Long-term timing of four millisecond pulsars

Abstract

We have timed four millisecond pulses, PSRs J1721−2457, J1745−0952, J1810−2005, and J1918−0642, for up to a total of 10.5 years each using multiple telescopes in the European Pulsar Timing Array network: the Westerbork Synthesis Radio Telescope in The Netherlands, the Nançay Radio Telescope in France and the Lovell telescope at Jodrell Bank in the UK. The long time span has enabled us to measure the proper motions of J1745−0952 and J1918−0642, indicating that they have transverse velocities of 200 (50) and 54(7) km s −1 respectively. We have obtained upper limits on the proper motion of J1721−2457 and J1810−2005, which imply that they have transverse velocities less than 140 and 400 km s −1 respectively. In all cases, the velocities lie in the range typical of millisecond pulsars. We present pulse profiles for each pulsar taken from observations at multiple frequencies in the range of 350 to 2600 MHz, and show that J1810−2005 shows significant profile evolution in this range. Using our multi-frequency observations, we measured the spectral indices for all four pulsars, and for J1810−2005 it appears to be very flat. The flux density of J1918−0642 shows extensive modulation which we attribute to the combined effects of refractive and diffractive scintillation. We discuss the possible use of including J1721−2457 or J1918−0642 in a pulsar timing array, and find that J1918−0642 will be useful to include when the timing precision of this pulsar is improved over the next few years. We have searched archival optical observations to detect companions of the binary pulsars, but none were detected. However, we provide lower limits on the masses of the white dwarf companions of PSRs J1745−0952 and J1918−0642.

The Nanograv Nine-Year Data Set: Mass and Geometric Measurements of Binary Millisecond Pulsars

“…An optical search for the companion of PSR J1918−0642 was unsuccessful (van Kerkwijk et al 2005), requiring that the apparent R-band magnitude of the WD be R > 24. A long-term timing study of this MSP was carried out by Janssen et al (2010) using the Westerbork, Nançay and Jodrell Bank radio observatories at 1400 MHz for a combined timespan of 7.4 years. While only Keplerian parameters were measured, Janssen et al (2010) combined their distance estimate to PSR J1918−0642 -based on their dispersion-measure estimate for this pulsar and the Cordes & Lazio (2001) electron-density model for the Galaxy -with the R > 24 limit, and the assumption that the white-dwarf cooling and pulsar spin-down are coeval, to further constrain the companion to be a He or CO white dwarf with a thin hydrogen atmosphere.…”

High-precision timing of 42 millisecond pulsars with the European Pulsar Timing Array

“…Thanks to an additional five years of data compared to Janssen et al (2010), the proper motion of this isolated MSP is now better constrained. Our current timing precision is most likely limited by the pulsar's large duty cycle (see Fig.…”

“…Using multi-telescope data on PSR J1012+5307, Lazaridis et al (2009) put a limit on the gravitational dipole radiation and the variation of the gravitational constant G. Janssen et al (2010) presented long-term timing results of four MSPs, two of which are updated in this work. More recently, van Haasteren et al (2011) set the first EPTA upper limit on the putative GWB.…”

The emission and scintillation properties of RRAT J2325−0530 at 154 MHz and 1.4 GHz

“…Jennings et al, 2018), long-term precision timing experiments (e.g. Janssen et al, 2010;Gonzalez et al, 2011), and scintillation analysis (e.g. Cordes, 1986;Johnston et al, 1998;Bhat et al, 2018).…”