tokens: rest of the sky. In that case, we take into account to first order the area on the sky that is lost by excluding 15 deg below and above the Galactic plane. This amounts to roughly 10 000 deg 2 , leaving 31 000 deg 2 of the sky that can be searched. In our work, we find four to eight transient candidates in 23.5 deg 2 , and taking into account that Gaia scans ∼1200 deg 2 day −1 , we arrive at a rate of four to nine fast Gaia transients per day. This order of magnitude estimate does not take into account the area on the sky that is eliminated around bright stars and is likely an overestimate. 4.1 Future improvements The implementation of a random forest classifier, based on the low resolution spectra that are measured quasi-simultaneously with the photometry, can help to classify the newly obtained transients into broad classes (Blagorodnova et al. 2014 ). Gaia has the unique feature that each transit has an associated Bp and Rp spectrum, taken during or very close to the transient event. This is especially useful for short duration transient events, as they are likely to be back in quiescence by the time of dissemination (typically the data downlinking and processing takes 48 h). These spectra may thus contain vital spectral information in addition to the colour information they provide regarding the nature of the transient events. The calibration of these spectra is envisaged to be performed in the near future, and may help to both reject spurious events as well as aid the (preliminary) classification of newly discovered fast transients. In addition, improvements in the astrometry will be implemented in the Gaia Science Alerts data base in the near future. Currently, the source positions are based on a first pass of the on-ground attitude determination (OGA1) during IDT. In addition, a second iteration is performed during the later stages of data processing, leading to improved source positions (OGA2). The accuracy of the OGA2 source positions is one to two orders of magnitude better than OGA1. Although for a newly identified transient only the OGA1 position will be available shortly after detection, the implementation of the OGA2 positions for the historic transits will help to reject brightness variations that are inconsistent with the quiescent source position and thus improve the rejection of spurious events. Finally, the reconstruction of the sky positions of sources on the secondary FoV will increase the confidence in detections of sources similar to FGTs 5 through 8, where it is currently unclear whether they are real or could be due to objects in the second FoV. Using the reconstructed second FoV will allow us to reject or confirm the astrophysical nature of these transient events and therefore will aid in the automatisation of the detection process. 5 SUMMARY In this work, we have explored the feasibility of using the Gaia CCD data to search for short time-scale transient events. Gaia provides sparsely sampled, high time resolution
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