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We present simultaneous and continuous observations of the H$\alpha$,H$\beta$, He {\sc i} D$_{3}$, Na {\sc i} D$_{1}$,D$_{2}$ doublet and the Ca{\sc ii} H & K lines for the RS CVn system HR 1099. The spectroscopicobservations were obtained during the MUSICOS 1998 campaign involving severalobservatories and instruments, both echelle and long-slit spectrographs. Duringthis campaign, HR 1099 was observed almost continuously for more than 8 orbitsof $2\fd8$. Two large optical flares were observed, both showing an increase inthe emission of H$\alpha$, Ca {\sc ii} H & K, H$\beta$ and He {\sc i} D$_{3}$and a strong filling-in of the Na {\sc i} D$_{1}$,D$_{2}$ doublet.{Contemporary photometric observations were carried out with the robotictelescopes APT-80 of Catania and Phoenix-25 of Fairborn Observatories. Maps ofthe distribution of the spotted regions on the photosphere of the binarycomponents were derived using the Maximum Entropy and Tikhonov photometricregularization criteria}. Rotational modulation was observed in H$\alpha$ andHe {\sc i} D$_{3}$ in anti-correlation with the photometric light curves. Bothflares occurred at the same binary phase (0.85), suggesting that these eventstook place in the same active region. Simultaneous X-ray observations,performed by ASM on board RXTE, show several flare-like events, some of whichcorrelate well with the observed optical flares. Rotational modulation in theX-ray light curve has been detected with minimum flux when the less active G5 Vstar was in front. A possible periodicity in the X-ray flare-like events wasalso found.

Simultaneous optical and X-ray observations of flares and rotational modulation on the RS CVn binary HR 1099 (V711 Tau) from the MUSICOS 1998 campaign