Radio AMI-LA and X-rays Swift/XRT observations of the new outburst from MAXI J1807+132
ATel #13107; Motta, S. E, Williams, D., Fender, R. (University of Oxford), Dave Green, David Titterington (University of Cambridge)
on 13 Sep 2019; 22:03 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Sara Elisa Motta (sara.motta@physics.ox.ac.uk)
Subjects: Radio, X-ray, Binary
We report radio and X-ray observations of the X-ray binary MAXI J1807+132.
Following the detection of a new outburst by MAXI/GSC on September 10th, 2019 (Atel #13097) we observed the target with the Arcminute Microkelvin Imager Large Array (AMI-LA) at 15.5 GHz on September 12th, 2019 for 4 hours (from 14:44 to 18:41 UTC). J1756+1553 and 3C 286 were used as the phase and absolute flux calibrator, respectively. We detect a source at phase center with flux density (200 +/- 10) uJy/beam, with an rms noise of ~40uJy.
AMI-LA also automatically pointed at MAXI J1807+132 on Sept. 10th, 2019, following a BAT trigger (GCN #25702), and observed the target for two hours (13:32 to 15:32:15.7 UTC). MAXI J1807+132 was however not detected in radio at this earlier epoch. The image we extracted shows an rms noise of ~140uJy (higher than expected due to the low declination of the target at the time of the observation, and a lower number of antennas used), from which we inferred an upper limit to the flux density of ~0.4 mJy.
Swift/XRT observed MAXI J1807+132 simultaneously with AMI at 16:20 UTC for 2ks. The resulting spectrum shows a bright source with a 1-10keV flux of (3.9 +/- 0.2)E-10 ergs/cm^2/s. The spectrum can be fit with an absorbed power law (Nh ~ 2E+21 cm^-2) with spectral index 2.17+/-0.02. We thus confirm the start of a new outburst from MAXI J1807+132.
We plan on continued monitoring of this source and would like to thank the Mullard Radio Astronomy Observatory staff for carrying out these observations. Multi-Wavelength observations are encouraged.
