Meeting Talks

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September 21st

Yanbo Pan (he/him) (

"Modelling Binary Orbits in the WIYN Open Cluster Survey - The alternative evolutionary tracks for binary stars"

Abstract: We utilized theJoker sampler, initially created for APOGEE's sparsely and noisily measured radial velocities, in our examination of the WIYN Open Cluster Survey. After utilizing rejection and MCMC sampling with theJoker, we scrutinized single-lined binary orbits in M67 and NGC 188. Our objective was to evaluate theJoker's efficacy on binaries with ample radial velocity data (RVD) and investigate the possibility of devising observing plans that would enable us to estimate binary orbital solutions with fewer RVD and better understand the alternative evolutionary tracks for binary stars.

Sophia Davis (

"Shockwaves in Space: Can One Satellite Tell Us What's Coming, or Do We Need a Fleet?"

Abstract: Interplanetary shocks in our solar system are driven by solar eruptions and solar wind stream interactions. When directed at Earth, these shocks interact with Earth’s magnetosphere, with ramifications that vary depending on the magnitude of the shock wave and the conditions presenting upstream. To forecast and mitigate their impact on the Earth, it is important that we can measure the magnitude and the attack angle of an interplanetary shock wave arriving at the Earth. These shock waves are independently observed and measured en route to the Earth at Wind, the Deep Space Climate Observatory (DSCOVR), the Solar Heliospheric Observatory (SOHO), and the Advanced Composition Explorer (ACE). In this project, we propose a new method of analysis using a multi-spacecraft fleet to characterize these shock waves. We compare two different methods for estimating the propagation vector of a shock prior to its arrival at Earth: a single spacecraft analysis using Wind and a multi-spacecraft geometric analysis using Wind, DSCOVR, SOHO, and ACE.  

Potential interplanetary shock waves are first cataloged in the Center for Astrophysics Interplanetary Shock Database by searching for abrupt jumps in the plasma and magnetic parameters. For each candidate, we follow the methodology of Szabo et al, 2004 and Viñas and Scudder, 1986 to determine the most probable propagation vector and whether the candidate represents a shock transition. We then corroborate the event in observations from ACE, DSCOVR, and SOHO. Using the set of four positions and times of shock observation, the shock’s magnitude and direction of propagation is fully determined under the assumption of planar geometry. We use this method to benchmark the performance of the single spacecraft analysis for different types of shocks, and we evaluate the relative utility of a single in situ L1 monitor versus a constellation for space weather forecasting. This work is supported by the NSF-REU solar physics program at SAO, grant number AGS-2244112. 

Sanil Mittal (he/him) (

"New temperature and surface gravity values for metal poor stars"


November 1st

Aster Taylor (they/them)

"Abnormal Nongravitational Accelerations on Solar System Objects"

Ryan Walker

"Amateur Astrophotography"



November 16th

Benjamin Velguth (he/him) (

"Spatially Resolving the Quenching Time in F8D1 with Luminous AGB Stars"

Abstract: Ultra-diffuse galaxies (UDGs) are a relatively new classification of dwarf galaxies, characterized by low stellar mass (<10^8 M_sun) high radii (>2 kpc), and low surface brightness (~25 mag/arcsec^2). These galaxies have been observed throughout the universe, and understanding how they form is critical to filling a gap in our knowledge of galactic evolution. Until now, these galaxies have only been studied as a population, but the proximity of F8D1 allows us to deeply analyze the stellar populations within this UDG to understand the inner workings of these galaxies. Recently, (Žemaitis, et. al. 2022) discovered that F8D1 has been tidally disrupted, estimating a tidal tail length of around 60 kpcs. We have used the ratio of AGB to RGB stars both in the main body of the galaxy and in its tidal tails to constrain its star formation history (SFH); in two central deep HST fields we also have deep enough color–magnitude diagrams to fit a full SFH. We find evidence of a burst of star formation that occurred roughly 2 Gyr ago in both the center and tail, which is consistent with the ratio of AGB to RGB stars in both regions. This implies that star formation stopped globally in F8D1 before or at the same time as its tidal disruption event.