Dr. Lai will conduct a theoretical investigation the physics of neutron stars, which are the highly dense evolutionary endpoints of massive stars. The research will investigate the physical and astrophysical processes occurring at or near highly magnetized neutron stars and magnetars. The major goal of the project is to understand the various observational manifestations of magnetized neutron stars and use this understanding to study physics under extreme conditions.
This project is expected to characterize the various types of neutron stars and the most important physical processes in each type, and will providing tools to interpret current and future observations. The research is multidisciplinary in nature, involving astrophysics, atomic physics, plasma physics and nuclear physics, and thus is of interest to the wider scientific community. Results from this research will be incorporated into the Cornell University curriculum, and the project will provide research opportunities for undergraduate and graduate students.
Intellectual Merit: During the last four years, this grant has provided key funding forthe research group of the PI (Professor Dong Lai). With this funding,the PI and graduate students have worked on understanding variousobservational manifestations of magnetized neutron stars (NSs),including radio pulsars, radio-quiet thermally emitting NSs andmagnetars, as well as other related problems (magnetic accretion ontoneutron stars, black holes and white dwarfs, binary mergers, disksaround magnetic protostars, etc). Our works have been motivated by therecent and ongoing observational progress, made possible byspace-based and ground-based telescopes, and the prospect of suchstudy in constraining the fundamental physics and astrophysics ofvarious astrophysical objects. Recent observations have raised anumber of puzzles/questions that beg for theoretical understanding andmodeling. Our research has resulted in a number of publications that arepublished in refereed journals. Some highlights of our findings include (More details and results can be found inour final project report):(1) With graduate student Natalia Storch and other collaborators(including former student Wynn Ho), we have modeled the the lightcurve and internal magnetic field of the mode-switching pulsar PSRB0943+10. Several of ourmodels are currentlyconsistent with data in radio and X-rays and can be tested orconstrained by future X-ray observations, providing new insights onneutron star magnetic field evolution.(2) With graduate student Natalia Storch, we have studied theobservational constraints on the internal magnetic fields of youngneutron stars in supernova remanants. Our research suggests thatsubstantial sub-surface magnetic fields, much stronger than the``visible'' dipole fields, may be buried in the crusts of some youngNSs, and such hidden magnetic fields can play an important role intheir observational manifestations.(3) We have studied magnetic interactions in neutron starbinaries. We find that in coalescing neutron star binaries, magneticinteractions produce negligible correction to the phase evolution ofthe gravitational waveform, even for magnetar-like fieldstrengths. However, energy dissipation in the binary magnetosphere maystill give rise to electromagnetic radiation prior to the finalmerger. (4) With graduate student James Fuller, we have studied theinteractions in compact white dwarf binary systems with periodsranging from minutes to hours. We find thatthat tidal effects makesignificant contribution to the WD luminosity for short-period (about10 min) systems such as SDSS J0651+2844. We also find that for WDscontaining a hydrogen envelope, tidal heating can trigger runawayhydrogen shell burning, leading to a nova-like event before the onsetof mass transfer. Overall, our research has enhanced our understanding of differentpopulations of NSs and other objects (black holes andwhite dwarfs) and their underlying physical processes, andprovide tools to interpret current and future observations. Broader impacts: Our research is multidisciplinary in nature, involving astrophysics,atomic physics, plasma physics and fluid dynamics, and thus is ofinterest to a broad scientific community. Our research results havebeen published in refereed journals and presented in a number ofscientific meetings. Most importantly, a number of graduate students(including two female students, Natalia Storch and Kassandra Andersonand a minority student, Ryan Miranda)have received training in many of the multidisciplinary areas, as wellas in scientific computing. In addition,the PI has integrated latest research results into formalgraduate/undergraduate courses and in educationallectures targeting the general public/students.Several undergraduate students have also been involved in our research.
