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Target RA (J2000): 219.848709 and deg Target Dec (J2000): -60.82949 and deg Gaia GMag: 0 Programme ID: CH_PR140064 Programme Manager: VANGROOTEL PI of observing programme: Benz Title of programme: Axis 1 - Is there a transiting planet around Alpha Centauri? (ALPHACEN) Abstract: Alpha Centauri is the third brightest star in the night sky and the closest stellar system to us. It is composed of two stars similar to the Sun Alpha Cen A and B and a more distant but gravitationally bound red dwarf Proxima (the actual closest star to the Sun). In 2012 Dumusque et al. (Nature 491 207) announced from RV measurements a planet orbiting Alpha Cen B but its existence is still under debate. In 2015 Demory et al. (MNRAS 450 2043) found in highly-saturated Hubble Space Telescope observations of Alpha Cen B a single transit-like event ~95 ppm deep and ~3.6 h long. A likely explanation is an Earth-sized planet with an orbital period shorter than 20 days (the median of the likely orbits is 12.4 d). With this program we aim to observe Alpha Cen with CHEOPS in order to try to recover the transit seen by Demory et al. (2015). More generally CHEOPS observations will allow us to place strong constraints on the presence of close-in transiting planets around Alpha Cen which is a very valuable objective on its own and complementary to the current efforts for direct imaging of farther planets around Alpha Cen (Kasper et al. 2019 The Messenger 178 5). [truncated! Please see actual data for full text]