Spectral and photometric analysis of the eclipsing binary ε Aurigae prior to and during the 2009-2011 eclipse

A series of 353 red electronic spectra (from three observatories, mostly from 6300 to 6700 )A obtained between 1994 and 2010, and of 171 UBV photometric observations (from two observatories) of the 2010 eclipse, were analyzed in an effort to better understand ε Aur, the well-known, but still enigmatic eclipsing binary with the longest known orbital period (~27 yrs). The main results follow. (1) We attempted to recover a spectrum of the companion by disentangling the observed spectra of the ε Aur binary failed, but we were able to disentangle the spectrum of telluric lines and obtain a mean spectrum of the F-type primary star. The latter was then compared to a grid of synthetic spectra for a number of plausible values of Teff and log g, but a reasonably good match was not found. However, we conclude that the observed spectrum is that of a low gravity star. (2) We examined changes in the complex Halpha line profiles over the past 16 years, with particular emphasis on the 2009-2011 eclipse period, by subtracting a mean out-of-eclipse Halpha profile (appropriately shifted in radial velocity) from the observed spectra. We find that the dark disk around the unseen companion has an extended "atmosphere" that manifests itself via blueshifted and redshifted Halpha "shell" absorptions seen projected against the F star. Significantly, the Halpha shell line first appeared three years before first contact of the optical eclipse when the system was not far past maximum separation. (3) Analyses of radial velocities and central intensities of several strong, unblended spectral lines, as well as UBV photometry, demonstrated that these observables showed apparent multiperiodic variability during eclipse. The dominant period of 66.21d was common to all the observables, but with different phase shifts between these variables. This result strongly supports our earlier suggestion that the photometric variability seen during eclipse is intrinsic to the F star, and therefore, the idea of a central brightening due to a hole in the disk should be abandoned. Although variability on similar timescales is also seen in the spectrum and in photometry out of eclipse, we were unable to find a coherent periodicity in these data. Nevertheless, theseresults appear to rule out regular stellar pulsations as the cause of this variability. Based on spectra obtained at the Dominion Astrophysical Observatory, Ondrejov Observatory and Castanet-Tolosan Observatory and on UBV photometry gathered at the Hvar Observatory and Hopkins Phoenix Observatory.Tables 1 and 2 are only available at the CDS via anonymous ftp to cdarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/530/A146

Applying the Steepest Descent Method with BINSYN on RY Per Photometry

Recent studies of the Algol-type binary RY Per presented strong evidence that there is an accretion disk around the primary in the system. We used new UBV photometry from Hvar Observatory and the BINSYN software package in order to determine the basic parameters of the disk. The search for the best parameter set was performed with a fully automated steepest descent method. The resulting disk is large and visible at all orbital phases. Somewhat surprising is the large mass transfer rate which should be tied with, currently unreported, secular period changes.

An Improved Metallicity Calibration with UBV Photometry

We used the data of 701 stars covering the colour index interval 0.32 < B − V ≤ 1.16, with metallicities −1.76 ≤ [Fe/H]≤+0.40 dex. The data were taken from the PASTEL catalogue and estimated metallicity-dependent guillotine factors, which provide a more accurate metallicity calibration. We reduced the metallicities of 11 different authors to the metallicities of Valenti & Fischer (2005), and thus obtained a homogeneous set of data which increased the accuracy of the calibration, i.e. [Fe/H]= −14.316δ20.6 − 3.557δ0.6+0.105. Comparison of the metallicity residuals for two sets of data based on the metallicity-dependent guillotine factors with the ones obtained via metal-free guillotine factors shows that metallicities estimated by means of the new guillotine factors are more accurate than the other ones. This advantage can be used in the metallicity gradient investigation of the Galactic components, i.e. thin disc, thick disc, and halo.