Radio timing constraints on the orbital orientation and component masses of PSR J1455$-$3330

Abstract

PSR J1455$-$3330 is a $\sim$7.98 ms pulsar in a $\sim$76.17 day nearly circular orbit with a white dwarf companion. In this work, we combine the available Lovell, Nançay decimetric Radio Telescope, Green Bank, and MeerKAT pulsar timing data spanning $\sim$ 30 years to measure the kinematic and relativistic effects of PSR J1455$-$3330 to constrain its 3D orbital geometry and component masses. We detect a relativistic Shapiro delay signal. We measure a significant orthometric amplitude $h_3=0.307_{-0.026}^{+0.022}$ $\hat{I}¼$s and an orthometric ratio $\ddot{I}‚=0.551_{-0.054}^{+0.057}$. We measure the change in projected semi-major axis $\dot{x}=-202.1_{-2.7}^{+2.5}\times 10^{-16}\mathrm{s}{\mathrm{s}}^{-1}$ with high significance, parallax, $\varpi$ = 1.11(6) mas, parallax derived distance 0.90(5) kpc, and a precise total proper motion magnitude of 12.432(2) mas yr${}^{-1}$. A self-consistent analysis of all kinematic and relativistic effects, assuming general relativity, yields two solutions: (1) a pulsar mass $M_{\mathrm{p}}=1.39_{-0.18}^{+0.38}{\mathrm{M}}_{\odot }$, a companion mass $M_{\mathrm{c}}=0.293_{-0.026}^{+0.056}$ ${\mathrm{M}}_{\odot }$, an orbital inclination, $i=63(2{)}^{\circ }$, and longitude of the ascending node, $\hat{I}\text{c◯}=212(12{)}^{\circ }$ or (2) a pulsar mass $M_{\mathrm{p}}=1.53_{-0.22}^{+1.10}{\mathrm{M}}_{\odot }$, a companion mass $M_{\mathrm{c}}=0.309_{-0.026}^{+0.163}{\mathrm{M}}_{\odot }$, an orbital inclination, $i=123(4{)}^{\circ }$, and longitude of the ascending node, $\hat{I}\text{c◯}=334(12{)}^{\circ }$. All uncertainties represent the 68.27$\%$ credibility region. These results strongly favour a helium-dominated white dwarf companion.