Effects of precession versus instabilities on the jets of GRS 1758–258

Abstract

Aims. The prototypical microquasar GRS 1758–258 exhibits large-scale morphological changes in radio maps over time which have been attributed to the rise of instabilities. Here, we investigate whether these effects could be attributed to jet precession instead. Methods. We used new and archival radio maps to fit a kinematic jet precession model. The value of the parameters thus obtained were analysed in order to get constraints on the physical properties of the GRS 1758–258 system. Their consistency with different theories of the origins for the jet precession, such as Lense–Thirring effect and tidal torques induced by the secondary star, has previously been studied. Alternatively, we also assessed the possibility that observations are compatible with eventual jet instabilities. Results. The new radio data presented here confirm that the large-scale radio morphology of GRS 1758–258 is changing over time. Our study shows that the 18.48 day period could plausibly be ascribed to precession, thus implying a reinterpretation of assumptions made for the orbital period to date. However, the observed structural changes in radio jets cannot be easily attributed to jet precession according to our analysis. In contrast, the growth of instabilities certainly appears to be a more realistic explanation of these effects.

Numerical simulations of relativistic jets

“…2001; Massi, Ros & Zimmermann 2012; Miller-Jones et al. 2019; Luque-Escamilla, Martí & Martínez-Aroza 2020). The origin of precession in microquasars is still debated for most of these sources.…”

“…The most relevant example of jet precession is the well-known microquasar SS 433, but there are many other examples (see e.g. Mioduszewski et al 2001;Massi, Ros & Zimmermann 2012;Miller-Jones et al 2019;Luque-Escamilla, Martí & Martínez-Aroza 2020). The origin of precession in microquasars is still debated for most of these sources.…”

“…For example, current-driven instabilities have been claimed to explain the large-scale morphology of the jet structures observed in GRS 1758-258 (Luque-Escamilla et al. 2020).…”