International observational campaign of the 2014 eclipse of EE Cephei^⋆

¹ Nicolaus Copernicus Astronomical Centre PAS, Warsaw, Poland
e-mail: dapien@camk.edu.pl, cgalan@camk.edu.pl
² Nicolaus Copernicus University, Toruń, Poland
³ Section of Astrophysics, Astronomy and Mechanics, Department of Physics, National and Kapodistrian University of Athens, 15784 Zografos, Athens, Greece
⁴ Sonoita Research Observatory/AAVSO, USA
⁵ Astronomical Observatory, Jagiellonian University, Cracow, Poland
⁶ Mount Suhora Astronomical Observatory, Cracov Pedagogical University, ul. Podchorazych 2, 30-084 Cracow, Poland
⁷ Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences, Sofia, Bulgaria
⁸ Department of Physics, Shumen University, Shumen, Bulgaria
⁹ PTMA, Szczecin, Poland
¹⁰ Furzehill House, Ilston, Swansea SA2 7LE, UK
¹¹ Instytut Astronomiczny, Uniwersytet Wrocławski, Poland
¹² Club d’astronomie de Mont-Bernenchon, France
¹³ BAA Variable Star Section, West Challow Observatory, Oxfordshire, UK
¹⁴ Department of Physics and Astronomy, York University, Toronto, Ontario, Canada
¹⁵ Instituto de Astronomía, Universidad Nacional Autonoma de Mexico, Ensenada, BC, Mexico
¹⁶ Observatorio Las Pegueras, NAVAS DE ORO (Segovia), Spain
¹⁷ Hellenic Amateur Astronomy Association, Athens, Greece
¹⁸ Astronomical Institute, Slovak Academy of Sciences, Tatranská Lomnica, Slovak Republic
¹⁹ ELTE Eötvös Loránd University, Gothard Astrophysical Observatory, 9700 Szombathely, Hungary
²⁰ MTA-ELTE Exoplanet Research Group, Szent Imre h. u. 112, 9700 Szombathely, Hungary
²¹ Guadarrama Observatory MPC458, Madrid, Spain
²² Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA, USA
²³ Astrolab Iris, Zillebeke Belgium, Belgium
²⁴ Institute of Physics, Astrophysics Division, Jan Kochanowski University, Kielce, Poland
²⁵ Stazione Astronomica Betelgeuse, Magnago, Milano, Italy
²⁶ Private Observatory, Maladziechna, Belarus
²⁷ The Faculty of Mathematics and Natural Sciences, Department of Physics, University of Oslo, Oslo, Norway
²⁸ Cerro del Viento Observatory (MPC I84), Badajoz, Spain
²⁹ Observatorio do Instituto Geografico do Exercito – Lisboa, Lisboa, Portugal
³⁰ AstroCamp Observatory (MPC I89), Nerpio, Spain
³¹ Institute of Physics, Faculty of Science, Ss. Cyril and Methodius University, Skopje, FYR of Macedonia
³² AAVSO, Cambridge, MA 02138, USA
³³ Groupe Européen d’Observations Stellaires (GEOS), Bailleau l’Evêque, France
³⁴ Private Observatory Madrid-Ventilla MPC J30, Spain
³⁵ Gualba Observatory, Spain
³⁶ Department of Physics and Astronomy, University of Leicester, Leicester, UK
³⁷ Menke Scientific, Barnesville, MD 20838, USA
³⁸ Amateur society “Astroblocknote”, Minsk, Belarus
³⁹ Mont Mégantic Observator, University of Montreal, Montreal, Canada

Received: 22 November 2019
Accepted: 17 January 2020

Abstract

Context. EE Cep is one of few eclipsing binary systems with a dark, dusty disc around an invisible object similar to ε Aur. The system is characterised by grey and asymmetric eclipses every 5.6 yr that have significant variations in their photometric depth, ranging from ∼0_.^m5 to ∼2_.^m0.

Aims. The main aim of the observational campaign of the EE Cep eclipse in 2014 was to test the model of disc precession. We expected that this eclipse would be one of the deepest with a depth of ∼2_.^m0.

Methods. We collected multicoloured observations from almost 30 instruments located in Europe and North America. These photometric data cover 243 nights during and around the eclipse. We also analyzed low- and high-resolution spectra from several instruments.

Results. The eclipse was shallow with a depth of 0_.^m71 in the V band. The multicoloured photometry illustrates small colour changes during the eclipse with a total amplitude of order ∼+0_.^m15 in the B − I colour index. We updated the linear ephemeris for this system by including new times of minima, measured from the three most recent eclipses at epochs E = 9, 10, and 11. We acquired new spectroscopic observations, covering orbital phases around the eclipse, which were not observed in the past and increased the data sample, filling some gaps and giving better insight into the evolution of the H_α and Na I spectral line profiles during the primary eclipse.

Conclusions. The eclipse of EE Cep in 2014 was shallower than expected, measuring 0_.^m71 instead of ∼2_.^m0. This means that our model of disc precession needs revision.