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.
