Isabella Almeida Guilherme

MIT Department: Physics
Faculty Mentor: Prof. Erin Kara
Undergraduate Institution: Columbia University
Hometown: Sao Paulo, Brazil
Research Poster
Lightning Talk


My name is Isabella Guilherme, and I am originally from Sao Paulo, Brazil. I am a junior at Columbia University, where I study physics with a concentration in mathematics. I am very interested in high-energy astrophysics, and I am currently investigating possible correlations between neutrinos and gamma rays in blazars. I am very excited about this field, and I plan to pursue my PhD in astrophysics.
In my free time, I like to cook, read and go to coffee shops.


2021 Abstract

How Black Holes Swallow Matter: Analyzing the Late X-ray Emission of a Tidal Disruption Event

Isabella A. Guilherme¹, Megan Masterson², and Erin Kara²
¹Department of Physics, Columbia University
²Department of Physics, Massachusetts Institute of Technology

When a star gets sufficiently close to a supermassive black hole (SMBH), it is torn apart by the SMBH’s tidal forces. Known as “tidal disruption event”, this can result in a luminous flare of radiation that allows us to detect dormant SMBHs and understand general features of accretion. However, the current canonical model for tidal disruption events (TDEs) does not satisfactorily explain the delayed X-ray emission observed in some UV/optically detected TDEs. Here we analyzed the spectrum and time evolution in X-rays of AT2019azh, a UV/optically detected source that shows a rise in X-ray flux ~250 days after the discovery. We collected and reduced data obtained by XMM-Newton, NICER and Swift, then modeled the spectra and generated light curves. The spectra are well described by a disk blackbody model, and in the highest quality XMM-Newton spectra, we also observe a high-energy tail, potentially associated with Comptonization in a hotter plasma. The disk luminosity scales with temperature as per the Stefan-Boltmann law, which is consistent with thermal emission from the accretion disk. It is still necessary, however, to further investigate the additional high-energy tail. Doing so will refine our understanding of TDEs and other complex accreting systems, such as active galactic nuclei.