Here's a compilation of all my first-author papers. For a full list of all papers I've worked on, check out my CV or look me up on ADS.
These papers are split into three categories:
Stochastic AGN Variability: these papers are focused on understanding the random variability that is seen in all AGNs. This variability is attributed to thermal perturbations in the central accretion disk surrounding the SMBH, but the physical mechanisms driving those perturbations are unclear. My work introduces a novel data transformation technique, using the observed data to create "maps" of the accretion disk, which would normally be unresolvable, in order to probe the unknown physical mechanisms driving the thermal perturbations we're so interested in understanding.Artist’s impression of an accretion disk surrounding a SMBH. Above the SMBH, an X-ray “lamppost” drives disk variability – or does it? Credit: NASA/JPL-Caltech.Transients around SMBHs: these papers are focused on understanding various forms of transient variability that are seen in AGNs and around normally quiescent SMBHs. Whereas all AGNs vary, not all of them show the large-amplitude flares and dimmings that are seen in these papers. Rather than random perturbations in the accretion disk, these events are indicative of large changes in the overall accretion flow of the AGN (or SMBH).Artist’s impression of a tidal disruption event around a SMBH. Credit: JPL/Caltech.The deaths of massive stars: All stars above a certain mass (~8 times the mass of our sun) will undergo core-collapse and "die". But, not all of these stars die the same way. The current understanding is that most explode as supernovae (SNe), creating a luminous transient that easily outshines its host galaxy. But, some of these stars instead implode as failed SNe (also called "unnovae"), possibly producing a faint flare as they do so. It's understandable, then, that the latter event is very hard to detect. That's why you need a project like the Search for Failed Supernovae with the Large Binocular Telescope, which monitors millions of stars in nearby galaxies in order to find those handful of stars that suddenly disappear as failed SNe. My papers focus on trying to detect these failed SNe, as well as using this unique dataset to study "successful" SNe.Artist’s impression of a red supergiant dying as a failed supernova. Credits: NASA, ESA, and P. Jeffries.I also include my first, first-author paper, written as an undergrad at Dartmouth, which focused on studying a supernova remnant.
The current understanding of AGN disks includes an X-ray “lamppost” that sits above the disc and variably illuminates it. This variable illumination causes the disk to vary in UV/optical wavelengths. This work attempts to map the disk itself using a sample of multi-filter AGN lightcurves, and we find that many of our maps are inconsistent with a lamppost being the only source of variability. Moreover, our maps are dominated by slow-moving fluctuations that are more consistent with being generated by the disk itself. These findings could have huge impacts in how we understand AGN variability, as intrinsic disk fluctuations have been hypothesized and simulated yet never directly observed.
Going from stellar mass BHs back to SMBHs, I’ve also done work on TDEs detected by ASAS-SN. TDEs are the luminous flares that occur when a star gets ripped apart by the tidal forces of a SMBH and is accreted. My first, first-author paper at OSU was characterizing ASASSN-18jd, a peculiar event that is not quite a TDE, and not quite an AGN. At the time, ASASSN-18jd was unique in its peculiarity, but newer work has shown there to be a handful of ambiguous nuclear transients (ANTs) with similar in-between-TDE-and-AGN properties.
We especially concentrated on the variability with respect to the exciting yet poorly understood “changing-look” phenomenon, where broad emission lines appear and/or disappear over the course of a few years. While all AGNs are variable, this specific type of variability is extremely important in that it poses a direct challenge to the “unified model”, where the presence/absence of broad lines is thought to be a line-of-sight effect. Moving back to NGC 5273, we report that the AGN changed-look at least once during the period from 2001 to 2022 (more tightly, between 2010 and 2014), and we claim that it may have done so multiple times based on its multi-wavelength variability. However, due to lack of consistent spectroscopic observations, we cannot definitively say that the AGN changed-look more than once, though perhaps future observations will prove (or disprove!) our claim. In any case, this study was a great experience and allowed me to personally handle data ranging from the near-infrared to hard X-rays, which is especially useful when AGNs emit at all these wavelengths.
I have also worked on finding failed supernova (SN) candidates with the OSU-co-owned Large Binocular Telescope (LBT). Failed SNe are what happen when stars are too massive to explode as SN and instead implode into BHs. We reported the discovery of a new candidate failed SN and updated the failed SN fraction based on our observations.
The LBT search for failed SN is also just a great dataset for successful SNe. The survey has been ongoing since 2008, and so we now have up to 15 years of archival observations that can be used to measure and constrain the pre-SN variability of the progenitor star. We do exactly this for SN 2023ixf, finding no evidence for optical variability in our data. We also put upper limits outbursts that we may have missed due to gaps in observation – namely, if the progenitor exceeded 5x its initial luminosity in an outburst, we would have been able to detect it because its long-lasting effects on the dust surrounding the progenitor.
This was first, first-author paper from my undergrad at Dartmouth. We report the optical detection of a distant, mid-plane supernova remnant. The highlight of this paper is its figures, where we showcase how we were able to detect the source despite its optical faintness.
