Aquila X-1 in outburst: radio detection with AMI-LA
ATel #13016; Sara E. Motta, David Williams, Rob Fender (Oxford, UK), Andrea Sanna (Cagliari), James Miller-Jones (Curtin), David Titterington, Dave Green (Cambridge), Yvette Perrott (VUW)
on 12 Aug 2019; 12:58 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Sara Elisa Motta (sara.motta@physics.ox.ac.uk)
Subjects: Radio, X-ray, Binary, Neutron Star, Transient
Aquila X-1 is a transient neutron star X-ray binary, known to show frequent (approximately once a year) outbursts, which typically last from a few weeks to a few months (e.g. Degenaar et al. 2019).
Data from the Swift/BAT transient monitor (https://swift.gsfc.nasa.gov/results/transients/AqlX-1/) show that Aquila X-1 has recently entered a new outburst phase, with an approximate outburst start between MJD 58702 and 58704 (Aug. 7th and 9th, 2019), based on the 15-150 keV BAT count rates.
In response to its recent re-brightening, we observed Aquila X-1 in the radio band at 15.5 GHz with the Arcminute Microkelvin Imager Large Array (AMI-LA; Zwart et al. 2008; Hickish et al. 2018). We used the custom pipeline REDUCE_DC (e.g. Perrott et al. 2015) to calibrate and flag the data, with 3C286 as the absolute flux calibrator and J1907+0127 as the interleaved phase calibrator.
Aquila X-1 is significantly detected at a flux density of 1.19 +/- 0.07mJy/beam on MJD 58707 (Aug. 12th, 2019). Assuming a flat radio spectrum, this flux would be approximately 2.5 times, 2 and 1.5 times higher than the radio fluxes reported in Tudose et al. 2009, Miller-Jones et al. 2010, and Diaz-Trigo et al. 2018, respectively. To the best of our knowledge, this appears to be the highest radio flux density yet reported from this system.
We will continue to observe Aquila X-1 in the radio band with AMI in the coming days. Multi-wavelength observations are encouraged.
We thank the MRAO staff for carrying out these observations.
