Decade Long Timing Study of the Black Widow Millisecond Pulsar J1544+4937 by Sangita Kumari et al. on Monday 28 November

Results from 11 years of radio timing for eclipsing black widow millisecond

pulsar (MSP) binary, J1544+4937, is presented in this paper. We report a

phase-connected timing model for this MSP, using observations with the Giant

Metrewave Radio Telescope (GMRT) at multiple frequencies and with Green Bank

Telescope (GBT). This is the longest-duration timing study of any galactic

field MSP with the GMRT. While extending the timing baseline from the existing

1.5 years to about a decade we report the first detection for a significant

value of proper motion ($\mathrm{\mu_{T}} \sim$ 10.14(5) $\mathrm{mas/year}$)

for this pulsar. Temporal variations of dispersion measure ($\mathrm{\Delta DM~

\sim 10^{-3}}$ pc $\mathrm{cm^{-3}}$) manifested by significant determination

of 1st, 2nd, and 3rd order DM derivatives are observed along the line of sight

to the pulsar. We also noticed frequency-dependent DM variations of the order

of $\mathrm{10^{-3}~ pc~ cm^{-3}}$, which could arise due to spatial electron

density variations in the interstellar medium. This study has revealed a

secular variation of the orbital period for this MSP for the first time. We

investigated possible causes and propose that variation in the gravitational

quadrupole moment of the companion could be responsible for the observed

temporal changes in the orbital period.

arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.14107v1