A Lifetime of Influence: Abstracts, Talks, and Posters
 

e-MERLIN Radio Observations of O and WR Stars in Cyg OB2

Allan Willis
University College London

Raman Prinja
University College London

Danielle Fenech
University College London

The upcoming enhanced radio facility in the UK - e-MERLIN - will provide a major improvement in sensitivity over previous observatories like the VLA. UCL is spearhheading a legacy project with e-MERLIN to assemble probing datasets of stellar populations in strategic clusters that comprise large numbers of massive stars. This e-MERLIN Cyg OB2 Radio Survey (COBRas) will yield extensive and deep 5 GHz wide field mapping of selected fields in the rich Cyg OB2 association. We anticipate a 50-fold increase in the number of radio detections, via about 100 pointings at 5 GHz of 6-hours each for mosaics of fields. A small number of fields will be re-observed at 3 additional epochs for astrometry and some also at 1.5 Ghz. rms sensitivities are 3 micro-Jy/beam and 6 micro-Jy/beam at 5 GHz and 1.5 GHz. Scientific goals include: (i) studying continuous populations of OB and WR stars to further detailed understanding of wind structure and clumping at each evolutionary stage, to try and resolve the current major uncertainties in mass loss rate estimates for massive stars, (ii) exploit the broadband capability of e-MERLIN at C and L bands to provide an unbiased and unique study of the incidence of non-thermal radiation in clusters and statistics on binarity - the high resolution images providing powerful probes of colliding wind zones in O+O and O+WR binaries. Additional science programmes will address gamma-ray sources, Young Stellar Objects and ongoing star formation, disc-wind systems in YSOs and Herbig Ae/Be stars, and proper motion measurements and velocity fields in selected fields in Cyg OB2. A pilot to this programme has been approved for the commissioning phase of e-MERLIN, which will be followed by the main legacy programme. The legacy team involves a large number of scientists from UCL and other UK and European/USA groups.