The 4 Pi Sky VOEvents Hub

Please note: If you make use of our VOEvents services for anything other than simply trying out the tools, please let us know! That way we can get in touch with any service announcements, and measure our ‘impact’ on the community. Thanks!

Update, 14th June 2016: We have just published a paper giving an overview of our VOEvent services and software, which is a good place to start reading if you’re new to VOEvents and 4 Pi Sky. You can find it on Arxiv here: http://arxiv.org/abs/1606.03735

We run an open-access VOEvent broker and a VOEvent archive-service as part of our efforts to encourage fully-robotic observation and reporting of astronomical transients.

What is VOEvent?

VOEvent is a standard format for distributing alerts regarding astronomical transients and other related information (current telescope pointings, planned observations, provisional classifications, etc). Open-source libraries and tools for working with VOEvents are available (see below). With a little effort and a few lines of Python code you can set up custom filters that trigger email alerts, SMS text alerts, desktop notifications or even fully robotic telescope-observation triggers (depending on your telescope!), or you can publish your own VOEvents describing what you have observed.

For a gentle introduction to VOEvents which gives a bit more background, see our previous blog post on the subject. For more comprehensive documentation you should consult John Swinbank’s Notes on VOEvent.

Contact details

The basic technical information you need to get started is provided below, but if you have further questions please don’t hesitate to get in touch – relevant people to contact are Tim Staley and Rob Fender.

Receiving real-time alerts through the 4 Pi Sky VOEvent broker

We run a VOEvent broker which provides real-time alerts from NASA-GCN, GAIA, and ASASSN. Our VOEvent broker can be accessed at voevent.4pisky.org (at the standard VOEvent port, 8099).  Anonymous subscription is allowed, so you can connect to our broker and start receiving VOEvent notices immediately. To do so, you’ll need a VOEvent client – we use Comet.

Historical alerts and the voeventdb archive

We also maintain an archive of previously published VOEvents, accessible at voeventdb.4pisky.org. To query the archive we recommend using the Python client-library voeventdb.remote.

Parsing and authoring VOEvents

At the raw-data level, VOEvents are just XML packets conforming to a particular XML schema. As such, they can be accessed and created from any modern programming language with support for XML. However, Python users may be interested in our package, voevent-parse, which aims to make working with VOEvent packets simpler.

Publishing VOEvents

Both Comet and Dakota can also submit VOEvent notices to a broker. Publishing notices via the 4PiSky broker is actively encouraged and we can even offer (limited) support to get you started, but note that you will need to contact us first in order for us to add you to the whitelist.

Example Python code (fourpiskytools)

Often, the easiest way to get code running that does what you need is to start from a working example and make modifications. With this in mind, we’ve put together a minimal working setup with Comet and voevent-parse, so that you can quickly get started both receiving and sending VOEvents. These examples can be found at https://github.com/4pisky/fourpiskytools.

Running your own VOEvents service

All the VOEvent handling code we use is open-source, and we encourage other research groups to re-use it and run their own VOEvent services. If you’re interested in doing this, a good place to start is the ArXiv paper on how the 4PiSky services are put together – don’t hesitate to get in touch if you have further questions.

A  listing of VOEvent brokers can be found at the IVOA wiki.


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