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^*

¹ Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland
² Research Support Division, ESA RSSD, ESTEC/SCI-SR postbus 299, 2200 AG Noordwijk, The Netherlands
³ Dept de Astrofísica, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
⁴ Centro de Astrofísica da Universidade do Porto, Rua das Estrelas s/n, 4150-762 Porto, Portugal
⁵ Astrophysics Group, School of Chemistry and Physics, Keele University, Staffordshire ST5 5BG, UK
⁶ Catania Astrophysical Observatory, Via S. Sofia, 78 95123 Catania, Italy
⁷ Department of Physics and Astronomy, Catania University, Via S. Sofia, 78 95123 Catania, Italy
⁸ Isaac Newton Group of Telescopes, NWO, Apartado 321, 38700 Santa Cruz de La Palma, Spain
⁹ Dept. of Physics and Astronomy, University College London, Gower St., London WC1E 6BT, UK
¹⁰ Kildrummy Technologies, Mill Lane, Lerwick, Shetland, ZE1 0LX
¹¹ School of Physics, University of Sydney, NSW 2006, Australia
¹² Dept of Physics and Astronomy, Johns Hopkins University, Baltimore, USA
¹³ South African Astronomical Observatory, PO Box 9, Observatory 7935, Cape Town, South Africa
¹⁴ Astronomical Institute Anton Pannekoek, Univ. of Amsterdam, 1098 SJ Amsterdam, The Netherlands
¹⁵ Beijing Astronomical Observatory, Datun Road A20, Chaoyang District, Beijing 100012, PR China
¹⁶ Laboratoire d'Astrophysique, Observatoire Midi-Pyrénées, 14 avenue Édouard Belin, 31400 Toulouse, France
¹⁷ California State University, Fullerton, CA, USA
¹⁸ Instituto de Astronomia e Geofisica, Universidade de Sao Paulo, 1226/05508-900 Sao Paulo, Brazil
¹⁹ GEPI/FRE K 2459 du CNRS, Observatoire de Paris-Meudon, France
²⁰ Observatoire de la Côte d'Azur, Dept FRESNEL, CNRS UMR 6528, 06130 Grasse, France
²¹ European Southern Observatory, Alonso de Cordova 3107, Santiago 19, Chile
²² Dept of Physics and Astronomy, College of Charleston, Charleston, SC 29424, USA
²³ Osservatorio Astronomico di Palermo “G.S. Vaiana", Piazza del Parlamento 1, 90134 Palermo, Italy
²⁴ Landessternwarte Heidelberg, Königstuhl 12, 69117 Heidelberg, Germany
²⁵ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
²⁶ Nordic Optical Telescope, Apartado 474, 38700 Santa Cruz de La Palma, Spain

Corresponding author: D. García-Alvarez, dga@star.arm.ac.uk

Received: 23 April 2002
Accepted: 8 October 2002

Abstract

We present simultaneous and continuous observations of the Hα, Hβ, He i D₃, Na i D₁,D₂ doublet and the Ca ii H & K lines for the RS CVn system HR 1099. The spectroscopic observations were obtained during the MUSICOS 1998 campaign involving several observatories and instruments, both echelle and long-slit spectrographs. During this campaign, HR 1099 was observed almost continuously for more than 8 orbits of . Two large optical flares were observed, both showing an increase in the emission of Hα, Ca ii H & K, Hβ and He i D₃ and a strong filling-in of the Na i D₁, D₂ doublet. Contemporary photometric observations were carried out with the robotic telescopes APT-80 of Catania and Phoenix-25 of Fairborn Observatories. Maps of the distribution of the spotted regions on the photosphere of the binary components were derived using the Maximum Entropy and Tikhonov photometric regularization criteria. Rotational modulation was observed in Hα and He i D₃ in anti-correlation with the photometric light curves. Both flares occurred at the same binary phase (0.85), suggesting that these events took place in the same active region. Simultaneous X-ray observations, performed by ASM on board RXTE, show several flare-like events, some of which correlate well with the observed optical flares. Rotational modulation in the X-ray light curve has been detected with minimum flux when the less active G5 V star was in front. A possible periodicity in the X-ray flare-like events was also found.