The transient sky has never been more exciting. Numerous current and near-future large-scale surveys (PanStarrs, PTF, SkyMapper, Gaia, SWIFT, OGLE, LOFAR, LSST) are promising vast numbers of new, transient objects corresponding to a wide range of astrophysical phenomena, from solar system objects, through new types of stellar variability and signatures of exoplanets, to Supernovae and orphan Gamma Ray Bursts. However without prompt and appropriate follow-up observations, much of the scientific potential of these new discoveries will be lost. It becomes crucial for transient astronomy that the new phenomena are rapidly observed with small and medium size telescopes and the data are analysed quickly to share the knowledge.
The Gaia Photometric Science Alerts team, is responsible for generating alerts on transient and anomalous events detected in the data stream of the Gaia satellite - cornerstone ESA mission scheduled for launch in August 2013. The alerts will become public immediately, and to assure the complex data processing pipeline produces reliable and robust alerts, they need to be thoroughly tested. Therefore, the first alerts will need to be verified with an extensive programme of dedicated follow-up observations.
Thorough and robust classification requires a dedicated network of telescopes and a well-organised team. Now, with the Gaia launch so close, we are approaching a crucial point in time. We need to organise our teams, choose instruments and telescopes, construct observing proposals, and prepare the community for the influx of Gaia alerts.
During the first two Gaia Science Alerts workshops we have addressed the requirements for the ground-based verification of alerts and their follow-up. We have established the foundations of the collaborative network of telescopes and scientists willing to get involved in the transients follow-up and Gaia alerts verification.
In the third workshop this summer we will present and discuss the early-stage tests performed by our partners based on alerts generated by the Catalina Real-Time Transient Survey (CRTS) and other surveys. We will also continue building and extending the network with new partners.
One of the main issues related with the follow-up of transients is their robust and rapid classification at the survey level and then evolving classification with the additional follow-up data. We will concentrate on this subject during the third workshop and present current techniques and methods of transient classification presented by experts in the field and astronomers applying the techniques to their data.
The main goals of the meeting
- Optimising ground-based transient follow-up
It can be shown that for any given transient, there exists a wide-range of follow-up observations that could be made, with differing degrees of effectiveness for improving classification. We will consider the general question what should we do next?, and investigate the dependence of the answer to this question on (i) the nature of the event, (ii) the availability and quality of measured data (photometry, astrometry, spectroscopy), (iii) the telescope and instrumentation available to the observer. This workshop session will look at the follow-up teams experiences with the CRTS and other surveys data.
- Machine learning approaches to the classification of transient data.
Classification of transients is a unique problem for computational astrophysics. In this part of the workshop we will discuss state-of-the-art techniques for transient classification, including: Gaussian Mixtures, Self-Organizing Maps, Random Forest, Neural Networks, naive Bayes and so on. A workshop session will focus on the application of these techniques to the transients surveys data stream, and comparison to the Gaia data stream.
- Expanding the follow-up community
There are a large number of telescopes and observers around the globe, both suitable and interested in taking part in the follow-up of the Gaia alerts. The list includes professional astronomers, as well as skilled,hard-working, well-equipped and well-organised amateur astronomers who would love to work closely with the Gaia mission. One of the main goals of our meeting is to identify new potential partners for the alerts follow-up and discuss common practises for the follow-up process, with an emphasis on the verification of the Gaia alerts. As an outcome of this we hope to prepare an agreed version of the Memorandum of Understanding, to be signed between the Gaia Science Alerts team and partners. This will cover all issues related with the data dissemination, processing and usage policy. An additional deliverable will be an evolving web site describing recommended follow-up procedures, providing detailed instructions on how to get involved, how to observe, how to share data, and instructing the astronomers how and who to credit.