A Twilight Search for Atiras, Vatiras and Co-orbital Asteroids: Preliminary Results

Near-Earth Objects (NEOs) that orbit the Sun on or within Earth's orbit are tricky to detect for 24 Earth-based observers due to their proximity to the Sun in the sky. These small bodies hold clues to the 25 dynamical history of the inner solar system as well as the physical evolution of planetesimals in extreme 26 environments. Populations in this region include the Atira and Vatira asteroids, as well as Venus and 27 Earth co-orbital asteroids. Here we present a twilight search for these small bodies, conducted using 28 the 1.2-m Oschin Schmidt and the Zwicky Transient Facility (ZTF) camera at Palomar Observatory. 29 The ZTF twilight survey operates at solar elongations down to 35 with limiting magnitude of r = 19:5. 30 During a total of 40 evening sessions and 62 morning sessions conducted between 2018 November 15 31 and 2019 June 23, we detected 6 Atiras, including 2 new discoveries 2019 AQ3 and 2019 LF6, but no 32 Vatiras or Earth/Venus co-orbital asteroids. NEO population models show that these new discoveries 33 are likely only the tip of the iceberg, with the bulk of the population yet to be found. The population 34 models also suggest that we have only detected 5{7% of the H < 20 Atira population over the 7-month 35 survey. Co-orbital asteroids are smaller in diameters and require deeper surveys. A systematic and 36 ecient survey of the near-Sun region will require deeper searches and/or facilities that can operate 37 at small solar elongations.