Search for water outgassing of (1) Ceres near its perihelion

(1) Ceres is the largest body in the main asteroid belt and one of the most intriguing object since the discovery of water outgassing in the infrared by the Herschel space observatory in 2014. Ceres is the current target of NASA's Dawn spacecraft. Recently, the possible influence of the local flux of solar energetic particles (SEP) on the production of a cerean exosphere and water vapor has been suggested. On the other hand the Herschel, IUE and ground-based observations seem to show a correlation between water vapor emission and Ceres heliocentric distance. We used the opportunity of both the perihelion passage of (1) Ceres in 2018 and the presence of Dawn in its vicinity (for measuring the SEP flux in real time) to check the influence of heliocentric distance on water outgassing. We searched for OH emission lines from the limb of Ceres in the near- UV. Despite a sensitivity level similar to the Herschel observations we did not detect any water outgassing.