AMI-LA observation of radio flaring from GRS 1915+105
ATel #12773; Sara Motta, David Williams (Oxford), Rob Fender (Oxford, UCT), David Titterington, Dave Green (Cambridge), Yvette Perrott (VUW)
on 17 May 2019; 11:24 UT
Credential Certification: Sara Elisa Motta (sara.motta@physics.ox.ac.uk)
Subjects: Radio, Black Hole, Transient
As part of a long-term monitoring programme, we observed the black hole binary GRS 1915+105 several times in 2019 (approximately every 3 weeks) 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 J1922+1530 as the interleaved phase calibrator. GRS 1915+105 was detected at a relatively low flux density between ~2 and 4 mJy up to MJD 58604 (May 1st, 2019).
Following the report of a sudden X-ray dimming of the source (ATel #12742, ATel #12743, ATel #12744) and its subsequent re-brightening (ATel #12761, ATel #12765, ATel #12766), we observed GRS 1915+105 on MJD 58616, MJD 58619 and MJD 58620 (May 13th, 16th and 17th) with AMI-LA for 6.5hr, 1hr and 2hr, respectively.
On MJD 58616 GRS1915+105 was significantly detected at a relatively low flux density of 2.84+/-0.08 mJy/beam, while on MJD 58619 the flux density had already increased by more than an order of magnitude, to 40+/-1 mJy/beam. On MJD 58620 we detected GRS 1915+105 at a flux density of 151+/-4 mJy/beam.
This indicates that radio flaring, associated with the X-ray re-brightening, and probably the signature of relativistic ejections, is taking place.
We will continue monitoring GRS1915+105 in the upcoming days.
Multi-Wavelength observations are encouraged. We would like to thank the MRAO staff for carrying out these observations.