RINGO3 - A 3 channel, rapid response polarimeter for the Liverpool Telescope

GRBs form when the core of a massive star collapses or two neutron stars merge together. The resulting explosions are the brightest events in the universe, vastly outshining entire galaxies containing hundreds of billions of stars. The energy output is believed to be largely concentrated in a jet however, rather than spread out in all directions. A GRB event is detected if the Earth happens to lie within the beam direction of its jet.

The jet contains rapidly moving electrons which will spiral around magnetic field lines. This causes them to emit light due to the synchrotron radiation process. This emitted light will be polarized (i.e. the electromagnetic waves will be vibrating in a preferred direction related to the direction of the magnetic field lines). By measuring the polarization (using a Polaroid similar to that used in sunglasses) we can therefore determine the strength and geometry of the magnetic fields.
This is important because it may be that the magnetic field is what powers the jet. Alternatively the magnetic field may be generated by the shock when the jet hits the surrounding medium.

So far we have built a series of polarimeters (RINGO and RINGO2) to investigate this by measuring the polarization of optical light from GRBs at a certain single wavelength. The instruments are mounted on the Liverpool Telescope, which is a fully robotic (i.e. unmanned) telescope on La Palma which reacts to triggers from satellites such as the NASA SWIFT mission. The satellites monitor the sky for Gamma Ray Bursts, and automatically notify ground based followup facilities such as the Liverpool Telescope if they detect one. The LT can then automatically react to slew to the coordinates it has been sent by the satellite and start taking data within 3 minutes. This has had great success, with the first ever detections of early time optical polarization being made. In addition the first measurements of the change in optical polarization from a GRB as the jet expands have recently been obtained.

We are now applying for funds to build RINGO3. This will be a multi-colour instrument that can observe simultaneously at three wavelengths. By doing so we will be able to unambiguously identify where in the burst the polarized emission is coming from. This will allow us to distinguish between three possibilities:

1. Magnetic instabilities generated in the shock front giving rise to independent ordered magnetic field patches (the polarised radiation would come from the non-perfect cancellation of the polarization
from a large number of these patches each of which was randomly oriented).

2. Another situation that could give rise to polarised light from a GRB is if the observer's line of sight lies along the edge of the jet. In this case the magnetic fields parallel and perpendicular to the shock front could have different strengths, producing a polarised signal.

3. Large-scale magnetic fields present throughout the relativistic outflow, originating from the
inside the "central engine" driving the explosion and accelerating and collimating the jet.

RINGO3 will also allow us to use GRBs to carry out tests of new theories of gravity which predict an energy dependance of the speed of light. This would cause rotation of the polarization of the
light from the GRB by different amounts at different wavelengths.

Finally RINGO3 will be a common-user instrument on the telescope, used for polarization monitoring of many other objects including asteroids (where is can help determine the surface texture and composition), X-ray binaries and Blazars (which like GRBs also contain jets of unknown origin).

ARI has a long tradition of strong industrial and PUS engagement. For this particular project we
will:

* Continue our process of engagement with the local engineering firm "Senar" who will be commissioned to manufacture the structure of the instrument. Senar is a long established (70 years) SME on Merseyside employing around 20 staff. Initial contact with ARI was through the Liverpool Telescope project, where they were contracted to build several parts of the telescope via the university owned company Telescope Technologies Ltd. Because of this, the company has had to upgrade its skills and machinery to deliver the high precision needed for astronomical instrumentation, allowing it to received a grant from MAS (Manufacturing Institute, via the local council organization Wirral Direct) in order to upgrade their precision machining capability with a new, more accurate, CNC lathe and safeguarding a number of jobs at the time. Their ongoing work for the Liverpool Telescope features as part of their adverting as an example of a high-profile/high-technology client. The reputation that SENAR have developed in terms of precision engineering for astronomical applications over the past 10 years has assisted them in gaining contacts with other international observatories (e.g. work on the new William Herschel Telescope Auxiliary camera) and recently with CERN where they produced the chain links that carry cooling pipes and electrical cables for LHC.

* Work with EMCCD supplier Andor to develop the capability of their Linux Software Development Kit (SDK) to ensure the API supports multiple cameras with simultaneous readout, adding a capability which they can then exploit in other markets (e.g. microscopy).

* Use the data from RINGO3 as part of the new ARI distance learning course on Gamma Ray Bursts, which attracts non-traditional students and delivers them experience of cutting edge research.

* Use the data from RINGO3 as part of the National Schools Observatory. This major project has over 20,000 observations successfully delivered to over 1000 schools from the Liverpool Telescope already, and with over a million web pages served every year and an average of about 4,000 unique visitors each week, the NSO has established itself as a leading astronomy website for UK schools.

* Use the data from RINGO3 as part of the material on Gamma Ray Bursts and robotic telescopes for a planned update to the Spaceport visitor attraction. Spaceport is a key component of Mersey Travel's tourist portfolio which has the aim of enhancing the regeneration of the Seacombe and Birkenhead areas on the banks of the Mersey (other parts of the portfolio include the Beatles Experience). The attraction regularly exceeds visitor number predictions (currently at 100,000 per year) and brings considerable income into a regeneration area. Using the standard STEAM model (Digest of Tourism Statistics, Dec. 2009 - The Mersey Partnership) for determining the economic benefits of tourism in the City Region for day visitors, this equates to a net gain of more than £2m per year and the creation of an estimated 50 new jobs.