AMI-LA radio observations of the galactic X-ray transient Swift J1858.6-0814

ATel #12184; Joe Bright, Rob Fender, Sara Motta, Lauren Rhodes (University of Oxford), David Titterington (University of Cambridge), Yvette Perrott (Victoria University of Wellington)
on 7 Nov 2018; 16:31 UT
Credential Certification: Sara Elisa Motta (sara.motta@physics.ox.ac.uk)

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Swift J1858.6-0814 was discovered by the Swift Burst Alert Telescope (BAT; ATel #12151) on 2018-10-31, and was identified as a possible galactic object due to its proximity to the galactic plane. We performed a followup observation with the Arcminute Microkelvin Imager Large Array (AMI-LA) at the reported BAT position on 2018-11-02.57, and two additional observations on 2018-11-03.71 and 2018-11-05.55 at the later refined Swift position (ATel #12158). The observations lasted 2, 2 and 4 hours respectively and were performed at a central frequency of 15.5 GHz with a 5 GHz bandwidth. We detect a source consistent with the Swift position in all three of our images.

The declination of Swift J1858.6-0814 is near the observing limit for the AMI-LA, and the synthesised beam dimensionsions are large (~85x27" for the 4 hour observation). We notice structured noise in our images, again likely due to calibration issues at this low declination. We therefore report only approximate flux measurements from our three observations of ~300, 400 and 600 uJy, respectively.

We thank the Mullard Radio Astronomy Observatory staff for carrying out these observations.