|Submitter:||G. Janssen, C. Bassa, A. Archibald, J. Hessels, A. Patruno|
|Description:|| Pulsar J1023+0038 is a special case. First detected in 2001 as a low-mass X-ray binary in an active phase, the source switched to an X-ray quiet state shortly after that and was detected as a bright radio millisecond pulsar in 2007; it was received as the "missing link" object in pulsar evolutionary scenarios (Archibald et al. 2009; Archibald PhD Thesis 2013).|
The plot shows the monitoring of the radio pulsar since 2009 by the WSRT and the Lovell telescope at Jodrell Bank, UK. The horizontal axis shows time, with a zoom-in of 2013 at the right, and the phase of the 4.75-h orbit is shown on the vertical axis. The size of the circles correspond to the signal-to-noise of the observation (black: 1.4GHz WSRT and Lovell; red: 0.35GHz WSRT). The horizontal lines show the part of the orbit where the pulsar is normally eclipsed by its binary companion and surrounding material (a larger range is affected at lower radio frequencies).
At the end of June 2013 (vertical dashed lines) we realized something interesting was happening with the source again, as it was suddenly not detected anymore at radio frequencies. An intense monitoring campaign followed, with additional frequencies observed at GBT (blue; 2GHz) and Arecibo (green; 4.5GHz). However, no pulsations have been detected in any of our efforts since June 15th, 2013 (Stappers et al. 2013).
Concurrent with the radio disappearing, the gamma-rays originating from this system have shown a five-fold increase. Recent X-ray observations have shown a dramatic increase in count rates as well as rapid fluctuations on timescales of only 10 to 100 seconds (Patruno et al. 2013). Optical spectra have shown double-peaked emission lines confirming that a new accretion disk has formed around the pulsar.
To find out what exactly is happening in this special system, we are currently following up this source with a dedicated, simultaneous, multi-wavelength campaign.