Phygas birth-cluster search: pulsar PSR J1124-5916

Abstract

What this is. The complete, unfiltered result of the Phygas search for the pulsar PSR J1124-5916: for each of 4,086 young open clusters and moving groups (of 4,087 in the catalogue; the others were excluded by a distance prefilter) it records how close, how long ago and at what relative speed the pulsar and the cluster came together when both are traced backwards through the Milky Way. Phygas ("fugitive") searches for the birth places of runaway stars and neutron stars. It runs on the volunteer-computing project bitboinc (https://bitboinc.athena.org.tr); this result was computed on volunteers' computers and confirmed by two independent computations. An illustrated explanation with an animation is at https://bitboinc.athena.org.tr/phygas_pulsars.php. The idea A pulsar is the neutron star left behind by a supernova, and many are thrown out of their birth place at hundreds of kilometres per second. Most massive stars are born in clusters, so a pulsar's backwards path can be compared with the positions of young clusters: if the path crosses a cluster at a time not later than the cluster's age, that cluster is a candidate birth place. How the numbers were obtained Pulsar. Position, proper motion and distance come from the ATNF pulsar catalogue (HEASARC copy, December 2024). For this pulsar the distance is 5000 pc, a dispersion-measure distance (log-normal uncertainty); proper motion (μαcosδ, μδ) = (-17.00, -12.00) mas/yr. The radial velocity is not measured for pulsars, so it is drawn from the Galactic-rotation expectation at the pulsar's position with a 265 km/s standard deviation. Clusters. 4,087 open clusters and moving groups of Hunt & Reffert (2024) (Gaia DR3) that can be younger than 100 Myr, each with its position, distance, proper motion, radial velocity (when measured; otherwise the Galactic-rotation expectation ± 10 km/s), half-mass radius, total radius and age. Monte Carlo. 1,000 copies ("clones") of the pulsar and 1,000 clones of the cluster are drawn from these measurement uncertainties. Integration. Each copy is integrated backwards in time through the Allen & Santillan (1991) Milky Way potential (bulge, disc and halo) with a kick-drift-kick leapfrog (step 0.05 Myr), starting from the Sun at R0 = 8.122 kpc, up to the age of the cluster (at most 100 Myr). The closest approach of each pulsar copy to its cluster copy is refined between steps. Result per pair. The 5th, 50th and 95th percentile (over the copies) of the closest-approach distance, its lookback time and the relative speed at that moment, and the fraction of copies that came closer than the cluster's half-mass radius and than its total radius. Files in this record J1124-5916_summary.png: one figure summarising this pulsar (sky positions of the best candidate clusters, ranking by share of copies inside the cluster, when and how close each approach was, relative speeds). J1124-5916_cluster_pairs.txt.gz: one line per cluster, whitespace separated, columns: pulsar, cluster, cluster_kind (m = moving group, o = open cluster), n_clones, d05, d50, d95 (closest-approach distance in pc), t05, t50, t95 (lookback time of the closest approach in Myr), v05, v50, v95 (relative speed at the closest approach in km/s), f_r50, f_rtot (fraction of the copies inside the cluster's half-mass / total radius at the closest approach). Lines starting with # are the header. J1124-5916_pulsar_input.txt: the pulsar's row exactly as given to the search (columns in its header line). young_clusters.txt.gz: the cluster catalogue used (identical in every record of this series): idx, name, type, ra, dec [deg], dist_pc, e_dist_pc, pmra, e_pmra, pmdec, e_pmdec [mas/yr], rv, e_rv [km/s], r50_pc, rtot_pc, age16, age50, age84 [Myr], tmax [Myr] (how far back the cluster was traced). This pulsar Of the 4,086 clusters tested, 1 have at least one of the 1,000 pairs of copies passing inside the cluster's total radius, and 0 inside its half-mass radius. The five pairs with the largest share inside the half-mass radius (ties broken by the total radius) are: #clustertypeclones inside half-mass radiusclones inside total radiuslookback time of closest approach, median [Myr]closest-approach distance, median [pc]1HSC 2310moving group0.0%0.1%13.517844 How to read the numbers The share of copies inside a cluster counts how many of the Monte Carlo copies met the cluster; it is not a probability that the pulsar was born there. Clusters are numerous, so some pairs meet by chance, and no control against chance alignment has been applied to this data. Because the pulsar's radial velocity is unknown and drawn from a broad range, the relative speeds mostly reflect that range. The data are published as raw search output, with no claim about any birth association. References Hunt, E. L. & Reffert, S. 2024, A&A 686, A42 (cluster catalogue, VizieR J/A+A/686/A42). Manchester, R. N. et al. 2005, AJ 129, 1993 (ATNF pulsar catalogue; HEASARC copy). Allen, C. & Santillan, A. 1991, RMxAA 22, 255 (Milky Way potential). Schönrich, R., Binney, J. & Dehnen, W. 2010, MNRAS 403, 1829 (solar motion); GRAVITY Collaboration 2018, A&A 615, L15 (R0). Software (open source, GPL-3.0): https://github.com/alplix/phygas.