The First Very Long Baseline Interferometric SETI Experiment

The First Very Long Baseline Interferometric SETI Experiment1H. Rampadarath, J. S. Morgan, S. J. Tingay and C. M. TrottInternational Centre for Radio Astronomy Research, Curtin University, GPO Box U1987,Perth, WA, Australiahayden.rampadarath@icrar.orgReceived ; accepted1ARC Centre of Excellence for All Sky Astrophysics (CAASTRO)arXiv:1205.6466v1 [astro-ph.IM] 29 May 2012– 2 –ABSTRACTThefirstSearchforExtra-TerrestrialIntelligence(SETI)conductedwithVeryLong Baseline Interferometry (VLBI) is presented. By consideration of the basicprinciples of interferometry, we show that VLBI is efficient at discriminatingbetween SETI signals and human generated radio frequency interference (RFI).The target for this study was the star Gliese 581, thought to have two planetswithin its habitable zone. On 2007 June 19, Gliese 581 was observed for 8 hoursat 1230-1544 MHz with the Australian Long Baseline Array. The dataset wassearched for signals appearing on all interferometer baselines above five timesthe noise limit. A total of 222 potential SETI signals were detected and byusing automated data analysis techniques, were ruled out as originating from−1the Gliese 581 system. From our results we place an upper limit of 7 MWHzon the power output of any isotropic emitter located in the Gliese 581 system,within this frequency range. This study shows that VLBI is ideal for targetedSETI, including follow-up observations.