TITLE: GCN CIRCULAR NUMBER: 18349 SUBJECT: LIGO/Virgo G184098: SkyMapper observations DATE: 15/09/20 02:53:43 GMT FROM: Fang Yuan at ANU Fang Yuan, Christian Wolf, Richard Scalzo, Brian Schmidt (ANU) We report tiled observations of LIGO/Virgo G184098 using the 1.3m SkyMapper telescope located at Siding Spring Observatory in Australia. Starting UTC 2015-09-18 17:11:53 (4.3 days after the trigger), SkyMapper observed 5 fields, covering a sky area of about 27.5 sq. deg, with 2x60s i-band exposures. Footprint of the observations has been uploaded to GraceDB. These fields are selected based on weight calculated from the GW skymap, the GW Galaxy Catalogue (augmented by 2MASS Ks photometry) and existence of SkyMapper pre-trigger observations. Using the latest GW skymap, we estimate a chance of 6% that these fields contain the true location of the source. Images were taken under poor (>4") seeing with limiting mag of about 19. Image subtraction have been performed against SkyMapper templates taken in January and March 2015 as part of the Southern Sky Survey. No transient source has been detected in preliminary analysis. The same fields are observed again on 2015-09-19, and analysis is ongoing. In addition, at UTC 2015-9-16 16:56:54 (2.3 days after the trigger), one 120s v-band image (limiting mag ~17.7), centered at ra, dec =115.9322, -68.888 was taken as part of the SkyMapper Transient Search. No transient was detected, comparing to template taken in June 2015. [GCN OPS NOTE(19sep15): This Circular was originally published on 00:06 20-Sep-2015 UT.]