Issue |
A&A
Volume 678, October 2023
|
|
---|---|---|
Article Number | A187 | |
Number of page(s) | 18 | |
Section | Astrophysical processes | |
DOI | https://doi.org/10.1051/0004-6361/202346953 | |
Published online | 23 October 2023 |
The MPIfR-MeerKAT Galactic Plane Survey
II. The eccentric double neutron star system PSR J1208−5936 and a neutron star merger rate update
1
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
e-mail: mcbernadich@mpifr-bonn.mpg.de
2
Landessternwarte, Universität Heidelberg, Königstuhl 12, 69117 Heidelberg, Germany
3
INAF – Osservatorio Astronomico di Cagliari, Via della Scienza 5, 09047 Selargius, CA, Italy
4
South African Radio Astronomy Observatory, 2 Fir Street, Black River Park, Observatory 7925, South Africa
5
Max Planck Institute for Gravitational Physics (Albert Einstein Institute), Callinstraße 38, 30167 Hannover, Germany
6
Leibniz Universität Hannover, Welfengarten 1, 30167 Hannover, Germany
Received:
19
May
2023
Accepted:
29
August
2023
The MPIfR-MeerKAT Galactic Plane survey at L-band (MMGPS-L) is the most sensitive pulsar survey in the Southern Hemisphere, providing 78 discoveries in an area of 900 sq. deg. Here, we present a follow-up study of one of these new discoveries, PSR J1208−5936, a 28.71-ms recycled pulsar in a double neutron star system with an orbital period of Pb = 0.632 days and an eccentricity of e = 0.348, merging within the Hubble time. Through timing of almost one year of observations, we detected the relativistic advance of periastron (ω̇ = 0.918(1) deg yr−1), resulting in a total system mass of Mt = 2.586(5) M⊙. We also achieved low-significance constraints on the amplitude of the Einstein delay and Shapiro delay, in turn yielding constraints on the pulsar mass (Mp = 1.26−0.25+0.13 M⊙), the companion mass (Mc = 1.32−0.13+0.25 M⊙), and the inclination angle (i = 57 ± 12°). This system is highly eccentric compared to other Galactic field double neutron stars with similar periods, possibly hinting at a larger-than-usual supernova kick during the formation of the second-born neutron star. The binary will merge within 7.2(2) Gyr due to the emission of gravitational waves, making it a progenitor of the neutron star merger events seen by ground-based gravitational wave observatories. With the improved sensitivity of the MMGPS-L, we updated the Milky Way neutron star merger rate to be RMWnew = 25−9+19 Myr−1 within 90% credible intervals, which is lower than previous studies based on known Galactic binaries owing to the lack of further detections despite the highly sensitive nature of the survey. This implies a local cosmic neutron star merger rate of Rlocalnew = 293−103+222 Gpc−3 yr−1, which is consistent with LIGO and Virgo O3 observations. With this, we also predict the observation of 10−4+8 neutron star merger events during the LIGO-Virgo-KAGRA O4 run. We predict the uncertainties on the component masses and the inclination angle will be reduced to 5 × 10−3 M⊙ and 0.4° after two decades of timing, and that in at least a decade from now the detection of Ṗb and the sky proper motion will serve to make an independent constraint of the distance to the system.
Key words: binaries: close / ephemerides / gravitational waves / stars: neutron / celestial mechanics / stars: fundamental parameters
© The Authors 2023
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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Open access funding provided by Max Planck Society.
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