Artur defends his MsC dissertation

The black hole group has a new master: Artur Vemado defended his MsC dissertation, entitled “radiative cooling and state transitions in stellar mass black holes”. The defense was very successful.

Here, Artur reported his numerical simulations of black hole accretion flows where he incorporated radiative cooling (with some approximations otherwise the problem is essentially intractable!). We observe the self-consistent emergence of a hot corona enveloping a cold thin accretion disk. Artur quantified the inner radius of the thin disk, the size of the corona, and how these properties respond to varying the mass accretion rate onto the black hole. The resulting simulated black holes are similar to observations of stellar mass black holes in binary systems.

We are looking forward to reporting these exciting results on the emergence of the corona (not the covid-19!) and truncated disk in an upcoming publication.

Many thanks to FAPESP funding through grant 2017/25710-1.

Dr. Gustavo R. R. Soares, PhD in Astrophysics

Congratulations to the now Dr. Gustavo R. R. Soares, for a successful PhD thesis defense! 🎉🍾

The thesis is entitled “Accretion discs, jets, and black hole spins: a study of blazars” and was done under my supervision. The whole defense was entirely online, following the social distancing recommendations of the World Health Organization and the SĂŁo Paulo State government, in order to ensure the safety of all involved with respect to COVID-19.

The defense lasted for almost five hours (!!), with the thesis committee members in two countries—Brasil and US—and in three states in Brasil: Pernambuco, Rio de Janeiro and SĂŁo Paulo.

Gustavo presenting his thesis work

Thanks to Dr. Soares’s work, we now we know a bit more about the role of black holes in the universe, and how the supermassive ones power relativistic jets.

Gustavo will begin a postdoc at Oregon State University in the Fall. We are all wishing Gustavo a huge success for his future career!

Our thanks to the Brazilian science funding agencies CAPES, CNPq and FAPESP. Without them, this work would not have been possible.

Ivan defends his MsC dissertation

Let’s congratulate Ivan on his brilliant masters dissertation defense. His dissertation’s title is “Winds and feedback from supermassive black holes accreting at low rates”. In this work, Ivan performed a suite of hydrodynamical simulations of hot accretion flows with a large dynamical range and long durations (comparable to the viscous timescale), aiming at better understanding black hole wind production and feedback in low-luminosity AGNs hosted by quiescent galaxies.

We have a paper coming out soon, where we will report the results of this work. Stay tuned!

From left to right: Diego Falceta Gonçalvez, Rodrigo Nemmen, Ivan de Almeida, Thaisa Storchi Bergmann and Roderik Overzier.

The evaluation committee was composed of Thaisa Storchi Bergmann, Roderik Overzier and Diego Falceta Gonçalvez.

This work was funded by a FAPESP scholarship, grant number 2016/24857-6. It has made use of the following computing facilities:

  • Laboratory of Astroinformatics (IAG/USP, NAT/Unicsul; FAPESP grant 2009/54006-4)
  • Aguia cluster, HPC resources of Universidade de SĂŁo Paulo

Raniere visiting Torino to continue exploration of the unknown gamma-ray sky

Raniere will be visiting the University of Torino over the next year, working with Prof. Francesco Massaro, in order to continue our group’s research to understand the unidentified gamma-ray sources observed with Fermi Large Area Telescope. In particular, he will use a suite of optical observations to try to pinpoint the nature of such sources.

Raniere’s visit will be funded by a FAPESP BEPE scholarship, grant number 2018/24801-6.

Roberta joins the group

I’m Roberta Duarte Pereira and I’m a physicist graduated at IFSC-USP. I just started my master’s degree in the Black Hole Group at IAG-USP under the supervision of Prof. Rodrigo Nemmen.
Since my childhood, one of my main passions in life is Astronomy, mainly Black Holes because they are so interesting and they always fascinated me. During my time in undergrad course, Computational Physics also called my attention. So I decided to connect both of my passions.
Recently, I started a project – under the supervision of Professor Rodrigo—in astrophysical simulations with deep learning. It’s a project that may bring some new insights about how we see numerical simulations nowadays and we could gain so much in this area!
I’m very happy and greatly motivated with this project and also for being in the Black Hole Group.

Roberta will work on applying machine learning and deep learning to numerical simulations of black holes, in collaboration with JoĂŁo Paulo Navarro from NVIDIA.

Welcome aboard, Roberta! We are glad you chose to come work in our group, and excited for the discoveries in the computational universe that will come from your project.

Roberta Duarte Pereira and Rodrigo Nemmen

Fermi Symposium + Collaboration meeting + NASA GSFC visit

The PhD students of the group working on gamma-ray observations—Fabio and Raniere—spent the last two weeks in Washington DC and surroundings. They went to the Fermi LAT Collaboration meeting at George Washington University, where they interacted with gamma-ray astronomers in the Fermi Collaboration. Raniere presented his ongoing analysis of the gamma-ray emission of a population of nearby AGNs.

Raniere de Menezes presenting his work on low-luminosity AGNs at the Fermi LAT Collaboration Meeting, Washington DC.

Following the Collaboration meeting, the students presented their research at the Fermi Symposium in Baltimore. Raniere presented a poster about his work on the pulsar populations in Milky Way globular clusters—which is about to be submitted for publication—while Fabio gave a talk describing his analysis of the gamma-ray emission from the Galactic Center on constraints on Sgr A* physics.

Fabio Cafardo presenting his work on the gamma-ray emission of Sgr A* at the Fermi Symposium, Baltimore.

After the symposium, Fabio and Raniere spent a couple of days visiting NASA Goddard Space Flight Center to discuss their research with GSFC scientists.

Their visit was possible thanks to NASA funds, grant xxxxxx.

Undergrad working on GPU research advances to international phase of research symposium

Matheus Tavares Bernardino, an undergraduate student working in our group, presented his work on the acceleration of black hole radiative transfer with OpenACC in GPUS at the undergraduate science symposium at USP and now will compete in the international phase of the symposium which will happen in November.

Congratulations, Matheus!

Matheus (right) and collaborator Alfredo Goldmann (left) happily showcasing the poster

Group will teach analysis of Fermi LAT data in dark matter school

On the final week of July, members of our research group (Fabio, Raniere & Rodrigo) will be teaching a lesson on the analysis of Fermi LAT gamma-ray observations in the School and Workshop on Dark Matter and Neutrino Detection at ICTP-SAIFR. In this hands-on activity, we will teach how to analyze gamma-ray data for a dwarf galaxy, do a simple estimate of the dark matter cross section and reproduce the analysis described in Ackermann et al. (2015).

It will be fun!

New grad student in the group obtains FAPESP scholarship

Let’s congratulate Artur Vemado─the newest graduate student in the group─who got a prestigious FAPESP scholarship. Artur just graduated with an astronomy degree at USP. His project will consist of incorporating radiative cooling in the energy equation of hot accretion flows, in order to investigate state transitions in black hole binaries.