The bright subdwarf-O star ( sdO ) HD 49798 is in a 1.55 day orbit with a compact companion that is spinning at 13.2 seconds .
Using the measurements of the effective temperature ( T _ { eff } ) , surface gravity ( \log g ) , and surface abundances of the sdO , we construct models to study the evolution of this binary system using Modules for Experiments in Stellar Astrophysics ( MESA ) .
Previous studies of the compact companion have disagreed on whether it is a white dwarf ( WD ) or a neutron star ( NS ) .
From the published measurements of the companion ’ s spin and spin-up rate , we agree with Mereghetti and collaborators ( 2016 ) that a NS companion is more likely .
However , since there remains the possibility of a WD companion , we use our constructed MESA models to run simulations with both WD and NS companions that help us constrain the past and future evolution of this system .
If it presently contains a NS , the immediate mass transfer evolution upon Roche lobe ( RL ) filling will lead to mass transfer rates comparable to that implied in ultraluminous X-ray sources ( ULXs ) .
Depending on the rate of angular momentum extraction via a wind , the fate of this system is either a wide ( P _ { orb } { \approx } 3 day ) intermediate mass binary pulsar ( IMPB ) with a relatively rapidly spinning NS ( { \approx } 0.3 s ) and a high mass WD ( { \approx } 0.9 M _ { \odot } ) , or a solitary millisecond pulsar ( MSP ) .