Kyle Kremer

SPIN TILTS IN THE DOUBLE PULSAR REVEAL SUPERNOVA SPIN ANGULAR-MOMENTUM PRODUCTION

The system PSR J0737–3039 is the only binary pulsar known to consist of two radio pulsars (PSR J0737–3039 A and PSR J0737–3039 B). This unique configuration allows measurements of spin orientation for both pulsars: pulsar As spin is tilted from the orbital angular momentum by no more than 14 deg at 95% confidence; pulsar Bs by 130 ± 1 deg at 99.7% confidence. This spin-spin misalignment requires that the origin of most of Bs present-day spin is connected to the supernova that formed pulsar B. Under the simplified assumption of a single, instantaneous kick during the supernova, the spin could be thought of as originating from the off-center nature of the kick, causing pulsar B to tumble to its misaligned state. With this assumption, and using current constraints on the kick magnitude, we find that pulsar Bs instantaneous kick must have been displaced from the center of mass of the exploding star by at least 1 km and probably 5-10 km. Regardless of the details of the kick mechanism and the process that produced pulsar Bs current spin, the measured spin-spin misalignment in the double pulsar system provides an empirical, direct constraint on the angular momentum production in this supernova. This constraint can be used to guide core-collapse simulations and the quest for understanding the spins and kicks of compact objects.

LONG-TERM EVOLUTION OF DOUBLE WHITE DWARF BINARIES ACCRETING THROUGH DIRECT IMPACT

We calculate the long-term evolution of angular momentum in double white dwarf binaries undergoing direct impact accretion over a broad range of parameter space. We allow the rotation rate of both components to vary, and account for the exchange of angular momentum between the spins of the white dwarfs and the orbit, while conserving the total angular momentum. We include gravitational, tidal, and mass transfer effects in the orbital evolution, and allow the Roche radius of the donor star to vary with both the stellar mass and the rotation rate. We examine the long-term stability of these systems, focusing in particular on those systems that may be progenitors of AM CVn or Type Ia Supernovae. We find that our analysis yields an increase in the predicted number of stable systems compared to that in previous studies. Additionally, we find that by properly accounting for the effects of asynchronism between the donor and the orbit on the Roche-lobe size, we eliminate oscillations in the orbital parameters which are found in previous studies. Removing these oscillations can reduce the peak mass transfer rate in some systems, keeping them from entering an unstable mass transfer phase.

Accreting Black Hole Binaries in Globular Clusters

We explore the formation of mass-transferring binary systems containing black holes within globular clusters. We show that it is possible to form mass-transferring black hole binaries with main sequence, giant, and white dwarf companions with a variety of orbital parameters in globular clusters spanning a large range in present-day properties. All mass-transferring black hole binaries found in our models at late times are dynamically created. The black holes in these systems experienced a median of

Characterizing Accreting Double White Dwarf Binaries with the Laser Interferometer Space Antenna and Gaia

\sim 30

Accreting Double White Dwarf Binaries: Implications for LISA

dynamical encounters within the cluster before and after acquiring the donor. Furthermore, we show that the presence of mass-transferring black hole systems has little correlation with the total number of black holes within the cluster at any time. This is because the net rate of formation of black hole-non-black hole binaries in a cluster is largely independent of the total number of retained black holes. Our results suggest that the detection of a mass-transferring black hole binary in a globular cluster does not necessarily indicate that the host cluster contains a large black hole population.

How Black Holes Shape Globular Clusters: Modeling NGC 3201

We demonstrate a method to fully characterize mass-transferring double white dwarf (DWD) systems with a helium-rich (He) WD donor based on the mass--radius relationship for He WDs. Using a simulated Galactic population of DWDs, we show that donor and accretor masses can be inferred for up to

LISA Sources in Milky Way Globular Clusters

\sim\, 60

Low-mass X-ray binaries ejected from globular clusters

systems observed by both Laser Interferometer Space Antenna (LISA) and Gaia. Half of these systems will have mass constraints

How initial size governs core collapse in globular clusters.

\Delta\,M_{\rm{D}}\lesssim0.2M_{\odot}

Characterizing accreting double white dwarf binaries with LISA and Gaia

and