Description:

"Optical Trapping and Optimal Detection of Microdisks for Detection of High Frequency Gravitational Waves"

Shelby Klomp, PhD Student, Geraci Group

I present an update on the Levitated Sensor Detector (LSD) project for detection of high frequency gravitational waves, above the region previously probed by LIGO. The experiment will make use of optically-levitated flat dielectric micro-scale particles as force sensors with the advantage of reduced photon recoil heating. I therefore discuss numerical simulations of light scattering from various shapes of particles and how these inform our position detection scheme. Additionally, I will comment on initial experimental trapping and cooling results of high-aspect-ratio NaYF4 hexagonal prisms, and the experimental progress of the 1-meter LSD prototype that is in construction in the CFP.

"Uncovering Double-Detonation Type Ia Supernovae from Sub-Chandrasekhar-Mass White Dwarfs"

Chang Liu, PhD Student, Miller Group

While there is a broad consensus that Type Ia supernovae (SNe Ia) arise from explosions of carbon/oxygen (C/O) white dwarfs (WDs), the traditional scenario involving a Chandrasekhar-mass WD cannot account for the entire population. The detonation of a thin (~0.01 Msun) helium shell atop a ~1 Msun C/O core is a promising mechanism to explode sub-Chandrasekhar-mass WDs. These double-detonation explosions may be the origin of many normal SNe Ia. More massive helium shells and/or less massive C/O cores may explain some recently observed peculiar objects. In this talk, I will present observations of two SNe Ia discovered by the Zwicky Transient Facility (ZTF), SNe 2020jgb and 2022joj. Their remarkable peculiarities point toward a double-detonation origin - (i) unusual color evolution and prominent continuous absorption in near-ultra-violet probe Fe-group elements formed in helium-shell detonations; (ii) tentative features of unburnt helium is detected in the near-infrared spectrum of SN 2020jgb; (iii) the nebular-phase spectra of SN 2022joj indicate a low Ni/Fe abundance ratio in the SN ejecta, which is only expected in the explosion of a sub-Chandrasekhar-mass WD. To close, I will briefly introduce the La Silla Schmidt Southern Survey (LS4), a new wide-field time-domain survey. With a customized color-evolution filter in the transient alert stream, LS4 will naturally power the discovery of double-detonation SNe Ia in a prompt and systematic way.