4 M ⊙, situated at different evolutionary stages after the Main Sequence (MS), up to the Asymptotic Giant Branch (AGB). The sample contains 45 stars. Up to now, 29 stars are observed (that is about 64% of the sample), each observed at least twice. For 2 stars in the Hertzsprung gap, one is definitely Zeeman detected. Only 5 G and K giants, situated mainly at the base of the Red Giant Branch (RGB) and in the He-burning phase are detected. Surprisingly, a lot of stars ascending towards the RGB tip and in early AGB phase are detected (8 of 13 observed stars). For all Zeeman detected stars v sin i is redetermined and appears in the interval 2-3 km/s, but few giants with MF possess larger v sin

What a Local Sample of Spectroscopic Binaries can tell us about the Field-Binary Population

We study a sample of spectroscopic binaries (SBs) in the local solar neighbourhood to 100 pc and to an absolute magnitude of 4 in an attempt to find the distributions of the period, primary mass and the mass ratio as well as the IMF of the local population of field binaries. The sample was collated using available SB data and the Hipparcos catalogue, the latter being used for distances and to refer numbers of objects to fractions of the local stellar population as a whole. We use the better-determined double-lined SBs (SB2s) to calibrate a Monte-Carlo approach to modelling the mass ratio distribution of the single-lined SBs (SB1s) from their mass functions and primary masses. While a complete sample is not possible, given the data available, we are able to address important questions of incompleteness and parameter-specific biases by comparing subsamples of SBs with different ranges in parameter space. Our results show a clear peak in the mass ratio distribution of field binaries near unity. This is dominated by the SB2s, but the flat distribution of the SB1s is inconsistent with their components being chosen independently at random from a steep IMF.Comment: 9 pages, 9 figures, 4 tables. Published in MNRA

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