LIGO/Virgo G275697: Swift-XRT source 23 no longer fading
Abstract
As discussed in LVC Circular 20841, Swift is conducting further observations of the 'rank 3' X-ray sources detected in our initial search of the LIGO/VIRGO error region. These are uncatalogued X-ray sources which are below existing catalogue limits and therefore cannot be distinguished as new or pre-existing sources. Previously, Source 23 (Evans et al, LVC Circ. 20812, 20841) appeared to be fading with a significance of 3.5 sigma. Swift subsequently performed a series of daily observations, between 2017-03-13 and 2017-03-16, which have shown that the source flux is remaining approximately constant, so is unlikely to be related to the GW event and is therefore no longer considered a source of interest. In addition, sources 30, 88, 100 and 108 also show no signs of variability. Source 89 matches a catalogued object which appears to be a flare star, so the X-ray detection was most likely simply a stellar flare. Observations of the other 'rank 3' sources are ongoing. This circular is an official product of the Swift-XRT team.
- Publication:
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GRB Coordinates Network
- Pub Date:
- March 2017
- Bibcode:
- 2017GCN.20884....1E