Astronomy Colloquium (2018 Fall Semester)

* Date.         Nov 08

* Speaker.   Chunglee Kim (Ewha Womans Univ.)

* Title.         Searching for Neutron Stars in the Galactic Center

* Abstract 

The gravitational-wave search for Galactic neutron star population targets a subgroup of neutron stars that can emit “persistent” gravitational waves, either fast-spinning (new-born or old millisecond pulsars) or extremely magnetized neutron stars that build up instabilities and generate time-dependent variations in their moment of inertia. Due to the expected source signal strength (i.e. gravitational-wave strain amplitude), the advanced LIGO/Virgo sensitivity would be able to detect the Galactic neutron star population (recall the GW170817 binary neutron star merger was in 40 Mpc!). Directional search/survey toward the Galactic Center is attractive for those who search for neutron stars, as the Galactic Center is one of the most dense stellar environments in our Galaxy and is considered to harbor many neutron stars. Although empirical expectations of the number of neutron stars in the Galactic Center is high, confirmed neutron stars within a few degrees about Sgr A* are only handful. Moreover, the physical associations of the observed neutron stars and the Galactic Center are often unclear. Observation of neutron stars in the Galactic Center is quite challenging due to the limited sensitivity/ resolution (by the far distance and/or by propagation effects). Looking forward more sensitive observations toward the Galactic Center, in particular for the third observation run (O3) with the advanced LIGO/Virgo gravitational-wave detector and for the square-kilometer array (SKA), it is a good timing to check out recent progresses made for the neutron star population in the central region of our Galaxy.  In this talk, I will present how a neutron star can be a “persistent” gravitational-wave source, summarize highlights of observational efforts with various disciplines, and discuss prospects of finding the neutron stars in our Galaxy  via gravitational waves as well as electromagnetic waves.