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Astron. Astrophys. 320, 101-108 (1997)

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H emission in the chromospherically active binary o2  Coronae Borealis (TZ CrB)

A. Frasca 1, S. Catalano 2 and D. Mantovani 1, 3

1 Istituto di Astronomia, Università di Catania, Viale A. Doria 6, I-95125 Catania, Italy
2 Osservatorio Astrofisico di Catania, Viale A. Doria 6, I-95125 Catania, Italy
3 Visiting graduate student from Strasbourg Observatory, France

Received 2 July 1996 / Accepted 10 September 1996


Spectrophotometry of the chromospherically active system [FORMULA] Coronae Borealis was obtained in the H [FORMULA] region, during two observing campaigns at Catania Observatory. During the first campaign, 1988 June 22 - 29, 135 spectra were collected, while 12 spectra were obtained during the second campaign which spanned from June [FORMULA] to June [FORMULA] 1989.

We have recorded the spectra of the two stars composing the visual binary ([FORMULA] and [FORMULA] CrB) on the same frame by placing the spectrograph slit along the line connecting the two stars. This enabled us to obtain a light curve in the red band ([FORMULA] 6410 - 6590 Å), using [FORMULA]  CrB as comparison star. The light curve exhibits changes in the amplitude and in the phase of minimum light between the two observing seasons. The equivalent width of the H [FORMULA] emission core has been evaluated using the spectrum synthesis method. H [FORMULA] emission from both components of the inner system is detected in the spectra near quadrature, but it is stronger in the cooler G0 V star. The H [FORMULA] equivalent width shows low-amplitude modulation in both years which seems to be anti-correlated with the simultaneous light curve.

Comparing our results of the 1988 campaign with the contemporaneous X-ray, UV, and Radio measurements reported by Stern et al. (1992) we show that the Mg II flux of the cooler component is anti-correlated with our light curve, and a similar behaviour is displayed by the Ly- [FORMULA] flux reported by Hannikainen et al. (1990).

Key words: stars: chromospheres – stars: activity – stars: binaries: close – object: oe2 CrB; TZ CrB

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© European Southern Observatory (ESO) 1997

Online publication: July 3, 1998