About Me

Predoc, Astronomy graduate student, and admirer of stars.

Hello! My name is Ben, and I am currently a 3rd year graduate student at Boston University studying Astronomy. I got my B.S. from Clarkson University in May of 2016 with a major in Physics and a mathematics minor, and my Masters in Astronomy from Boston University in May of 2018.

As an undergrad I worked on the binary system R81 in the Large Magellanic Cloud with Dr. Joshua Thomas at Clarkson University and Dr. Noel Richardson at the University of Toledo. My research project focused on using spectra from the Cerro Tololo Inter-American Observatory and long baseline sampled photometric data from the All Sky Automated Survey to determine if there was mass transfer taking place in this close binary system. A more detailed description of my work can be found in the Research page of my website.

One of my current research projects is working with Dwarf Carbon Stars from the Sloan Digital Sky Survey. Carbon stars have atmospheres that are enhanced with carbon (C/O > 1), giving them distinctive spectral features. These main sequence carbon dwarfs (dC) are unique since they can not have produced their own carbon yet! One theory is that these dwarf carbon stars are the product of mass transfer from a higher mass companion, which I am currently using SDSS spectra to investigate. More information can be found in my Research section.

If you have any interest in my research, or questions, feel free to contact me at one of the email addresses below! I am always looking to share my interests with people and to help spread astronomy to everyone!

Research

Dwarf Carbon Stars

One of my recent research projects is working with Dwarf Carbon (dC) stars. Carbon stars have atmospheres that are saturated with carbon, giving them distinctive spectral features. It was thought that all carbon stars are post-main sequence stars that had their atmospheres polluted by dredge ups, bringing carbon to the surface. This made the discovery of a dwarf carbon star (dC) a surprise. One theory is that these dwarf carbon stars are the product of mass transfer from a higher mass companion.

I used repeat epochs of spectroscopy from SDSS to measure the radial velocity shift (∆RV) between epochs of repeat spectra for a sample of 240 dC stars. By comparing the ∆RV distribution of dC stars to a well chosen sample of control stars, I used a combination of deconvolution and MCMC methods to show that the dCs have larger ∆RVs than the control sample (which corresponds to tighter orbits) and fit a binary separation distribution to show how close those orbit are.

The top left figure shows an example of what a dC spectrum looks like in the range or 5000Å to 6000Å. Two of the prominent C2 bands are visible and marked. The top panel of the figure shows both epochs overplotted while the bottom panel shows the same epochs, but the later MJD epoch has been shifted by the measured ∆RV value.

The top right figure shows both the dC (blue) and control (red) ∆RV histograms as well as a Gaussian mixture model that accounts for errors called Extreme Deconvolution (XD). From this figure it is clear the the dC stars have many more systems that extend past the error dominated core due to their close orbits.

If you want to read more about this research project and the details of what went into it, feel free to read through my recent paper submitted to ApJ. If you have any comments on how to improve this work please send me an email to one of the addresses below.

 

R81

The main objective of my undergrad research project was to characterize a binary system, R81. in the Large Magellanic Cloud; with a secondary goal of finding traces of mass transfer via in-falling material on the secondary star. I used both photometric measurements from the All Sky Automated Survey (ASAS) and spectroscopic measurements from Cerro Tololo Inter-American Observatory (CTIO) provided by Dr. Noel Richardson of the University of Toledo.

My analysis used approximately 30 years of photometric data from ASAS to refine the period given by Tubbesing et al. (2001). I used a multitude of photospheric lines to define a radial velocity curve for R81. However, the main line of interest for my project was the Hα line at 656.28nm. The Hα line comes from the shell of material surrounding the binary system and if there is in-falling material this is where the signature would show up.

The above images are from my work on this project. The left image shows a binned and phase-folded light curve for R81 from the ASAS data. The vertical red lines show the important phases in this system and more detail can be found in my thesis below. The right image is a dynamical spectrum for the Hα line showings its variability and intensity.

If you want to read more about this research project and the details of what went into it, feel free to read through my complete Honors Thesis. If you have any comments on how to improve this work please send me an email to one of the addresses below.