Orbital elements and physical parameters of ten chromospherically active binary stars

Orbital elements have been determined for 10 chromospherically active binaries from a combination of new velocities and velocities in the literature. First orbits for three binaries, HD 33363, HD 152178, and HD 208472, are presented, as well as updated orbits for seven other binaries. Two of the latter systems, LN Peg and HD 106225 were discovered to be triple, and both short- and long-period orbits have been computed for each. Fundamental properties have been determined for the chromopherically active primary in each system

Doppler maps and surface differential rotation of EI Eri from the MUSICOS 1998 observations

We present time-series Doppler images of the rapidly-rotating active binary star EI Eri from spectroscopic observations collected during the MUSICOS multi-site campaign in 1998, since the critical rotation period of 1.947 days makes it impossible to obtain time-resolved images from a single site. From the surface reconstructions a weak solar-type differential rotation, as well as a tiny poleward meridional flow are measured.Comment: 4 pages, 3 figures, 1 table, proceedings of Cool Stars 15, St Andrews, July 2008, to be published in the Conference Proceedings Series of the AI

The Blazhko behaviour of RR Geminorum I - CCD photometric results in 2004

Extended CCD monitoring of RR Gem revealed that it is a Blazhko type RRab star with the shortest Blazhko period (7.23d) and smallest modulation amplitude (Delta Mmax<0.1 mag) currently known. The short period of the modulation cycle enabled us to obtain complete phase coverage of the pulsation at each phase of the modulation. This is the first multicolour observation of a Blazhko star which is extended enough to define accurate mean magnitudes and colours of the variable at different Blazhko phases. Small, but real, changes in the intensity mean colours at different Blazhko phases have been detected. The Fourier analysis of the light curves shows that, in spite of the mmag and smaller order of the amplitudes, the triplet structure is noticeable up to about the 14th harmonic. The modulation is concentrated to a very narrow, 0.2 phase range of the pulsation, centred on the supposed onset of the H emission during rising light. These observational results raise further complications for theoretical explanation of the long known but poorly understood Blazhko phenomenon.Comment: 10 pages, 12 figures, 3 tables. Accepted for publication in Astronomy and Astrophysic

A study of the chromospherically active binaries UX Fornacis and AG Doradus

This paper presents a time-series spectrum analysis of the two chromospherically active binary stars, UX Fornacis and AG Doradus. To investigate the rotational behaviour, in combination with activity in the Hα line, we obtained almost 40 high-resolution, high-$S/N$ spectra for each system. Both binaries, UX For and AG Dor, show Hα of the primary star in absorption but filled in by chromospheric emission while the Hα line of the secondaries appear in pure emission. Line variations are seen and are approximately 5-σ detections but are not linked to the orbital nor the rotational periods and seem to be erratic. We obtained new orbital elements for both systems and used them in combination with Hipparcos parallaxes and our Hα-spectrum synthesis to determine absolute parameters. We present the first Doppler image of the AG Dor primary using line-profile variations of the Fe

Orbital elements and physical parameters of ten chromospherically active binary stars

Orbital elements have been determined for 10 chromospherically active binaries from a combination of new velocities and velocities in the literature. First orbits for three binaries, HD 33363, HD 152178, and HD 208472, are presented, as well as updated orbits for seven other binaries. Two of the latter systems, LN Peg and HD 106225 were discovered to be triple, and both short- and long-period orbits have been computed for each. Fundamental properties have been determined for the chromopherically active primary in each system

The Vienna-KPNO search for Doppler-imaging candidate stars

We present the results from a spectroscopic Ca i

Doppler imaging of stellar surface structure

We present a simultaneous photometric and spectroscopic imaging analysis of the long-period RS CVn binary σ Gem, covering 3.6 consecutive rotation cycles with high time resolution. From six overlapping but consecutive Doppler maps we trace the evolution of individual spots throughout the time range covered. All spots group either along a band at approximately +45°latitude and a width of 30°, or appear centered at the equator. No polar spot is detected. We did not find a conclusive migration pattern from the cross-correlation maps from one rotation to the next and attribute this to a masking effect of short-term spot changes