A census of galactic spider binary millisecond pulsars with the Nançay Radio Telescope

¹ LPC2E, OSUC, Univ Orléans, CNRS, CNES, Observatoire de Paris, F-45071 Orléans, France
² Observatoire Radioastronomique de Nançay, Observatoire de Paris, Université PSL, Université d’Orléans, CNRS, 18330 Nançay, France
³ LUX, Observatoire de Paris, Université PSL, Sorbonne Université, CNRS, 92190 Meudon, France

^⋆ Corresponding author: clara.blanchard@cnrs-orleans.fr

Received: 18 December 2024
Accepted: 12 April 2025

Abstract

Context. Spider binary pulsars are systems in which a millisecond pulsar (MSP) tightly orbits (P_b ≲ 1 day) a low mass (m_c ≲ 0.5 M_⊙) non-degenerate or semi-degenerate star. Spider systems often display eclipses around superior conjunction, and their orbital periods often exhibit rapid time variations. The eclipse phenomenon is currently poorly understood. However, eclipses are excellent probes of plasma physics and intrabinary shocks, and they can also be used to study MSP formation processes.

Aims. In this work, we present Nançay Radio Telescope (NRT) observations of a sample of 19 spider pulsars conducted over several years. The sample includes 11 eclipsing and eight non-eclipsing systems. We aim to provide a homogeneous phenomenological study of the eclipses in order to compare spiders and study their group properties, as those eclipsing systems are often studied individually. We compare our results with those derived from other studies, mainly optical observations and analyses of the pulsar companions.

Methods. We analysed eclipses via pulsar timing by using a 2D template-matching technique that allowed us to simultaneously determine radio pulse times of arrival (TOAs) and dispersion measures (DMs) along the lines of sight to the pulsars. The eclipses were then fit with a phenomenological model that gives a measurement of the duration and asymmetry of the eclipses. We then compared these parameters to other eclipse and system measurements in order to discuss the potential link between the presence of eclipses and orbital inclination, as eclipsing systems are known to have higher mass functions than non-eclipsing ones. Finally, we formed polarisation-calibrated profiles for the pulsars in our sample and derived some of their main polarisation properties.

Results. We present a comprehensive review of the NRT NUPPI backend spider pulsar dataset. We also present the first review and systematic analysis of a large sample of eclipsers monitored with the NRT over several years. The phenomenological fit allowed us to derive a number of parameters to compare the eclipsers with each other, which led to the categorisation of eclipsers depending on the shape of their eclipses. We present the polarimetric properties of the 19 spiders in the sample alongside their profiles, which were previously unpublished in some cases. We compared the mass function distributions of the eclipsing and non-eclipsing systems in our sample and found (in agreement with previous studies) that eclipsing systems have higher mass functions than their non-eclipsing counterparts, suggesting that the latter have lower orbital inclinations. For the eclipsing systems, we found evidence of a positive correlation between eclipse duration and mass function, as expected if more eclipsing material crosses the line of sight in higher inclination systems. For the entire sample, we found marginal evidence for increasing pulse profile width with decreasing mass function, possibly indicating that the low mass function spiders are indeed those seen under low inclinations. Finally, we conducted a comprehensive literature review of the published inclination measurements for the pulsars in the sample and compared the inclinations to eclipse parameters, (unexpectedly) finding no clear correlations between orbital inclination and eclipse properties. Nevertheless, the small number of available orbital inclination constraints, which contradict each other in some cases, hinders such searches for correlations.