Unraveling the Formation History of the Black Hole X-ray Binary LMC X-3 from ZAMS to Present

Abstract

We have endeavoured to understand the formation and evolution of the black hole (BH) X-ray binary LMC X-3. We estimate the properties of the system at 4 evolutionary stages: 1) at the Zero Age Main Sequence (ZAMS), 2) just prior to the supernova (SN) explosion of the primary, 3) just after the SN, and 4) at the moment of RLO onset.We use a hybrid approach, combining detailed stellar structure and binary evolution calculations with approximate population synthesis models. This allows us to estimate potential natal kicks and the evolution of the BH spin. In the whole analysis we incorporate as model constraints the most up-to-date observational information, encompassing the binary's orbital properties, the companion star mass, effective temperature, surface gravity and radius, as well as the black hole's mass and spin. We find that LMC X-3 began as a ZAMS system with the mass of the primary star in the range $M_{\rm{1,ZAMS}}$ = 22-31 $\rm{M_{\odot}}$ and a secondary star of $M_{\rm{2,ZAMS}} = 5.0-8.3M_{\odot}$, in a wide ($P_{ZAMS} \gtrsim 2.000\, \rm days$) and eccentric ($e_{\rm{ZAMS}} \gtrsim 0.23$) orbit. Just prior to the SN, the primary has a mass of $M_{\mathrm{1,preSN}} = 11.1-18.0\,\rm M_{\odot}$, with the secondary star largely unaffected. The orbital period decreases to $0.6-1.7\, \rm days$, and is still eccentric $0 \leq e_{\rm{preSN}} \leq 0.44$. We find that a symmetric SN explosion with no or small natal kicks (a few tens of $\rm km\, s^{-1}$) imparted on the BH cannot be formally excluded, however, large natal kicks in excess of $\gtrsim 120 \,\rm km\, s^{-1}$ increase the estimated formation rate by an order of magnitude. Following the SN, the system has a BH $M_{\mathrm{BH,postSN}} = 6.4-8.2\,\rm M_{\odot}$ and is put into an eccentric orbit. At the RLO onset the orbit is circularised and it has an orbital period of $P_{\rm{RLO}} = 0.8-1.4\,\rm days$.