We are actively monitoring a number of current transients with radio telescopes, as well as doing wide-field searches with LOFAR
AMI-LA Rapid Response Mode (ALARRM) Transients
AMI robotically triggers on Swift transients. The majority of these transients are gamma-ray bursts (GRBs) but Swift also detects gamma-ray events from other interesting objects like X-ray binaries, magnetars and flare stars. AMI is capable of being on target within 2 minutes after the Swift trigger and we continue to monitor all our targets with AMI up to 2 months post-burst.
ALARRM recently triggered on the following Swift transients. These transients are currently being monitored with AMI:
- GRB 141005A: AMI was on target within 8 hrs post-burst having robotically triggered on this event just as it had risen above the horizon.
- GRB 140930B: Swift detected a short GRB on 30 Sept. ALARRM was triggered resulting in AMI being on target within 70 seconds, which is our record fastest response time!
Below is a list of interesting Swift transients that have recently been observed with AMI:
- GRB 140808A/iPTF 14eag: The new 4 Pi Sky and Intermediate Palomar Transient Factory (iPTF) collaboration is off to a great start as we triggered AMI on the optical counterpart of the Fermi GBM GRB 140808A. AMI has been monitoring this GRB since shortly after discovery and first detected its radio counterpart at 11 days post burst.
- GRB 140713A: AMI has been following this dark bursts for the last several months and is only now fading below detectability. AMI was first on target within 5 minutes post-burst. AMI first detected GRB 140713A at 3.1 days post-burst. We have been coordinating simultaneous radio observations with the Westerbork Synthesis Radio Telescope (WSRT).
- GRB 140709A: AMI possibly detected the counterpart to GRB 140709A at 3 days post-burst. This radio counterpart was blended with the nearby NVSS source. AMI was the first telescope to detect the radio counterpart from this GRB.
- GRB 140703A: AMI has detected the radio counterpart to this distant GRB (z=3.14). Our first AMI observation triggered at <12 minutes post-burst, yielding a 3-sigma upper-limit of 0.18 MJy. Our second AMI observation at 1 day post-burst detected the radio counterpart at 0.25 mJy. This GRB has also been detected with the VLA at 19 GHz and CARMA at 93 GHz.
- GRB 140304A: We observed GRB 140304A with AMI starting within 1 hour post-burst with regular monitoring until 32 days post-burst. AMI successfully detected its radio counterpart.
- DG CVn: Swift detected this ultra-fast rotating M dwarf star emitting a giant gamma-ray flare on 23 April, 2014. AMI was on target within 5 minutes post-burst and observed this star recovering from a giant radio flare >100 mJy. Our second AMI observation, which took place a day later, clearly detected another bright radio flare, which can be seen in the figure below. We continued to monitor this event with AMI until 42 days post-burst.
AMI Radio Transient Follow-up
AMI is also used to conduct ongoing observations of known radio transients. Below is a list of some of the interesting objects that we are currently monitoring.
- Del 2014
- SN 2014C
Zenith monitoring strip: 1500 square degrees of the northern sky, between (approximately) 48 degrees < Declination < 57 degrees. Full 24hr runs on (currently) monthly cadence.
North Celestial pole: we are repeatedly monitoring the north celestial pole with the Low Band Antennas.