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ORT observations of the recent glitch in the Crab pulsar

ATel #10947; M A Krishnakumar(NCRA-TIFR), Bhal Chandra Joshi(NCRA-TIFR), Avishek Basu(NCRA-TIFR), P K Manoharan(NCRA-TIFR)
on 10 Nov 2017; 17:39 UT
Credential Certification: Bhal Chandra Joshi (bcj@ncra.tifr.res.in)

Subjects: Radio, Neutron Star, Pulsar

Crab pulsar (PSR B0531+21) is monitored about once every day as part of our routine pulsar monitoring program at the Ooty Radio Telescope. These observations are carried out at the central frequency of 326.5 MHz, with a 16-MHz passband. The data are coherently dedipsersed in real time using the pulsar backend PONDER (Naidu et al. 2015) to a dispersion measure obtained from the nearly simultaneous monitoring at the L band of the Giant Metrewave Radio Telescope.

Our monitoring confirms the recent large glitch reported by Shaw et al. (ATEL #10939). Our preliminary estimate of the fractional spin up is about (0.47+-0.07)E-6, which is consistent with that reported by Shaw et al. The phase connected residuals with the pre-glitch solutions can be seen at http://rac.ncra.tifr.res.in/data/pulsar/crab/glitch58064.pdf

The average profiles of the pulsar before and after the glitch look visually similar (See http://rac.ncra.tifr.res.in/data/pulsar/crab/prepostprof.pdf ). However, the pulse energy under the pre-cursor as well as the inter-pulse seems to have increased with respect to that of the main pulse after the glitch. Our preliminary estimates of the ratio of areas under the main pulse (MP), inter-pulse (IP) and pre-cursor (PC) are as follows

Ratio Pre-glitch Post-glitch
MP/IP 1.55 1.27
MP/PC 1.05 0.82
IP/PC 0.68 0.64

Thus, after the glitch, the ratios of MP/IP, MP/PC and IP/PC have reduced by factors of 1.2, 1.3 and 1.1, respectively. Follow up observations at other wavebands, particularly at high energies, are encouraged to investigate corresponding changes in those wavebands.

We continue to monitor the pulsar to characterize the post glitch behaviour at an increased cadence.