GPSAC 2019a

The Seventh Annual Conference of the Graduate Physics Society

Wednesday, April 17th, 2019

Oral Presentations – 4:00-5:00PM, NSH 118

4:00-4:15 – The Slowly Fading Light Echo Around Type Ia Supernova 2009ig, Charlotte Wood

The light echo around Supernova 2009ig (SN2009ig) is the sixth known and most luminous around a type Ia supernova. Light echoes can provide information on the local environment around supernovae, which is particularly important for type Ias since they are used as standard candles. The presence of gas and dust in the local environment of a type Ia can affect the observed luminosity and could impact measurements of the Hubble constant. Using photometric data from the Large Binocular Telescope between 2010 and 2018, we present new observations of the SN2009ig light echo that confirm a slow fading of the echo over the past 6 years since its discovery in 2013. The fading is similar to that seen in the light echo of SN1991T and suggests that some of dust producing the echo may be local to the event.

4:15-4:30 – First Measurement of the 7Be B(E2; 3/2- –> 1/2-) Transition Strength and Comparisons to Ab Initio Predictions, Samuel Henderson

Several ab initio methods have made predictions on the E2 transition strengths for the first excited state transition in $^7Be$ and $^7Li$. These values provide strong constraints for ab initio theories, but due to issues with convergence, some of these methods can only compare ratios of the two E2 transition strengths instead of the individual transition strengths. The $^7Li$ B(E2) is known, but the $^7Be$ B(E2) has never been measured. We measured the $^7Be$ B(E2; 3/2^- \rightarrow 1/2^-) transition strength to test the validity of these ab initio predictions, which can help provide guidance on the structures of importance in this nucleus. To measure this E2 transition strength, a Coulomb Excitation experiment was performed at the University of Notre Dame. $^7Be$ was produced and separated using TwinSol, two solenoid magnets designed to separate out ions of interest. A beam of $^7Be$ ions were scattered off a gold target and the gamma rays from the inelastically scattered ions were detected using six clover Ge detectors. The results for the E2 transition strength and its comparison to multiple Ab-Initio approaches will be shown.

4:30-4:45 – A Feasibility Study for Using the ERAU Echelle Spectrograph to Improve Orbital Parameters of Spectroscopic Binary Systems, Stanimir Letchev

Binary stars are critical for establishing knowledge of stellar masses and refining the mass-luminosity relationship when used in conjunction with precise parallax measurements. However, many spectroscopic binaries have poorly defined orbital parameters as they have not been revisited with newer CCD technology since their first observations on photographic plates. I examined the feasibility of using the high-resolution \'{e}chelle spectrograph at Embry-Riddle Aeronautical University (ERAU) to obtain radial velocities of spectroscopic binary stars, and established a software pipeline to obtain their orbital parameters. This was done for two double-lined binaries and one single-lined binary. Twenty-five nights of data were taken from October 18th, 2016 to December 18th, 2016. I will talk about the process I used to obtain the orbital parameters and the results of the study.

4:45-5:00 – Actinide-Boost Stars may not Suggest a Separate r-Process Site, Erika Holmbeck

The astrophysical production site of the heaviest elements in the universe remains a mystery. One way to observationally investigate the production site of heavy elements is by studying metal-poor stars that retain imprints of nucleosynthetic event material in their photospheres. We introduce and apply the “Actinide-Dilution with Matching” model to a variety of \$r\$-process enhanced stellar groups ranging from actinide-deficient to actinide-enhanced to empirically characterize the ejecta mass from \$r\$-process events. We find that actinide-boost stars do not indicate the need for a unique and separate \$r\$-process progenitor. Rather, a range of actinide abundances can be produced by small variations within the same type of \$r\$-process event, covering all observed levels of actinide abundance. Further, we find that our empirical mass distributions are consistent with studies of GW170817 mass ejecta ratios, supporting that neutron-star mergers could be a source of the heavy elements in metal-poor, \$r\$-process enhanced stars.