We present a model for atmospheric wind circulation in binary millisecond pulsar ( MSP ) companions , showing how the optical light curve ( LC ) and radial velocities ( RV ) are sensitive to the wind flow , causing LC orbital phase shifts and asymmetries , as observed for several ‘ spider ’ MSP .
Velocity widths of spectral lines offer additional opportunities for measuring surface wind speed .
As examples , we fit optical data for a black widow pulsar J1959+2048 and a redback pulsar J2215+5135 ; the wind heating models ( WH ) are statistically strongly preferred over direct heating ( DH ) for both objects , although the latter is even better fit with a heated spot .
In general , WH effects tend to increase the inferred orbital inclination i and decrease the inferred companion center-of-mass radial velocity amplitude K _ { \mathrm { c } } ; both effects decrease the inferred neutron star mass .
Even with such a decrease , we find large masses for the two neutron stars : 2.18 \pm 0.09 M _ { \odot } and 2.28 ^ { +0.10 } _ { -0.09 } M _ { \odot } , respectively ( for the modest surface speeds fit from the bulk heat flow ; supersonic photospheric winds can slightly change these values ) .
These are among the highest masses known , and our improved modeling increases confidence that the results are important for understanding the dense matter equation of state .